Breaking with clickbait-y writing wisdom, I’ll start with the answer for the impatient ones familiar with the von Braun wheel concept: it is in 1961. Or 1962. Buried in the archival memories of NASA Langley, alongside many other great projects undertaken there. While this is stark, it is far less interesting than understanding how Apollo-era technologies diverted focus from building artificial gravity space stations and how that eventually catapulted us towards zero-gravity space stations. That is what I unpack here while also considering if a course-correction is needed.

What is a vBW?

We know that, rephrasing Heinlein, space is a harsh mistress. Alongside radiation, microgravity in various Earth orbits is a concern for human health leading to muscle atrophy, bone loss, and vision problems. Modern-day astronauts spend a few hours each day exercising to overcome some of these issues. For this reason, early space visionaries, such as Werner von Braun, strongly believed that settling the solar system required developing technologies to generate artificial gravity within orbiting habitats.

von Braun believed his technological solution - the rotating-wheel space station - was ‘as inevitable as the rising sun’. In his 1949 sci-fi novel, “Project Mars”, humans reached the red planet using such stations and, in 1956, Disney worked with him to create the first visuals of this “von Braun wheel” , shown in the image below. In such systems, humans live along the periphery of a spinning wheel, within which they experience gravity. While it was popularized by von Braun, the concept traces back to Herman Potočnik’ in 1928. The legacy of the idea is probably why many felt that an operational station was, at best, a couple decades away.

This elegant solution to generate artificial gravity, however, comes with a major engineering challenge. The gravity along the wheel is generated by rotating it and, like ferris wheels, motion sickness in astronauts would likely be prevented by spinning at low speeds. The resulting physics then dictates that these wheels be quite large. For example, one of von Braun’s designs called for a massive 75-metre diameter wheel that generated lunar gravity if spun at 3 rpm and Earth-like gravity at 5 rpm, which are considered as safe speeds to avoid disorientation among astronauts. However, the physics of rockets work in the opposite way; to enable taking things into space, a rocket must itself be slender, like an arrow, to escape earth’s gravity well. For context, Starship’s upper-stage is about 9 metres wide and 22 metres tall with most launchers being far smaller. This defines the main upstream engineering challenge: how can we realise enormous space structures using slender rockets?

Challenge: Building large stations

Architects of the International Space Station (ISS), the largest largest space structure ever built, tackled this packing problem using multiple smaller spacecraft which connect, like space Ikea, into a structure greater than its parts. Such in-space assembly involves spacecraft either gently crashing into each other at specific connection points (a manoeuvre called rendezvous and docking) as well as astronauts and space cranes supporting finer assembly tasks. While this works great in theory, the ISS’s assembly needed over 40 rocket launches spanning several years (and even more launches for cargo resupply and repairs). More damning is the typical ISS crew size of 7, which is a little over twice that of the first ever space station, Salyut, from 1972. These numbers are a far-cry from von Braun’s anticipated 80 humans or, more relevant today, Starship’s 100. As a result, civilisation-scale habitats like the Stanford Torus and O’Neill cylinders appear even more ridiculous today than when they were first proposed.

Clearly 50 years of space station development shows that modular in-orbit assembly has not provided evidence of scaling crew size nor a pathway to artificial gravity space station designs (whether we need these, I’ll tackle later).

From today’s vantage point, it is quite clear that the architectural bottleneck is a technology running through all operational space stations so far: their use of the Apollo-era small ‘tin can’ modular spacecraft as the centerpiece for assembly. This, in my opinion, is unfit for building large space stations for hundreds- at least not at scale or speed. But how did we get here?

To understand this, we have to look at pre-Apollo era space technology development programs. Yet from 1958 till 1961, NASA Langley pursued far more radical ideas to making artificial gravity stations. They explored two radically different architectures to accelerate towards Braun’s vision. The first explored the use of large tyre tubes (obviously made by Goodyear!) that inflate into wheel-shaped space stations- this is what James Webb is standing under in the first image of this essay and the image below shows engineers walking within this human-scale tube. Made from soft materials, like rubber and nylon, there were concerns that collisions with micrometeorites could puncture the station and be fatal to astronaut life.

In parallel, North American Aviation was looking into hexagonal space stations made from hinge-connected rigid pipes. This station could fold neatly into a rocket for launch and later deploy in-orbit. The rigidity of the habitable elements would offer better protection to micrometeoroid collisions than Goodyear’s rubber donut. A 15-foot prototype of the system was developed based on the table-top concept shown below.

While these efforts were ongoing,

Perhaps a line of research would have been initiated in 1961- we will never know. Soon after Apollo was announced by Kennedy, cancellation threats were issued to the ongoing space station development projects which had little relevance to landing man on the Moon in 8 years. The program survived through Langley’s leadership lobbying who convinced NASA HQ that larger stations were a logical successor to Apollo. The space station vision shrank to meet Apollo’s more modest needs: no artificial gravity and much smaller crews of 3. Post-Apollo era, NASA’s funding shrank and the Space Shuttle became the “logical successor” with a very limited station, Skylab, was launched based on Apollo technologies. The Soviet Union also cooled their interest in their lunar programme and started Salyut, the first serious space station programme.

These early concepts are notable not only in their ambition in directly pursuing von Braun’s vision but also for what now feels like a very counterintuitive way of realising large stations as “unitised” structures i.e., a single structures that avoids or reduces needing in-orbit assembly. The initial plans for these architectures were designed for repeatability and scale which would leade to greater scientific output than all stations so far while offering a deeper understanding of the impact of artificial gravity on human health. We might even had several orbiting settlements distributed across the Solar System by now, taking us closer to an Asimovian future or that of Philip K. Dick’s imagination of Mars settlements in Do Androids Dream of Electric Sheep?

In other words, the ISS and everything before it is the opposite of “faster, cheaper, better”.

Given all that these years have taught us, it would be natural to presume that stations from rigid, metallic modules was always the foundational idea. The reason is on account of technology choices and organisational decision-making underpinning them.

When one imagines early space station designs, the natural assumption might be that NASA always pursued rigid, metallic structures - the kind of ‘tin can’ engineering that defined the Apollo Era. But through the history of the ISS and prior stations runs a common technological thread traceable to Apollo: small rigid, metallic habitable spacecraft modules. These are a legacy bequeathed from the Apollo Era to modern space station design which, in my opinion, are unfit to realising genuinely large space stations. Let me explain why. Yet from 1958 till 1961, NASA Langley was pursuing something far more radical: inflatable space stations that would deploy into giant donuts. This seemingly fragile approach wasn’t just an engineering curiosity - it represented perhaps our best shot at achieving von Braun’s vision of large rotating stations quickly. ==While these rates are thought to be within safe ranges, long-term human tests in orbit are needed for confirmation.

</mark>So can we create such large stations when rockets are nowhere near large enough? Have we tried to make them? Could they have other uses prior to becoming stations for deep space human exploration? I’ll try to unpack these questions, somewhat systematically.==

Have we tried to make them? Yes. What is The challenge and bottleneck? We have but rockets must be shaped a certain way so space stations need to be packed into them.

Today, the largest largest space structure ever built, the International Space Station (ISS), is home to 7 astronauts free-falling in a near zero-gravity environment. Through it, and all realised stations (past and present), runs a common technological thread: their use of small rigid, metallic habitation modules. These are a legacy bequeathed from the Apollo Era to modern space station design which, in my opinion, are unfit to realising truly large space stations. Let me explain why this was a bad idea and how it happened.

Why a bad idea? The aerodynamics of rockets requires that they be slender, like an arrow, to escape earth’s gravity well. To overcome this challenge, the ISS makes use of modules that combine, like orbting Lego pieces, into a structure greater than its parts. While this sounds great in principle, over 40 rocket launches were needed to realise the ISS. While it allows significantly longer duration stays than the first space station (Salyut), the ISS usually holds only twice as many astronauts.

==This seemingly fragile approach wasn’t just an engineering curiosity - it represented perhaps one of our best shots at achieving von Braun’s vision of large rotating stations quickly.==

So what happened to these programs?

So, yes- this was quite an active period of commercial and NASA-led space station development. 1960’s NASA and today’s NASA are hamstrung in different ways. The Space Race era was about competition whereas today it is about cooperation. Competitions have proven to have short-term rewards that are hard to repeat; maybe it’s because they have incorrect targets or the wrong means to get to those targets or both. Apollo, an insane feat of engineering, probably had incorrect means because getting humans on the moon by 1970 while deprioritising a long-term reusable infrastructure like a space station doesn’t sit right. Especially when we haven’t gone back in 50 years but also because more progress was made by 1961 on the idea of large stations as platforms for routine and repeatable access to the Moon or Mars.

OTOH. Cooperation comes with coordination costs; for example, coordination between NASA, ESA, JAXA, Roscosmos gave an impressive ISS but underperforms as a research lab (tho I will say it is better than having nothing) and took a long time to build and has issues affected by the politics of the day. It’s not easy to build another ISS- let alone a bigger one- and also isn’t a platform for launching deep space missions (e.g., it has never been used as a staging platform for any Martian missions).

So why does an org like SpaceX seem to work? Elon is a clear reason but also sometgin common to companies is the internal collaboration culture (which is more fluid than cooperation, ). This means coordination costs are low and paperwork/processes are also minimised. These systems are better at course correction- something govt orgs won’t typically do (maybe they can’t?). NASA’s Space Launch System is a terrific example of not course correcting.

Today, ITAR has a pretty massive impact on both NASA and SpaceX; America basically uses it to regulate who can and cannot work in the US space sector. This Elon reply (and the thread before the reply) are pretty good at summarising ITAR: https://x.com/elonmusk/status/1695002550251213268

That said, it is in fashion to bash NASA right now. But I would like to remind readers that NASA excels at solving complex engineering challenges when given a clear mission focus- whether it was Apollo’s lunar landings or the Space Shuttle’s reusable orbiter development. This capability is perhaps best exemplified by JPL’s remarkable track record with Mars missions: their evolution from early Viking landers to the sophisticated Curiosity and Perseverance rovers demonstrates an ability to build on experience and consistently execute challenging interplanetary missions. While other space agencies have struggled with Mars landings (like ESA’s Beagle 2 and Russia’s Mars 96), JPL has developed a repeatable expertise that makes the extraordinary seem routine. Their technologists pioneered a Martian landing technology that is now used to land SpaceX’s rockets. So, the issue isn’t NASA’s engineering capability - it’s about ensuring these formidable technical skills are directed toward the right long-term priorities for space development. And it’s about greeting a regulatory environment that allows more players to join in from all over the world by making ITAR a thing of the past.

Will I ever get my von Braun Wheel?

Possibly. The commercial potential for rotating space stations is gaining attention once again. Jed McCaleb of Vast, one of the big players in commercial space station development, echoes von Braun that space stations would be useful for Mars transport as they’d be ‘much nicer to live on than inside Starship’ and artificial gravity stations are essential for humans living in space beyond a year. Mars transport can range from months to years, depending on when we launch. That said, Vast appears to only be looking at spinning sticks building on the maturity of the Apollo-ear technologies. This is a step in the right direction but the limiting feature of this design is that any artificial gravity will only be at the very ends of the sticks. Every space station manufacturer today also believes they could help scale in-space manufacturing for companies like Varda and Space Forge.

But the challenge remains a technical one, we need to work on scaling BEAM from its meagre 16 m3 inflated cylindrical-ish shape towards a >6000 m3  von Braun wheels. To put these numbers in human terms: BEAM offers less space than the 65 m³ per person currently available on the ISS. What is ideal for a large von Braun wheel is actually unknown at this time.

The researchers at Langley have given us hints of the intermediate scales to test at but we need to revisit subscale testing using these newer materials. This will help identify/anticipate needs for larger modules. Current research indicates that we need new materials to make larger-than-BEAM space structures from inflatables (see Figure 4). Further, the Langley designs and architectures were for Earth orbiting stations. New ones must be conceptualized and woven into the tapestry of space exploration that Starship is stitching. This design space will have to address:

• developing systems for inflation/deployment unique to these stations and understanding the structural dynamics throughout the process.
• crew transportation/docking for cargo and crew transfer.
• power systems for station operations in a Mars transport context.
• corresponding actuators and motion control (AOCS) to rotate the station for artificial gravity and also evaluate dynamic stability (eg movement of humans in a station can create a wobble).

This work won’t be straightforward but we do need to push for it because minimising modularity could reduce the slow in-space assembly as seen with the ISS.

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 could have 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.

Could they have other uses prior to becoming stations for deep space human exploration?

towards widespread intergalactic intelligence imagined by Isaac Asimov and Douglas Adams