Vehicle Modeling during the Burning of Cotton Samples in the Saffire IV and V Experiments

Predicting the transport of combustion products and heat during a spacecraft fire can help design a safer vehicle and mission. The Saffire project has provided data on the spread of large fires in a microgravity environment within Northrup Grumman’s Cygnus vehicle after a resupply mission to the ISS. Solid materials, including cotton-based samples were ignited to study flame spread and the effect a fire has on a vehicle. Sensors were placed within Cygnus that measured carbon dioxide concentration and temperature. A model of the Cygnus vehicle was developed using inlet and outlet data of Saffire and the descent phase cargo configuration photos. The initial gas phase volume of the model did not match volume measurements provided by the release of CO2, likely due the porous nature of the trash and cargo in Cygnus. Holes were placed in the model cargo to match the experimental volume, providing a better prediction of species transport. Surface heat transfer was calibrated to match the closest remote sensor to the Saffire IV outlet, (RS3) in the forward port standoff, providing a better prediction of the temperature throughout the vehicle.