Monday, July 4, 2011

The hanging gardens of space

I've been thinking about how things would be arranged to make the best use of the room inside a Stanford Torus. The depictions that we get in books promoting space colonies usually show something similar to suburbia, but without the cars, but when it comes down to it, those designing the internal layout are going to do it based around the requirements imposed by the loads and properties inherent in the physical structure of the colony. On Earth, everything we do, we do from the ground up, whereas in a Stanford Torus everything, everything will hang from the axis of rotation. It will make far more sense to support structures and surfaces as directly from that axis as is possible, as that'll reduce the amount of weight required, both because it's a more direct way of transferring loads, and because structures built under tension are far lighter than structures built under compression.

So rather than the boring flat geography we usually see depicted, perhaps the inside of space colonies will be steep, with lots of nooks and crannies, with winding paths through a landscape covered with wild vegetation to hide the engineers suspension cables.


  1. Hello Andrew,

    I've added a pair of drawings of the inside of a mid size oneil cylinder to my web site. In the Napa valley view, the winery in the middle of the picture is a tensioned structure, directly inspired by this essay. I'm a bit worried about the problem of shadow with larger hanging structures. I'll try to make a version of the Barcelona view with more hanging elements.
    Comments welcome!

    Michel Lamontagne

  2. Hi Michel,

    I've refined the idea a little after a bit more thought.

    Like I said before, you start with a Stanford Torus design and hang the rim structure from tethers (or spokes) under tension, a lot of them. they come down through the roof of the "tube" from the axis and are spread to anchor the floor, occupying a volume the shape of a triangular prism or small "mountain range" that extends around the entire rim from floor to roof. platforms are fixed to these tethers, I think in a random pattern to provide a natural appearance which is then covered with flora to give a natural appearance.

    The effect I'm thinking of is for it to look like a steep rock face covered with indentations holding homes.

    I was thinking of it being located in a dusk to dawn sun-synchronous LEO and so getting away without needing the thick radiation shield that the deep space Stanford Torus that was originally proposed had.

    Then, instead of having all the lighting reflected down vertically into the habitat, just have transparent tinted habitat walls, with a space mirror behind the colony so light is coming in both directly from the sun, and from the anti-sunward direction, as the light comes in at a low angle it'll penetrate deep into the indentations in the "rock" face.
    Roads and other transport would be deep inside the "mountain range"

    If the diameter of the rim or tube were 100m, and the base of the "mountain range" was 30m across, with the platforms separated by 10m vertically you would have a total area of about 60ha over all the platforms.

    I think the whole thing could be incredibly light weight, even with a diameter of 2km.

  3. Hello Andrew,

    I had trouble visualizing the concept, so I drew it. I’ve uploaded a technical illustration of the Hanging Garden Torus on my web site. A 2 km in diameter,100m cylindrical torus in a sun synchronous orbit. The shadeside mirrors are on a non-rotating section, as are the photocells and the docking port for the orbital shuttles.
    The different levels are cable supported, perhaps a little wider than what you described in the text. Movement in the torus is by a personal rapid transit system, up to the core by elevators. Energy input to the torus, as well as the night/day cycle is controlled by movable shades located on the inside of the window bays. The support cables incorporate some kind of motion damping system for vibration control. There is little radiation shielding, since the station is in low orbit.

    Hope you enjoy it, regards,

    Michel Lamontagne

  4. Hi, Michel, yep, that's what I'm talking about.
    What're your thoughts on the mass of such a structure and the population it could support? I'm thinking that a structural mass of less than 100,000 tonnes and total mass less than 200,000 tonnes might be possible, with a population, most of whom would be short staying visitors, of 50,000 people. I know that sounds ridiculously light, but I'm trying to push the boundaries of what's possible.
    I'll offer some numbers when I've time.

  5. Hello Andrew,

    100 000 tons seems much too light, since i calculate the atmosphere alone will weight 57 000 tons!

    Numbers in the Torus1 calculations spreadsheet on my website.

    3 or 4 hundred thousand at least. Lower air density might help, though, or i may have screwed up the math !


    Michel Lamontagne

  6. Hello Andrew,

    I've added some calculations on hoop stresses in the habitat wall (Torus 1 calculations on my web site) and they impact significantly on the weight of the habitat. For high yield aluminium 150mm wall are required, for a total weight of about 1 million tons. This is directly proportional to air pressure, so a lower air pressure would reduce the requirements. It would also reduce the weight of the air, which would be good. Do you know how low the pressure can be and remain breathable? I expect a higher oxygen ratio would also allow lower air pressure but make everything a lot more flammable...
    It might also be possible to use fiber reinforced materials, for higher yield strengths. Any ideas?


    Michel Lamontagne