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Thread: Motives for colonization of space

  1. #241
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    (about an end-over-end cylindrical configuration)
    Quote Originally Posted by jamesabrown View Post
    Would the atmosphere pool at the ends?
    To a small extent, depending on the height.

    For a 2km tall cylinder (1km spin radius), the pressure difference is only about 5%. For a 20km tall cylinder (10km spin radius), the pressure is roughly halved but this is still well within the human comfort zone.

    Some floors could also be used as internal partitions to provide extra pressure to the middle regions, if desired.

  2. #242
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    In a segmented torus, if you lose air in one section, you only lose that section. This is a precious commodity on a
    space station.

    Dan

  3. #243
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    Quote Originally Posted by danscope View Post
    In a segmented torus, if you lose air in one section, you only lose that section. This is a precious commodity on a
    space station.

    Dan
    This is also true for a compartmentalized cylinder.

    I suppose a sphere could also be compartmented, but it would be more difficult-- perhaps you could put a cylinder in the middle and a torus on the equator!
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  4. #244
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    Quote Originally Posted by IsaacKuo View Post
    The problem with your "D" shaped cross section is that it simply isn't a natural cross section for an inflated structure. It could be done, but the radius of curvature for the outer floor is such that it would require far greater mass than what's needed for a circular cross section. You actually minimize mass by going with a full circular cross section and then including a cylindrical floor within that torus. The "wasted" volume underneath the floor is worth it for the great reductions in mass.
    The underfloor space can be used for transport and pipes, and other infrastructure that need not take up space on the surface. For that matter, the only parts of a house that needs to be above ground are the door and an air vent. The majority of the floor can be used for farming and recreation.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  5. #245
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    An alternative design might be to build the "floor" ring first (like a circular suspension bridge)

    |>--<|

    and then build the air-filled sections on "top" of it, on the ring interior.

    |)>--<(|

    How feasible is this idea?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  6. #246
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    Quote Originally Posted by Noclevername View Post
    An alternative design might be to build the "floor" ring first (like a circular suspension bridge)

    |>--<|

    and then build the air-filled sections on "top" of it, on the ring interior.

    |)>--<(|

    How feasible is this idea?
    A pretty standard, traditional torus design (all the way down to the suspension bridge analogy!).
    You can then stack rings to get cylinders, if you desire.

  7. #247
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    I think one advantage to sectional design would be that you could start habitation before the entire hab structure is completed. A bit like the traditional "bow tie" beaded ring, but with a stabilizing ring structure (and half of the radiation shielding) already in place.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  8. #248
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    Quote Originally Posted by IsaacKuo View Post
    By this standard, a cylinder can theoretically be more efficient, but only if the cylinder is relatively long compared to its diameter. This is a problem because it's inherently unstable. The stable configuration is for a long thin cylinder to end up rotating end-over-end. This is something which can be actively managed using stationkeeping thrusters, but it's something to consider.

    ...I actually favor a cylindrical shape--but rotating end-over-end in the stable configuration. This allows for convenient flat floors with perfectly rectilinear rooms, marred only by the annoying endcaps at the bottom and top (or other bottom, if the cylinder continues all the way to the other end).
    The problem with that design is that you'd need extra supports for each floor above the base, adding a mass penalty.

    Any rotating inhabited structure will need some sort of active balancing mechanism (e.g., pumping water will do) to prevent wobble. By the time we can get to the point of permanent colonization, we'll no doubt have decades or generations of experience in building and balancing such objects in space.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  9. #249
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    Quote Originally Posted by Noclevername View Post
    The problem with that design is that you'd need extra supports for each floor above the base, adding a mass penalty.
    No, actually the floors support themselves. A cylinder is excellent for supporting itself and extra load from artificial spin gravity. It just happens to be inferior to a sphere for holding in atmospheric pressure.

    Any rotating inhabited structure will need some sort of active balancing mechanism (e.g., pumping water will do) to prevent wobble. By the time we can get to the point of permanent colonization, we'll no doubt have decades or generations of experience in building and balancing such objects in space.
    No, there's no particular need to avoid wobble.

    Some ill-conceived science fiction colony designs have issues with water slosh, but these are the results of design flaws which would not be present in a practical colony design.

  10. #250
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    Quote Originally Posted by Noclevername View Post
    An alternative design might be to build the "floor" ring first (like a circular suspension bridge)

    |>--<|

    and then build the air-filled sections on "top" of it, on the ring interior.

    |)>--<(|

    How feasible is this idea?
    This could work assuming you start off with dead weight ballast equal to five tons per square meter. As you build air-filled sections, you remove the ballast. Otherwise, you end up with excess air pressure pushing "bubbles" underneath the air-filled sections. (Hopefully, your floor material doesn't mind stretching, or this will cause the floor to rip and fail.)

    Alternatively, you could build air-filled sections both on "top" and below. That way, you end up with the air pressure above and below balancing out. This just leaves the weight of the stuff inside, with no worries about air pressure. This requires much less mass, because you don't waste lots of mass on dead weight ballast, and it simplifies the whole construction process.

    The end result is that each air "bubble" is a full sphere which is cut into two hemispheres by the main floor.

  11. #251
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    Quote Originally Posted by Noclevername View Post
    The underfloor space can be used for transport and pipes, and other infrastructure that need not take up space on the surface. For that matter, the only parts of a house that needs to be above ground are the door and an air vent. The majority of the floor can be used for farming and recreation.
    Sure, although it would make more sense to reserve the near 1-gee floors for human residential/working areas. Farming need not be at 1-gee and recreation could be in low/zero gee.

    In any case, the same thing applies to a sphere with an internal cylindrical floors. A sphere with internal cylindrical floors is more efficient than a torus with internal cylindrical floors.

    Still, like I said there can be compelling reasons to choose a non-spherical design. A stubby cylinder is easier to construct and maintain, as I noted above. It's also easier to expand. You can build a new floor around the outside surface. The old outer floor becomes an internal floor. The space between them is pressurized, which allows the previous outer floor to accept more payload. The spin rate is gradually reduced a little, so the outermost several floors have an average of 1-gee.

  12. #252
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    With an "onion-skin" layering, you'd have to allocate a certain percentage of each level's area for getting sunlight into the interior, unless you plan to use all-electric lighting.

    The radiation shielding layer would also have to be expanded each time you add a floor layer-- I would think that simply building another habitat would be easier engineering.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  13. #253
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    Quote Originally Posted by Noclevername View Post
    I think one advantage to sectional design would be that you could start habitation before the entire hab structure is completed. A bit like the traditional "bow tie" beaded ring, but with a stabilizing ring structure (and half of the radiation shielding) already in place.
    A major disadvantage is uneven mass distribution. The only reason I can imagine a cylinder or toroid design would be for spin-gravity. Real estate development would have to be tightly regulated. Heck, even population distribution would have to be monitored. As bad as static loads being unevenly balanced would screw things up, imagine the dynamic stresses of say, a major assembly of station personnel in one area?

  14. #254
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    Quote Originally Posted by Noclevername View Post
    With an "onion-skin" layering, you'd have to allocate a certain percentage of each level's area for getting sunlight into the interior, unless you plan to use all-electric lighting.
    Electric lighting is actually a very good option, since the lighting can be tuned to visible frequencies only and it's trivial to create a natural 24 hour day/night cycle.

    However, there is still the option of using natural light. This involves windows to let natural sunlight in, but no more or less window area than is necessary for any other habitat design. For the torus/sphere/cylinder designs we have been talking about, there are three basic window locations:

    1) Ceiling windows: These are suitable for providing a view of stars or a planet, but generally will be blocked from sunlight at least twice a year.

    2) Floor windows: These are suitable for providing direct natural sunlight. For a multi-layer habitat, these windows should be lined up. Whether the habitat is a single layer or multi-layer, you sacrifice a certain fraction of the floor area to windows. The "wasted" area is still available for traffic, though--it may be used for roads.

    3) Side windows: These are suitable for providing indirect natural sunlight, if mirrors are used to reflect the sunlight into the side. This works the same regardless of how many layers are used.

    The exception is the dumb-bell configuration. A dumb-bell habitat can provide direct natural sunlight with side windows even when the rotation axis is perpendicular to the Sun. The dumb-bell configuration is an excellent option for smaller near term habitats.

    In all cases, multiple layers are in much the same situation as a single layer.

    There's a hybrid option, which provides most of the advantages of electrical lighting but is more passive--light pipes. You use fiber optics to route light from a solar concentrator to just where/when you want the light.

    Another option which I like for side windows is to use planet-light rather than sunlight. You make the spin axis parallel to the planet's axis, so not much sunlight goes directly into your side windows. But you orbit the planet in a 24 hour polar orbit, so you get light from the planet. You get a natural 24 hour day/night cycle. This is somewhat similar to options which use mirrors, but you use a planet instead of a mirror.

    The radiation shielding layer would also have to be expanded each time you add a floor layer-- I would think that simply building another habitat would be easier engineering.
    No, you don't even need a dedicated radiation shielding layer. You can leave the outermost floor(s) uninhabited, and it acts as radiation shielding. The outermost floor may be used to store supplies and/or farming and/or water volume. I like water volume, because it can be used for recreational swimming and aquaculture while still providing radiation shielding. When the next floor is complete, the water may simply be drained from the previous outer floor to the new outer floor.

  15. #255
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    Personel migration within the torus is compensated by water ballast, pumped to other sections to compensate.
    It's easy enough to do.

    Dan

  16. #256
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    Quote Originally Posted by Doodler View Post
    A major disadvantage is uneven mass distribution. The only reason I can imagine a cylinder or toroid design would be for spin-gravity. Real estate development would have to be tightly regulated. Heck, even population distribution would have to be monitored. As bad as static loads being unevenly balanced would screw things up, imagine the dynamic stresses of say, a major assembly of station personnel in one area?
    That's true of any shape of rotating habitat. But to the people who grow up in that environment, it will be second nature, and they won't think about it any more than we think about traffic laws or the complexities of postal delivery every time we mail a letter.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  17. #257
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    Quote Originally Posted by Doodler View Post
    A major disadvantage is uneven mass distribution. The only reason I can imagine a cylinder or toroid design would be for spin-gravity. Real estate development would have to be tightly regulated. Heck, even population distribution would have to be monitored. As bad as static loads being unevenly balanced would screw things up, imagine the dynamic stresses of say, a major assembly of station personnel in one area?
    Wouldn't seem that big a problem, it would just have to be planned for in the design. Water mass is easy to move. With a well designed ballast system, the shifting of ballast to account for changing mass distribution is fairly straight forward and relatively simple to accomplish.

  18. #258
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    Quote Originally Posted by danscope View Post
    Personel migration within the torus is compensated by water ballast, pumped to other sections to compensate.
    It's easy enough to do.

    Dan
    Ah, I see this was already mentioned!

  19. #259
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    Hi, just to illustrate the concept , I mention balance and ballast.... as well as the tankage, which is an item quite under-rated until you start to build biospheres in space. If it is going to have gravity, the design and strength of
    tankage takes a huge design consideration , just as it does in a submarine, which also has a dedicated trim and ballast system , with a round the clock watch as to control and condition.

  20. #260
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    Water is almost universally useful in space-- it can be ballast and radiation shielding and heat-transfer/radiator fluid and a necessary component of life support (all at once), or separate the H and O for chemical rocket fuel or fuel-cell fuel; or as reaction mass for thermal rockets of various types. Don't leave home without it!
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  21. #261
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    I wonder how this news might help with LEO resources
    http://www.space-travel.com/reports/...Earth_999.html
    http://www.nasaspaceflight.com/2012/...sample-return/

    Check out Nov 2011 edition on worldships and heavy lift
    http://www.bis-space.com/products-pa...ight-magazine/
    http://www.bis-space.com/

    Nice Skylon model available

  22. #262
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    Quote Originally Posted by publiusr View Post
    Check out Nov 2011 edition on worldships and heavy lift
    For non-subscribers, could you summarize?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  23. #263
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    It has nice artwork of the largest craft as seen below in this link:
    http://up-ship.com/blog/?p=7249
    I don't subscribe myself either; I just remember the ship---if indeed it is the same vessel Scott has researched

    This is interesting
    http://www.nasaspaceflight.com/2011/...-living-space/

    From the site:
    "The results were both startling and unexpected: the longer the drugs had been in space, the more potency they had lost."
    I suspect it has more to do with Humidity and the U-boat like close conditions--container design, etc.

    Vision problems?
    "While some astronauts noted an improvement in vision once they returned to Earth, for one astronaut the vision changes were permanent. According to the medical journal Ophthalmology, one astronaut stated that he could 'only see the Earth clearly while looking through the lower portion of his progressive reading glasses.'"

    Artificial gravity will keep fluids from ballooning.

    In good news, JAXA's "discovery showed that astronaut bone loss in microgravity, long thought of as a serious problem for BEO missions, could be severely reduced simply by having astronauts take standard osteoporosis drugs."

    More to come:

    http://www.nasaspaceflight.com/2012/...evements-2011/

  24. #264
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    Quote Originally Posted by publiusr View Post
    I wonder how this news might help with LEO resources
    http://www.space-travel.com/reports/...Earth_999.html
    Hundreds of tiny moons may be orbiting Earth, as small asteroids get snagged by gravity and spend some time in orbit around the planet...

    ...one asteroid about 1 yard across is in Earth's orbit at any given time, and 1,000 or so smaller space rocks down to 4 inches across should be in orbit too.
    It's an interesting find, but will probably have little effect on space construction. Given the small size and scattered orbits, chasing down and capturing the mini-moons would probably waste more fuel and provide less resources than just launching materials from Earth.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  25. #265
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    Quote Originally Posted by Noclevername View Post
    It's an interesting find, but will probably have little effect on space construction. Given the small size and scattered orbits, chasing down and capturing the mini-moons would probably waste more fuel and provide less resources than just launching materials from Earth.
    Most of the small moons are thought to be several lunar distances from earth. Rendezvous would take around 3.2+ km/s from LEO. And LEO is 9 to 10 km/s from earth's surface. Given a 13 km/s delta V budget, what you say is correct.

    Given OTVs and a staging platform at EML1 or EML2 and it's a different story. I would expect many of the theoretical moons to be reachable with .5 km/s from EML1 or EML2.

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    Quote Originally Posted by Hop_David View Post
    Most of the small moons are thought to be several lunar distances from earth. Rendezvous would take around 3.2+ km/s from LEO. And LEO is 9 to 10 km/s from earth's surface. Given a 13 km/s delta V budget, what you say is correct.

    Given OTVs and a staging platform at EML1 or EML2 and it's a different story. I would expect many of the theoretical moons to be reachable with .5 km/s from EML1 or EML2.
    Some might be .5 each, if we're fortunate, but they would still be only a handful of rocks a few inches wide. We might someday collect them, but for science, not for construction materials.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    You can simply accelerate to 35,000 miles per hour and 'catch' them . Right.

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    Quote Originally Posted by danscope View Post
    You can simply accelerate to 35,000 miles per hour and 'catch' them . Right.
    Methods potentially useful for clearing orbital debris, such as robot lightsails, could also be adapted to pick up samples of these mini-moons. It's not going to happen anytime soon, but it's hardly impossible.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  29. #269
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    Quote Originally Posted by danscope View Post
    You can simply accelerate to 35,000 miles per hour and 'catch' them .
    .5 km/s is about 1116 miles per hour. Your arithmetic's only off by a factor of 31.

    Quote Originally Posted by danscope View Post
    Right.
    .5 km/s is tiny compared to most delta V budgets.

  30. #270
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    Speaking of water, does anyone know what sort of equipment will likely be needed to exctract useable water from the Lunar poles?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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