NASA and the Inflatable Space Station

NASA is planning to investigate making inflatable space-station modules to make roomier, lighter, cheaper-to-launch spacecraft, it reveals in its budget proposal released on 22 February. We look into the technologies involved.

What are the attractions of inflatable spacecraft?

The weight of material that must be boosted to orbit is the major contributor to a space mission's cost, due to the expense of sending anything into Earth orbit. Folded fabric packages that inflate, concertina style, to full size once in orbit offer more spacecraft volume for a given launch mass than a traditional metal-based unit.

Where did the idea come from?

NASA engineers came up with the idea in the early 1960s, and tire manufacturer Goodyear was even commissioned to build prototypes, which initially looked much like giant rubber inner tubes (see image, right).

The idea was developed up until the 1990s, when development of an inflatable living quarters unit for the nascent International Space Station (ISS), called TransHab, was scrapped due to budget constraints. The relevant NASA patents were then licensed to a commercial start up, Bigelow Aerospace of Las Vegas, Nevada. See a video interview with a Bigelow engineer above.

How has Bigelow developed the idea?

The firm's team of 100 space-flight and aerospace engineers has developed a whole family of what it calls "expandable" spacecraft and has even tested some uncrewed versions in orbit.

The small 3-metre-long, 2-metre-diameter Genesis I and Genesis II test craft were launched in 2006 and 2007 on decommissioned former Russian SS18 nuclear missiles. Both expanded in orbit successfully and maintained pressure well enough to make a full size module habitable.

A 180-cubic-metre version called Sundancer is now being assembled, with a 330-cubic-metre version in planning.

How are the modules inflated?

Bigelow modules are made from flexible, airtight fabric. Once in orbit tanks of nitrogen and oxygen release a breathable mix inside, expanding the structure by 40 per cent as the gas inside pushes the skin outwards into the vacuum of space. The structure's diameter expands but its length does not change. Air pressure of just 1 atmosphere is needed to expand a module. This is all that astronauts moving in will need to breathe.