From THE ECONOMIST - April 2016

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Space travel

Pump it up, Scotty

The International Space Station is about to get an inflatable extension

AT 73 metres long and 420 tonnes, the International Space Station is the biggest artificial object in space. And it is growing: its 15 existing modules are due to be joined by five more before the decade is out. On April 8th, if all goes according to plan, a rocket will lift off from Cape Canaveral in Florida carrying the first of these new additions. But it is no ordinary module.

The Bigelow Expandable Activity Module (BEAM) is the first bit of the ISS created entirely at the initiative of a private company. Bigelow Aerospace, its manufacturer, is an American space firm set up in 1999 by Robert Bigelow, a businessman who made his money in the hotel trade. And unlike the rest of the ISS, which is essentially a series of space-going aluminium cans, the beam is made from cloth. It is folded up and stowed for the journey into orbit, much like a tent, and then inflated to its full size after being attached to the station.

An inflatable space station might sound a bit mad (perhaps for that reason, Bigelow Aerospace prefers the word "expandable"). But many space cadets are fans of the idea. In the 1950s Wernher von Braun, a Nazi rocket prodigy poached by the Americans after the second world war, described a space station 75 metres across with room for 80 people, made of reinforced, inflatable rubber tubes. In the 1960s, with the space race in full swing, nasa built a full-sized test model of a smaller, 7.3 metre model. And in the 1990s the agency returned to the idea with a design called the TransHab, an inflatable spaceship designed to take a crew of humans all the way to Mars. But that mission never happened. In 1999, in a neat bit of symmetry, Bigelow Aerospace bought the relevant patents from NASA and began working on the technology itself.

Inflatable spaceships offer several advantages, but the main one is mass. An inflatable module is much lighter than its metal counterpart, and mass is the rocket scientist's worst enemy. Lugging mass into orbit requires a lot of energy. Adding extra mass requires more fuel. That fuel, in turn, has mass of its own, requiring yet more fuel to lift, meaning that even a small increase in mass can end up requiring a dramatically bigger rocket. Bigelow Aerospace reckons that its inflatable designs offer more than twice as much internal volume per kilo as a traditional, metal design.

Space is another advantage. The size of a rigid spacecraft is limited by the size of the rocket that launches it. But inflatable craft can be launched folded up, reducing the amount of room they occupy, and then blown up once they reach their destination. When packed away for launch the beam measures 2.2x2.4 metres, compared with 4x3.2 metres when fully inflated. At the same time, the module's thick fabric walls-made of tough layers of exotic materials such as Vectran, a Kevlar - like substance used in ropemaking, or Nomex, which is used to make firefighting cloth-ing - ought to offer astronauts better protection from the hazards of space than metal walls do. Multiple layers of fabric should be good at absorbing impacts from micro-meteoroids: tiny pieces of space-going debris whose high speed makes them dangerous. Finally, fabric walls should offer better protection against radiation than metal ones.

Nor is all this mere theory. In 2006 and 2007 Bigelow Aerospace launched two free-flying, uncrewed stations, Qenesis I and II, using repurposed Ukranian nuclear missiles. Both stations have been circling the Earth ever since, providing data on how they cope with the rigours of orbit. Attaching an inflatable module to a crewed space station will, the firm hopes, be the final step in proving that its technology works.

Swelling ambition

Assuming it does, Bigelow has bigger plans for the future. One idea is to attach a much larger module, called a B-330, to the ISS, for use as a fully-fledged, crewed part of the station. That would be a substantial boost: a B-330, as the name suggests, offers 330 cubic metres of room, about a third of the total space presently available on the ISS. A more adventurous option is to launch a separate, free-flying station, called Space Complex Alpha, made from a pair of B-330s. Such a structure would offer about two-thirds as much pressurized space as the entire ISS at a fraction of the price. (The best guess for the ISS's cost is $150 billion, making it one of the most expensive objects humans have ever built.) The main reason is that the ISS required dozens of rocket launches to assemble; Bigelow's station could, in theory, be put in orbit with just a handful. The firm reckons it could lease a third of a single module (ie, 110 cubic metres) to interested customers for 60 days for around $25m. That is a lot of money, but it is considerably less than the $70m NASA presently pays Russia to fly its astronauts to the ISS.

But Alpha will have to wait for the rest of the private space industry to catch up. Bigelow's business plan depends on the development of privately-built spaceships capable of cheaply ferrying astronauts aloft. That may not be too distant: the beam is being flown to the ISS by Spacex, another private firm that offers rocket launches at far lower prices than more established competitors. For now, Spacex is restricted to cargo flights (it has a bulging order book of satellite launches as well as ISS flights for nasa). But next year it hopes to start flying astronauts to the ISS. Boeing, a big aerospace firm, hopes to do the same thing. And on April 2nd Blue Origin, a private rocketry firm set up by Jeff Bezos, the founder of Amazon, made the third successful flight of its New Shepard rocket. Although it only inched into space by crossing the Karman Line, the somewhat arbitrary barrier 100km up deemed to mark the beginning of space, Mr Bezos hopes one day to carry passengers into orbit proper.

If it ever flies, Bigelow hopes to rent Alpha for specialized scientific research that requires zero gravity, leasing space on the station to private companies, or perhaps national governments without space programmes of their own. That fits with NASA's plans. The agency has been nurturing the private space business in the hope that, once it is established, private firms can take over the comparatively routine business of flying to low-Earth orbit, leaving it free to concentrate on Apollo-style mega projects such as missions to the asteroids and Mars. But history suggests that it may be tricky to fund a space station from scientific research alone: the ISS is supposed to be a platform for science, but its contribution has so far been measly.

If that does not work, another option might be to turn the station into the world's most exclusive hotel, an idea that Bigelow flirted with in its early days. After all, there is already a small but proven market. The ISS has hosted several tourists, including Richard Garriott, a British videogame designer, and Dennis Tito, an American investment manager, each of whom paid tens of millions of dollars for the trip. The B-330 comes with four windows built in. The views, one presumes, would be magnificent. ■