NASA: We'll try again in the morning after friction ruins engorgement
Happens to us all, space-station inflatable podule boffins
After halting the first try on safety grounds, NASA is going to make another attempt to inflate the Bigelow Expandable Activity Module (BEAM) aboard the International Space Station (ISS) on Saturday.
The module, made up of layers of micrometeoroid-resistant fabric, was delivered to the ISS by SpaceX last month and was due for inflation on Thursday, but NASA called a halt prematurely and gave a press conference on Friday to explain why.
Jason Crusan, director of Advanced Exploration Systems at NASA Headquarters, said that the inflation process was stopped because the habitat wasn't expanding as quickly as the computer models predicted. This is most likely because of friction forces in the skin of the BEAM slowing the rate of inflation.
"The BEAM spacecraft has been in a packed state for a significantly longer time than expected. It has undergone a tremendous squeeze for over 15 months, which is 10 months longer than planned. Therefore, there is a potential for the behavior of the materials that make up the outside of the spacecraft to act differently than expected," said Bigelow in a statement accompanying the press conference.
NASA started feeding air into the BEAM on Thursday using the ISS' own air supply rather than the canisters of compressed gas within the module, because this gave them better control. Before beginning inflation they closed the valve that vented the module to vacuum, cut the three retaining straps keeping the module in place, and unfastened the retaining bolt holding the module shut.
Air was fed in under low pressure and the habitat expanded slowly, but not as expected. NASA decided to halt the attempt, and reduced pressure. But the module continued to expand slightly, indicating that the fabric friction was slowly easing as the module unfolded.
"When the fabric is compressed it has memory of its shape and it takes time for materials to relax and come back from its uncompressed state," explained Lisa Kauke, aerospace project manager at Bigelow Aerospace. "We are confident nothing is wrong with the BEAM."
The fact that the habitat continued expanding without extra gas being added reinforces the fabric friction theory, Crusan said, and so the team will try for reinflation on Saturday, varying the amount of pressure used. Once the fabric is unfolded, the internal gas tanks will bring it up to full pressurization.
NASA is playing it very safe on this one, over safety fears for the ISS. The BEAM is attached to node 3 of the ISS, which is attached just off the central spine of the space station, and if something went wrong with the inflation it might push against the node and risk damaging the ISS' frame.
If the next attempt to inflate the habitat fails, NASA is going to halt operations for at least a week. It's due to start launching CubeSats (miniaturized satellites for space research) on Monday using the station's robotic arm, and will try again once that task is completed.
NASA has agreed to host the BEAM for two years, although it won't definitely be inhabited by astronauts. Once inflated, there's a mandatory 80-hour testing of its structural and air-holding integrity that must take place, and then the BEAM will be left alone while its internal state is monitored.
Crusan didn't rule out using the module to house equipment or to give the astronauts a new playroom later on, but for the moment it's primarily a test platform to see how well the structure holds up in space.
Bigelow is touting its inflatable habitats as a logical and cost-efficient way to build space structures in orbit. Inflatable modules slash the costs of orbital delivery and could prove as sturdy as metal structures for protecting their occupants. ®