(1) Assuming Starship makes it to orbit, it enables a range of structures larger than the ISS but smaller than the O'Neill colonies. A mission to Luna or Mars involves 12-20 launches of fuel tankers, for the same cost you can put up a lot of mass to LEO. A really flashy space hotel seems practical, as would simulation environments for Lunar, Mars and Asteroidal technology development.
(2) O'Neill colonies with large airspaces seem impractical because you'd need large amounts of nitrogen or some other inert gas: you can find oxide rocks everywhere in space but pure oxygen environments aren't safe. On the other hand, the atmosphere for an LEO baby Bernal sphere would be about 15 Starship loads and probably worth it for the visual appeal.
(3) The later work of O'Neill's students focused a lot on manufacturing. The proposal to build large structures by vapor deposition of metals onto a balloon still looks feasible. The solar power satellites shrank considerably in mass and it seemed that they could be built more practically from terrestrial materials.
(4) Any space colonization effort runs into the problem that it needs to be self-sufficient in terms of manufacturing (especially Mars) which led Eric Drexler to go off and develop his vision of molecular assemblers. Drexler's proposals haven't aged well but something equivalent that combines 3-d printing with flow chemistry, synthetic biology, fermentation and other technologies is probably possible -- and I think is the critical path. That flashy space hotel, however, really is about rocketry and space assembly of large structures which really is the unique application of space manufacturing; I don't think space manufacturing can ever be competitive for the terrestrial market but it can be competitive for things that can only be made in space.
(5) Colonization of Ceres dominates all other space colonization opportunities in the solar system because there is no shortage of water and no shortage of nitrogen. It seems possible to take the whole thing apart and build a colony with more floor space and a larger population than Earth. You don't get the 0.2 cubic kilometers of ocean that we get, but I think you can culture all the fish you can eat anyway.
Ceres is very far away orbitally. It's three times further than Mars, but also has no braking atmosphere or gravity. If you send a payload to Ceres, that payload has 5 km/s of relative velocity that can only be zeroed out with rocket propulsion. (That's a lot).
It's not coincidence the first Ceres orbiter was also a flagship prototype for advanced electric propulsion. It's a deceptively remote target.
Granted. I don't see it as a Muskian "send 10,000,000 people and keep sending them supplies" kind of thing but rather "send 100 people, 1,000,000 eggs and the closest thing to a Drexler machine that we can make" kind of thing. The latter is what I think the BoM for a successful Mars colony looks like too.
I had a back of the napkin design that was basically a sleeve that fitted over Starship and could be launched into orbit. Those sleeves had angled ends that could then be bolted together in orbit to make a station with an octagon shape that could be spun at 2 or 3 rpm to get 1/2 Earth gravity. Obviously still an enormous engineering challenge, but one that I think is solvable using today's tech. Well, tomorrows tech, but nothing that requires a breakthrough in materials science or basic physics or anything like that.
My plan was to fit the inside with huge water bags that would help to reduce cosmic radiation, provide thermal mass, and slow any micrometeorites that puncture the hull. The water could be launched on cheaper rockets and transferred in orbit. The water could also be pumped between sections to keep the wheel balanced. The central hub area would be more of a challenge, probably having to be assembled (or at least unfolded) in orbit.
Probably the biggest downside is that you wouldn't be able to spin it up until the entire structure was somewhat balanced, which means installing things like solar panels and radiators in pairs and the docking bit of the central hub would probably need to be on bearings so it can counter rotate to be effectively stationary or you wouldn't be able to dock more than 2 spacecraft at a time. The ISS was built in sections over the course of decades, this would need to be built all in one go, which is a huge commitment.
NASA's plans for two tethered stations (or one station and a counterweight) are probably more feasible, but much less cool.
Starship feels like the ultimate engineering gamble, so many moving parts (literally) that getting it right might be as hard as building the habitats it’s meant to launch.
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?
Starship to LEO is technologically conservative -- it's hard for me to believe that something like that couldn't be made to work. The uncertainty is that there's not a big market right now for launching things that size but the hope is that the low cost creates the market and maybe Starlink bootstraps it. If it succeeds as an LEO cargo hauler it can be successful without getting man rated or perfecting refueling.
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)
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.
Hard challenges are good and setbacks are to be expected if you are pushing every limit. I would love to be on such a fast moving team with such a massive payoff if they succeed.
How far forward are we looking - just use a fusion react to synthesis any material from any other by dissociating baryons then running nucleosynthesis. Stars do it, so we know it works!
"(5) Colonization of Ceres dominates all other space colonization opportunities in the solar system because there is no shortage of water and no shortage of nitrogen."
I’d say this paper thoroughly debunks all other space colonization plans in comparison. For instance it is not sustainable to use rockets for routine transformation. The moon doesn't have enough volatiles. Who knows if gravity on the Martian surface is enough to be healthy.
Even if you could take, say, Mercury, apart it would be silly to build a ‘Dyson swarm’ but rather you would build a big framework like that or a ‘Dyson foam’ (e.g. if you took Mercury apart and turned it into a solar collecting structure 1m thick you could capture enough energy to make a few tons of antimatter a second for interstellar travel)
I vaguely remember O'Neil's book talking about zero g manufacturing by welding together plates of Aluminium. Although I may be remembering some other work. Could we use an inflatable workshop to weld together cylindrical sections of a torus? I can imagine sealing the end of the torus secrion and extruding it out the side of the inflatable. Very hazardous for the workers, I imagine.
O'Neill colonies are impractical because they involve large wasted air spaces. The mass needed to resist pressure loads is proportional to (volume) x (pressure), so it's best to stack floors so all that volume can be put to use.
In space, NASA worked with Sierra Space to test their 300 cubic meter "Orbital Reef". The next go.is supposedly 500 m^3, about half the ISS size. Still seems way to small to spin though, I'd guess? Lockheed has their own inflatable hab station too. https://www.nasa.gov/humans-in-space/commercial-space/leo-ec...
It seems like an obvious & amazing unmaterial leap, versus needing metal walls. If it works! Very fun having this history of rings post. Feels a little light on where we are though, what of promise is happening!
Cargo ships have been powered by huge inflatable airfoils for at least thousands of years, possibly much longer than that.
Inflatable structures in general are fantastic in theory: air or hydrogen is cheap, easy to put into the desired shape, and has immense compressive strength per gram, effectively unlimited. Same for impact energy. So you can separate out the compressive and shock-absorbing parts of your structure from the tensile parts, and only pay for the tensile parts. The main difficulty is recovery from rupture, especially in a space environment where not only don't you have a steady wind filling your sails, you have a limited, nonrenewable gas supply. Well, and high compressive strength in a small space.
> Popularised by von Braun in his 1949 sci-fi novel, Project Mars
Von Braun's novel was written in 1949 but wasn't published until 2006. Perhaps the author means the technical appendix "The Mars Project" [0] which was published in 1952, which spawned a series of articles [1] in the popular magazine Collier's from 1952 to 1954.
All the things worth doing in space turned out to be do-able without humans. Telescopes, radio relays, etc. The ISS doesn't really have much of a mission. Here's the list of current ISS experiments.[1] Many are aimed at the problems of keeping humans alive long term without gravity.
I like thinking about the ISS as primarily engineering (and operational) experiments rather than hard science. As a space platform, it's provided learning on how to contract private companies for space flights, and in turn, how they should operate, plan, etc. Or how to do internationally coordinated space operations. All of the work it takes to mature a new tech to a 7,8, or 9 on the NASA Technology Readiness Level[0] while Curiosity and Ingenuity and other long-distance (and JPL) missions focus on the hard science of 1's and 2's.
That said, I too think the main value of ISS declined several years ago or more. Looking forward to the next generation, whatever it is
> As a space platform, it's provided learning on how to contract private companies for space flights, and in turn, how they should operate, plan, etc.
This would be great if we knew where we are heading. Without a clear goal/destination the most likely outcome is we get board and lose the institutional knowledge we paid so much money to gain.
The was a long discussion about benefits of human space exploration. A comparison was made between that and basic science: just like the basic science doesn't bring immediate benefits, so do humans in space. However over long periods of time both could prove to be worthwhile.
Long term zero gravity experience and experiments were very important information for future space flight. Now we know a lot more about the muscle atrophy, bone loss, and vision problems that the author complains of. Having the first space station be zero-g was probably the right move.
But for the second one, more information on artificial gravity through centripetal force makes a lot of sense.
The problem is the ISS wasn't the first station and we already knew zero-g fucks people up long before the ISS was built. Building the ISS anyway so we can waste more time studying the minutia of exactly how badly and quickly it fucks people up was a mistake. In truth the ISS exists for political reasons, not because it was a sound investment from a science and research perspective.
Congratulations, your alternate history has delayed Mars colonization by several decades.
Because of the ISS we know that stays of greater than 12 months in zero gravity have real but minor impacts on the human body. So 3-4 month trips to Mars in zero-g are feasible.
If we assume they aren't, those trips would be far more resource intensive.
The article mentions that the inflatable Goodyear torus has become much more realistic since the inflatable BEAM module (2016) on the ISS. That one has a volume of 16m^3.
But since then, Sierra Space has been working on much larger inflatable modules. Their latest test volume was already 285 m^3:
According to the report, Sierra wants to move to testing a 500 cubic meter volume this year. And the roadmap on their website lists two further habitats with volumes of 1400 and 5000 cubic meters:
That would already be pretty close to the 6000 m^3 von Braun wheel mentioned in the original article. Though Sierra doesn't seem to plan for creating something like the flexible Goodyear torus which could rotate, just pill-shaped inflatable capsules. Not sure whether this has technical reasons.
If you're wondering why we can't just accelerate at 1G for half the journey there, then with a brief but fun interlude at 0G, flip around and decelerate at 1G the rest of the way: today's rockets would deplete their fuel too quickly (minutes or maybe hours at best).
I wonder if a hypothetical, high-Isp fusion rocket could manage it (incidentally the journey would only take a couple days or so).
> For example, one of von Braun’s designs called for a massive 75 metre diameter wheel
That’s a radius of about 5% of the length of a human body, so I guess we would soon find out how humans react to living in an environment where ‘gravity’ at eye height is about 5% lower than at toe height or do we already know something about that?
Readit News
(2) O'Neill colonies with large airspaces seem impractical because you'd need large amounts of nitrogen or some other inert gas: you can find oxide rocks everywhere in space but pure oxygen environments aren't safe. On the other hand, the atmosphere for an LEO baby Bernal sphere would be about 15 Starship loads and probably worth it for the visual appeal.
(3) The later work of O'Neill's students focused a lot on manufacturing. The proposal to build large structures by vapor deposition of metals onto a balloon still looks feasible. The solar power satellites shrank considerably in mass and it seemed that they could be built more practically from terrestrial materials.
(4) Any space colonization effort runs into the problem that it needs to be self-sufficient in terms of manufacturing (especially Mars) which led Eric Drexler to go off and develop his vision of molecular assemblers. Drexler's proposals haven't aged well but something equivalent that combines 3-d printing with flow chemistry, synthetic biology, fermentation and other technologies is probably possible -- and I think is the critical path. That flashy space hotel, however, really is about rocketry and space assembly of large structures which really is the unique application of space manufacturing; I don't think space manufacturing can ever be competitive for the terrestrial market but it can be competitive for things that can only be made in space.
(5) Colonization of Ceres dominates all other space colonization opportunities in the solar system because there is no shortage of water and no shortage of nitrogen. It seems possible to take the whole thing apart and build a colony with more floor space and a larger population than Earth. You don't get the 0.2 cubic kilometers of ocean that we get, but I think you can culture all the fish you can eat anyway.
It's not coincidence the first Ceres orbiter was also a flagship prototype for advanced electric propulsion. It's a deceptively remote target.
My plan was to fit the inside with huge water bags that would help to reduce cosmic radiation, provide thermal mass, and slow any micrometeorites that puncture the hull. The water could be launched on cheaper rockets and transferred in orbit. The water could also be pumped between sections to keep the wheel balanced. The central hub area would be more of a challenge, probably having to be assembled (or at least unfolded) in orbit.
Probably the biggest downside is that you wouldn't be able to spin it up until the entire structure was somewhat balanced, which means installing things like solar panels and radiators in pairs and the docking bit of the central hub would probably need to be on bearings so it can counter rotate to be effectively stationary or you wouldn't be able to dock more than 2 spacecraft at a time. The ISS was built in sections over the course of decades, this would need to be built all in one go, which is a huge commitment.
NASA's plans for two tethered stations (or one station and a counterweight) are probably more feasible, but much less cool.
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)
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.
Deleted Comment
What does this even mean? Transmutation?
You could ship liquid ammonia and then burn it to produce nitrogen and water.
What about gravity?
https://arxiv.org/abs/2011.07487
I’d say this paper thoroughly debunks all other space colonization plans in comparison. For instance it is not sustainable to use rockets for routine transformation. The moon doesn't have enough volatiles. Who knows if gravity on the Martian surface is enough to be healthy.
Even if you could take, say, Mercury, apart it would be silly to build a ‘Dyson swarm’ but rather you would build a big framework like that or a ‘Dyson foam’ (e.g. if you took Mercury apart and turned it into a solar collecting structure 1m thick you could capture enough energy to make a few tons of antimatter a second for interstellar travel)
In space, NASA worked with Sierra Space to test their 300 cubic meter "Orbital Reef". The next go.is supposedly 500 m^3, about half the ISS size. Still seems way to small to spin though, I'd guess? Lockheed has their own inflatable hab station too. https://www.nasa.gov/humans-in-space/commercial-space/leo-ec...
China launched and tested some kind of inflatable, just last fall. https://spacenews.com/china-quietly-tested-its-first-inflata...
It seems like an obvious & amazing unmaterial leap, versus needing metal walls. If it works! Very fun having this history of rings post. Feels a little light on where we are though, what of promise is happening!
Inflatable structures in general are fantastic in theory: air or hydrogen is cheap, easy to put into the desired shape, and has immense compressive strength per gram, effectively unlimited. Same for impact energy. So you can separate out the compressive and shock-absorbing parts of your structure from the tensile parts, and only pay for the tensile parts. The main difficulty is recovery from rupture, especially in a space environment where not only don't you have a steady wind filling your sails, you have a limited, nonrenewable gas supply. Well, and high compressive strength in a small space.
Von Braun's novel was written in 1949 but wasn't published until 2006. Perhaps the author means the technical appendix "The Mars Project" [0] which was published in 1952, which spawned a series of articles [1] in the popular magazine Collier's from 1952 to 1954.
0: https://en.wikipedia.org/wiki/The_Mars_Project
1: https://en.wikipedia.org/wiki/Man_Will_Conquer_Space_Soon!
[1] https://www.nasa.gov/mission/station/research-explorer/searc...
That said, I too think the main value of ISS declined several years ago or more. Looking forward to the next generation, whatever it is
[1] https://www.nasa.gov/directorates/somd/space-communications-...
Tiangong [1]
[1] https://en.wikipedia.org/wiki/Tiangong_space_station
This would be great if we knew where we are heading. Without a clear goal/destination the most likely outcome is we get board and lose the institutional knowledge we paid so much money to gain.
But for the second one, more information on artificial gravity through centripetal force makes a lot of sense.
Because of the ISS we know that stays of greater than 12 months in zero gravity have real but minor impacts on the human body. So 3-4 month trips to Mars in zero-g are feasible.
If we assume they aren't, those trips would be far more resource intensive.
But since then, Sierra Space has been working on much larger inflatable modules. Their latest test volume was already 285 m^3:
https://www.theverge.com/2024/7/25/24206219/nasa-sierra-spac...
According to the report, Sierra wants to move to testing a 500 cubic meter volume this year. And the roadmap on their website lists two further habitats with volumes of 1400 and 5000 cubic meters:
https://www.sierraspace.com/commercial-space-stations/life-s...
That would already be pretty close to the 6000 m^3 von Braun wheel mentioned in the original article. Though Sierra doesn't seem to plan for creating something like the flexible Goodyear torus which could rotate, just pill-shaped inflatable capsules. Not sure whether this has technical reasons.
I wonder if a hypothetical, high-Isp fusion rocket could manage it (incidentally the journey would only take a couple days or so).
That’s a radius of about 5% of the length of a human body, so I guess we would soon find out how humans react to living in an environment where ‘gravity’ at eye height is about 5% lower than at toe height or do we already know something about that?