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Thread: What Shape Would You Prefer For A Starship And Why?

  1. #101  
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    Quote Originally Posted by Ken Fabos View Post
    Radar/scanning ahead and around probably should be a fleet of separate robotic probes that can be far enough ahead for sufficient warning for leisurely evasive measures.
    Unless they're bloody large (i.e. their own propulsion and sufficient fuel) you'd lose them after the first evasive manoeuvre.
    You'd be going one way and they'd be going another...
    Or you could make tons of small disposable ones.
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    Barring a better way to simulate gravity, I think a very large cylinder would be the best shape as you could maximize the inner surface area for living space where a spinning cylinder would generate the most artificial gravity and closer to the center of the cylinder would make a very good storage area for all the necessitates of life needed for a very long trip.

    Off hand I'm not sure what the cylinder diameter should be, but wouldn't be surprised at a mile or more with maybe 3 to 5 mile length. Something similar to the Babylon 5 station but with modifications for interstellar travel.

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  3. #103  
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    Quote Originally Posted by Dywyddyr View Post
    Quote Originally Posted by Ken Fabos View Post
    Radar/scanning ahead and around probably should be a fleet of separate robotic probes that can be far enough ahead for sufficient warning for leisurely evasive measures.
    Unless they're bloody large (i.e. their own propulsion and sufficient fuel) you'd lose them after the first evasive manoeuvre.
    You'd be going one way and they'd be going another...
    Or you could make tons of small disposable ones.
    Better to lose some sensor probes than lose ships; I'm assuming very high velocities and no magic shields.

    Maybe the only way to other stars will be by hopping from kuiper object to oort object to interstellar object to oort object of next star, perhaps with main ships or fleets not stopping but with an auxilliary fleet that gets far enough ahead to mine for fuel and raw materials and launching them to a future rendezvous. Hopscotch on a big scale.
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    I could see that working (after a fashion).
    Baby steps all the way, and few of them irrevocable...
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  5. #105  
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    Quote Originally Posted by skeptic View Post
    To Pong

    My view is that fuel packages will not be needed. I am not an expert here.

    If a fuel package is to be attached to a starship and accelerated ahead, then why not make it part of the same starship? It is, effectively the same thing. You accelerate a fuel package ahead of our main starship, or you attach it and accelerate the two together. So build it into the main starship, rather than accelerating it separately. Duh!
    I'm no expert either. Honestly, I've got to suspend common sense to appreciate why even multi-stage launch vehicles work. A Rocket doctor could answer this debate regarding multi-stage starship thrust.
    Quote Originally Posted by skeptic View Post
    Intercepting fuel packages would be so difficult. For example, if a fuel package was intercepted at a distance of one light year from Earth, incredible precision would be needed in navigaton, just to find it, even with a radio beacon to home in on.
    Isn't this a bit of incredulity and discounting of the incredible precision demonstrated by historic space missions? I'm not asking to weave through a chain of moons and planets over many years while they're all in motion. Once vehicles exit our solar system under power for the same star, their paths can only converge. That sort of navigation should be relatively simple.



    @Ken Fabos. That Kojax Bola is a goody ain't it? Evasive maneuvers would be possible, as an ordinary bola may be thrown without tangling in flight. It's self-balancing.

    I worked out the overall design yesterday, solved a few major problems:

    1) Acceleration applied to the axis is going to converge the modules, increasing their angular speed. You could have a bad playground accident if you did this carelessly. So with changes in acceleration the bola rotation must be dampened or increased. Assuming cables fixed to the thrust structure without any kind of bearing, we'd affect the bola speed by adding/subtracting rotation at the thrust structure. Crew will not experience changes in gravity at any stage of their mission.

    2) Presumably a thruster shouldn't be aiming at any part of the bola. So thruster(s) towing the bola can't work. Also, in 1G acceleration the bola will hang "at rest" with the modules clustered together and a length of taut cables extending pretty far above them. So between the bola axis and thruster a tall column is necessary.

    3) For a starship doing 1G, you can get a feel for the structural loads by imagining it standing/hanging on Earth. That gives some idea of the compression in the column, and the tension in the cables. I can't say many other starship designs pass this basic test.

    4) The number of modules is constrained by their clustered arrangement against the column base during full 1G acceleration - I guess that means six modules? Alternately the starship could accelerate less than 1G to afford more modules... but I don't know people like this compromise. If we keep adding modules to effectively comprise the area of a torus, we can't accelerate at all. If we put additional bolas up the height of the column (like a cylinder) the load of acceleration grows excessive, so again we're stuck with a slow starship.

    5) Some of the above could be solved by tethering modules to each other and/or allowing the interior of a module to shift. This latter option could work nicely if each module contains a cushion/shield of water, and a slightly buoyant crew chamber within, a sort of double-hull. All this really complicates periodic docking of the modules to each other.



    The trouble with cylinders is when the captain accelerates your marbles go rolling aft. You can taper the cylinder to compensate, but then you have the same problem when not accelerating (which is at least three stages of the mission). I can't imagine a starship mission that doesn't include long periods of both conditions.
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  6. #106  
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    We are talking of a starship. Such a vessel will take decades at least to get to its destination. Thus, it has to be large. I would expect any starship to be the size of an ocean liner, at least. Such a vessel does not need the tether system, since it will be big enough that rotation of its body will be sufficient. The tether system creates its own problems, including access from one part of the vessel to another. Since space walking while rotating is not practical, the tethers would need to be rigid structures that are hollow and able to serve as a personnel passageway. So why not simply rotate the whole vessel?

    The tether system would be more practical for a small vessel, such as is used for shorter voyages, such as to Mars.
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    (Regarding: English assignments)

    Hello there

    I am student from Denmark who has an English assignment on a weekly basis that I have to do who usually is 2 pages. I am not that good at grammar and would love for someone to quickly look my assignments through and give me some feedback. My dream is to become a journalist but it depends on my marks. The level of English is very basic and I mostly do analysis of texts.

    If someone is willing to help, please feel free to share your e-mail or PM me.


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  8. #108  
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    Quote Originally Posted by Pong View Post
    The trouble with cylinders is when the captain accelerates your marbles go rolling aft. You can taper the cylinder to compensate, but then you have the same problem when not accelerating (which is at least three stages of the mission). I can't imagine a starship mission that doesn't include long periods of both conditions.
    To some extent you are going to have that problem with any shape ship. Where ever you are going you will need to have a constant acceleration at about 1G for half the distance then deceleration for the back half of the trip. So just change the shape of the cylinder a bit. Very large diameter and fairly short length. That will give you large flat surfaces to walk on with 1G force holding you to it for the entire trip as you will just reverse your direction 180o during deceleration. Depending on your need for surface space, you can have as many decks or floors as you want or need. A sphere could also be used in the same way, but in space the shape doesn't really matter as long as the ship remains functional for your needs. Of course when you park in orbit, you will lose your simulated gravity and I can't think of any good way around that problem.
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  9. #109  
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    Quote Originally Posted by sebastian.nielsen View Post
    (Regarding: English assignments)

    Hello there

    I am student from Denmark who has an English assignment on a weekly basis that I have to do who usually is 2 pages. I am not that good at grammar and would love for someone to quickly look my assignments through and give me some feedback. My dream is to become a journalist but it depends on my marks. The level of English is very basic and I mostly do analysis of texts.

    If someone is willing to help, please feel free to share your e-mail or PM me.


    Sebastian
    Hi Sebastian, you could start a new thread and post your assignments to it to get feedback from anyone interested in helping or just commenting on your work. And if you have any special request associated with the assignment include those too.

    But, don't think for a minute that anybody will do your homework for you.
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  10. #110  
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    On cylinders and acceleration.

    If using an ion drive system, it is worth remembering that your acceleration will be very small. Perhaps 1% of 1G. That is not a major problem. It merely causes the floors you live on to appear to be on a slight slope.
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  11. #111  
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    Quote Originally Posted by skeptic View Post
    On cylinders and acceleration.

    If using an ion drive system, it is worth remembering that your acceleration will be very small. Perhaps 1% of 1G. That is not a major problem. It merely causes the floors you live on to appear to be on a slight slope.
    If that's the best the drives can do then you are right. Hopefully we will be using atomic fusion thrusters for any trip to other star systems and even then it will be a slow long trip. I'd think to conserve on supplies that most of the population on the trip would need to be rotated through periods of stasis if they were to have any hope of seeing the new world.
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    I think the idea of a bola configuration was used in a basic way back in a Heinlein story, where two independent spaceships going the same direction tethered to each other for mutual comfort and convenience.

    I was thinking each of the bola pair - I wouldn't try to connect more than two masses - would have it's own propulsion which would work in synch. If there were significant mass at the axis point it wouldn't be a stable configuration but a low mass structure might be possible there. I don't know about connecting tubes and lifts; it could be easier simply to use a transfer craft, in which case there would be no need to physically connect any temporary zero gee structures to the bola pair. Course changes could get interesting if you don't want the tedium of losing the angular momentum and spinning it up in a new orientation.

    As for the slowest way to colonise another star of all - a never ending migration from deep space object to deep space object, with people colonising each one in turn, spawning new colonies in the general direction of a target star? Whether such a 'civilisation' could survive it's scattered nature and the thousands of generations to cross interstellar distances, whilst retaining the capabilities it began with may be the question that matters; will the minimum knowledge and skill base survive intact? Technology that is beyond what superpower nations can currently achieve, like safe, cheap, reliable working fusion power are going to be everyday essentials so I remain unconvinced.

    Fun speculating, but I think this belongs in General Discussion or maybe Science Fiction.
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  13. #113  
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    Quote Originally Posted by skeptic View Post
    The tether system creates its own problems, including access from one part of the vessel to another. Since space walking while rotating is not practical, the tethers would need to be rigid structures that are hollow and able to serve as a personnel passageway.
    There's a better way, if you have at least four modules on the bola: two adjacent modules may be gently tugged together and docked. Of course the opposite two would mirror them automatically (you'd have to work to make the bola not balanced). This sort of docking by consolidation may be periodic, and if performed at leisurely pace would require very little energy, since a bola of two pairs is just as dynamically stable as a bola of four spread equally. With six modules you could have a sort of newton's cradle effect continuously running round and round the bola (not that modules would actually strike with force). See? There'd always be two opposing pairs plus two opposing modules going between them. Probably match the docking schedule with daily cycles of human activity.

    And all this goes on undisturbed by changes in acceleration, so the 1G "floor" remains constant through every stage of the mission including outfitting the starship before it begins.

    Quote Originally Posted by Ken Fabos
    I was thinking each of the bola pair - I wouldn't try to connect more than two masses - would have it's own propulsion which would work in synch.
    Why not have the bola on one central column you apply thrust or torque to? ....and why not more than two modules? BTW for clarity when I say "pair" above I mean docked adjacent modules.


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    On bolas

    Whatever number of modules you have, the bolas will have to be tethered to a central object, which will contain the ion drive engines plus carry reaction mass. Since the reaction mass will need to be so incredibly bulky, this part will be the largest part of the starship. So you end up with a very large central and rotating object with tethers to modules hanging out to the side.

    Frankly, I totally fail to see why you would not have the tethers rigid and hollow so that you can move up and down inside them. Someone will need to be able to tend the engines from time to time, meaning a need to move to the central object. Hollow tethers are the obvious way. Also a need to visit each other's modules for social reasons.

    Since the starship will also need to be very large, to carry enough people for a very long time, it would be no big deal to extend the bolas sideways till they join. At which time, you have the cylinder. ( An alternative is a giant wheel, which is really just a shortened version of the cylinder design.) For simple logistics, a cylinder is better than tethered bolas, since the people can move around the cylinder to visit each other or to go to the parts of the ship where they work, as well as up a lift shaft to the engines. Remember that the people will be stuck on that starship for decades or even centuries. It must be big. It also needs to carry a hell of a lot of people - an entire society. Assuming the starship is as big as the Queen Mary, or bigger, then it is logical to make it as a rotating cylinder or giant wheel.

    By the time such a vessel is built, we will have people living in space habitats, probably also rotating cylinders built around a central axle carrying the drive engines. A starship going to Alpha Centauri or some other 'close' star system, will not return in a hurry. There is little chance it will find a habitable planet. Much more likely that an artificial habitat will need to be built on an icy world, or even more space habitats built so people can live and move in the new star system. Either way, the starship will be carrying a lot of people.
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  15. #115  
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    Quote Originally Posted by skeptic View Post
    On bolas
    Okay, I apologize for possible confusion - earlier I'd used "a bola" to mean the entire weapon. But that's properly called "a bolas".
    I was saying "module" to mean a single bola.
    Quote Originally Posted by skeptic View Post
    Whatever number of modules you have, the bolas will have to be tethered to a central object
    Yes.
    Quote Originally Posted by skeptic View Post
    ...which will contain the ion drive engines plus carry reaction mass. Since the reaction mass will need to be so incredibly bulky, this part will be the largest part of the starship. So you end up with a very large central and rotating object with tethers to modules hanging out to the side.
    I don't know. Does it have to employ an ion engine? Does it have to carry all its fuel?

    Since the design can handle 1G acceleration I assume we'll use whatever drive system most approaches that potential. Such a system might be staged thrusters.
    Quote Originally Posted by skeptic View Post
    I totally fail to see why you would not have the tethers rigid and hollow so that you can move up and down inside them. Someone will need to be able to tend the engines from time to time, meaning a need to move to the central object. Hollow tethers are the obvious way.
    Well, this appears to be a steel column and cable structure, comparable to a suspension bridge. As you know, a twisted cable is a lot stronger in tension than a steel tube.

    I believe you're right about access to the central part for servicing. We could have external elevator boxes running beside the main cables, exactly same as as those used in highrise construction.
    Quote Originally Posted by skeptic View Post
    Also a need to visit each other's modules for social reasons.
    How many times must I repeat the modules could periodically dock with each other, side-to-side?
    Quote Originally Posted by skeptic View Post
    it would be no big deal to extend the bolas sideways till they join. At which time, you have the cylinder.
    No, because then they don't deflect back to compensate for acceleration. The wall would become the floor. Tightest density of bolas possible is such that at maximum acceleration they all touch.
    Quote Originally Posted by skeptic View Post
    the people will be stuck on that starship for decades or even centuries. It must be big. It also needs to carry a hell of a lot of people - an entire society.
    ... A starship going to Alpha Centauri or some other 'close' star system, will not return in a hurry.
    A Kojax Bolas using pre-accelerated thrust stages appears to be the fastest trip possible. And if we drop the prerequisite that a vehicle must set out hauling its entire fuel requirement, you must realize of course we'd send fuel/thrusters for the return trip.
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  16. #116  
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    Pong

    Forget this 1 G acceleration. Aint gonna happen. This is a starship. Not a shuttle to the moon. The only way to get the velocity needed is to use a technique to accelerate your reaction mass out the back at a very high fraction of light speed - probably in excess of 99.99%. You cannot do this except with tiny amounts at any one time, meaning steady, but minimal acceleration. I suggested 0.01G maximum.

    The alternative is the Orion drive, using nukes exploded under your arse. You could not use bolas with the Orion system, since the vibrational shocks are extreme. With the Orion system, everything has to be built solidly and rigidly. I still do not think Orion will ever be used, since the technical problems of exploding nukes under your rear end are extreme. The advanced ion drive system is much more likely, which will provide gentle but long term acceleration/deceleration.

    I hope I do not have to explain why a chemical rocket will not work for a starship.
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  17. #117  
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    Quote Originally Posted by skeptic View Post
    The only way to get the velocity needed is to use a technique to accelerate your reaction mass out the back at a very high fraction of light speed
    That's because a starship using something more like rocket fuel would need to haul a ridiculous mass of fuel. Is that why?
    Quote Originally Posted by skeptic View Post
    steady, but minimal acceleration. I suggested 0.01G maximum.
    You appear to be sold on a particular technology. Name it.
    Quote Originally Posted by skeptic View Post
    You could not use bolas with the Orion system, since the vibrational shocks are extreme. With the Orion system, everything has to be built solidly and rigidly.
    You mean the cables would transmit shock to the bolas. Lol no, if rigidity is the best answer to shocks your car should have no suspension.

    I dunno skeptic, you keep throwing up protests and misunderstandings, which I answer, but not once have you acknowledged these answers. I've explored the ideas of Kojax Bolas and staged thrusters well enough, now it's time to explore new ideas.
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    Quote Originally Posted by Bad Robot View Post
    Quote Originally Posted by sebastian.nielsen View Post
    (Regarding: English assignments)

    Hello there

    I am student from Denmark who has an English assignment on a weekly basis that I have to do who usually is 2 pages. I am not that good at grammar and would love for someone to quickly look my assignments through and give me some feedback. My dream is to become a journalist but it depends on my marks. The level of English is very basic and I mostly do analysis of texts.

    If someone is willing to help, please feel free to share your e-mail or PM me.


    Sebastian
    Hi Sebastian, you could start a new thread and post your assignments to it to get feedback from anyone interested in helping or just commenting on your work. And if you have any special request associated with the assignment include those too.

    But, don't think for a minute that anybody will do your homework for you.
    Oh okay, how do I start a new thread BadRobot? And of course, no one has to do my homework! I just want someone to correct my English assignments for mistakes and my English grammar.. I think it would be an easy job for a native English speaker/writer.
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  19. #119  
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    To Pong

    Re technology.

    I have read of numerous suggestions for the technology required to accelerate a starship to a velocity able to travel interstellar in a time less than thousands of years. The only two that continue to look promising are ion drive and Orion (exploding nukes under your arse). The latter has so many problems to be overcome that I am doubtful about its practicality, though I could be proven wrong. For this reason, I concentrate on ion drives. Basic ion drives already exist, so we know this technology is practical.

    On tethers versus hollow solid links. The latter is more practical, since it forms a conduit to move people and goods from one place to another. Since ion drives have very low acceleration, they do not need to be enormously strong to resist that acceleration. However, if need be, a brace could be part of the structure.

    Let me again emphasize another point. A starship has to be very large, since it will carry an entire, if small, society to another star system, and because it will take decades at least. With a vessel that large, tethers are unnecessary, since you just rotate the whole ship.
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  20. #120  
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    Quote Originally Posted by Pong View Post
    You mean the cables would transmit shock to the bolas.
    The shock acceleration would mean the the ends of each bolas arm would gradually drift backwards (unless the spin is massively high).
    This would then place each module (at the end of the tethers) would be behind the shock plate and directly in line with the nuclear explosions.
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  21. #121  
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    Quote Originally Posted by skeptic View Post
    To Pong

    Re technology.

    I have read of numerous suggestions for the technology required to accelerate a starship to a velocity able to travel interstellar in a time less than thousands of years. The only two that continue to look promising are ion drive and Orion (exploding nukes under your arse). The latter has so many problems to be overcome that I am doubtful about its practicality, though I could be proven wrong. For this reason, I concentrate on ion drives. Basic ion drives already exist, so we know this technology is practical.

    On tethers versus hollow solid links. The latter is more practical, since it forms a conduit to move people and goods from one place to another. Since ion drives have very low acceleration, they do not need to be enormously strong to resist that acceleration. However, if need be, a brace could be part of the structure.

    Let me again emphasize another point. A starship has to be very large, since it will carry an entire, if small, society to another star system, and because it will take decades at least. With a vessel that large, tethers are unnecessary, since you just rotate the whole ship.
    I agree that very large ships will be needed for interstellar trips that will most likely take hundreds of years to reach the target system. But just building that big of a ship in space will take enormous amounts of money and resources. I don't see it happening until we have an off world presence in our own solar system. A mars base and most likely a moon base and an asteroid mining industry that's well established at the very least. Plus we will need better instruments for detecting worlds that will support human life. No point in going unless you have good knowledge about where you are going.

    So getting started will be at least several decades away. By that time hopefully we will have better drive technology for interstellar travel.
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  22. #122  
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    I agree on the time scale, and the need for off Earth resources. I worked out once that, assuming exponential progress in ion drive engines, with a doubling time of 20 years, it will take 300 years before we have the technology to go to Alpha Centauri.
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    Quote Originally Posted by skeptic View Post
    I agree on the time scale, and the need for off Earth resources. I worked out once that, assuming exponential progress in ion drive engines, with a doubling time of 20 years, it will take 300 years before we have the technology to go to Alpha Centauri.
    We are going to have to do better than 300 years and Alpha Centauri is not where we will be sending humans. To bad most of the world powers can't combine their resources on these type of projects while working together stabilizing the world trouble spots in their neighborhood. But anyway I'm still thinking humans are in a precarious position on this planet. There are to many things than can happen that will set us back or distract us from long term goals such as this will have to be. If most of the worlds ice melts in the next 100 years, I'd call that a long term distraction, that would be a long time recovering from and that's beginning to look more like a sure thing, regardless of what else might happen.
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    The statement that most of the world's ice will melt in the next 100 years is just plain wrong. The vast bulk of that ice is in Antarctica, and only a tiny fraction of that immensity will melt. The sheer bulk of ice, and its incredibly low temperature are too much for less than thousands of years to melt.
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    Quote Originally Posted by skeptic View Post
    Bad robot

    The statement that most of the world's ice will melt in the next 100 years is just plain wrong. The vast bulk of that ice is in Antarctica, and only a tiny fraction of that immensity will melt. The sheer bulk of ice, and its incredibly low temperature are too much for less than thousands of years to melt.
    Greenland would be enough to cause us major problems. But just a little more rise in temperature could release copious amounts of methane gas from the permafrost as it thaws. Or so I've read, and methane is much worse for global warming that CO2. That could be a major tipping point that will take out all coastal cities around the world. I'll admit we don't know what is going to happen, but I don't see our divided world doing enough to prevent it from happening, at least to the point of taking most of the worlds attention and resources away from going to the stars.
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    Quote Originally Posted by skeptic View Post
    The only two that continue to look promising are ion drive and Orion (exploding nukes under your arse).
    These address the problem of needing a ridiculous amount of reaction mass. But not without trade-offs. The ion drive is analogous to choosing a radial propeller room fan vs. a vacuum-cleaner blower: fantastic speed, pathetic thrust. And Orion seems reckless, like building a particle accelerator or nuclear plant near populated areas. Both are also extremely energetic relative to fuel mass, so in terms of energy economy they'd be "wasting" world-class amounts of energy. With any propulsion system we'd need a means of dumping heat accumulating in the engine/powerplant.

    Am I following you Skeptic?

    Quote Originally Posted by skeptic
    tethers versus hollow solid links. The latter is more practical, since it forms a conduit
    This is a generally incorrect engineering statement. Putting aside bolas, any structure rotating for artificial gravity is going to involve huge loads. You can get a feel of that by imagining a segment of the proposed structure, on Earth, supported just above ground level. I haven't chided this before, but depictions of ring/cylinder habitats with open "sky" are unrealistic, for they'd surely be crisscrossed by cables, like so many spokes in a bicycle wheel.

    I think many people imagine huge structures as scaled-up versions of what's sturdy enough as a solid plastic toy.

    Quote Originally Posted by Dywyddyr
    The shock acceleration would mean the the ends of each bolas arm would gradually drift backwards (unless the spin is massively high).
    This would then place each module (at the end of the tethers) would be behind the shock plate and directly in line with the nuclear explosions.
    If you read my earlier posts regarding Kojax Bolas, you'll find that answered. Maybe someday I'll have cause to draw a picture, rather than rephrasing the description.

    Quote Originally Posted by Bad Robot
    Alpha Centauri is not where we will be sending humans
    You shouldn't have to persuade a New Zealander we should aim for farther, more fertile shores.
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  27. #127  
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    Pong

    Your view of ion drive and Orion seems more or less accurate. On ion drive, the pathetic acceleration is not really such a problem relatively. If it is going to take 50 years plus to get to a destination, an extra ten years to allow for pathetic acceleration is not too bad.

    Re the destination,

    We cannot judge that at this point in time. Over the next 100 years or so, I expect new space telescopes which will deliver far more information about our near stellar neighbours. We should have a good picture of the star systems when we send the first robot probes, possibly in a few centuries. The robot probes will return better data, and we will have a good basis for destination decisions long before any human bearing star ship departs.

    Long before we get to that stage, I see humanity having sizeable space habitats - very likely city size. I suspect they will be very large rotating cylinders, possibly with an outer shell of more than 3 metres thickness water ice, to stop cosmic radiation. A space habitat can be moved using something like those ion drive engines. The experience so gained will stand us in good stead for exploring away from our own solar system. The first star ship may well be one of those space cities with massive ion drive motors strapped on, and pushing a comet ahead of it to provide the reaction mass. Manipulating things in space will be easy, when sophisticated robots are built that operate in vacuum.
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  28. #128  
    Genius Duck Moderator Dywyddyr's Avatar
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    Quote Originally Posted by Pong View Post
    This is a generally incorrect engineering statement. Putting aside bolas, any structure rotating for artificial gravity is going to involve huge loads. You can get a feel of that by imagining a segment of the proposed structure, on Earth, supported just above ground level. I haven't chided this before, but depictions of ring/cylinder habitats with open "sky" are unrealistic, for they'd surely be crisscrossed by cables, like so many spokes in a bicycle wheel.
    Except that the entire structure is treated as suspension bridge with no end points.
    Sure, it's easier having spokes (for safety reasons - belt & braces), but...

    If you read my earlier posts regarding Kojax Bolas, you'll find that answered. Maybe someday I'll have cause to draw a picture, rather than rephrasing the description.
    You mean this:
    1) Acceleration applied to the axis is going to converge the modules, increasing their angular speed. You could have a bad playground accident if you did this carelessly. So with changes in acceleration the bola rotation must be dampened or increased. Assuming cables fixed to the thrust structure without any kind of bearing, we'd affect the bola speed by adding/subtracting rotation at the thrust structure. Crew will not experience changes in gravity at any stage of their mission.
    You're wrong.
    The bolas is rotating around the thrust axis (unless you've got some weird I-can't-see-how-it-would-work idea) therfeore there's going to be acceleration at right angles to the usual (outward) gravity PLUS increased gravity as you spin faster in an effort to stop the modules "falling behind".
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  29. #129  
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    Quote Originally Posted by Dywyddyr View Post
    Quote Originally Posted by Pong View Post
    huge loads ...crisscrossed by cables
    Except that the entire structure is treated as suspension bridge with no end points.
    Yup, that's a good sense of the appropriate engineering.
    Quote Originally Posted by Dywyddyr View Post
    The bolas is rotating around the thrust axis (unless you've got some weird I-can't-see-how-it-would-work idea) therfeore there's going to be acceleration at right angles to the usual (outward) gravity PLUS increased gravity as you spin faster in an effort to stop the modules "falling behind".
    I didn't say the bolas would be on any sort of bearing, if that's what you're assuming. They'd be anchored to the "top" (by way of acceleration) of a tall column, that has a thruster at the base. To rotate the bolas, torque is applied (by/near) the thruster, that rotates the thruster/fuel/shaft and consequently the bolas.

    When the starship begins to accelerate, starship/bola rotation will be reduced by the same method, until at theoretical 1G the bolas would be completely collapsed back ("down") and use no rotation for artificial gravity. For a starship with lower peak acceleration the collapsed angle would be less. In any case the size and spacing of bolas would be designed so they all connect for the starship's peak (cruising?) acceleration.
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  30. #130  
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    Quote Originally Posted by Pong View Post
    I didn't say the bolas would be on any sort of bearing, if that's what you're assuming.
    I'm not.

    They'd be anchored to the "top" (by way of acceleration) of a tall column, that has a thruster at the base. To rotate the bolas, torque is applied (by/near) the thruster, that rotates the thruster/fuel/shaft and consequently the bolas.
    When the starship begins to accelerate, starship/bola rotation will be reduced by the same method, until at theoretical 1G the bolas would be completely collapsed back ("down") and use no rotation for artificial gravity. For a starship with lower peak acceleration the collapsed angle would be less. In any case the size and spacing of bolas would be designed so they all connect for the starship's peak (cruising?) acceleration.
    Okay, I think I get it now.
    The "down" in the modules will vary seen from outside? From "radial" to the thruster stalk (at low/ no thrust) right down to coaxial with it (at max thrust)?
    Pretty smart idea.
    One problem: since, at 1g acceleration the modules will be flush against the thruster stalk, the mating (for moving from one module to another) is going to have to be flexible (and therefore not particularly safe or durable) because they'll match on a circumference (stalk radius + half module diameter).
    Meh, probably just an "engineering problem".
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  31. #131  
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    Quote Originally Posted by Dywyddyr View Post
    Okay, I think I get it now.
    Thanks, few people would get it without a picture.
    Quote Originally Posted by Dywyddyr View Post
    One problem: since, at 1g acceleration the modules will be flush against the thruster stalk, the mating (for moving from one module to another) is going to have to be flexible (and therefore not particularly safe or durable) because they'll match on a circumference (stalk radius + half module diameter).
    Meh, probably just an "engineering problem".
    Prolonged acceleration at 1G is wishful thinking on my part. A more realistic application could look like this:

    Under peak acceleration bola modules fall back 30 degrees. There is no need for a tall standoff column between the thruster and bolas anchorage. The size and number of modules is designed such that during this stage of acceleration they form an unbroken ring. Each module is docked with its two neighbours. Maybe 6, 12, 24 modules so long as it's even.

    The arrangement of modules at less than peak acceleration is best explained by considering deceleration. Initially, the ring is broken into two chains of connected modules. This is a perfectly balanced means of "fanning out" as the bola continues to spin up in speed slightly to maintain 1G crew gravity. Docking connections will need to be flexible, to accommodate a range of acceleration; or several to accommodate at least two conditions. Now, having crew divided is bad, so the modules are allowed to shuffle like a sort of low-impact newton's cradle. If the traveling part is limited to two opposite (counterbalancing) modules very little energy is required. As the starship continues to decelerate the two chains may need breaking into four or six or whatever. This depend on how the bolas anchorage is set up. In any case an opposing pair of free traveling modules would communicate between the chains, at probable rate of several times per day.


    If peak acceleration is very low, so modules fall just, like 1 degree, they may be permanently (though flexibly) connected. Then stacking levels of modules to extend the ring as a collapsible cylinder is worth consideration. Why not just use a solid ring or cylinder - because from an engineering perspective it must be divided into supported sections anyway.
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  32. #132  
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    Quote Originally Posted by kojax View Post
    Instead of a cylinder, I'd prefer to tether two space ships together with a big long cable. It's simpler, and then the two space ships can choose a strategic pattern when they accelerate so they're always circling one another at the same speed. Maybe the crew could have some kind of elevator thing that moves along the cable to enable them to get from one ship to the other.
    So my space pair of space ships would look kind of like a bola.

    I always liked the interstellar ship in Avatar, because the thrust system ("engines" if you will) were up front, and "pulling" the rest of the craft, mostly light weight connections, along. "Pulling" requires far less structural rigidity than "pushing" from the back like a rocket, therefore a weight saving.

    The only issue was the structural issues of having the thrust being delivered 'outboard' of the structure on pole-like mounted engines/thrust bells. They made this work by having large panels that would direct the thrust away from the ship itself, but I never felt this was the best option.

    No reason not to have 3 instead of 2 'legs/pods' either. It could actually turn out more stable than just 2! This "tripod" like design is great because it is still a "Thrust pulls the structure" system, but adds even more inherent strength by design by putting the thrust line in the centre of the structure, Ensuring the "capsules and arms" of the structure follow in such a way as not to interact with the thrust-line would be fairly easy, even allowing the structure to flex a little by design like an aircraft wing.

    The structure is best set up for a constant thrust or G interplanetary/interstellar profile. The main structure would not ever 'land' on a planet, but rather just insert itself into orbit. One or more of the pods would presumably then detatch for landing craft.

    Not sure how weight distribution would be managed, but I'm guessing some shifting of fuel through several tanks could do that kinda work.

    Some design issues include fuel pumps working 'against thrust-G' when accelerating, and ensuring clearance of the exhaust/thrust plume from the rest of the structure.

    It'd be nice to get some amount of acceleration through the whole flight, because this thing is just so well designed for it. Doesn't have to be as much as 1G.

    Of course this makes the amount of fuel usage huge.
    I would percieve the modules to be similar, but only one occupied by "Crew"
    Other pods would be occupied by supplies or what have you.

    "Legs" would be full of fuel. I also suggest, depending on the size of this thing, that pushing oxygen and water around through piping between the pods, even all the way up over the top of the craft's "engine" join, would be possible, although the ability to travel between pods is desired for maintenance purposes at least. This could be achieved through various methods.

    Method 1: Cheapest and lightest - Maintenence is done at 0g, by nothing more than a spacewalk.
    Disadvantage - This stops the acceleration while maintenence is carried out. Changing location from one module to another is a big deal.
    Workaround - Each pod has one task only, and all crew are in only one pod. The other pods are landing craft and supplies.

    Method 2: "Cables" between each pod which are "slightly loose" at 0G and 'at rest' flex, and "very loose" at full acceleration. Some kind of 'cable car' can run between the cables.

    I actually like Method 1, although this runs the risk of having to stop accelerating through the journey and extending trip time if the crew have to visit another module to fix something.

    The flexible legs are easy. They only need to experience 2 states.
    1: 0G - this occurs any time the engine is not running.
    2: Acceleration - This occurs any time the engine is running.

    If you want to slow down, then turn the ship around so it is facing another direction and "accelerate" - therefore only 1 engine complex is needed, and the arm flexing is only occurring in one direction which is much easier to engineer and less susceptible to fatigue cracking than something that bears load in several directions.

    Spinning for gravity is possible, but actually requires more moving parts (you're going to have to move the arms out to a wider position so that the G load is borne down through the length of the arms rather than at an oblique angle). If it is at all possible to use acceleration as the Gravity generator that is much preferred.

    Again, you don't need 1G acceleration. 0.3g sustained should be enough. (Yes I know even that is crazy large for current modern technology as we are talking maybe decades of 0.3g)
    Last edited by musicalaviator; January 9th, 2014 at 12:43 AM.
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  33. #133  
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    Even 0.3 G is unlikely. My guess is that 0.01G would be optimistic.
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  34. #134  
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    @musicalaviator. I can't begin to imagine what you're describing. I'm sure only it isn't the picture in your post.

    Quote Originally Posted by musicalaviator View Post
    liked the interstellar ship in Avatar... thrust system "pulling"... 'outboard' of the structure on pole-like mounted engines/thrust bells... large panels that would direct the thrust away from the ship
    Google images doesn't conjure anything like that.

    Could you describe the basic plan of this starship, as if no one's seen it before?
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    Quote Originally Posted by Pong View Post
    @musicalaviator. I can't begin to imagine what you're describing. I'm sure only it isn't the picture in your post.

    Quote Originally Posted by musicalaviator View Post
    liked the interstellar ship in Avatar... thrust system "pulling"... 'outboard' of the structure on pole-like mounted engines/thrust bells... large panels that would direct the thrust away from the ship
    Google images doesn't conjure anything like that.

    Could you describe the basic plan of this starship, as if no one's seen it before?
    There are weaknesses in the "ISV" shown, which I believe the 3 pronged style may address, but basically:


    http://www.youtube.com/watch?v=f8Cqc1vdhKU

    I'd rather not have to explain the entire already-existing fictional spacecraft, so..
    Enjoy Space : Avatar

    It appears I mis-remembered the 'deflected thrust' and that the engines just exhaust outwards anyway in opposite directions.
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