Inflatable Space Stations

ChuckMcM 3 hours ago | parent | next [-]

The Bigelow stuff was very promising and showed that it could work. The larger units on extruded spokes was a viable path to a .5G space station. This would be doable with three (possibly 4) Starship launches[1].

[1] Caveat Starship has to reach its goal of transporting 100 tonnes to LEO

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zackmorris 2 hours ago | parent [-]

Ya I really like their airship to orbit concept. I asked AI about lift to drag (L/D) ratios in plasma at 10,000-17,5000 mph (5-8 km/s) and it suggested that lifting bodies achieve between about a 1:1 and 3:1 L/D ratio. If we assume the generous 3:1 L/D ratio, that would seem to make a single-stage to orbit space plane possible.

A bit off-topic, but an aerospike engine is half of a rocket nozzle, with a virtual half created by the supersonic shockwave. So we could envision a retractable nozzle half that moves through subsonic, transonic and supersonic modes to power the airship.

Also the SABRE engine uses (according to AI) 16,800 thin-walled tubes filled with liquid hydrogen to cool ambient air to -238 F (-150 C or 123 K) in 10 milliseconds so that it can be compressed up to 140 atmospheres and fed into a combined-cycle engine. That would allow it to be air-breathing up to mach 5.4 (3,600 mph or 1.6 km/s) and transition to liquid oxygen after leaving the atmosphere.

I also asked it about using something like titanium to withstand the heat of exiting the atmosphere (since the titanium SR-71 reached mach 3+) but it said that it can't withstand a high enough temperature. So an ablative coating might need to be applied between launches. Quite a bit of research was done for that through about the 1970s before NASA chose the space shuttle with its reusable tiles.

It seems like most of the hard work has already been done to achieve this. So I don't really understand why so many billions of dollars get devoted to other high-risk ventures like SpaceX. When for a comparatively smaller amount of money, a prototype spaceplane could be built. I'm guessing that the risk/reward value just wasn't proven yet. But really shouldn't VC money chase the biggest bet?

This is the kind of stuff that I went down rabbit holes for when I dreamed of winning the internet lottery. Now that AI is here, I can feel the opportunity for that slipping away. A more likely future is the democratization of problem solving, where everyone knows everything, but has little or no money and doesn't want to pay for anything. So really not much different from today. So maybe it's better to let these half-baked ideas go so that someone else can manifest them.

	▲	pixl97 2 hours ago \| parent [-]
		Pretty sure it's Scott Manley that did an episode on the aerospike and just how hard they are to get to work right. Needless to say, getting anything to go to space is hard.

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maxcan 4 hours ago | parent | prev | next [-]

I never understand why the rotating station concepts seem to all have rigid tethers, either in the form of a central boom or a rigid circular structure. It would seem like you could get a much larger diameter, so less rotational velocity and more comfort, by attaching rigid, or inflatable in this case, structures with a tether. Compressive loads are non existent, you just need to resist tensile loads.

Maybe I'll go ask the AI.

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xixixao 2 hours ago | parent | next [-]

See Project Hail Mary.

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_dain_ 3 hours ago | parent | prev [-]

Stationkeeping would be a problem. And difficult to stop it precessing away from the rotation axis you want.

	▲	schiffern an hour ago \| parent [-]
		An array of steerable ion engines hanging below the station (ie on the edge not in the center) can provide both reboots / stationkeeping and precess the axis, eg once per year to track the Sun. Because trig, by "mixing" both maneuvers together it uses less propellant vs doing the two maneuvers separately.

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voakbasda 3 hours ago | parent | prev | next [-]

This is a really nice article that covers the history of space habitats, but it also made me realize that the future of habitable structures has questionable value outside of space tourism.

We have entered an age where humanoid robots are beginning to do many tasks that we thought were exclusively in our domain. At our current pace, I expect they will be able to outperform us in most work settings within a decade or two.

As those robots scale up in their capabilities and numbers, we will send up a fleet of them to space to do the work there. They are far more suited for the environment than humans, and the cost savings would be huge.

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hinkley 2 hours ago | parent | next [-]

The humans will end up spending 99% of their aggregate time in locations that are large enough to bore habitat out of solid rock. Moons, planetoids, substantial asteroids.

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rotexo an hour ago | parent [-]

I thought most asteroids were basically just gravel piles loosely held together by internal gravity?

	▲	mr_overalls 14 minutes ago \| parent [-]
		If we're talking about objects in the asteroid belt, the internal consistency varies wildly. Most smaller objects are indeed rubble piles: boulders, pebbles, and sand-like grains, down to dust. As you'd expect, they're very weak structurally. Notably, the OSIRIS-REx probe was nearly swallowed by its loose material during the sample collection on Bennu. Some of the other large, iron-rich asteroids like Ceres, Vesta, Pallas, and Interamnia are more like protoplanets than rubble piles. Besides the concern for structural integrity/stability, they also have reasonable amounts of water ice, volatiles, metals, ad other resources needed to supply an outpost.

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Retric 3 hours ago | parent | prev [-]

The vast majority of work done in space is already done by machines.

Humanoid robots are potentially useful when operating in human environments, but that doesn’t really apply if we’re never sending humans to these locations.

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hinkley 3 hours ago | parent | prev | next [-]

One of the problems with space stations is that we can make them longer, or we can pull off pieces and replace them with bigger ones. We don’t have a way to make them larger around.

And the way contact points work, I don’t think we have a way to even inflate a new section around an existing one.

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aDyslecticCrow 4 hours ago | parent | prev | next [-]

I suspect without ISRU production of bulk orbit sheet metal, the most feasible solution is to repurpose rockets in their whole.

Building a station this large is gonna be costly even within the cargo hold of starship. But six of them, gutted of insides as welded end to end could provide the vast majority of the bulk mass.

This assume rather sophisticated orbital welding and object manipulation; but its feasible we could do it with robots.

	▲	ceejayoz 4 hours ago \| parent \| next [-]
		This was considered with the orange Space Shuttle fuel tanks; they went almost all the way to orbit anyways.
	▲	xavxav 3 hours ago \| parent \| prev [-]
		aren't rockets like the starship almost the opposite of what you want in a space station? They want to minimize the integrity of the rocket as much as possible (without blowing up) to reduce the mass while for a station you want robustness (for pressure & impacts).

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peteforde 4 hours ago | parent | prev [-]

Anything that can be inflated can usually be deflated.

	▲	aDyslecticCrow 4 hours ago \| parent [-]
		so what? it's only one bar of pressure. Bring some gum.