

Video: How inflatable spacecraft could be cheaper and safer than conventional metal craft Video: How inflatable spacecraft could be cheaper and safer than conventional metal craft

Gallery: Build your own space station

This 9-metre-diameter ring is an inflatable space station built by tyre manufacturer Goodyear in 1961. Prototypes of the design were made but none were ever flown. It was in theory big enough to house two people (Image: NASA) The Genesis 1 module was lifted into orbit on a retired Russian SS18 nuclear missile in 2006. It expanded to 3 metres in length by 2 metres in diameter, demonstrating that a craft could be inflated in orbit and maintain its shape through air pressure alone (Image: Bigelow Aerospace) Expandable spacecraft could be placed on the lunar surface (Image: Bigelow Aerospace) Advertisement

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.

What about punctures?

Bigelow’s craft are made from multiple layers of Vectran, a double-strength variant of Kevlar, the tough polymer used to make bulletproof vests. This is coated with an outer layer of the conventional Micro Meteorite Orbital Debris (MMOD) shielding seen on most spacecraft – essentially metallic foil.

Bigelow Aerospace says that in tests, simulated micrometeoroids that completely punctured samples of ISS skin penetrated only halfway through the skin of an expandable. “It’s absolutely not like a balloon that’s going to pop. It provides better than ISS-safety levels,” insists the firm’s operations director, Mike Gold.

“If a leak were to occur, you would have 24 hours or more to identify and patch it before there was any impact on the module’s structural integrity,” says Gold. Traditional metallic structures would not provide such time, he adds, because shattering around a puncture makes for more serious damage.

What is NASA’s plan for inflatables?

The agency is considering connecting a Bigelow expandable craft to the ISS to verify their safety by testing life support, radiation shielding, thermal control and communications capabilities.

How long before we can expect a crew to move into an inflatable space station module?

That’s the big unknown. The US will not be able to be take astronauts into orbit on its own vehicles for some years once the space shuttle is retired this year.

If the US Congress agrees with NASA’s proposal to cancel the troubled Constellation programme then the agency will be forced to invest more in its commercial crew development initiative, which aims to stimulate private firms to develop crewed spacecraft.

Bigelow is already working with Boeing to develop crew capsules for future launchers as part of that programme. “Everything depends on the availability of commercial crew transportation,” says Gold.