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brucep
Gilese 581 b
http://www.flickr.com/photos/kqedquest/253...in/photostream/

In my opinion the most feasible interstellar travel is discussed at this site.

http://math.ucr.edu/home/baez/physics/Rela.../SR/rocket.html

It's theoretically possible to travel great distance measured in the coordinate frame [laboratory frame] in a very short time recorded in the proper frame [rocket frame]. For instance at 1 g constant acceleration for first half of the journey and 1 g constant deceleration for the 2nd half of the journey the rocket could reach Andromeda in 28 years proper rocket time. Time recorded in the coordinate frame would be 2 billion years. That's an extreme example but for Gilese 581 b which is 20 ly distant the journey would take

1.94 arccosh (20_earth years/1.94 + 1) = 6.0466 earth years

In the rocket proper frame and 20 earth years in the Earth coordinate frame. Those left on Earth would be able to receive signals from the ship and after 40 years Earth time we could know when the ship arrived and what's happening in the future

One huge problem would be propulsion and everything associated with it. Look at this paper you can access from waitedavid137 website Modern Relativity. David is a member of this forum.

http://xxx.lanl.gov/abs/gr-qc/0106003/

If we had Davids technology the propulsion issue would be resolved with no fuel requirement. We would need David to give us some feedback on the stress issue for a constant acceleration g_earth. Also I think David understands how to shield the ship. Just reading Davids conclusion section of the paper will give enough infomation to get the gist of his solution.

So what I thought would be fun would be to brainstorm all the other stuff associated with such a monumental project. I'll just add this: So far I've read that the mass of G 581 b is in the range of 5.6 to 13.8 Earth mass and that there isn't any such certainty to the radius. I did see an estimate of ~ 1.96 Earth radius. If that was the case g_surface G 581 b at 5.6_earth mass and 1.96_earth radius would be ~ 1.5 g_earth. That would mean a 200 lb person on Earth would weigh 300 lb on G 581 b. Maybe there's a way to prepare the crew during the voyage?

If you think of an issue that needs to be addressed post that issue rather than putting everything in one post. Then we could brainstorm and find a solution to that issue. Maybe we could have threads designated for issues? Assuming anyone finds this interesting Hope somebody will. Come back NA for this. Need a really smart womens perspective on all the issues. The more the merrier.

BTW I'm more interested in views other than my own.
brucep
QUOTE (brucep+May 19 2011, 12:01 AM)
Gilese 581 b
http://www.flickr.com/photos/kqedquest/253...in/photostream/

In my opinion the most feasible interstellar travel is discussed at this site.

http://math.ucr.edu/home/baez/physics/Rela.../SR/rocket.html

It's theoretically possible to travel great distance measured in the coordinate frame [laboratory frame] in a very short time recorded in the proper frame [rocket frame]. For instance at 1 g constant acceleration for first half of the journey and 1 g constant deceleration for the 2nd half of the journey the rocket could reach Andromeda in 28 years proper rocket time. Time recorded in the coordinate frame would be 2 billion years. That's an extreme example but for Gilese 581 b which is 20 ly distant the journey would take

1.94 arccosh (20_earth years/1.94 + 1) = 6.0466 earth years

In the rocket proper frame and 20 earth years in the Earth coordinate frame. Those left on Earth would be able to receive signals from the ship and after 40 years Earth time we could know when the ship arrived and what's happening in the future

One huge problem would be propulsion and everything associated with it. Look at this paper you can access from waitedavid137 website Modern Relativity. David is a member of this forum.

http://xxx.lanl.gov/abs/gr-qc/0106003/

If we had Davids technology the propulsion issue would be resolved with no fuel requirement. We would need David to give us some feedback on the stress issue for a constant acceleration g_earth. Also I think David understands how to shield the ship. Just reading Davids conclusion section of the paper will give enough infomation to get the gist of his solution.

So what I thought would be fun would be to brainstorm all the other stuff associated with such a monumental project. I'll just add this: So far I've read that the mass of G 581 b is in the range of 5.6 to 13.8 Earth mass and that there isn't any such certainty to the radius. I did see an estimate of ~ 1.96 Earth radius. If that was the case g_surface G 581 b at 5.6_earth mass and 1.96_earth radius would be ~ 1.5 g_earth. That would mean a 200 lb person on Earth would weigh 300 lb on G 581 b. Maybe there's a way to prepare the crew during the voyage?

If you think of an issue that needs to be addressed post that issue rather than putting everything in one post. Then we could brainstorm and find a solution to that issue. Maybe we could have threads designated for issues? Assuming anyone finds this interesting  Hope somebody will. Come back NA for this. Need a really smart womens perspective on all the issues. The more the merrier.

BTW I'm more interested in views other than my own.

Looks like I picked the wrong planet in the system I think it's the 581 d. I thought the picture was a bit fishy looking [gas giant].
saikat.prabhakar
@brucep : I might sound naive but I suppose the initial thrust or propulsion requires a serious thought to counter the inertia for astronauts too. Any food for thought in that regard ?
brucep
QUOTE (saikat.prabhakar+May 19 2011, 08:32 AM)
@brucep : I might sound naive but I suppose the initial thrust or propulsion requires a serious thought to counter the inertia for astronauts too. Any food for thought in that regard ?

The idea is to maintain a constant 1g acceleration /deceleration during the journey. This would mean it would feel like we were standing on Earth. The internals of the ship would have to be designed to accomplish this in the living space. We would build our ship while in a freefall orbit like the space station. Once we started the journey we could smoothly bring the ship to 1g. There are so many things to think about since the journey will take 6 years proper ship time and most likely we would be looking to start a colony at the destination. We would also want the option to come back if need be. It would have to be a bit like Noahs ark with a biosphere, etc.. That's a bit of a very rough concept. I'd like to here what you come up with. Anybody read the Rama books by A.C.Clarke?
waitedavid137
With the method I investigated in that section the passengers inside wouldn't feel the acceleration. Their free fall inside matches the acceleration of the ship. You could have any acceleration while feeling weightless throughout the trip because you aren't really accelerating with respect to your local inertial frame. A dipole pressure state in the matter of the hull causes the local space to accelerate with respect to a remote observer. It requires no fuel because the massive crew aren't actually accelerating with respect to the local free fall frame. The space itself is what is dynamically reacting to the matters pressure state. Creating a pressure dipole is easy enough, just put conductor Casimir effect producing plates on one side parallel to a plastic wall holding pressurized gas. The problem is this method produces immeasurably small acceleration for reasonably achievable pressures. I am much more convinced that much the same effect can be measurably achieved by using electric or magnetic fields. Not long ago I figured out the exact solution to Einstein's field equations for an arbitrary static electric field. You can find that in section 1 of chapter 7. Extremely charged matter will produce a gravitational acceleration field in the direction of the electric field with a proportional magnitude. It is consistent with general relativity for lifters which are ion drives to have a supplemental gravitational effect.
brucep
QUOTE (waitedavid137+May 20 2011, 09:17 AM)
With the method I investigated in that section the passengers inside wouldn't feel the acceleration. Their free fall inside matches the acceleration of the ship. You could have any acceleration while feeling weightless throughout the trip because you aren't really accelerating with respect to your local inertial frame. A dipole pressure state in the matter of the hull causes the local space to accelerate with respect to a remote observer. It requires no fuel because the massive crew aren't actually accelerating with respect to the local free fall frame. The space itself is what is dynamically reacting to the matters pressure state. Creating a pressure dipole is easy enough, just put conductor Casimir effect producing plates on one side parallel to a plastic wall holding pressurized gas. The problem is this method produces immeasurably small acceleration for reasonably achievable pressures. I am much more convinced that much the same effect can be measurably achieved by using electric or magnetic fields. Not long ago I figured out the exact solution to Einstein's field equations for an arbitrary static electric field. You can find that in section 1 of chapter 7. Extremely charged matter will produce a gravitational acceleration field in the direction of the electric field with a proportional magnitude. It is consistent with general relativity for lifters which are ion drives to have a supplemental gravitational effect.

Thanks for clarifying my misunderstanding wrt the spacetime for the ships coordinates. I listened to your youtube presentation 'Electric field tensor's gravitational solution of Einstein's field equations' and the power number, to generate the electric field, you associated with a g_earth acceleration blew my mind. Your solution blew my mind. You're a real life Zephram Cochrane. Youtube presentation:

For the Inertia Manipulation we could create an artificial g_earth environment inside spaceship. Do you think it would be plausible to develop, anytime in the future, Casimir type technology to make such a journey feasible? The ship would be huge so it seems we would have to find a way to manipulate spacetime with minimal power requirement. For the electric field solution which would be the most advantageous experimental result for sign +/-? Maybe a sufficiently large Casimir arrangement married to a very large ship in free fall wrt the remote coordinates could work? Any further ideas from you would be the most interesting. Thanks for the discussion.
dhcracker
I was just looking at that article and wondering the same thing. But Bruce, I know you are aware of the original Orion project correct? Why not build a 2,000 ton spacecraft in earth orbit or even on the moon? An unmanned craft could accellerate at 100g's up to a significant % of the speed of light... and we could dismantle our nuclear weapons to provide the fuel!!

http://en.wikipedia.org/wiki/Project_Orion...ear_propulsion)

I like this article you provide as well, think of what they will have come up with in another 20 years... but it would be cool to already have a probe on the way wouldn't it.
brucep
QUOTE (dhcracker+May 20 2011, 11:05 PM)
I was just looking at that article and wondering the same thing. But Bruce, I know you are aware of the original Orion project correct? Why not build a 2,000 ton spacecraft in earth orbit or even on the moon? An unmanned craft could accellerate at 100g's up to a significant % of the speed of light... and we could dismantle our nuclear weapons to provide the fuel!!

http://en.wikipedia.org/wiki/Project_Orion...ear_propulsion)

I like this article you provide as well, think of what they will have come up with in another 20 years... but it would be cool to already have a probe on the way wouldn't it.

The purpose of the thread was to plan a manned interstellar journey to colonize a habitable planet and all that entails I was hoping we would get different people with different knowledge base to contribute to the thread since it potentially covers every aspect of the scientific literature, philosophy, and the living interaction of humans, animals, plants.....etc.. There is lots to think about. Actually I would like to do a minimum of 'running my jaw' and listen to other folks.
AlexG
QUOTE (brucep+May 20 2011, 07:04 PM)
The purpose of the thread was to plan a manned interstellar journey to colonize a habitable planet and all that entails I was hoping we would get different people with different knowledge base to contribute to the thread since it potentially covers every aspect of the scientific literature, philosophy, and the living interaction of humans, animals, plants.....etc.. There is lots to think about. Actually I would like to do a minimum of 'running my jaw' and listen to other folks.

Are we looking at a generation ship, a suspended animation journey, or a high boost ship?
boit
QUOTE (AlexG+May 21 2011, 06:09 AM)
Are we looking at a generation ship, a suspended animation journey, or a high boost ship?

A generation ship I guess. The idea of de frosting humans does not appeal to me. For the third option it is just my fear of the unknown.
brucep
QUOTE (AlexG+May 21 2011, 03:09 AM)
Are we looking at a generation ship, a suspended animation journey, or a high boost ship?

Read my first post but I'm ready to listen to anything. At constant g_earth acceleration/deceleration it would take ~6 years ship proper time to arrive at low velocity while 20 years would pass in the earth coordinate frame. I was envisioning
a very large ship full of folks trained in some valuable regimen for making the journey and starting a colony. Animals, plants, pets, and other meaningful stuff. During the voyage they could cross train, maintain a biosphere [if feasible], have children, etc... Is suspended animation feasible? I don't know? I was hoping to learn something from forum members who have a different knowledge set than me. I was hoping we could brainstorm a list of topics which folks feel would be important for accomplishing such a goal. discussing, and finding some consensus [that's probably a bit of a pipe dream]. In the original post I picked the wrong planet. It should be the d planet.
waitedavid137
QUOTE (brucep+May 20 2011, 03:42 PM)
Do you think it would be plausible to develop, anytime in the future, Casimir type technology to make such a journey feasible? The ship would be huge so it seems we would have to find a way to manipulate spacetime with minimal power requirement. For the electric field solution which would be the most advantageous experimental result for sign +/-? Maybe a sufficiently large Casimir arrangement married to a very large ship in free fall wrt the remote coordinates could work? Any further ideas from you would be the most interesting. Thanks for the discussion.

We might be able to make the journey feasible with ordinary electric fields instead of Casimir effect based technology. This sign doesn't matter. It just determines the direction of the gravitational acceleration field with respect to the direction of the electric field.
Of course we could also consider doing it by wormhole travel or by a warp drive of some form.
brucep
QUOTE (waitedavid137+May 21 2011, 07:29 AM)
We might be able to make the journey feasible with ordinary electric fields instead of Casimir effect based technology. This sign doesn't matter. It just determines the direction of the gravitational acceleration field with respect to the direction of the electric field.
Of course we could also consider doing it by wormhole travel or by a warp drive of some form.

I picked the < light speed warp because of WEC violation in the > light speed warp solutions thinking that would be more feasible. Also it fit my fascination with the 'Relativistic Rocket' which basically needs a form of propulsion where a huge part of the ships mass wouldn't be fuel. The > warp is what we would all want. I know you've resolved some related problems associated the > warp but I kinda assumed the exotic matter requirement had monkey wrenched the feasibility? The other paper we looked at recently said Krasimov had set a limit for the exotic matter of - 10kg. Tell me what you think is possible sometime in the future. Another thing that I've wondered about is how the exotic matter would be contained. It seems you need it to manipulate the spacetime but using it doesn't neccessarily mean an expenditure of a portion of the -10kg? As you come out of warp the boundaries of the spacetime collapse and the exotic matter can be reconfined? As an analogy the 'Genie going back into the bottle'? If we had a warp we could visit other phenomena at will. Go to the supermassive black hole at the center of the galaxy. Doesn't look like I've generated much interest in this esoteric discussion but as always I like to hear what you think.
dhcracker
Well if I was president of the world, I would start building a nuclear "orion type" craft, the journey would be around 220 years at current technology and materials knowledge, the problem is going to be its actually going to take maybe 1,000 years for the entire mission. First i would send a small probe to the planet with a whole set of landers to take all kinds of data, second stage I would build two city sized orion craft.. maybe 5 years of the US's GNP would pay for them but we'd pay for it cause we're human and thats what we do we explore. The first craft would be supplies and anything we may need to make a biosphere on the planet or maybe even supplies we can start a multi-generation terra-forming project with. I mean no matter what we are going to find issues with any host planet that we won't find useful for life.. well 99.99% sure of that anyway. The probe would tell us what sites are most suitable on the planet and what we will have to bring with us as well as what we can use from the host planet. Finally once our supplies have safely arrived we set off in the last ship with representatives from all humanity and all walks of life down to the janitors and burger flippers lol. It would take probably 1,000 years but I bet that would be a grand 1,000 years of peace and a united humanity like we don't have today. Actually a project like this would do this world some good and help people set aside differences. After all we don't want to go planting flags in the galaxy like we have to our planet.

Don't get me wrong I like the op provided, see the problem anyone will have with planning anything like this is before we get our hardware built it will be obselete lol. Think about it after starting to build such massive ships we may come up with entirely new ways to power the craft and travel in space. However that doesn't mean we shouldn't start building something.

Great op with that I'm going to listen as well.
waitedavid137
QUOTE (brucep+May 21 2011, 02:32 PM)
I picked the < light speed warp because of WEC violation in the > light speed warp solutions thinking that would be more feasible. Also it fit my fascination with the 'Relativistic Rocket' which basically needs a form of propulsion where a huge part of the ships mass wouldn't be fuel. The > warp is what we would all want. I know you've resolved some related problems associated the > warp but I kinda assumed the exotic matter requirement had monkey wrenched the feasibility? The other paper we looked at recently said Krasimov had set a limit for the exotic matter of - 10kg. Tell me what you think is possible sometime in the future. Another thing that I've wondered about is how the exotic matter would be contained. It seems you need it to manipulate the spacetime but using it doesn't necessarily mean an expenditure of a portion of the -10kg? As you come out of warp the boundaries of the  spacetime collapse and the exotic matter can be reconfined? As an analogy the 'Genie going back into the bottle'? If we had a warp we could visit other phenomena at will. Go to the supermassive black hole at the center of the galaxy. Doesn't look like I've generated much interest in this esoteric discussion but as always I like to hear what you think. The worries some have about not getting back out of warp are totally unfounded. Just let the warp matter dispers on its own any which way it naturally does as you drop the ship out aside.

The Alcubierre warp drive which grounded the speed of the warp itself to the ship had a WEC violation for any speed even less than c. There is no WEC violation at all for pulsed electromagnetic sublight warpdrive that I've discussed in video. The main difference being that in the pulsed electromagnetic warp drive the speed of the warp is not grounded to the ship. The ship surfs the warp as it passes by. Because the Alcubierre warp had a WEC violation for any speed and this pulsed warp has no violation This tells me that faster than c warp drive solutions mathematically exist corresponding to much lower WEC violating exotic matter requirements. It may be that you just don't ground such solutions to the speed of the ship, you pulse them in the same sense and ride the pulse as it passes over the ship. That combined with the method of reducing the negative energy requirement I discovered by manipulating the value of the lapse function in the warp matter region means that the exotic matter can be much lower than others researching the possibility knew. Whether or not the matter required to do faster than c warp drive is possible to produce, the electromagnetic pulsed sublight version requires no exotic matter so I think warp drive is something worth looking at more closely in the future. Worries that you can't drop out of warp are completely unfounded. Just let the warp matter dissperse on its own however it naturally does going on ahead of you as you drop out aside.
waitedavid137
QUOTE (dhcracker+May 21 2011, 05:20 PM)
Well if I was president of the world, I would start building a nuclear "orion type" craft, ...

We can't do Orion because of an international nuclear test treaty.
brucep
QUOTE (waitedavid137+May 22 2011, 01:46 AM)
The Alcubierre warp drive which grounded the speed of the warp itself to the ship had a WEC violation for any speed even less than c. There is no WEC violation at all for pulsed electromagnetic sublight warpdrive that I've discussed in video. The main difference being that in the pulsed electromagnetic warp drive the speed of the warp is not grounded to the ship. The ship surfs the warp as it passes by. Because the Alcubierre warp had a WEC violation for any speed and this pulsed warp has no violation This tells me that faster than c warp drive solutions mathematically exist corresponding to much lower WEC violating exotic matter requirements. It may be that you just don't ground such solutions to the speed of the ship, you pulse them in the same sense and ride the pulse as it passes over the ship. That combined with the method of reducing the negative energy requirement I discovered by manipulating the value of the lapse function in the warp matter region means that the exotic matter can be much lower than others researching the possibility knew. Whether or not the matter required to do faster than c warp drive is possible to produce, the electromagnetic pulsed sublight version requires no exotic matter so I think warp drive is something worth looking at more closely in the future. Worries that you can't drop out of warp are completely unfounded. Just let the warp matter dissperse on its own however it naturally does going on ahead of you as you drop out aside.

Thanks David
You're the man so you shoose the propulsion system we want.
Confused1
While I think it is 'moral' for explorers to take any risks they like I'm not so sure it is 'moral' to bring children into the world Universe to service a spaceship that is most likely on a suicide mission. So no children until/unless a stable colony is established.

I'm guessing suspended animation (cryogenic/other) will be possible in the fairly near future. If/when suspended animation is achieved a crew could wake up their replacements after (say) a forty year shift - this would extend the time of flight to (possibly) hundreds of years.

-C2.
dhcracker
QUOTE (waitedavid137+May 21 2011, 08:50 PM)
We can't do Orion because of an international nuclear test treaty.

Yes and if I was president of the world I could violate any treaties I wanted to lol . But seriously I think thats a ban that shouldn't apply to international space projects, see under current technology we can build probes based on an orion design today. I know I'm sounding like a nuclear lobbyist but I can't help it, if such a project went along with a treaty to dismantle all our nuclear weapons for this project then all the better than a test ban.
brucep
QUOTE (Confused1+May 22 2011, 08:37 AM)
While I think it is 'moral' for explorers to take any risks they like I'm not so sure it is 'moral' to bring children into the world Universe to service a spaceship that is most likely on a suicide mission. So no children until/unless a stable colony is established.

I'm guessing suspended animation (cryogenic/other) will be possible in the fairly near future. If/when suspended animation is achieved a crew could wake up their replacements after (say) a forty year shift - this would extend the time of flight to (possibly) hundreds of years.

-C2.

Thanks for the comments. The journey to the star planetary system is 20ly. If our ship completed the journey at g_earth acceleration/deceleration the ships proper time would be ~ 6 years and the earth coordinate time would be 20 years [read the first post]. We would need to know Davids decision on the propulsion system to determine the actual proper time frame for the ship. Going on a suicide mission isn't feasible. We would need to be able to safely get to our destination and back to Earth if need be. Otherwise it would be a non starter. If I was on such a journey I wouldn't want to sleep through it but that's just my preference. I completely understand your feelings about children but if it's not a suicide mission then families could make up our group. We could educate our children and cross train the adults. I'll see if I can educate myself on the suspended animation.
Confused1
@Brucep et al,

QUOTE (Brucep+)
We would need to be able to safely get to our destination and back to Earth if need be. Otherwise it would be a non starter.

If the first destination proved to be unsuitable (discuss?) or impractical for some technical reason - I suspect the on-board vote would be to attempt to go on to another destination instead of returning to Earth - even if that meant passing the point of no return.

-C2.
bar_room_physist
QUOTE (Confused1+May 22 2011, 08:37 AM)
I'm guessing suspended animation (cryogenic/other) will be possible in the fairly near future. If/when suspended animation is achieved a crew could wake up their replacements after (say) a forty year shift - this would extend the time of flight to (possibly) hundreds of years.

I have often thought Tetrodotoxin or some derivative would be good for this.

brucep
QUOTE (Confused1+May 23 2011, 12:16 AM)
@Brucep et al,

QUOTE (Brucep+)
We would need to be able to safely get to our destination and back to Earth if need be. Otherwise it would be a non starter.

If the first destination proved to be unsuitable (discuss?) or impractical for some technical reason - I suspect the on-board vote would be to attempt to go on to another destination instead of returning to Earth - even if that meant passing the point of no return.

-C2.

I agree with that. By the time we have the technology to do something like this we'll probably have a good list of prospects. I've always wanted to discuss this as a team. Like the brainstorm we used to do at the refinery when we needed to do something complicated with unit operations or had problems which needed to be addressed in a planned way. What about the prospect for a ships biosphere. I know the project in Arizona was a failure so I don't know what would be feasible for Interstellar Travel. I think I heard the main failure was folks not being able to work and live together in an isolated environment. Not sure about that though. Any way thanks to you and B_R_P for the comments.
bar_room_physist
QUOTE (brucep+May 23 2011, 02:04 AM)
I've always wanted to discuss this as a team. Like the brainstorm we used to do at the refinery when we needed to do something complicated with unit operations or had problems which needed to be addressed in a planned way.

i think it would be fun, I also think we should remove political and economic factors from the brainstorm session. It would probably take more money than the GPD of the entire world to accomplish a task like this, and political opinion can be changed.

i think we should begin with a list of dangers/technical issues with long term space travel.

Biosphere
Lack of gravity
Food production
Fuel

that's what i got off the top of my head.
brucep
QUOTE (bar_room_physist+May 23 2011, 03:13 AM)
i think it would be fun, I also think we should remove political and economic factors from the brainstorm session. It would probably take more money than the GPD of the entire world to accomplish a task like this, and political opinion can be changed.

i think we should begin with a list of dangers/technical issues with long term space travel.

Biosphere
Lack of gravity
Food production
Fuel

that's what i got off the top of my head.

Good list. The gravity one will be either the constant g_earth acceleration/deceleration or if David chooses a warp where the ship spacetime is a free float frame then we'll need to create g_earth in the ship living areas. David knows how to shield the warp by manipulation of the warp spacetime. We'll need to know the method of propulsion to discuss fuel. I'm guessing it will be one of the warps David has discovered solutions for.

How many folks and what are they're qualifications

How big is this ark and what does it look like. We'll probably have to build it in zero gravity.

What type system do you design to store the history and scientific literature of all species on Earth

Politics and bankers hit the bricks,
synthsin75
I think the first prerequisite, both for the economics of starting such a project and the sustainability of the journey, is a cheap and renewable energy source. Only freed of energy constrictions will we ever be able to tackle such projects. Once we do, we'll need such an energy source to sustain biosphere/hydroponics away from a good solar source. So a sufficient energy source could go a long way toward augmenting, if not providing, food and oxygen supplies. An abundant enough energy supply could even provide protection from cosmic radiation, if we could produce an great enough electromagnetic field.

Many other things would rely on what drive technology we develop.
bar_room_physist
114 billion v/m !!!!!

Sorry I felt like the doc from back to the future.

I'm unaware of any material that could withstand even the force of electrons flowing through it (in a reasonably compact device) to produce an E field of this size.

the voltage if i'm correct, should be 31 167 979 volts with a plate separation of 12 ft or 3.6576 m to achieve 1 g with his calculations.

the plates would push apart with
F= K_e {q1q2/ r^2} which although i haven't done the math I would assume is probably in the 1000's of newtons range. so the ship would continually be trying to tear it's self apart.

BTW David loved the video!!! I'm sure you have thought of these things and maybe have an answer to them.

edit: I was referring to using the plates as a gravity plating.
also the thought occurs to me we could use a QED system to amplify the EM field.

as for the power source why not fusion or good old fashion nuclear?

second edit: just did some quick calculations and that is 56 X10^3 the power output for the entire world yearly and we need that as continuous power. about 971 442 915 108 052 Watts
brucep
QUOTE (bar_room_physist+May 23 2011, 06:56 AM)
114 billion v/m !!!!!

Sorry I felt like the doc from back to the future.

I'm unaware of any material that could withstand even the force of electrons flowing  through it (in a reasonably compact device) to produce an E field of this size.

the voltage if i'm correct, should be 31 167 979 volts with a plate separation of 12 ft or 3.6576 m to achieve 1 g with his calculations.

the plates would push apart with
F= K_e {q1q2/ r^2} which although i haven't done the math I would assume is probably in the 1000's of newtons range. so the ship would continually be trying to tear it's self apart.

BTW David loved the video!!! I'm sure you have thought of these things and maybe have an answer to them.

edit: I was referring to using the plates as a gravity plating.
also the thought occurs to me we could use a QED system to amplify the EM field.

as for the power source why not fusion or good old fashion nuclear?

Mind blowing isn't it. I've read all the papers written on this subject and David has solved problems others still think are impossible to solve. When I listened to the video I thought just like you. It was the first time I saw the pulsed electromagnetic warp solution. Go back in the thread and read all the response he made to my questions and see what you think. The whole idea of this thread is really esoteric meant to be possibly realized in a very distant future. The nuclear pulse propulsion can do ~ .045 coordinate light speed. My fantasy journey isn't going to settle for that Think big since we don't have to pay for it and we won't be around anyway.
dhcracker
What about the boundary conditions for the casimir effect? I still haven't grasped all his concepts yet but they are very interesting, I really haven't understood it completely enough to start asking questions yet other than this one lol. cool though
Confused1
I'm not sure about Davids propulsion system - mostly because I don't understand it (actually I'm ignoring it, but I wouldn't understand it if I didn't so the result is the same). So I'm thinking of big rocket engines. Very big.

Howzabout starting with a fair sized asteroid? I think they might come with a high iron content which would be ideal for forming a hull - or possibly simply hollow out the living quarters, dance hall, tennis courts etc and plug any leaks as and when they occur.

If the asteroid included a sensible amount of uranium or thorium it might even come complete with its own fuel supply - are the Gods that generous? (I suspect not). Given time one might calculate the percentage of fissionable material required to accelerate itself and surrounding dross at the desired 1g. If it comes out at a remotely plausable figure one might start sniffing out likely looking asteroids.

For uranium ..
1ppb in carbonaceous meteorites .. I'm guessing (without calculating) that this is a few orders of magnitude too small. Maybe higher metal content would give a higher U content?

More guesses may follow.

-C2.

waitedavid137
QUOTE (bar_room_physist+May 22 2011, 11:56 PM)
114 billion v/m !!!!!

Sorry I felt like the doc from back to the future.

I'm unaware of any material that could withstand even the force of electrons flowing through it (in a reasonably compact device) to produce an E field of this size.

the voltage if i'm correct, should be 31 167 979 volts with a plate separation of 12 ft or 3.6576 m to achieve 1 g with his calculations.

the plates would push apart with
F= K_e {q1q2/ r^2} which although i haven't done the math I would assume is probably in the 1000's of newtons range. so the ship would continually be trying to tear it's self apart.

BTW David loved the video!!! I'm sure you have thought of these things and maybe have an answer to them.

edit: I was referring to using the plates as a gravity plating.
also the thought occurs to me we could use a QED system to amplify the EM field.

as for the power source why not fusion or good old fashion nuclear?

second edit: just did some quick calculations and that is 56 X10^3 the power output for the entire world yearly and we need that as continuous power. about 971 442 915 108 052 Watts

You don't use plates to get that. With a uniform field of that magnitude you'll short even through vacuum. You use wires or metals coming to points or edges. The field isn't uniform that way and is only so strong immediately near the matter of the wire where you want the gravitational effect to act on the wire.
bar_room_physist
QUOTE (waitedavid137+May 23 2011, 04:30 PM)
You don't use plates to get that. With a uniform field of that magnitude you'll short even through vacuum. You use wires or metals coming to points or edges. The field isn't uniform that way and is only so strong immediately near the matter of the wire where you want the gravitational effect to act on the wire.

I'm gonna spend a couple of days this week seeing if there is a particular arrangement of wires that according to QED will produce a stronger EM field.

I absolutely agree that you would get a short in the system. I think it's 3 million volts in air and 20 million volts in a vacuum. Using a thin point or fine edged wire is simply going to vaporize, it would work for experimentation, but I don't think we could achieve continuous output from it.

also what does the solution tell you about synchrotron radiation? I would imagine that a flat plate would be preferable to a wire because it only emits the radiation on the edges of the plate where the E field is not uniform.

This will probably also put off neutron radiation, similar to a Fusor;
Cause population inversion(LASE) in what ever medium you put it in (except vacuum).

electricity does really weird things when you get it that powerful...it would be really fun to play with.

as a side note what do you think of Martin Tajmar's work?
waitedavid137
QUOTE (bar_room_physist+May 23 2011, 10:37 AM)
I'm gonna spend a couple of days this week seeing if there is a particular arrangement of wires that according to QED will produce a stronger EM field.

I absolutely agree that you would get a short in the system. I think it's 3 million volts in air and 20 million volts in a vacuum. Using a thin point or fine edged wire is simply going to vaporize, it would work for experimentation, but  I don't think we could achieve continuous output from it.

also what does the solution tell you about  synchrotron radiation? I would imagine that a flat plate would be preferable to a wire because it only emits the radiation on the edges of the plate where the E field is not uniform.

This will probably also put off neutron radiation, similar to a Fusor;
Cause population inversion(LASE) in what ever medium you put it in (except vacuum).

electricity does really weird things when you get it that powerful...it would be really fun to play with.

as a side note what do you think of Martin Tajmar's work?

My solution is a static state solution. You don't have changing currents to produce Larmor radiation. You don't need QED, just Maxwell's electrodynamics. for a short in vacuum its the average field between the electrodes that has to be about 3 million V/m. So, don't use a uniform field. Use a very thin wire or needle for one of the electrodes so the average field between them is reasonably low, but so the strength of the field entering the wire is huge. You make use of the gravitational field's effect on the wire.
I suspect the superconductor gravity experiments are a magnetic effect, not gravitational. The lab had an ambient magnetic field. Superconductors resist changes in magnetic flux. They'll resist dropping in the external magnetic field.
bar_room_physist
QUOTE (waitedavid137+May 23 2011, 06:48 PM)
Use a very thin wire or needle for one of the electrodes so the average field between them is reasonably low, but so the strength of the field entering the wire is huge. You make use of the gravitational field's effect on the wire.

oooohhhhhhh! thanks
brucep
QUOTE (waitedavid137+May 23 2011, 06:48 PM)
My solution is a static state solution. You don't have changing currents to produce Larmor radiation. You don't need QED, just Maxwell's electrodynamics. for a short in vacuum its the average field between the electrodes that has to be about 3 million V/m. So, don't use a uniform field. Use a very thin wire or needle for one of the electrodes so the average field between them is reasonably low, but so the strength of the field entering the wire is huge. You make use of the gravitational field's effect on the wire.
I suspect the superconductor gravity experiments are a magnetic effect, not gravitational. The lab had an ambient magnetic field. Superconductors resist changes in magnetic flux. They'll resist dropping in the external magnetic field.

Thanks for the details which make it easier to understand. So we have the ability to use Davids Pulsed Electromagnetic Sublight Warpdrive for our futuristic journey.

Q. For confirmation purpose the ships proper frame is free float. We could artificially create a g_earth environment in the living space.

Q. Is there a practical limit on the ships external surface area? IE how big a ship can we build and what is the best shape?

Q. Can you shield the ship in the same way you would with the exotic matter warp? If so could you briefly explain how the spactime is manipulated to achieve shielding and would maximum shielding place a limit on the ships size and shape?

So far this has been a fun discussion on warpdrive.
dhcracker
QUOTE (waitedavid137+May 23 2011, 01:48 PM)
My solution is a static state solution. You don't have changing currents to produce Larmor radiation. You don't need QED, just Maxwell's electrodynamics. for a short in vacuum its the average field between the electrodes that has to be about 3 million V/m. So, don't use a uniform field. Use a very thin wire or needle for one of the electrodes so the average field between them is reasonably low, but so the strength of the field entering the wire is huge. You make use of the gravitational field's effect on the wire.
I suspect the superconductor gravity experiments are a magnetic effect, not gravitational. The lab had an ambient magnetic field. Superconductors resist changes in magnetic flux. They'll resist dropping in the external magnetic field.

Ok now we are getting to something I know a little about yay! I have some concerns about pushing so much power through a "tiny wire". Also did I miss the rest of the current data? Whats the figures for current, power, voltage, and what material and exact size is this tiny wire or needle? Is it a solid stranded wire or is it braided? How long is the wire this current is running through? I don't see how you won't simply fry any wire you try to run that much power through.

Bar,

How did you come up with watts and amps? I'm missing some data somewhere ??

I'm sorry if I've missed the data I'm asking for, finally the topic has moved to something I know how to contribute to lol. I am the Hillbilly wire expert round these parts lol

cheers all

brucep
QUOTE (Confused1+May 23 2011, 04:25 PM)
I'm not sure about Davids propulsion system - mostly because I don't understand it (actually I'm ignoring it, but I wouldn't understand it if I didn't so the result is the same). So I'm thinking of big rocket engines. Very big.

Howzabout starting with a fair sized asteroid? I think they might come with a high iron content which would be ideal for forming a hull - or possibly simply hollow out the living quarters, dance hall, tennis courts etc and plug any leaks as and when they occur.

If the asteroid included a sensible amount of uranium or thorium it might even come complete with its own fuel supply - are the Gods that generous? (I suspect not). Given time one might calculate the percentage of fissionable material required to accelerate itself and surrounding dross at the desired 1g. If it comes out at a remotely plausable figure one might start sniffing out likely looking asteroids.

For uranium ..
1ppb in carbonaceous meteorites .. I'm guessing (without calculating) that this is a few orders of magnitude too small. Maybe higher metal content would give a higher U content?

More guesses may follow.

-C2.

Missed it. That's a novel idea. The constant g acceleration would have a huge fuel requirement. First you're worried about the kids safety now you want to go by barge. You're fun. Keep the ideas flowing.
bar_room_physist
QUOTE (dhcracker+May 24 2011, 12:07 AM)
Ok now we are getting to something I know a little about yay!  I have some concerns about pushing so much power through a "tiny wire".  Also did I miss the rest of the current data?  Whats the figures for current, power, voltage, and what material and exact size is this tiny wire or needle?  Is it a solid stranded wire or is it braided?  How long is the wire this current is running through?  I don't see how you won't simply fry any wire you try to run that much power through.

Bar,

How did you come up with watts and amps?  I'm missing some data somewhere ??

I'm sorry if I've missed the data I'm asking for, finally the topic has moved to something I know how to contribute to lol.  I am the Hillbilly wire expert round these parts lol

cheers all

in Davids video he gave the field strength for 1 g which is 114 billion v/m. I worked all the rest out assuming the wire would heat and have a graduated resistance. Simple stuff, however he has worked out a solution where we are using an non uniform field and it becomes a L/R Circuit. Which are a little harder to figure and do some strange things. I have a pretty big project that I'm working on this week but when i get some time I will see if I can't get some schematics drawn up for our gravity plating.
brucep
QUOTE (bar_room_physist+May 24 2011, 05:09 AM)
in Davids video he gave the field strength for 1 g which is 114 billion v/m. I worked all the rest out assuming the wire would heat and have a graduated resistance. Simple stuff, however he has worked out a solution where we are using an non uniform field and it becomes a L/R Circuit. Which are a little harder to figure and do some strange things. I have a pretty big project that I'm working on this week but when i get some time I will see if I can't get some schematics drawn up for our gravity plating.

Good luck with your project. A schematic would be interesting for me.
Confused1
@Brucep - please say if you would rather I did not continue on this thread. So far I get the impression you are OK with it.

Staying with the non-warp route..
There is Thorium on the Moon. Lots of it. ( http://www.astronomy.com/~/media/import/im...x?mw=900&mh=650 )
The target is 1g or 50W/kg of total ship mass.
I calculate that a 4GW reactor at 10% efficiency (how?) could propel a 8*10^6Kg ship (or 8,000 metric tons).
I was kinda thinking of a ship mass of at least 5,000,000 200,000 tons but ten reactors would be in the right league and give a bit of redundancy.
I'll continue speculation in this direction unless otherwise instructed.
-C2.

Edit..
The rate at which waste heat can be lost (radiated) might turn out to be (one of) the limiting factors.
brucep
QUOTE (Confused1+May 25 2011, 12:23 AM)
@Brucep - please say if you would rather I did not continue on this thread. So far I get the impression you are OK with it.

Staying with the non-warp route..
There is Thorium on the Moon. Lots of it. ( http://www.astronomy.com/~/media/import/im...x?mw=900&mh=650 )
The target is 1g or 50W/kg of total ship mass.
I calculate that a 4GW reactor at 10% efficiency (how?) could propel a 8*10^6Kg ship (or 8,000 metric tons).
I was kinda thinking of a ship mass of at least 5,000,000 200,000 tons but ten reactors would be in the right league and give a bit of redundancy.
I'll continue speculation in this direction unless otherwise instructed.
-C2.

Of course continue. So far the entire thread has been about propulsion which is fine with, me even if it ends there. Calculate how much of the ships mass would have to be fuel for 6 years constant 1g acceleration/deceleration. The reason I like warp is because were speculating for the future [allows latitude on what's feasible] we can shield the ship by manipulating the warp, and that we would be able to go elsewhere or come home if need be. You're discussing issues brought up in the Relativistic Rocket scenario that I like so much. You probably read it but if not it's linked in the first post.
flyingbuttressman
Unless we somehow discover a way to travel FTL, I don't think humanity can ever really explore the cosmos, at least in our current form.

On the other hand, if we can create machines that we can claim as our memetic descendants, we just have to package them up as Von Neumann machines and send them out to spread humanity across the galaxy. Maybe we could send a few frozen human embryos along to create human populations on planets that can support human life.
Guest
QUOTE (flyingbuttressman+May 25 2011, 02:18 AM)
Unless we somehow discover a way to travel FTL, I don't think humanity can ever really explore the cosmos, at least in our current form.

On the other hand, if we can create machines that we can claim as our memetic descendants, we just have to package them up as Von Neumann machines and send them out to spread humanity across the galaxy. Maybe we could send a few frozen human embryos along to create human populations on planets that can support human life.

Read some of the posts on sublight and FTL warpdrive we've been discussing. Including the first post. This is a pretty esoteric thread but fun. David has solved several key issues first associated with the Alcubierre warp solution. Including a very large reduction in exotic matter requirement , how to shield buy manipulating the warp spacetime, and how to turn the warp off from inside the ship. Obviously getting exotic matter is a huge if but we can suspend this requirement to a distant future for our proposed journey. Think about some of the other issues associated with a trip like this. Reading the first post will get you thinking about this specific proposal
brucep
QUOTE (Guest+May 25 2011, 03:15 AM)
Read some of the posts on sublight and FTL warpdrive we've been discussing. Including the first post. This is a pretty esoteric thread but fun. David has solved several key issues first associated with the Alcubierre warp solution. Including a very large reduction in exotic matter requirement , how to shield buy manipulating the warp spacetime, and how to turn the warp off from inside the ship. Obviously getting exotic matter is a huge if but we can suspend this requirement to a distant future for our proposed journey. Think about some of the other issues associated with a trip like this. Reading the first post will get you thinking about this specific proposal

Guest is me I forgot to log on.
flyingbuttressman
I'll add more tomorrow, but for the time being, here's a great resource:
projectrho.com
brucep
QUOTE (flyingbuttressman+May 25 2011, 04:26 AM)
I'll add more tomorrow, but for the time being, here's a great resource:
projectrho.com

Thanks.
flyingbuttressman
I'm curious as to how this Alcubierre warp drive manages to avoid the Causality problem. Why FTL implies time travel
bar_room_physist
FBM and bruce

i'm curious what FTL actually means...what reference frame? Because you can never go FTL in a local frame no matter how fast you actually go. light always goes by at c no matter how fast you are going in your frame. could you please explain FTL a little better?

thanks
flyingbuttressman
QUOTE (bar_room_physist+May 25 2011, 09:30 AM)
i'm curious what FTL actually means...what reference frame? Because you can never go FTL in a local frame no matter how fast you actually go. light always goes by at c no matter how fast you are going in your frame. could you please explain FTL a little better?

The method that they are discussing isn't necessarily moving the ship through space, but moving space itself. They are trying to "warp" space using exotic matter. This actually sounds similar to the warp method used in Star Trek...

The main problem with FTL travel, aside from the fact that it is impossible to accelerate to c, is that FTL travel and time travel are synonymous. Any FTL travel violates causality, which depends on the speed of light to keep things in check.
QUOTE
Causality, Relativity, FTL travel: chose any two.

http://www.projectrho.com/rocket/fasterlight.php#Causality
bar_room_physist
yes I'm familiar with Godel loops and the warping of space....But what frame is FTL, I hear this tossed about, but by definition it seems like a null term. You can never go FTL. So what happens if I am in a rocket ship and it goes 299,792,458 + 10 m/s? ignoring all the paradoxical constraints. Light still goes past me at 299,792,458 m/s so I'm not really going FTL. What is the definition of FTL used in this context ? I feel like i've missed something.
flyingbuttressman
QUOTE (bar_room_physist+May 25 2011, 10:09 AM)
yes I'm familiar with Godel loops and the warping of space....But what frame is FTL, I hear this tossed about, but by definition it seems like a null term. You can never go FTL. So what happens if I am in a rocket ship and it goes 299,792,458 + 10 m/s? ignoring all the paradoxical constraints. Light still goes past me at 299,792,458 m/s so I'm not really going FTL. What is the definition of FTL used in this context ? I feel like i've missed something.

If I am correct, the idea is that this method would create a bubble of normal space around the spacecraft while the space in front contracts and the space behind expands. Thus, the spacecraft is not travelling FTL, but space itself is travelling FTL.
http://en.wikipedia.org/wiki/Alcubierre_drive
bar_room_physist
oh i get it, it's a misnomer like 'quantum teleportation'...It should really be: no object can travel faster than c because of the Lorentz factor and relativity of simultaneity and cause and effect and has nothing to do with the velocity of light other than, it is the definition of c. light still passes at light speed.

Is that right?

BTW thanks for the responses.

brucep
QUOTE (flyingbuttressman+May 25 2011, 03:35 PM)
If I am correct, the idea is that this method would create a bubble of normal space around the spacecraft while the space in front contracts and the space behind expands. Thus, the spacecraft is not travelling FTL, but space itself is travelling FTL.
http://en.wikipedia.org/wiki/Alcubierre_drive

That's it. The ships proper frame for the Alcubierre warp is a local inertial rest frame[ free float frame]. John Cramer of the Transactional Interpretation of QM wrote this after Miguel Alcubierre published his warp solution to the EFE.

http://www.npl.washington.edu/AV/altvw81.html

Over the years since the Alcubierre paper was published the metric solution has been improved and many issues associated with it have been resolved. Davids lapse function reduces the exotic matter requirement exponentially and he figured out how to turn off the warp from the ship. Initially the ships proper frame was thought to be behind a horizon at the warp boundary. He also figured out how to shield the ship by manipulating the metric that describes the warp spacetime.

flyingbuttressman
QUOTE (brucep+May 25 2011, 02:27 PM)
Over the years since the Alcubierre paper was published the metric solution has been improved and many issues associated with it have been resolved. Davids lapse function reduces the exotic matter requirement exponentially and he figured out how to turn off the warp from the ship. Initially the ships proper frame was thought to be behind a horizon at the warp boundary. He also figured out how to shield the ship by manipulating the metric that describes the warp spacetime.

Aside from the fact that exotic matter is still within the realm of science fiction, how does this avoid the Causality paradox?
brucep
QUOTE (bar_room_physist+May 25 2011, 04:12 PM)
oh i get it, it's a misnomer like 'quantum teleportation'...It should really be: no object can travel faster than c because of the Lorentz factor and relativity of simultaneity and cause and effect and has nothing to do with the velocity of light other than, it is the definition of c. light still passes at light speed.

Is that right?

BTW thanks for the responses.

The real limit is information can't be transfered faster than the local coordinate speed of light. Which is what we call c. Many quantum experiments have been devised to test this. Cramer discusses one here.

http://www.analogsf.com/0612/altview.shtml

Looks like Cramer hasn't posted an article in several years. Must be to busy doing science and teaching.
dhcracker
QUOTE (bar_room_physist+May 24 2011, 12:09 AM)
in Davids video he gave the field strength for 1 g which is 114 billion v/m. I worked all the rest out assuming the wire would heat and have a graduated resistance. Simple stuff, however he has worked out a solution where we are using an non uniform field and it becomes a L/R Circuit. Which are a little harder to figure and do some strange things. I have a pretty big project that I'm working on this week but when i get some time I will see if I can't get some schematics drawn up for our gravity plating.

Ok, now I"m a little confused because I still don't get how a non-uniform field would really change the physical limitations on the wires ability to withstand such a large current. When I plug your figures into my own electrical calculations I get the same amps as I do volts which is .. well its crazy but then again I've never tried to calculate such high voltage so maybe this is normal?

Also I still don't see any mention of the size of said wire and its length, I would imagine even in a vacuum the physical limitations on materials would still be the same. For instance if you took even 480 volts and tried to run say even just 2 amps through what I would consider small wires, 14 guage or smaller you instantly just fry the wire. Even in an induction circuit this appears to me to be impossible and I don't see how it would ever be possible unless the laws of physics change somehow in this situation.

I have on this PC dozens of different EM field calculations related to passing current through wires and the air, I've been an electrician and cable television tech for most my life (family has two small cable systems and they don't believe in hiring help lol), I'm dying to crunch these numbers and solve the equations. Which video should I be looking at the one linked I didn't catch a mention of any more data than volts, I didn't catch any data related to power. I don't see how one can get watts or amps with just volts???? You have to have at least two variables known right??

Maybe you can point me to what I'm missing I'm sure I have to be missing some principle or special rules to apply to this situation??
dhcracker
QUOTE (bar_room_physist+May 24 2011, 12:09 AM)
in Davids video he gave the field strength for 1 g which is 114 billion v/m. I worked all the rest out assuming the wire would heat and have a graduated resistance. Simple stuff, however he has worked out a solution where we are using an non uniform field and it becomes a L/R Circuit. Which are a little harder to figure and do some strange things. I have a pretty big project that I'm working on this week but when i get some time I will see if I can't get some schematics drawn up for our gravity plating.

Hey btw if you get a schematic I'll see if I can build a scale experiment. I can generate up to 20,000 DC volts, not at a 1 to 1 amp scale of course but maybe I can try to set up some kind of representation of this field. I do have a vacuum pump in the shop and way too much free time lol
brucep
QUOTE (flyingbuttressman+May 25 2011, 07:47 PM)
Aside from the fact that exotic matter is still within the realm of science fiction, how does this avoid the Causality paradox?

It's not completely in the realm of science fiction. This is an article from the site you linked. BTW the guy who wrote it worked with David on several projects [papers].

Demystifying exotic energy [negative energy].

http://members.tripod.com/da_theoretical1/exoticfields.html

The issue is getting some. Initially the estimates needed for warp was as high as the mass of the Sun [mind boggling]. Most recently I read Krasnikov says -10kg. With the lapse function it would probably be less though we would need David to confirm that. Like I said this project is futuristic.

flyingbuttressman
QUOTE (brucep+May 25 2011, 03:17 PM)
It's not completely in the realm of science fiction. This is an article from the site you linked. BTW the guy who wrote it worked with David on several projects [papers].

Demystifying exotic energy [negative energy].

http://members.tripod.com/da_theoretical1/exoticfields.html

Crazy stuff

So it might exist, but we currently have no way of detecting or harnessing it.
Kino
I'm not sure there's much I can add to the propulsion discussion, although I can do a decent Scottish accent if you're looking for a chief engineer.

I'd be inclined to do gravity by centrifugal force, on the 'keep it simple' principle. Even numbers of rings counter-rotating would go a long way to cancel out the gyroscopic effect. We might want some ability to adjust the mass distribution (big, moveable weights on the spokes of the wheels, for example) to keep the ship gyro-free while allowing people and stuff to move between rings.

Confused1 mentioned heat loss. Most of the ship would be at around 293K which, if the ship is an ideal blackbody, would radiate at about 420W/m^2. A human produces around 120W of heat. I think the living quarters would be ok (actually, need insulation), unless there were a LOT of decks. Not sure about the reactor. Presumably we'd be doing our best to turn the heat into space warp.

A couple of thoughts before we set off. As we have a working ship, let's use the prototype to deploy the mother of all long-baseline telescope arrays, and get a good look at where we're going. An array 2AUs across would enable us to resolve an object around half a meter across at 20 light years, according to the Rayleigh criterion. Light gathering power would suck, so don't expect to see that much detail, but we should be able to get a good look at our new home before we go.

Second, we send robot ships first. I'm thinking quite dinky things, but autonomous. They'd be designed to map the system, looking for mineral-rich asteroids and the like and to deploy bots to the surface of the planet to take a look round. They phone home by deploying a huge mirrored surface and using it like a signalling glass. You modulate the reflectivity rather than tilting the mirror, though.

One last thought about the ship. We are going to need to load and offload a lot of stuff. That would be easier if the ship came with an orbital tether, if we can get the materials tech working.

All rather high level thinking. Do we have any idea how big this ship is going to be? Does the warp limit it? That would be a big help in hardening ideas.
Confused1
On the non-warp front..
QUOTE (Brucep+)
Calculate how much of the ships mass would have to be fuel for 6 years constant 1g acceleration/deceleration.

F= v dm/dt
Where F is the force, dm/dt is the mass ejected per second and v is the jet velocity.

For an order of magnitude guess I'm going for 10N and 0.5kg mass (half of an original 1kg) ejected over a 5 year period. There are about 30*10^6 seconds in a year. So (ignoring relativistic effects)

10 = v * 0.5/(5 * 30*10^6)

v ~= 3000 *10^6 m/s // speed of light is a mere 300*10^6 m/s

I'm thinking we need m_relative = considerable * m_rest for this to have legs.

From the start I was thinking of feeding thorium (or breeding something from it) to feed into a suitable neutron flux to initiate fission - the fuel is also the ejecta (I may have made that word up). I doubt if enough of the fission products have sufficient velocity for the intended purpose but I'll have a look (unless anyone already knows).

The next line of attack would be a particle accelerator producing near c particles (lots of them) at 10% efficiency or better - this is beyond my ability to speculate about.

@Brucep - a point well made.

Best wishes,
-C2.
brucep
QUOTE (Kino+May 25 2011, 10:32 PM)
I'm not sure there's much I can add to the propulsion discussion, although I can do a decent Scottish accent if you're looking for a chief engineer.

I'd be inclined to do gravity by centrifugal force, on the 'keep it simple' principle. Even numbers of rings counter-rotating would go a long way to cancel out the gyroscopic effect. We might want some ability to adjust the mass distribution (big, moveable weights on the spokes of the wheels, for example) to keep the ship gyro-free while allowing people and stuff to move between rings.

Confused1 mentioned heat loss. Most of the ship would be at around 293K which, if the ship is an ideal blackbody, would radiate at about 420W/m^2. A human produces around 120W of heat. I think the living quarters would be ok (actually, need insulation), unless there were a LOT of decks. Not sure about the reactor. Presumably we'd be doing our best to turn the heat into space warp.

A couple of thoughts before we set off. As we have a working ship, let's use the prototype to deploy the mother of all long-baseline telescope arrays, and get a good look at where we're going. An array 2AUs across would enable us to resolve an object around half a meter across at 20 light years, according to the Rayleigh criterion. Light gathering power would suck, so don't expect to see that much detail, but we should be able to get a good look at our new home before we go.

Second, we send robot ships first. I'm thinking quite dinky things, but autonomous. They'd be designed to map the system, looking for mineral-rich asteroids and the like and to deploy bots to the surface of the planet to take a look round. They phone home by deploying a huge mirrored surface and using it like a signalling glass. You modulate the reflectivity rather than tilting the mirror, though.

One last thought about the ship. We are going to need to load and offload a lot of stuff. That would be easier if the ship came with an orbital tether, if we can get the materials tech working.

All rather high level thinking. Do we have any idea how big this ship is going to be? Does the warp limit it? That would be a big help in hardening ideas.

Thanks for reviewing that. We actually could use more brainstorm and project planning not related to propulsion. I asked questions about limits for ship external surface area, and optimum shape, including any that might be associated with manipulating the warp spacetime for shielding. That was probably in lane two of the thread. For our team David needs to answer those questions. Also we need to decide which type warp spacetime is more feasible. We have sublight warp and FTL warp. I think David feels the sublight Pulsed Electromagnetic Warp is best for this project. Not sure though. If you go back in the thread you'll see several have been discussed. Anybody have a thought about the feasibility for biospheres in space and whether that would be something we would look at? Your idea for creating the g_earth living space is great.
bar_room_physist
QUOTE (dhcracker+May 25 2011, 08:10 PM)
Ok, now I"m a little confused because I still don't get how a non-uniform field would really change the physical limitations on the wires ability to withstand such a large current. When I plug your figures into my own electrical calculations I get the same amps as I do volts which is .. well its crazy but then again I've never tried to calculate such high voltage so maybe this is normal?

Also I still don't see any mention of the size of said wire and its length, I would imagine even in a vacuum the physical limitations on materials would still be the same. For instance if you took even 480 volts and tried to run say even just 2 amps through what I would consider small wires, 14 guage or smaller you instantly just fry the wire. Even in an induction circuit this appears to me to be impossible and I don't see how it would ever be possible unless the laws of physics change somehow in this situation.

I have on this PC dozens of different EM field calculations related to passing current through wires and the air, I've been an electrician and cable television tech for most my life (family has two small cable systems and they don't believe in hiring help lol), I'm dying to crunch these numbers and solve the equations. Which video should I be looking at the one linked I didn't catch a mention of any more data than volts, I didn't catch any data related to power. I don't see how one can get watts or amps with just volts???? You have to have at least two variables known right??

Maybe you can point me to what I'm missing I'm sure I have to be missing some principle or special rules to apply to this situation??

@dhcracker
yes i did that on purpose i figure the material will heat up and provide more and more resistance until you have to pump the same amps as volts to get the current to move all. This is of course in a 'perfect material' which doesn't really exist.

as for the wire and r/l circuit what we are doing is using each charge in the wire to produce an em plane wave. that wave can be pumped and cycled like a standing wave to reach the required field density which will be cross the B wave. So the material is not an issue as the wave itself is storing the energy and the wire is inducing it. That is at least my understanding of it.

@bruce

Thanks the project is going well and i'm sure between me and dhcracker we will have a pretty good idea of just how possible this really is in a few weeks.

dhcracker
QUOTE (bar_room_physist+May 26 2011, 12:41 AM)
@dhcracker
yes i did that on purpose i figure the material will heat up and provide more and more resistance until you have to pump the same amps as volts to get the current to move all. This is of course in a 'perfect material' which doesn't really exist.

as for the wire and r/l circuit what we are doing is using each charge in the wire to produce an em plane wave. that wave can be pumped and cycled like a standing wave to reach the required field density which will be cross the B wave. So the material is not an issue as the wave itself is storing the energy and the wire is inducing it. That is at least my understanding of it.

@bruce

Thanks the project is going well and i'm sure between me and dhcracker we will have a pretty good idea of just how possible this really is in a few weeks.

Ok thats what I was figuring, however heat is still a problem. Am I correct in thinking of this as a parallel R/L circuit? What I now am wondering and haven't really got into in any of my reading yet is how this type of circuit would be preferred for a gravitational effect? Wouldn't a series circuit or some other type of self sustaining non-uniform domain inductance be fitting? They are lab tested and once you start them up you need no power source to keep the loop going, in other words you get zero input, natural inductance.

I've always understood parallel circuits cannot reach a natural state and require constant external current, this would mean even a perfect material most likely will lo? See one can come up with a huge charge for a short instant to start up something like this.. maybe we can remove this from the science fiction realm?

I already see a problem for an experiment because there is no way I can generate 1 amp for 1 volt lol, also the parallel circuit if thats what this is will give us huge problems.

But actually this may coincide with my dynamo toys, I'm trying to make a similar circuit actually for a far different purpose.. interesting though I haven't though of any of this as it may apply to a dynamo...
bar_room_physist
QUOTE (dhcracker+May 26 2011, 07:07 AM)
Ok thats what I was figuring, however heat is still a problem. Am I correct in thinking of this as a parallel R/L circuit?  What I now am wondering and haven't really got into in any of my reading yet is how this type of circuit would be preferred for a gravitational effect?  Wouldn't a series circuit or some other type of self sustaining non-uniform domain inductance be fitting?  They are lab tested and once you start them up you need no power source to keep the loop going, in other words you get zero input, natural inductance.

I've always understood parallel circuits cannot reach a natural state and require constant external current, this would mean even a perfect material most likely will lo?  See one can come up with a huge charge for a short instant to start up something like this.. maybe we can remove this from the science fiction realm?

I already see a problem for an experiment because there is no way I can generate 1 amp for 1 volt lol, also the parallel circuit if thats what this is will give us huge problems.

But actually this may coincide with my dynamo toys, I'm trying to make a similar circuit actually for a far different purpose.. interesting though I haven't though of any of this as it may apply to a dynamo...

I agree that a series circuit would be a better choice. I also have a fear that what we are doing is basically making a giant lase chamber and while the device may produce gravitational wave, it will probably also cause any material in it to suffer a population inversion and i'm not sure it would feel that pleasant. lol i'll bring the BBQ sauce.

as for the specifications, we get to just make em up. no one that i know of has ever tried to construct a device like this and no plans exist, only a mathematical hypothesis by david.
Kino
QUOTE (brucep+May 25 2011, 11:17 PM)
I asked questions about limits for ship external surface area, and optimum shape, including any that might be associated with manipulating the warp spacetime for shielding.

Yeah - I saw that and was re-iterating because it's an absolutely critical question. Referencing failure on my part - sorry.

I have a related question though. Can we manipulate the warp to handle the changing mass distribution as things move around the ship? I realise that this isn't a rocket, but does our own mass not affect the shape of space-time and hence warp the warp a bit?

QUOTE
Anybody have a thought about the feasibility for biospheres in space and whether that would be something we would look at?

I had a couple of thoughts about the biosphere. Will gather some numbers at some point, so these are just talking points.

1. Artificial leaves can be more efficient than real ones. Nocera et al created ones that make electrolyse water to produce H and O using just sunlight. We'd be more interested in carbon scrubbing, whichMitsubishi are allegedly working on. We're going to need light anywhere there's anybody breathing. We might as well use those photons.

2. If we're not going to put ourselves to sleep for the journey, what about the animals? We live vegan-plus-mycoprotein on the journey and wake up the animals when we get there.

3. I suspect that the biosphere will be a major challenge. Everything else is physics or engineering and mostly under our control. The biosphere is complex because the Earth's ecosystem is insanely complex and we don't know everything that's critical.
bar_room_physist
QUOTE (Kino+May 26 2011, 07:32 AM)
1. Artificial leaves can be more efficient than real ones. Nocera et al created ones that make electrolyse water to produce H and O using just sunlight. We'd be more interested in carbon scrubbing, whichMitsubishi are allegedly working on. We're going to need light anywhere there's anybody breathing. We might as well use those photons.

sridhar of bloom box fame also constructed plates that turn hydrocarbons into o2 when he worked for nasa.
Quantum_Conundrum
QUOTE (brucep+May 23 2011, 04:53 PM)
Thanks for the details which make it easier to understand. So we have the ability to use Davids Pulsed Electromagnetic Sublight Warpdrive for our futuristic journey.

Q. For confirmation purpose the ships proper frame is free float. We could artificially create a g_earth environment in the living space.

Q. Is there a practical limit on the ships external surface area? IE how big a ship can we build and what is the best shape?

Q. Can you shield the ship in the same way you would with the exotic matter warp? If so could you briefly explain how the spactime is manipulated to achieve shielding and would maximum shielding place a limit on the ships size and shape?

So far this has been a fun discussion on warpdrive.

Based on the tensile strength of steel, a ship CANNOT be built any larger than an absolute maximum of around 600 meters in length along any axis that will ever experience one or more g forces of angular acceleration (spin, rotate, turning, etc,) else it will tear itself apart when it spins or rotates.

Based on compressive strength of Steel and titanium, the limit of length of a ship which is intended to accelerate at 1 g-force along the length is probably somewhere around 150 miles (240km). Here, I'm talking about building something the size of something you see in Star Wars which would need walls several meters thick. Not very practical, BUT theoretically possible if you had the raw material.

However, you would need to turn VERY, VERY slowly to avoid angular g forces during navigation which would destroy the ship, even with several maters thick walls and skeleton frame structure. You would need to stay away from planets, because the tidal force in LEO equivalent from one end to the other, or from middle to ends would destroy it.

A more realistic limit is probably around 1.5 to 15 miles (2.4 to 24km) using steel or titanium alloys.

Use of composite materials such as graphene would allow you to overcome the tensile strength limitations and build a much larger ship, if you can manage to shield the graphene structural components from the cosmic radiation without adding too much extra weight.

However, Graphene might not be strong enough for compressive forces, so you might need alternating layers of graphene and titanium, and to get into the kilometer to 2 kilometer long range, you'd need like a meter thickness worth of Titanium for walls and framework per kilometer length, else it will collapse under it's own "weight" during acceleration.
Quantum_Conundrum
Perhaps more dangerous and difficult than the journey itself would be actually landing on any of the Gliese 581 planets and living to tell the tale.

Some of these are just flat out too hot, and among the two "good" candidates, they require too much atmosphere to be stable.

So just assuming they are stable atmosphered planets, you are looking at tens of atmospheres surface pressure.

The high pressure environment will mean you require pressurized suits and humans inside will need to be pressured. Additionally, the SLIGHTEST cut or rupture and it's bye-bye baby: you will be smashed worse than if you were hit by a ton of bricks.

While a pressure suit or some pressurized vehicle may be possible, you cannot solve the gravity problem,w hch is also compounded by the fact that in a high pressure environment, you would need a RIGID pressure suit with internal over pressure, not just a skin tight suit, which would be useless.

Thus if you weigh 180lbs and you are wearing a 100lbs suit (which is a stretch given existing technologies,) and you are in 1.5g force, then you would weight 270lbs and your suit would weight 150lbs for a total of 420lbs.

There is no way for even the fittest human being to survive extended periods in gravity wells above about 1.5g, even at just 1 atmosphere, because your heart and diaphragm would get worn out from their weight alone.

For reasons discussed by myself in the past, exoskeletons do not and cannot address the problem.

The surface gravity range for this particular planet would be 1.5g at a MINIMUM, and up to 3.6g at the maximum end of the mass estimate.

I don't think anyone needs me point this out, but just in case, at 3.6g, 100lbs on Earth would become 360lbs...

This makes this planet extremely unlikely to be suitable to manned exploration, nevermind permanent habitation, because the probability is actually pretty good that it is above 1.5g surface gravity...
Quantum_Conundrum
Now I have never seen anyone model this, but for planets with exceptionally dense atmospheres, it might be possible to build rigid airships which can float in the upper atmosphere.

I have heard something similar mentioned by NASA regarding Venus and Titan, but I am not sure how well that would work on a Super Earth type planet under Super Earth gravity.

The ideal for a rigid airship would actually be less-than-earth gravity, but more-than-earth atmosphere, which would make buoyant flight practically the ideal mode of transportation.

Now if you pressurize your ship to 1 atmosphere, then you can float on top of the ultra-thick atmosphere at roughly the 1000bar layer, because of buoyancy.
flyingbuttressman
QUOTE (Quantum_Conundrum+May 26 2011, 03:10 PM)
Perhaps more dangerous and difficult than the journey itself would be actually landing on any of the Gliese 581 planets and living to tell the tale.

Kino
Despite saying I've nothing to add to the propulsion discussion, I've got a few more questions. I haven't had a chance to watch David's video yet, so apologies if they are dumb - please feel free to tell me to WTFV.

1 - A modification of my earlier question - can we control the warp enough to maneuver the ship both in deep space and close to a planet? Asked another way, will we need attitude thrusters?

2 - As I understand the description, the ship does not exactly accelerate. Does this mean that we're going to wind up at our destination with more or less the same velocity as when we left Earth? If so, we're going to have to carry some kind of reaction drive for fine maneuvering, although we could do a lot of gravitational assist jiggery-pokery to avoid needing a "main engine" other than the warp. Also note that we could use this as a safety feature - leave the Sol system with a velocity and course such that if the warp ever fails, we're drifting home (I suspect that there is such a curved course; haven't proved it). Might need to be a generation ship for that one.

3 - Can we use warp for launch and landing? As I'm sure you're aware, deep in the gravity well is where fuel usage soars, and a reactionless drive would be a big help. Edit: I'm talking shuttles here, not the whole ship...
brucep
QUOTE (Quantum_Conundrum+May 26 2011, 07:53 PM)
Based on the tensile strength of steel, a ship CANNOT be built any larger than an absolute maximum of around 600 meters in length along any axis that will ever experience one or more g forces of angular acceleration (spin, rotate, turning, etc,) else it will tear itself apart when it spins or rotates.

Based on compressive strength of Steel and titanium, the limit of length of a ship which is intended to accelerate at 1 g-force along the length is probably somewhere around 150 miles (240km). Here, I'm talking about building something the size of something you see in Star Wars which would need walls several meters thick. Not very practical, BUT theoretically possible if you had the raw material.

However, you would need to turn VERY, VERY slowly to avoid angular g forces during navigation which would destroy the ship, even with several maters thick walls and skeleton frame structure. You would need to stay away from planets, because the tidal force in LEO equivalent from one end to the other, or from middle to ends would destroy it.

A more realistic limit is probably around 1.5 to 15 miles (2.4 to 24km) using steel or titanium alloys.

Use of composite materials such as graphene would allow you to overcome the tensile strength limitations and build a much larger ship, if you can manage to shield the graphene structural components from the cosmic radiation without adding too much extra weight.

However, Graphene might not be strong enough for compressive forces, so you might need alternating layers of graphene and titanium, and to get into the kilometer to 2 kilometer long range, you'd need like a meter thickness worth of Titanium for walls and framework per kilometer length, else it will collapse under it's own "weight" during acceleration.

The ships proper frame is a free float frame. Inertial rest frame. Not an accelerated frame. There could be an issue with net force due to a poor design in the ships artiificial g_earth system but our team [kino, and crew] could design a system where the net force would be 0 and not disrupt the ships proper free float frame. Keep in mind our project is set in the far distant future where we could hope such a journey would be feasibe. Just having fun with it. Thanks for the feedback.
brucep
QUOTE (Kino+May 26 2011, 07:32 AM)
Yeah - I saw that and was re-iterating because it's an absolutely critical question. Referencing failure on my part - sorry.

I have a related question though. Can we manipulate the warp to handle the changing mass distribution as things move around the ship? I realize that this isn't a rocket, but does our own mass not affect the shape of space-time and hence warp the warp a bit?

I had a couple of thoughts about the biosphere. Will gather some numbers at some point, so these are just talking points.

1. Artificial leaves can be more efficient than real ones. Nocera et al created ones that make electrolyse water to produce H and O using just sunlight. We'd be more interested in carbon scrubbing, whichMitsubishi are allegedly working on. We're going to need light anywhere there's anybody breathing. We might as well use those photons.

2. If we're not going to put ourselves to sleep for the journey, what about the animals? We live vegan-plus-mycoprotein on the journey and wake up the animals when we get there.

3. I suspect that the biosphere will be a major challenge. Everything else is physics or engineering and mostly under our control. The biosphere is complex because the Earth's ecosystem is insanely complex and we don't know everything that's critical.

I'm working on getting some answers to the technical issues only David can answer for the warp related ships size, shielding [major issue], etc. If it turns out that shielding doesn't come with the EM Pulse Warp [but I think it does] then we can switch to the FTL warp. This paper talks about shielding and it was written by several folks David worked with on several other warp related solutions. David told me it isn't even this complicated.

http://arxiv.org/abs/gr-qc?0207109

The ships proper frame is a free float frame [in this case an inertial rest frame] like on the Space Station. Most of the ship could remain in freefall [weightless]. We could even have the sleeping quarters in a weightless section of the ship [they say that's pretty cool]. An important part, you've already started a discussion on, is the section of the ship where we would want to create a gravitational environment similar to Earths. It would be my thought the operation of this would require 0 net force wrt the ships proper frame. If there was a positive net force it would act like a thruster, but this is better left up to you smart guys to figure out. Your idea to put the animals to sleep along with the vegan idea makes complete sense. The animals would probably need to sleep at g_earth so when they awoke they would have minimum issues with muscular atrophy. Maybe some would want to sleep for the journey but not me. If we used the FTL warp we could even check out something like the supermassive Kerr hole at the center of the galaxy [just going off the deep end]. Hopefully we'll get the answer to questions which will also give some direction wrt feasibility for B_R_P and dhC.
Quantum_Conundrum
Since this is an imaginary voyage, I figure why not plug in some imaginary distance to the velocity variables in rlativity.

Now if you square an imaginary number, then you get a real number with a negative sign.

V = 0.9ic

gamma = 1 / sqrt(1 - (0.9ic/c)^2)

gamma = 1 / sqrt(1 + 0.81)

gamma = 1/ 1.345 = 0.7433

It turns out that if you move an imaginary velocity, gamma approaches ZERO if v aproaches imaginary infinity, which implies that when v = ci (imaginary speed of light,) gamma approaches 1/2.

Thus, relativity would cause Mass to be reduced to 1/2 at a speed of imaginary c, instead of being infinite at a speed of real c.

The result of this is that if you were moving along an imaginary axis then the faster you move the less massive the ship becomes. This means it would get easier and easier to accelerate the ship. Indeed, there isn't even a mathematical basis for the Speed of Light Postulate along the imaginary axis...

Therefore, the imaginary journey to Gliese would cost half as much energy as the real journey would cost if Relativity did not exist.

So in conclusion, if we could travel along an imaginary axis of distance, we would reach the destination using far less fuel than a real distance journey. In fact, we would use only half as much fuel as would be predicted by pre-Einstein Newtonian dynamics...

Just some mathematical amusement.

Don't take it too seriously though.

Hope everyone sees how absurd it is that this formula is actually used in science.
brucep
QUOTE (Kino+May 26 2011, 10:09 PM)
Despite saying I've nothing to add to the propulsion discussion, I've got a few more questions. I haven't had a chance to watch David's video yet, so apologies if they are dumb - please feel free to tell me to WTFV.

1 - A modification of my earlier question - can we control the warp enough to maneuver the ship both in deep space and close to a planet? Asked another way, will we need attitude thrusters?

2 - As I understand the description, the ship does not exactly accelerate. Does this mean that we're going to wind up at our destination with more or less the same velocity as when we left Earth? If so, we're going to have to carry some kind of reaction drive for fine maneuvering, although we could do a lot of gravitational assist jiggery-pokery to avoid needing a "main engine" other than the warp. Also note that we could use this as a safety feature - leave the Sol system with a velocity and course such that if the warp ever fails, we're drifting home (I suspect that there is such a curved course; haven't proved it). Might need to be a generation ship for that one.

3 - Can we use warp for launch and landing? As I'm sure you're aware, deep in the gravity well is where fuel usage soars, and a reactionless drive would be a big help. Edit: I'm talking shuttles here, not the whole ship...

Forgot 3. What about leaving the Ark in orbit. It should have auxiliary propulsion for maintaining stable orbit and performing other tasks. Maybe several recon/barge vehicles which could glide to the planet surface with the capability of flying to upper atmosphere to be recovered by another appropriately designed auxiliary vehicle and towed to the Ark. Getting crazy. Jet engines and jet fuel.

I just saw your note on shuttle propulsion. Just so you know I didn't think you would try to land the Ark on the surface of the planet.
brucep
QUOTE (Confused1+May 25 2011, 10:38 PM)
On the non-warp front..
QUOTE (Brucep+)
Calculate how much of the ships mass would have to be fuel for 6 years constant 1g acceleration/deceleration.

F= v dm/dt
Where F is the force, dm/dt is the mass ejected per second and v is the jet velocity.

For an order of magnitude guess I'm going for 10N and 0.5kg mass (half of an original 1kg) ejected over a 5 year period. There are about 30*10^6 seconds in a year. So (ignoring relativistic effects)

10 = v * 0.5/(5 * 30*10^6)

v ~= 3000 *10^6 m/s // speed of light is a mere 300*10^6 m/s

I'm thinking we need m_relative = considerable * m_rest for this to have legs.

From the start I was thinking of feeding thorium (or breeding something from it) to feed into a suitable neutron flux to initiate fission - the fuel is also the ejecta (I may have made that word up). I doubt if enough of the fission products have sufficient velocity for the intended purpose but I'll have a look (unless anyone already knows).

The next line of attack would be a particle accelerator producing near c particles (lots of them) at 10% efficiency or better - this is beyond my ability to speculate about.

@Brucep - a point well made.

Best wishes,
-C2.

Ok. Forget non warp. I got a problem for you. Whatever habitable planet we go to will need to have the surface gravity, g, within a suitable range for our species. Say between 1/2 to 1 1/5 g_Earth. Lets choose the mass of the planet to be 2M_Earth [2*Earths mass]. Find the suitable range of r for that range of g_earth and then sum 15,000m to the mean of r_range. That will be r_orbit for our Ark. Now calculate the orbital velocity. Look at the post I wrote to Kino about the crazy scheme to fly our surface shuttle to the top of the atmosphere and recover it with another vehicle we could design 'to snatch and tow' back to our Ark. Then give an opinion whether it makes sense to change Ark_orbit, higher or lower, to optimize design parameters for a 'snatch and tow vehicle'.

Looks like the Earths atmosphere extends out ~ 11,000m so the planet with twice the mass of the Earth might extend out over the 15,000m. Think about it and extend it if you think it's neccessary.
brucep
QUOTE (Quantum_Conundrum+May 27 2011, 12:11 AM)
Since this is an imaginary voyage, I figure why not plug in some imaginary distance to the velocity variables in rlativity.

Now if you square an imaginary number, then you get a real number with a negative sign.

V = 0.9ic

gamma = 1 / sqrt(1 - (0.9ic/c)^2)

gamma = 1 / sqrt(1 + 0.81)

gamma = 1/ 1.345 = 0.7433

It turns out that if you move an imaginary velocity, gamma approaches ZERO if v aproaches imaginary infinity, which implies that when v = ci (imaginary speed of light,) gamma approaches 1/2.

Thus, relativity would cause Mass to be reduced to 1/2 at a speed of imaginary c, instead of being infinite at a speed of real c.

The result of this is that if you were moving along an imaginary axis then the faster you move the less massive the ship becomes. This means it would get easier and easier to accelerate the ship. Indeed, there isn't even a mathematical basis for the Speed of Light Postulate along the imaginary axis...

Therefore, the imaginary journey to Gliese would cost half as much energy as the real journey would cost if Relativity did not exist.

So in conclusion, if we could travel along an imaginary axis of distance, we would reach the destination using far less fuel than a real distance journey. In fact, we would use only half as much fuel as would be predicted by pre-Einstein Newtonian dynamics...

Just some mathematical amusement.

Don't take it too seriously though.

Hope everyone sees how absurd it is that this formula is actually used in science.

Go to the first post in the thread and look at the Relativistic Rocket site, If you havn't seen it before you'll probably enjoy it. I'll just link it again. BTW I'll repeat that I picked the wrong planet for that star system in the original post. It should be the d planet.

http://math.ucr.edu/home/baez/physics/Rela.../SR/rocket.html

brucep
QUOTE (brucep+May 27 2011, 01:49 AM)
F= v dm/dt
Where F is the force, dm/dt is the mass ejected per second and v is the jet velocity.

For an order of magnitude guess I'm going for 10N and 0.5kg mass (half of an original 1kg) ejected over a 5 year period. There are about 30*10^6 seconds in a year. So (ignoring relativistic effects)

10 = v * 0.5/(5 * 30*10^6)

v ~= 3000 *10^6 m/s // speed of light is a mere 300*10^6 m/s

I'm thinking we need m_relative = considerable * m_rest for this to have legs.

From the start I was thinking of feeding thorium (or breeding something from it) to feed into a suitable neutron flux to initiate fission - the fuel is also the ejecta (I may have made that word up). I doubt if enough of the fission products have sufficient velocity for the intended purpose but I'll have a look (unless anyone already knows).

The next line of attack would be a particle accelerator producing near c particles (lots of them) at 10% efficiency or better - this is beyond my ability to speculate about.

@Brucep - a point well made.

Best wishes,
-C2.[/QUOTE]
Ok. Forget non warp. I got a problem for you. Whatever habitable planet we go to will need to have the surface gravity, g, within a suitable range for our species. Say between 1/2 to 1 1/5 g_Earth. Lets choose the mass of the planet to be 2M_Earth [2*Earths mass]. Find the suitable range of r for that range of g_earth and then sum 15,000m to the mean of r_range. That will be r_orbit for our Ark. Now calculate the orbital velocity. Look at the post I wrote to Kino about the crazy scheme to fly our surface shuttle to the top of the atmosphere and recover it with another vehicle we could design 'to snatch and tow' back to our Ark. Then give an opinion whether it makes sense to change Ark_orbit, higher or lower, to optimize design parameters for a 'snatch and tow vehicle'.

Looks like the Earths atmosphere extends out ~ 11,000m so the planet with twice the mass of the Earth might extend out over the 15,000m. Think about it and extend it if you think it's neccessary.

Now that I look at that method the recovery vehicle is a pretty dumb idea.
brucep
QUOTE (brucep+May 27 2011, 12:56 AM)
Forgot 3. What about leaving the Ark in orbit. It should have auxiliary propulsion for maintaining stable orbit and performing other tasks. Maybe several recon/barge vehicles which could glide to the planet surface with the capability of flying to upper atmosphere to be recovered by another appropriately designed auxiliary vehicle and towed to the Ark. Getting crazy. Jet engines and jet fuel.

I just saw your note on shuttle propulsion. Just so you know I didn't think you would try to land the Ark on the surface of the planet.

My recovery vehicle is a monumentally stupid idea. Our work vehicle should have the capability to fly like an airplane in atmosphere and have rocket propulsion for the rest of the journey to the orbiting Ark.
Quantum_Conundrum
QUOTE

t = (c/a) sh(aT/c) =  sqrt[(d/c)2 + 2d/a]
d = (c2/a) [ch(aT/c) - 1] =  (c2/a) (sqrt[1 + (at/c)2] - 1)
v = c th(aT/c) = at / sqrt[1 + (at/c)2]
T = (c/a) sh-1(at/c) = (c/a) ch-1 [ad/c2 + 1]
γ = ch(aT/c) = sqrt[1 + (at/c)2] = ad/c2 + 1

The amount of energy required to abuse time dilation due to acceleration exceeds anything we can ever reasonably expect to achieve through nuclear or antimatter.

Consider this. If you annihilate 1 kg of antimatter with 1kg of ordinary matter, then at a maximum that would be:

E = 2c^2

E = 1.7975E17 Joules

This looks like a lot of energy by ordinary standards, but it is nothing really.

If you had a 1000 metric tons ship, i.e. a million kilograms, and if you had an ideal engine converting 100% of rest mass energy to kinetic energy, (but conserving momentum,) this would only be enough energy to accelerate the ship to 423.97km/s, which is just over 1 thousandth of the speed of light...

This is already just over 8 or 9 times as fast as our fastest space probes that are currently in development, and remembering this hypothetical ship would be around 1000 times more massive than our most massive probes....

I think I once calculated the ESA's solar sail used as a first stage to push a Vasimir second stage for as long as possible before disengaging and starting the Vasimir, then this should be able to get a space probe up to around 95km/s...

Anyway, I figure it would cost like a quadrillion dollars equivalent worth of energy to send one manned mission to another planet using any form of nuclear or anti-matter; effectively a couple centuries worth of world GDP...

The solar sail is probably THE most efficient real world engine imaginable, but it only works for a relatively short time, till you are out of the Solar System, then it's just dead weight which should be discarded. It's not even worth carrying it for braking purposes on the other end, since you would have to accelerate the mass of the sail via any other propulsion methods you intended to employ after exiting the solar system, and this would cost more energy in the long term than the Sail saved during the first phase of the journey, therefore it would be best to disengage it....

So you need something better than anti-matter. Particularly since I'm not even convinced anti-matter would produce a net gain vs fusion, due to all the extra containment costs and safety measures. If you're using most of the energy to pay containment costs, then it's not even worth it really.

ZPM

Some interpretations of Zero Point Energy put it's density somewhere between 10^34 and 10^70 Joules per cubic meter.

The upper end of this range may be a stretch, bu tit is actually so high that it is similar to the rest mass of the matter in the universe itself.

By comparison, the Rest Mass of the Sun equals:

1.9891E30kg => 1.7877E47 Joules equivalent.

and the Rest Mass of the Earth:

5.98E24kg => 5.375E41 Joules equivalent.

So, on a low end estimate, 60 million cubic meters worth of Zero Point Energy would theoretically equal the rest mass energy of the entire planet earth.

60 million cubic meters looks like a large number, but it is not beyond the realm of possibility, and is equivalent to a cube 392 meters in length on each edge, or a cylinder with radius and height both being 268 meters, for a total diameter of 536meters...

In other words, a ship this size would automatically contain more "Free" Energy in the form of Zero Point Energy than the mass of the Earth would if converted to energy.

These dimensions are well within the tensile strength and compressive strength tolerances of a skeleton frame and hull made of conventional materials, as I discussed previously...

So while it seems science fiction, Zero Point Energy would be as close to ideal as imaginable, since you would not even need "fuel storage". Even the lowest estimate of the ZPE in the volume of the ship itself would be sufficient to push it to obscene kinetic Energy levels, that is, if it could be harnessed...
flyingbuttressman
QUOTE (Quantum_Conundrum+May 27 2011, 09:20 AM)
So while it seems science fiction, Zero Point Energy would be as close to ideal as imaginable, since you would not even need "fuel storage". Even the lowest estimate of the ZPE in the volume of the ship itself would be sufficient to push it to obscene kinetic Energy levels, that is, if it could be harnessed...
Quantum_Conundrum
After some calculations, the amount of energy contained in 1 cubic meter of ZPE is theoretically enough to accelerate an 18 trillion kilogram ship to 299,792,457m/s, or one meter per second less than c...

Here is the calculation, with taking into account relativity of mass.

I started with the arbitary velocity, and calculated gamma to be:

gamma = 12243.21

This is what you divided into relativistic mass from the relativised kinetic energy formula to find what the rest mass was.

So if we set the hypothetical ZPE of 1 cubic meter equal to the relativised Kinetic Energy, and knowing velocity and gamma, we get:

Ek = Gamma * (0.5)mv^2

2E34 Joules / (gamma * v^2) = m

m = 1.81757E13 kg

Considering a ship is mostly hollow for living space and cargo, this mass actually greatly exceeds the limits of a ship's size given compressive and tensile strengths of known materials.

One trillion kilograms is one cubic kilometer of water, or using round numbers, a cubic kilometer of ship composed of roughly 1/9th steel 8/9ths air by volume (walls, floors, ceilings, hull, frame, braces, etc,). But this is still larger than the tensile strenght of steel would allow.

Which is to say, 1 cubic meter of Zero Point Energy could theoretically accelerate 83 (eighty three) "maximum scale" ships to one meter less than the speed of light, counting relativity of mass...

QUOTE

Machio Kaku does not agree with you.

I've seen him present Zero Point Energy as potentially one day being harvstable...
flyingbuttressman
QUOTE (Quantum_Conundrum+May 27 2011, 10:47 AM)
Machio Kaku does not agree with you.

I've seen him present Zero Point Energy as potentially one day being harvstable...

Kaku is a borderline crackpot. He says all kinds of nonsense for the cameras, but he has done nothing to actually work on any of these fantastical technologies. He is the last person you should be listening to for realistic technology projections. Hell, I'd take RAY f*cking KURZWEIL over him.

(edit)
To ensure that this isn't an Ad-Hominem defense, make note that Kaku has released zero research on the subject, and his statements clash with everyone in that field who HAS released research.
bar_room_physist
QUOTE (Quantum_Conundrum+May 27 2011, 03:47 PM)
After some calculations, the amount of energy contained in 1 cubic meter of ZPE is theoretically enough to accelerate an 18 trillion kilogram ship to 299,792,457m/s, or one meter per second less than c...

Here is the calculation, with taking into account relativity of mass.

I started with the arbitary velocity, and calculated gamma to be:

gamma = 12243.21

This is what you divided into relativistic mass from the relativised kinetic energy formula to find what the rest mass was.

So if we set the hypothetical ZPE of 1 cubic meter equal to the relativised Kinetic Energy, and knowing velocity and gamma, we get:

Ek = Gamma * (0.5)mv^2

2E34 Joules / (gamma * v^2) = m

m = 1.81757E13 kg

Considering a ship is mostly hollow for living space and cargo, this mass actually greatly exceeds the limits of a ship's size given compressive and tensile strengths of known materials.

One trillion kilograms is one cubic kilometer of water, or using round numbers, a cubic kilometer of ship composed of roughly 1/9th steel 8/9ths air by volume (walls, floors, ceilings, hull, frame, braces, etc,). But this is still larger than the tensile strenght of steel would allow.

Which is to say, 1 cubic meter of Zero Point Energy could theoretically accelerate 83 (eighty three) "maximum scale" ships to one meter less than the speed of light, counting relativity of mass...

Machio Kaku does not agree with you.

I've seen him present Zero Point Energy as potentially one day being harvstable...

believe it or not, i don't disagree with that, the problem so far is harvesting the ZPE. we only have the casimir effect which is at this point is a lab curiosity and you could theoretically construct an arrangement that could produce energy from a piezoelectric crystal, it would not however produce very much energy.

It is highly unlikely that we will develop a revolutionary technology that would be able to harness ZPE to create any real effect. ZPE is highly understood, thanks to QED and if a workable solution was available someone would have stamped their name and the word effect on the end to seal their Nobel prize claim.
Quantum_Conundrum
QUOTE (flyingbuttressman+May 27 2011, 10:53 AM)
Kaku is a borderline crackpot. He says all kinds of nonsense for the cameras, but he has done nothing to actually work on any of these fantastical technologies. He is the last person you should be listening to for realistic technology projections. Hell, I'd take RAY f*cking KURZWEIL over him.

Just because something is not currently possible does not mean it WONT be possible.

It could just mean we don't yet have the technology.

This is sort of like how we WILL have molecular nano-machines. We DONT have them today, but that DOESN'T make them impossible. It just means we have to invent a few more intermediate steps before we are able to make them.

I realize you don't even believe that, because it's impossible for you to conceive of anything you haven't seen with your own eyes, but it's well established science.

We know or a fact that there are other forms of energy in the universe besides just fusion and antimatter, including gravity and whatever Dark Energy may be.

We know for a fact these energies act on matter, and consequently there is no good reason they, or something like them, can't one day be harnessed to do useful work.
flyingbuttressman
QUOTE (Quantum_Conundrum+May 27 2011, 11:01 AM)
Just because something is not currently possible does not mean it WONT be possible.

It's not even theoretically possible.
QUOTE
This is sort of like how we WILL have molecular nano-machines. We DONT have them today, but that DOESN'T make them impossible. It just means we have to invent a few more intermediate steps before we are able to make them.

Nanotech isn't even in the same spectrum. We already have nanotech, but we just need a way to manufacture nano-machines in bulk.
QUOTE (->
 QUOTE This is sort of like how we WILL have molecular nano-machines. We DONT have them today, but that DOESN'T make them impossible. It just means we have to invent a few more intermediate steps before we are able to make them.

Nanotech isn't even in the same spectrum. We already have nanotech, but we just need a way to manufacture nano-machines in bulk.
I realize you don't even believe that, because it's impossible for you to conceive of anything you haven't seen with your own eyes, but it's well established science.

It's well established science that animals can fly, so why won't you believe me when I say that I can flap my arms and fly like a bird?
QUOTE
We know or a fact that there are other forms of energy in the universe besides just fusion and antimatter, including gravity and whatever Dark Energy may be.

Gravity is not a form of energy. It's a fundamental force. It allows you to release and store energy, not create it (except for the fact that it facilitates fusion).

Fusion and fission work thanks to the Mass Defect, which is just another way of storing and releasing energy. Energy that already exists.

Dark energy is a placeholder for whatever force is causing the universe to expand. It's unlikely that it will be useful at human scales.
QUOTE (->
 QUOTE We know or a fact that there are other forms of energy in the universe besides just fusion and antimatter, including gravity and whatever Dark Energy may be.

Gravity is not a form of energy. It's a fundamental force. It allows you to release and store energy, not create it (except for the fact that it facilitates fusion).

Fusion and fission work thanks to the Mass Defect, which is just another way of storing and releasing energy. Energy that already exists.

Dark energy is a placeholder for whatever force is causing the universe to expand. It's unlikely that it will be useful at human scales.
We know for a fact these energies act on matter, and consequently there is no good reason they, or something like them, can't one day be harnessed to do useful work.

Can you extract heat energy from an ice cube? An ice cube can have a maximum temperature of 273 Kelvin. Shouldn't you be able to take than energy and do something with it? You can't, and you know that you can't. The ice cube is colder than all of your energy-producing equipment. You would have to find something even colder than the ice cube to enable a useful energy transfer.

Energy can only be extracted when regions of high energy transfer to regions of low energy. The difference can be "skimmed" for useful mechanical or electrical energy. You can't extract energy from Zero Point Energy for the same reason you can't extract energy from an ice cube.
Kino
QUOTE (Quantum_Conundrum+May 26 2011, 07:53 PM)
Based on the tensile strength of steel, a ship CANNOT be built any larger than an absolute maximum of around 600 meters in length along any axis that will ever experience one or more g forces of angular acceleration (spin, rotate, turning, etc,) else it will tear itself apart when it spins or rotates.

OK - would you mind posting some maths supporting that? I got a figure about five times higher assuming a yield strength of 250MPa, which is apparently the figure for structural steel. On the other hand, I just took the formula for hoop stress in a cylindrical pressure vessel (s=Pr/t) and substituted the centripetal force per unit area (P=F/A=m.w^2.r/A=mu.A.t.w^2.r/A=mu.t.w^2.r), equated the hoop stress to the yield stress, and hoped that was the right thing to do...

For the ship, I was envisioning something in the hundreds of meters size range. If we turn out to need more volume, I would tend to think that a fleet of smaller ships would be more flexible and less vulnerable than a single ship anyway.
Kino
QUOTE (brucep+May 27 2011, 06:54 AM)
My recovery vehicle is a monumentally stupid idea. Our work vehicle should have the capability to fly like an airplane in atmosphere and have rocket propulsion for the rest of the journey to the orbiting Ark.

I'm not sure it's totally dumb. I'd be half inclined to suggest that we keep the ship in synchronous orbit and build a way-station in low orbit. We could use fairly simple rockets to get from the ship to the way-station and fancier stuff - like the Skylon - to get to the surface.

Not quite sure why I don't want to bring the ship(s) into low orbit. It's just an (as yet unexamined) feeling that we shouldn't be taking big ships any deeper into gravity wells and closer to atmospheres than we have to.

Anyway, I do think we want separate work vehicles for atmospheric operations and space-only operations. Possibly even have two or three types of space-only ones - one an overgrown space-suit like the "pods" from 2001, one for short-range orbit-to-orbit operations, and one for long-range missions if we want to set up asteroid mining or similar.
Quantum_Conundrum
QUOTE (Kino+May 27 2011, 11:56 AM)
OK - would you mind posting some maths supporting that?  I got a figure about five times higher assuming a yield strength of 250MPa, which is apparently the figure for structural steel.  On the other hand, I just took the formula for hoop stress in a cylindrical pressure vessel (s=Pr/t) and substituted the centripetal force per unit area (P=F/A=m.w^2.r/A=mu.A.t.w^2.r/A=mu.t.w^2.r), equated the hoop stress to the yield stress, and hoped that was the right thing to do...

For the ship, I was envisioning something in the hundreds of meters size range.  If we turn out to need more volume, I would tend to think that a fleet of smaller ships would be more flexible and less vulnerable than a single ship anyway.

Honestly, the 600meters is me working roughly from memory. It's been a year or two since I did that calculation, so I may be just flat out wrong.

The way I did that to find the maximum size limit due to tensile strength was to assume some maximum acceleration tolerance, and since any ship would have humans, I assumed we would not want our humans experiencing above 1 g force. Forces above 1 g force shrink the maximum size limit of the ship very rapidly.

In order to get a ball park number, you need to make some assumptions about how thick your hull and walls, etc, would be and how much volume you are trying to contain to support life and other functions on the ship...

If you use 250mpa, and a density of 7800kg/m^3, you can get an upper limit by assuming the maximum length of a rod of 1 meter square area to make the round numbers, and assume the rod is under 1 g-force of acceleration on one end to simulate a hard turn, which by extension, the g-force reduces to zero linearly along the length of the rod towards the pivot point, thus the pivot point "feels" half the weight of what the entire rod would feel if the entire rod were under 1 g force.

A pascal is 1 newton per square meter, in this case cross sectional area of the rod.

Therefore, somewhat convoluted, but we need to multiply half of a g-force by the mass of the entire rod, and set this equal to the tensile strength. Half is because again, the g-force alone the entire length of the rod is from 0 on one end to 1 on the other end, making an average "weight" proportionate to half of a g force.

Note that "meters squared" is implicit since we defined a rod 1 meter squared area.

250,000,000pa = 4.9m/s^2 * mass

51020408.1633kg = mass

That is the breaking mass of a rod of steel with one meter cross sectional area under tensile stress at 1 g of acceleration during rotation. The one end would presumably be in the outer hull, and the other end would be at the center of mass of rotation.

Now, based on the density of steel, we can find the length of the rod...

51020408 / 7800 = 6541 meters.

Note that this neglects the gravitational attraction of the metal to itself, but that should be mostly negligible for realistic applications...

Now remember, this is the maximum length of a solid rod, not a hollow ship or platform......

Since a ship would need very, very thick hulls to hold itself together, and since it is hollow, I divided the length by 10 in my older calculations back last time I did this, because a hollow cylinder or rectangle, i.e. a ship, is not going to be anywhere near the tensile strength of a solid rod...

Therefore, my rough memory of 600 meters was very close to a realistic, practical limit, at least, for round numbers.

Some sort of composite carbon material may push this farther, but I think you get the point...

So it may be hard to visualize, but the tensile strength of the SHIP along any given axis is limited by it's mass in the other two axis.

Walls and other structural components perpendicular to a given axis do not contribute to the tensile strength of the SHIP along that axis, yet their mass DOES contribute to the "weight" or tension the ship would feel along that axis if it were turning or rotating.
bar_room_physist
since we are going in the super sci, stretching the limits of feasibleness any way, how about making the ship out of programmable matter?

http://ieeexplore.ieee.org/xpl/freeabs_all...rnumber=1439465
brucep
QUOTE (Quantum_Conundrum+May 27 2011, 03:47 PM)
After some calculations, the amount of energy contained in 1 cubic meter of ZPE is theoretically enough to accelerate an 18 trillion kilogram ship to 299,792,457m/s, or one meter per second less than c...

Here is the calculation, with taking into account relativity of mass.

I started with the arbitary velocity, and calculated gamma to be:

gamma = 12243.21

This is what you divided into relativistic mass from the relativised kinetic energy formula to find what the rest mass was.

So if we set the hypothetical ZPE of 1 cubic meter equal to the relativised Kinetic Energy, and knowing velocity and gamma, we get:

Ek = Gamma * (0.5)mv^2

2E34 Joules / (gamma * v^2) = m

m = 1.81757E13 kg

Considering a ship is mostly hollow for living space and cargo, this mass actually greatly exceeds the limits of a ship's size given compressive and tensile strengths of known materials.

One trillion kilograms is one cubic kilometer of water, or using round numbers, a cubic kilometer of ship composed of roughly 1/9th steel 8/9ths air by volume (walls, floors, ceilings, hull, frame, braces, etc,). But this is still larger than the tensile strenght of steel would allow.

Which is to say, 1 cubic meter of Zero Point Energy could theoretically accelerate 83 (eighty three) "maximum scale" ships to one meter less than the speed of light, counting relativity of mass...

Machio Kaku does not agree with you.

I've seen him present Zero Point Energy as potentially one day being harvstable...

Please stay on topic. If you want to discuss zero point energy then start a thread on it. It'll be easier for this thread if we don't have to sort through off topic posts.
brucep
QUOTE (bar_room_physist+May 27 2011, 03:59 PM)
believe it or not, i don't disagree with that, the problem so far is harvesting the ZPE. we only have the casimir effect which is at this point is a lab curiosity and you could theoretically construct an arrangement that could produce energy from a piezoelectric crystal, it would not however produce very much energy.

It is highly unlikely that we will develop a revolutionary technology that would be able to harness ZPE to create any real effect. ZPE is highly understood, thanks to QED and if a workable solution was available someone would have stamped their name and the word effect on the end to seal their Nobel prize claim.

That's not what he's talking about. He's talking about the crackpot claims that there's an infinite amount of energy to be mined from the quantum vacuum. The Casimir experiment proofs that the energy density of the vacuum can be negative. That was obviously predicted by QM but the Casimir experiment confirmed the prediction. Theoretically if you could build a big enough Casimir machine you could use that to power the FTL warp. I think we mentioned this at the beginning of the thread. Can't remember if it was a post or PM.
Kino
QUOTE (Quantum_Conundrum+)
Now, based on the density of steel, we can find the length of the rod...

51020408 / 7800 = 6541 meters.

Note that this neglects the gravitational attraction of the metal to itself, but that should be mostly negligible for realistic applications...

Now remember, this is the maximum length of a solid rod, not a hollow ship or platform......

Since a ship would need very, very thick hulls to hold itself together, and since it is hollow, I divided the length by 10 in my older calculations back last time I did this, because a hollow cylinder or rectangle, i.e. a ship, is not going to be anywhere near the tensile strength of a solid rod...

Therefore, my rough memory of 600 meters was very close to a realistic, practical limit, at least, for round numbers.

Consider a thin rod of density mu and length l spinning about its center at an angular velocity w. Noting that there are two bits of the rod (one each sider) at a distance r from the center, the centripetal force due to the elementary mass at a distance r is

dF=2.dm.w^2.r
=2.(mu.A.dr).w^2.r

where A is the (negligible) cross-sectional area of the rod. You can then integrate that from the spin axis (r=0) to the ends of the rod (r=l/2) to find the force experienced by the rod at the center. That is

F=mu.A.w^2.(l/2)^2

That means that the rod experiences a maximum stress of F/A, which we can require not to exceed yield stress, s. Substituting w^2=a/(l/2) to get an expression in terms of the acceleration, a, at the end of the rod, we get

l<=2s/(mu.a)

I'm not totally convinced there isn't a factor of two wrong there, but subbing in the yield stress of steel - 250MPa - and density - 7800kg/m^3 gives us (using SI units throughout):

l<=64,000/a

Using g=10 and knocking a factor of ten off for a safety limit gives more or less the same answer you got. I've actually got the exact same formula as I got for the maximum possible radius of a spinning ring using my dubious pretend-centripetal-force-is-a-pressure method, which adds to my suspicion that something's not quite right. I'm not sure Quantum_Conundrum is right to worry about the ship not being solid - I think that a hollow cylinder whose walls have a cross-section of 1m^2 has the same tensile strength as a (much thinner) rod of area 1m^2. Clearly that's not quite true because my "thin rod" approximation is less true for the cylinder than the rod.

However, for a back-of-an-envelope calculation it'll do.

Basically, our life-support rings, if made of regular steel and not reinforced by high-tensile steel, cannot exceed 6km in diameter; 600m if we want a factor of ten safety margin. Assuming that we're not going to try tumbling the ship at over 0.1g (this is a colony ship, not a fighter), we can go up to 6km long using just regular steel.
brucep
QUOTE (Kino+May 27 2011, 05:13 PM)
I'm not sure it's totally dumb.  I'd be half inclined to suggest that we keep the ship in synchronous orbit and build a way-station in low orbit.  We could use fairly simple rockets to get from the ship to the way-station and fancier stuff - like the Skylon - to get to the surface.

Not quite sure why I don't want to bring the ship(s) into low orbit.  It's just an (as yet unexamined) feeling that we shouldn't be taking big ships any deeper into gravity wells and closer to atmospheres than we have to.

Anyway, I do think we want separate work vehicles for atmospheric operations and space-only operations.  Possibly even have two or three types of space-only ones - one an overgrown space-suit like the "pods" from 2001, one for short-range orbit-to-orbit operations, and one for long-range missions if we want to set up asteroid mining or similar.

Your plan is a great start. The low orbit thing was the result of trying to make a bad idea work.
David wrote:
"As for size and shape that can vary but if you want to spin for gravity and minimize material I'd have two pods for the people separated by a shaft which rotates. A perpendicular shaft can extend from the midpoint back to where you can contain a nuclear reactor with little shielding being held far away and since the pods or suits will have to have minimal shielding from the radiation in space anyway. If your using any kind of warp drive including the pulsed sublight warp drive you don't have to worry about extra shielding from forward radiation because of the frame dragging effect of the warp on the incoming radiation. Essentially, it gravitationally red shifts it with respect to the crew. For the sublight pulsed warpdrive the lapse function is fixed. There will be time dilation experienced, the amount of which I show in the video on the EM pulsed warpdrive geodesic calculation. If you're talking about using the gravitational effect of the static electric field solution on the other hand, there is some gravitational effect on time dilation, but for the most part it is the same as special relativity. I do think rotation is the best solution for artificial gravity."

There's no practical limit on the size of the ship or a preferred shape of the ship.

Most all the shielding issues are resolved as a consequence of being in warp.

The ships proper frame is equivalent to a geodesic observers natural motion, free float, in a gravitational field.

Thanks David.
brucep
QUOTE (Kino+May 27 2011, 11:54 PM)
QUOTE (Quantum_Conundrum+)
Now, based on the density of steel, we can find the length of the rod...

51020408 / 7800 = 6541 meters.

Note that this neglects the gravitational attraction of the metal to itself, but that should be mostly negligible for realistic applications...

Now remember, this is the maximum length of a solid rod, not a hollow ship or platform......

Since a ship would need very, very thick hulls to hold itself together, and since it is hollow, I divided the length by 10 in my older calculations back last time I did this, because a hollow cylinder or rectangle, i.e. a ship, is not going to be anywhere near the tensile strength of a solid rod...

Therefore, my rough memory of 600 meters was very close to a realistic, practical limit, at least, for round numbers.

Consider a thin rod of density mu and length l spinning about its center at an angular velocity w. Noting that there are two bits of the rod (one each sider) at a distance r from the center, the centripetal force due to the elementary mass at a distance r is

dF=2.dm.w^2.r
=2.(mu.A.dr).w^2.r

where A is the (negligible) cross-sectional area of the rod. You can then integrate that from the spin axis (r=0) to the ends of the rod (r=l/2) to find the force experienced by the rod at the center. That is

F=mu.A.w^2.(l/2)^2

That means that the rod experiences a maximum stress of F/A, which we can require not to exceed yield stress, s. Substituting w^2=a/(l/2) to get an expression in terms of the acceleration, a, at the end of the rod, we get

l<=2s/(mu.a)

I'm not totally convinced there isn't a factor of two wrong there, but subbing in the yield stress of steel - 250MPa - and density - 7800kg/m^3 gives us (using SI units throughout):

l<=64,000/a

Using g=10 and knocking a factor of ten off for a safety limit gives more or less the same answer you got. I've actually got the exact same formula as I got for the maximum possible radius of a spinning ring using my dubious pretend-centripetal-force-is-a-pressure method, which adds to my suspicion that something's not quite right. I'm not sure Quantum_Conundrum is right to worry about the ship not being solid - I think that a hollow cylinder whose walls have a cross-section of 1m^2 has the same tensile strength as a (much thinner) rod of area 1m^2. Clearly that's not quite true because my "thin rod" approximation is less true for the cylinder than the rod.

However, for a back-of-an-envelope calculation it'll do.

Basically, our life-support rings, if made of regular steel and not reinforced by high-tensile steel, cannot exceed 6km in diameter; 600m if we want a factor of ten safety margin. Assuming that we're not going to try tumbling the ship at over 0.1g (this is a colony ship, not a fighter), we can go up to 6km long using just regular steel.

And the ship won't feel any acceleration unless we're out of warp under auxillary power. IE pushing it. During warp the ships proper frame is a free float geodesic in the EM warp field which is equivalent to a gravitational field. Weightless and stressless.
Quantum_Conundrum
QUOTE (Kino+May 27 2011, 06:54 PM)
I think that a hollow cylinder whose walls have a cross-section of 1m^2 has the same tensile strength as a (much thinner) rod of area 1m^2. Clearly that's not quite true because my "thin rod" approximation is less true for the cylinder than the rod.

well, that's a bit complicated. You have to consider the cross sectional area of the material and subtract out the hollow space.

So for example, if you had a 10m diamter (5m radius,) cylinder and it has a 1 m thick wall, then using area of circle, you'd need to subtract out the 4m radius circle from the middle.

R = 5m

r = 4m

The area, A, corresponding to the wall is:

A = pi*R^2 - pi *r^2

A = 25pi - 16pi = 9pi = 28.28m^2 area...

Now if this was "just" a hollow tube all the way through, then from one end to the other, it would behave exactly as a solid tube of the same length and the same total mass.

Here, we'll call the length axis the z axis.

However, this tube is to represent the cylindrical walls of the hull of the ship. It's tensile strength must support the "weight" of the end walls of the hull, as well as any internal walls, floors, or structural components, cargo, passengers, etc.

If it's a ~600 meters long ship, it's not going to be all open spaces. You will have bedrooms, sick bay, kitchen, engine rooms, etc, and it's not really appropriate for all of this to be in the same open space. I realize real spacecraft are designed ultra-efficient, but even then, you have the mass of the payload and the mass of any internal walls.

Additionally, for reasons I discussed earlier, you will need some internal walls and supports just to support the tensile strength in the x and y axis for support in situations where you rotate around the z axis.

I agree you can just choose to spin the ship more slowly to avoid g forces above your tolerances.

However, if you are going to build something larger than the 600 to 650 meters 1g limit, then the lower the tolerances the farther you'll need to stay away from planets to avoid tidal forces.
brucep
QUOTE (Quantum_Conundrum+May 28 2011, 12:29 AM)
well, that's a bit complicated. You have to consider the cross sectional area of the material and subtract out the hollow space.

So for example, if you had a 10m diamter (5m radius,) cylinder and it has a 1 m thick wall, then using area of circle, you'd need to subtract out the 4m radius circle from the middle.

R = 5m

r = 4m

The area, A, corresponding to the wall is:

A = pi*R^2 - pi *r^2

A = 25pi - 16pi = 9pi = 28.28m^2 area...

Now if this was "just" a hollow tube all the way through, then from one end to the other, it would behave exactly as a solid tube of the same length and the same total mass.

Here, we'll call the length axis the z axis.

However, this tube is to represent the cylindrical walls of the hull of the ship. It's tensile strength must support the "weight" of the end walls of the hull, as well as any internal walls, floors, or structural components, cargo, passengers, etc.

If it's a ~600 meters long ship, it's not going to be all open spaces. You will have bedrooms, sick bay, kitchen, engine rooms, etc, and it's not really appropriate for all of this to be in the same open space. I realize real spacecraft are designed ultra-efficient, but even then, you have the mass of the payload and the mass of any internal walls.

Additionally, for reasons I discussed earlier, you will need some internal walls and supports just to support the tensile strength in the x and y axis for support in situations where you rotate around the z axis.

I agree you can just choose to spin the ship more slowly to avoid g forces above your tolerances.

However, if you are going to build something larger than the 600 to 650 meters 1g limit, then the lower the tolerances the farther you'll need to stay away from planets to avoid tidal forces.

Weak field tidal forces across small distance will have negligible effect. There will be no stress issues related to the propulsion of our ship.
Kino
QUOTE (brucep+May 28 2011, 10:23 PM)
Weak field tidal forces across small distance will have negligible effect. There will be no stress issues related to the propulsion of our ship.

The Roche limit for a steel sphere in Earth orbit is less than 800km altitude. Without doing any detailed calculations, I suspect tidal forces wouldn't be a problem for our ship as long as we don't try to land the thing. For example, lunar tidal forces are around 10^-7g across the earth - although note that they rise as the inverse cube.

Slightly concerning, though, is the effect that tidal forces could have on the bearings of our spinning section. Effectively, it would be spinning off-balance. Again without having done any detailed calculations, I'd suggest that this is reason to park (edit: or at least consider parking) the ship in high orbit (better, L4/5 if available) and build a low orbit transfer point for the spacelanes to fly from.
rpenner
The Roche Limit applies to a sphere of dust or water, not a steel construct where interatomic forces dominate self-gravity by many orders of magnitude.

A skim of Wikipedia is not your friend if you try to portray yourself as more knowledgeable than you actually are.
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