While the most interesting piece of cargo on its way to the ISS after SpaceX's successful Falcon 9 launch is almost certainly some intrepid Tokyo Bekana cabbages, a close second has to be the Bigelow Expandable Activity Module (BEAM), a pleasingly round inflatable space habitat that the astronauts are going to attach to the ISS and then blow up to see what happens. If everything goes according to plan, explosions will be minimal, and BEAM will inflate to its maximum curvaceousness. This will prove, over the course of the next two years, that the future of space habitation is something to get pumped up about.
There are a few different reasons why inflatable space station modules are so appealing. The biggest reason is that, relative to a rigid module, inflatable modules offer a better ratio of interior volume to mass, making them cheaper to launch. Doubling the interior volume of an inflatable module only increases the mass by about a third. The other reason is that using an inflation technique lets you launch bigger modules in smaller packages, which gets around launch size restrictions.
It's not a coincidence that the biggest interior volume ever launched into space, Skylab, was a repurposed Saturn IV upper stage with its main hydrogen fuel tank turned into living quarters and a workshop (the smaller oxygen tank got turned into a giant trashcan). Skylab was simply the largest diameter space that could be physically launched on top of a rocket (although there was some earlier discussion of using a full-width Saturn V second stage instead). Skylab offered a staggering 350 cubic meters of open space, nearly double the largest single module on the ISS today. Look how much fun it was:
Until the SLS comes online, there's no way we could launch a structure like this in one piece today. But a large module from Bigelow (the BA 330), could provide a similar amount of interior space to Skylab while requiring only about a third of the mass, and it could launch inside an Atlas V or the forthcoming SpaceX Falcon heavy.
We may be getting a little bit ahead of ourselves, though: BEAM is a quite modest 16 cubic meters in volume, which is easily enough for one person to comfortably stretch out, but probably not enough for a game of zero gravity bocce. At launch, it was folded up and stuffed into a cylinder about 2.2 meters tall and 2.4 meters wide, and has a mass of 1,400 kg. About five days after Dragon gets to the ISS, the space station’s arm will remove BEAM from Dragon’s fanny pack, and attach it to a spare hatch on the Tranquility module. In early June, BEAM will be slowly inflated to 101 kilopascals (equivalent to air pressure at sea level) over a period of about 45 minutes, increasing in volume by a factor of five. Bigelow isn't exactly sure what this is going to look like, but here are some animations showing very slightly different scenarios:
Once inflated, BEAM is going to spend most of its two years on the station being very, very lonely. Astronauts will check the module out and install some sensors after it inflates, and then seal it up again and only come back very briefly a few times a year to make sure that it hasn't been invaded by either radiation or micrometeoroids. Bigelow is reasonably confident that neither of these things are very likely: BEAM's skin is made up of a proprietary layered sandwich of films, fabrics, and foams that provide, Bigelow says, better radiation and micrometeoroid protection than the rest of the ISS. (For more background on the virtues of inflatable structures, James Oberg visited Bigelow Aerospace’s factory near Las Vegas back in 2007 for IEEE Spectrum.)
If everything goes flawlessly for BEAM over the next few years, the plan is to detach and deorbit the module (to free up the docking port for other stuff), letting it burn up in the atmosphere. It’ll be sad, but we’ll get over it, if a flawless BEAM test means that Bigelow can start launching its larger BA 330 inflatable modules sooner. And beyond that, Bigelow has even more crazy ideas, including the BA 2100 “Olympus,” which would look like this:
Concept of the Bigelow 2100 “Olympus” inflatable spacecraft carrier Illustration: Bigelow Aerospace
With over 2100 cubic meters of usable interior volume, Olympus would be over twice as spacious as the ISS. In fact, it would be so large, that it could carry other spacecraft inside it, as in the concept image above: the structure on the left hand side is a massive airlock, and there are astronauts working on lunar landers inside Olympus itself. Despite its size, Olympus could potentially be launched all at once by the SLS with mass to spare, and once in orbit, it would be as self-sustaining as the ISS currently is, with a lifespan of at least 20 years.
Again, we’re getting a little bit ahead of ourselves, but we’re about to see a fundamentally new (and, we hope, better) space habitation technology undergoing its very first human scale test, and it’s exciting! Check back in June for an update on the inflation process.