Understanding how fire spreads in a microgravity environment is critical to the safety of astronauts who live and work in space. And while NASA has conducted studies aboard the space shuttle and International Space Station, risks to the crew have forced these experiments to be limited in size and scope.
Now a new experiment, designed, built and managed at NASA’s Glenn Research Center, will ignite an understanding of microgravity fire on a much larger scale. The Spacecraft Fire Experiment, known as Saffire, is a series of experiments to be launched on three different flights beginning in March.
“A spacecraft fire is one of the greatest crew safety concerns for NASA and the international space exploration community,” says Gary Ruff, Saffire project manager.
Saffire will involve far larger flames than previous experiments and will investigate the way fire spreads on a variety of combustible materials. Because the experiments will be conducted away from the space station, there is no risk to the astronauts aboard.
Each Saffire experiment will be remotely operated inside a 3 x 5 foot module, split into two compartments. One side of the module is an avionics bay that contains sensors, high definition video cameras and signal processing equipment. The other side contains the hardware required to ignite a large flame and burn the fabrics and materials inside.
When the experiments begin, Saffire I and III will burn one large 16 by 37-inch piece of SIBAL cloth, which is a blend of fiberglass and cotton. This material has been studied in previous microgravity combustion experiments, although at a much smaller size. The SIBAL cloth will be burned from the bottom to see how the flame spreads. If the flame extinguishes itself, scientists will light it at the top and see what happens as the flame moves opposite to the airflow.
Saffire II, scheduled to launch in May from Wallops Flight Facility in Virginia, will ignite a mix of nine different samples of materials used routinely on the space station including flame retardant fabrics used for astronaut clothing, station Plexiglas window samples with edge variations and structures used for storage containers and silicone composites. Each sample is two by 11 inches, the size sample NASA uses to screen materials on Earth before they are used on a spacecraft.
“Saffire seeks to answer two questions,” says David Urban, principle investigator. “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?”
The Saffire I payload will hitch a ride on a resupply mission to the space station in an Orbital ATK Cygnus cargo vehicle from Kennedy Space Center in Florida. When Cygnus arrives, astronauts will unload their supplies, but Saffire will remain on board Cygnus.
“Within the first day after Cygnus pulls away from the space station, we will begin the experiment, which will run autonomously once the RUN command is sent,” says Steven Sinacore, deputy project manager. “It will only take a few hours to run the experiments, but Cygnus will remain in space for seven days to ensure complete data transmission back to the Saffire operations team on the ground.” Eventually, Saffire, along with Cygnus, will be destroyed upon reentry into Earth’s atmosphere.
Concepts for additional Saffire missions- IV, V, VI are in development to focus more on flame spread, smoke propagation, detection and suppression of fire.
As NASA continues to send astronauts to the space station and continues the path toward a human mission to Mars, improving understanding of the structure of spacecraft fires is critical. “Saffire is all about gaining a better understanding of how fire behaves in space so NASA can develop better materials, technologies and procedures to reduce crew risk and increase space flight safety,” says Ruff.