CHICAGO — Before the Cygnus cargo tug that reached the International Space Station on March 26 makes its mission-ending plunge back to Earth, NASA will spend a week playing with fire onboard the unmanned capsule in an effort to improve astronaut safety.
NASA has been igniting and extinguishing tiny fires aboard the ISS for years in pursuit of a better understanding of how fire behaves in a gravity-free environment. Since larger-scale experiments, cannot be staged safely inside the ISS, scientists at NASA’s Glenn Research Center came up with Saffire, which stands for Spacecraft Fire Experiment. The experiment is intended help NASA created safer materials and environments for humans working in space.
“Saffire will be the biggest man-made fire ever in space,” said Gary Ruff, NASA’s Spacecraft Fire Safety Demonstration project manager. “Currently, we can only conduct small combustion experiments in the microgravity environment of the space station. Saffire will allow us to safely burn larger samples of material without added risk to the station or its crew.”
The largest controlled fire in space prior to this experiment was only the size of a notecard. The three-part Saffire experiment will set fire to bath-towel-size samples of cloth as well as nine smaller stripes of materials commonly used in spacecraft.
To eliminate any risk to the ISS and its crew, NASA won’t start the Saffire experiments until at least 24 hours after Cygnus undocks from the ISS. The Orbital ATK-built spacecraft is scheduled to remain at the ISS for nearly two months, giving the station’s crew plenty of time to unpack its load of supplies and fill it back up with trash.
The combustion experiments will be performed inside a fire-proof box about the size of a gym locker. Using Cygnus, which burns up in the atmosphere after each cargo-delivery mission, solves another problem besides the lack of sufficient space on board ISS: the need to clean up the aftermath.
“The reason that we don’t really do this on ISS is that the piece that we’re not doing on Cygnus, that we would definitely have to do on ISS, is cleaning up the mess” Ruff said during a press conference ahead of the March 22 Atlas 5 launch of Cygnus.
After seven days in space to perform the experiment and transmit its results, the Cygnus vehicle and its singed cargo will burn up on reentry into Earth’s atmosphere.
Glenn Research Center so far has built a total of three Saffire modules, with the remaining two slated for launch later this year. The cost of this mission is $24 million, not including the cost of launch.
NASA plans to build three additional Saffire modules in 2018 for future Cygnus flights.
David Urban, the Saffire principal investigator, said the experiments aim to answer two questions: “Will an upward spreading flame continue to grow or will microgravity limit the size? Secondly, what fabrics and materials will catch fire and how will they burn?”
These questions are particularly important because, Urban told SpaceNews via email, “It is important to note that ALL inhabited structures/places on earth (buildings, planes, trains, cars, ships, submarines, mines, forests etc.) have been the subject of full scale testing to better understand the fire risk.
“Until now, NASA has not had the opportunity to safely do testing of this type. This collaboration with Orbital using an uninhabited (but habitable) vehicle is an excellent opportunity to fill a gap in our knowledge.”