On nitrogen, I keep wondering: if in-space manufacturing matured, couldn’t we generate atmosphere by cracking water for oxygen and synthesizing nitrogen analogues through hydrogen-based pathways? Or is Earth’s air mix so specific that importing nitrogen stays unavoidable?
Refueling to go father is technically risky and the performance often not that exciting. If you aren't able to refuel on the Moon, Starship lands and returns roughly 3.5 tons, not better than the Apollo LEM which a much larger vehicle that is tall and tippy -- landing on inner solar system bodies that it is covered with boulders.
Now it might make sense to put a full load of cargo on it, leave it on the Moon and use it as living space, storage tanks or something, but that's not the plan right now. Refueling on the Moon looks tough: water on the moon looks like a good bet, if we're lucky we find frozen carbon sources at the poles or in asteroid residues on the surface [1], but a hydrogen-oxygen rocket looks like a surer thing.
As for alternatives to local nitrogen there is: (1) producing it by nuclear processes which looks tough and (2) various other alternative breathing gases such as Argon, Helium, SF6, etc.
[1] Not clear though if we want to spend any of those on reaction mass or incorporate them in a circular economy. Actual colonists would see it differently than flatlanders. (See The Moon is a Harsh Mistress and The Martian Way)
Is that true? It seems like there have been the want of lifting large payloads that must be shrunk to fit the actual launch capabilities. This usually means sacrificing so the thing that is launched is not what was really wanted originally. I think the market is there and just waiting for the thing to work.
When it comes to things like space telescopes, a cheap 100 tons to LEO would change the paradigm of how things are developed completely. When it comes to deep space missions that are a one way trip it’s not clear Starship does better than something like the SLS which was cost optimized (see big dumb booster)
The way Starship is being developed, with failure being very much an option, could get to LEO with cost optimizations. Mars is a different animal —- if takes 10 tries to stick a landing you’re going to wait 25 years.
The key problem of deep space colonization or exploitation is the long turnaround time. I did an unpublished study of the problem of turning asteroids into solar sails and concluded that it would be impossible if you disn’t have a physical twin in space near the Earth to teat anything (like fixes to problems) that needs testing. The problem of landing Starship without chopsticks could be tested exhaustively at White Sands, for instance.
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Request ID: zte7dpy79ryEUqFA5UUBPv4Yl4t6NIL4lyHvs6yqTcdr8wCrXG5xHA==If SLS is "cost optimized", I shudder to think what a non-cost optimized rocket would look like. One launch a year at $2.5B a pop?
This book
https://www.amazon.com/Shuttle-History-Developing-National-T...
has wonderful illustrations of many of the hundreds of designs they considered before settling on what was to be the Space Shuttle and also talks about late 1980s studies that considered various ways of putting together Space Shuttle parts to make different vehicles (say a big-ass orbiter with more engines, a bigger ET and more SRBs) The hope was that you could reuse the development work that went into Space Shuttle parts but it seemed like anything you made out of Space Shuttle parts was unaffordable no matter what you tried.
You could certainly develop parts that are cheaper on a per unit basis but would it be worth developing them for the number you would make?
The US doesn't really have an attractive answer to getting to the moon or for aggressive deep space missions, Starship doesn't look great. Growing up in the 1980s I read the "Science Fact" columns in Analog Science Fiction magazine and was told that NASA sold us out and we could have had a much more intensive lunar program but really the architecture Apollo used was brilliant and much more achievable than everything else they considered.
Starship is almost an assisted single stage to orbit (ASSTO), the first stage gives rather modest part of total characteristic velocity.
This allows the second stage, Starship, to have a lot of delta-v. I guess it was optimized for Mars operations. Yes, Starship requires refueling for any flight away from Earth orbit, but in exchange for that it packs significant delta-v, so sending large payloads away from Earth - after refueling - becomes easier. That includes Mars, Moon, asteroids, the rest of the Solar system.
I think this makes Starship design rather good.
It's a no-lose gamble though. If they fail we still end up with SuperHeavy as a massive, cheaper Falcon like architecture. If it succeeds, finally our space dreams can start to be realized.
There have been lots of new releases of frozen water discoveries on various bodies. Typically in craters that pretty much stay in shadow. Water doesn't seem to be that scarce. It's just not as abundant as on Earth
The US Navy built a 2.5km/s railgun you could fit on a ship. A 3.5 km/s coilgun has to look like the Paris gun to be practical and be able to shoot at a high elevation to hit Earth-Moon L1/L2 or near-Earth space. A railroad car worth of material per day in 1kg or so increments seems plausible. A radiation shield for a deep space station or a simulated asteroid to test mining and manufacturing technology might compete with terrestrial materials.
O’Neill’s students never came up with believable catcher and I’ve yet to see one I like. I guess you could get to LEO if you could aerobrake but it looks tough because the outer atmosphere is always changing and a wild shot could trash your target, talk about a space junk problem.
The moon has at best a large glacier on it and my guess is Lunarians, if they could vote, would not want to export a gram of it but rather incorporate it into a circular economy.
Nitrogen needs a high-pressure bottle which is wasted mass, whereas water you can send to orbit in thin plastic and fabric bags like they do on ISS.
Often on ISS they're actually shipping oxygen as water, but still the wasted mass of water being 11% hydrogen plus the wasted mass of the bag is more efficient than a high pressure gas cylinder.
The water inventory of both N2 and H2O on Earth (0.2 cubic km of water per inhabitant) is extravagant. Ceres is roughly 50% water (like the generic outer solar system or interstellar object) and we could use all of it but it adds up to about the mass of our oceans, and that is most of the water inventory the asteroid belt.
I’ve looked at various large rotating structures up to the size of the Banks Orbital and concluded you could solve the structural problems if you could make a reliable journal bearing (structural parts don’t need to be spun) that could handle the velocity difference but no matter what you cannot afford tall mountains or deep oceans.
Very tempting to swap nitrogen for helium, but AIUI the main downsides are that the speed of sound is higher so air will leak out from a breach faster, and there may be negative effects on flammability due to helium's high thermal conductivity and low specific heat.
There have been proposals to use scoopers with structurally integrated electrodynamic propulsion ("tether without the tether"),[0] which would use zero propellant.
[0] https://forum.nasaspaceflight.com/index.php?topic=44542.msg1...
What does this even mean? Transmutation?