Inflatable Space Stations
worksinprogress.co
worksinprogress.co
[1] Caveat Starship has to reach its goal of transporting 100 tonnes to LEO
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.
Needless to say, getting anything to go to space is hard.
A nozzle engine doesnt have to account for this as much because the nozzle is keeping the pressure of the exhaust
If the pressure at exhaust is higher than ambient, the exhaust pushes outward against the ambient pressure and you get huge exhaust plumes, and lost efficiency.
Conversely, if the pressure at exhaust is lower, the ambient pressure pushes the exhaust inward into shock diamonds[1] and you, again, lose efficiency.
Engine bells specifically yield their max efficiency at one external pressure/altitude. The reason you see shock diamonds is most often from ground-level testing (or takeoff) of engines that perform best at altitude.
You should be for example totally able to build an inflatable frame for a launch loop, making it possible to launch payloads from above most of the atmosphere.
Also for re-entry the more you lower the density of something, the less re-entry stresses there will be. So you could construct a giant low-pressure inflatable decelerator device and have it essentially float down all the way from orbit, incrementally shedding energy as it comes down over a longer period of time, taking care to balance the rate of descent, heating and internal/external pressures.
Maybe I'll go ask the AI.
Because trig, by "mixing" both maneuvers together it uses less propellant vs doing the two maneuvers separately.
A rigid ring can resist some of this inherently, but a rigid spoke to the hub cleanly takes up all the inward forces.
If your ring is not rigid, any perturbations can cause oscillations that throw the whole thing out of balance. Like a gas leak in one compartment adding thrust at a weird angle. Soon the whole ring will be oscillating along its plane, which is obviously bad. You can actively correct with thrusters on each segment, but that's a lot of extra complexity.
Basically it's all about stability. A big rigid object is much harder to shake apart. A metal circle will stay a circle in a lot more circumstances than a circle of rope will. Doubly so when rotating in zero gravity.
Flexible tethers are mainly good for small scale. Swinging a crew capsule about a big mass (Project Hail Mary, Stardancer) is indeed cheap and easy. With the complication that you must completely spin down to maneuver or dock.
>Maybe I'll go ask the AI
Maybe I'll go ask the AI oracle, it's only slightly fallible
Maybe I'll go poke an ML model a few different ways to see if it emits interesting word sequences, that I'll then fact-check and study to develop real, deep knowledge.
This isn't new. It's the same person who used to say "but Google said...!" This is a solvable education problem, because we've solved it before.
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.
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.
This is why sending humans is often advantageous, we can do lots of different and new things. The ideal multipurpose space robot may not have to be humanoid, but it would need to replicate or ideally exceed this kind of flexibility of function.
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.
"The spacecraft risked being swallowed whole by the asteroid as it collected the sample. As OSIRIS-REx touched the ground in October 2020, pebbles began flying about. The timely ignition of its thruster kept it safe and led to the creation of a puzzling large crater 8 meters (26 feet) across." https://www.iflscience.com/nasas-osiris-rex-was-almost-swall...
Wow.
I had a thought experiment: if you could ride a bicycle (motorcycle?) against the direction of spin of the station you would essentially be "stationary". You would still have a velocity into the always-sloping-up wheel. What if you rode up a gentle ramp? Could you break away from the surface of the wheel then and become "weightless"?
The trick is that the bike is also accelerating (even at constant "speed") due to going in a circle.
If you decelerate and cancel your own angular velocity relative to the station hub, you do indeed simply stop experiencing gravity.
Imagine instead jumping off the 'stationary' hub of a rotating station. You simply float under no gravity until you hit the ring. The angular velocity imparted on you by the ring is the gravity you perceive. But once you have that angular velocity, you can jump from the ring's inner surface and fall back down as if the gravity were real.
One way such stations are imagined in media is with a spiral ramp from the surface of the ring up to the hub. It works just like you expect. You gradually shed your angular velocity by climbing the 'gravity well'.
Also the surface rotates at potentially quite a high speed compared to you, with likely various structures sticking out, that might smash to you as you get closer, so better watch for that. :)
See e.g. https://www.theverge.com/2024/7/25/24206219/nasa-sierra-spac...
The atmosphere is caustic, but that's just a design material issue. By maintaining a positive pressure, small punctures would just be a loss to O2 supplies; crew wouldn't need any special safety equipment to patch the holes.
Energy could be obtained via solar, chemical engines, or both. Temperature could be controlled by hovering at a spot near the day/night horizon; since the day sid is too hot and the night side too cold, there exists a Goldilocks region.
Venus is generally closer than Mars, with a weak magnetic field that would help reduce radiation (along with the atmosphere).
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.
And if the plan is to do this; you want to prepare the rocket for this purpose anyway so nothing stops you from making a thicker wall and sacrificing payload capacity since the hull is the payload.
Reminds me of a short sci-fi story:
> The engines are part of the orbiter, so they can be brought home and reused. The solid boosters drop off minutes after liftoff and are recovered for refurbishment. Even the unmanned heavy-lift cargo launchers use the same basic system. But until our group came along, the huge external tanks were simply dumped, after fueling the shuttle to almost orbital velocity.
> [...] The main purpose of the design is simply to keep the tanks from falling. The two massive ends of the Farm act like a dipole in the gradient of the Earth's gravitational field, so each deck winds up orbiting edge-forward, like a flat plate skimming. This reduces the drag caused by the upper fringes of the atmosphere, extending our orbital lifetime.
And the way contact points work, I don’t think we have a way to even inflate a new section around an existing one.