Inflatable von Braun space stations: an idea worth revisiting?
Background
Kepler’s SomniumAt the time of my writing this post, his sci-fi story was archived here in 1608 and Edward Everett Hale’s Brick Moon 1 from 1865 are early fantasy science-fiction of space-faring humans. Kepler faced more flak than fanfare for his workKepler’s mom was put on trial for witchcraft with some connections to Somnium. Also credit for the link where it’s due. but I was especially surprised to learn about his use of creative writing as a force for exploring ideas around space-faring and extra-terrestrial civilisations. His scientific work in astronomy influenced Newton and others indicating an enduring impact on science, engineering, and human civilisation stemming from a curiosity about the motion of stars. It suffices to say that space habitation has occupied us from a fictional and scientific lens for some time now.
Today’s technocultural space community of thinkers has conjured or realised astonishing visions like the Apollo program and reusable rockets in the $20^{th}$ and $21^{st}$ centuries. The technical community no longer battles claims of heresy but politics, as if fighting to overcome the limits of physics isn’t hard enough. Bureaucratic operators seek short-term justifications for projects and hinder progress towards sci-fi realities of large scale space travel and habitationnot so for space data services, as satellites have been miniaturised, commodified, and productised out of the hands of governments. , branding these pursuits as potentially irresponsible to justify with taxpayer money. Governments want to solve the flat-lining productivity problemI believe such investment justifies technical education which then creates skilled populations- some of whom work on new visions that generate jobs and others work in these jobs or enter the existing labour market. I can’t definitively prove this, of course, but it feels to me a pathway to solving the UK’s productivity puzzle. but want to do so without investing in visions of a limitlessly abundant future. Meanwhile, private investors want rapid returns on investment while making bold claims, like wanting flying cars but getting $140$ characters, extending the participation in space progress to mostly the superwealthy.
From hereon, this post will focus on the radical notion of space superstructures, such as rotating wheel space stations, that expand our presence in various Earth orbits and then extend our reach to go deeper into space. The post mostly argues for a focus on developing inflatable technologies to realise these structures in the near-term but it is possible that this is too ambitious a goal. Note that other options for realising space superstructures (e.g., robots) are not really considered here but are generally important. Along the way, readers may find claims that explain why supporting the development of space superstructures in the near-term is potentially valuable and socially relevant.
The vision
Simply put, the vision I am putting forward is of deploying monolithic space stations with crew capacities of at least $100$ astronauts, i.e., $>10x$ the ISS’s typical crew size; I call this the Hundred Person Habitat (HPH). To date, no station has offered an order of magnitude increase on its predecessors and none are in the pipelineThe in-development Lunar Gateway will operate at an orbit further to the International Space Station (ISS) with a crew of 4. See table here . Assuming that a pressurized volume $>20x$ of the ISS gives each crew member a hypothetical $\approx 200\,m^3$ of volume though, in practice, the habitable portion is roughly identical to the space occupied by on-board equipment/instruments for experiments and life support. The station will be a toroid and thus conceptually resembles von Braun’sHe was apparently inspired by Herman Potočnik’s $30\,m$ ring-shaped habitat described in The Problem of Space Travel rotating wheel station. The below table compares the HPH to the ISS and von Braun station:
Table 1: Comparison of different space station designs.
| Space Station Comparison | |||
|---|---|---|---|
| Parameters | ISS | von Braun wheel | Hundred person Habitat |
| Crew size (# of astronauts) | 7-13 | 50 | 100 |
| Diameter of the station (m) | n/a | 75 | ~75 |
| Total volume (m³) | 916 | 6217.85 | 20x of ISS |
| Habitable % | 42.35% | 60% (assumed) | ? |
| Max. volume per crew (m³/person) | 64.66 | 52.67 | 183.20 |
| Rotational speed for artificial gravity (RPM) | - | 3 | 3 |
| Gravity on-board (m/s²) | - | 1.655 | 1.655 |
As opposed to von Braun’s imagined multi-launch architecture, I am imposingNot proposing! that this identically sized structure be achievable from a single rocket launch by exploiting an idea as old as NASA itself: using an inflatable tube structure.
Inflatable tubular space stations: a counterintuitive idea
In 1961, Goodyear Aircraft Corporation prototyped an inflatable tube space station (see above) called the Erectable Torus Manned Space LaboratoryAround the same time, the Soviets were developing inflatable airlocks; a more modestly sized appendage to spacecraft that allows astronauts to move between a pressurized spacecraft and the vacuum of space. . The idea never made it to flight due to concerns that the soft materials it was made fromthree-ply nylon cords, held together by butyl elastomer. weren’t strong enough to withstand micrometeoroid collisions. Nonetheless, this was an early example of a monolithic space station; a tenth of von Braun’s wheel station that could be packaged to $2\%$ of its inflated volume (another cool image below).
A long lull on habitable space inflatables followed until NASA’s TransHab program (1997) which developed high strength materials capable of withstanding collisions with micrometeoroids and orbital debris (MMOD). TransHab inspired a cylindrical inflatable ISS module ($13\,ft$ in length and $10\,ft$ in diameter)- BEAM (Bigelow Expandable Activity Module)- in operation since 2016. The period between the GoodYear and TransHab inflatable space stations laid the foundations for today’s dominant design of rigid space stations. In my eyes, this is a classic example of where simpler elegant solutions were traded in for ones that are more complex when we think about scale. For example, monolithic rigid stations were followed by the modular ones, like the ISS, that have required in-space assembly, mostly by astronauts, or propellant-intensive rendezvous and docking manoeuvres. Building on this, most future scalable designs I have seen purport the idea of robotic assembly. My recent learnings on inflatables suggest that the same outcome might be realised by a simpler single inflatable system though the development process will be less straightforward. The decision to focus only on rigid stations/modules for several decades has made these inflatable solutions a forgotten one; it appears that we threw out the baby with the bathwater.
When I suggest this idea to people today, it seems a counterintuitive and potentially outrageous solution that exposes biases in thinking- even amongst experts who are, after all, only human. Firstly, there’s a widespread belief that inflatable structures are less safe due to the risk of MMOD collisions. The incorrect analogy of balloons bursting is often mistakenly applied but modern designs incorporate multiple layers of high-strength materials that are remarkably resistant to punctures and could even self-heal. In fact, their flexibility could make them more resilient than rigid structures. Secondly, prevalence of robotics in automating human tasks has led to an assumption that the same approach is optimal everywhere: we see robots building cars and assume they should build space stations. But space presents unique challenges where simplicity is paramount. Inflatable structures have minimal mechanical complexity, reduce failure points, and simplify construction. Moreover, our terrestrial experience doesn’t include living in inflatable habitats, making it non-obvious as a space solution. We’re accustomed to rigid structures so cannot envision lightweight, expandable living spaces as a viable alternative. Yet, in the vacuum of space, these structures provide vast habitable areas with superior radiation shielding and thermal management. This insight has profound implications for future space missions. By embracing inflatable technologies, we can dramatically reduce launch costs, simplify construction processes, and create larger, more versatile space habitats than ever before. It’s a reminder that in space engineering, sometimes the most effective solutions are those that challenge our Earth-biased intuitions.
Why is now a good time to return to inflatable space structures?
There are probably many more reasons than I describe below as to why nowUnlike was done with inflatables, we should maintain/increase support to mature in-space robotic assembly and maintenance technology development as I imagine that at even larger scales, a reliance on robots is inevitable. is a good time to revisit the GoodYear inflatable station ideaIn fact, such stations are just one application of inflatable technologies I see. They could totally transform space robotics by using pneumatic actuation for orbital applications thus eliminating the need for radiation-hardened components like joint motors- a pretty massive bottleneck in the development of space robotics. .
The first has to do with the emerging promise of Starship, which is seeing frequent impressive tests. In contrast, when GoodYear was developing its concept, the Saturn V was still in early development and the GoodYear project might have been easy to kill; I imagine the Moon missions would have also led to a reallocation of resources and focus. Second, the impending retirement of the ISS means there is a window (or even a need) for a successor with a larger volume for both crew sizes and science output. Third, there will be eventually be more commercial users of a large inflatable orbital volume than space agencies; in-space manufacturing companies like Varda could use these stations to scale their drug manufacturing, with the beneficiaries being patients on Earth. Other avenues here are for materials science research and protein crystal growth (not my domain of expertise at all). If in-space semiconductor manufacturing in microgravity becomes a thing, then larger inflatable volumes would, again, answer the question of scaling. Similarly, sci-fi outcomes such as at-scale 3-D printing artificial organs would benefit those in need of hearts and lungs- demands that are not being met by the donor organ market.
All of which is even before we consider making these stations rotate to produce an artificial gravity enabling safer long-haul journeys for astronaut crews heading to Mars or other locations away from the EarthI am currently reading James Hansen’s Spaceflight Revolution that should help me gain a deeper perspective on the early inflatable station. Fun fact: another of his books was adapted into First Man with Ryan Gosling playing Neil Armstrong. .
Notes
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I’ve only read a summary of Brick Moon, a story of workers building a 200-foot sphere that are accidentally launched into space to become first inhabitants of space. The moon was to serve as a navigational aid for sailors. It also estimates a cost for the construction at ${$}250k$ using $12$ million bricks. ↩