Results and Spacecraft Fire Safety Implications from the Saffire IV-VI Microgravity Combustion Experiments

CLAIRE FORTENBERRY, David Urban, John Easton, Justin Niehaus, NASA Glenn Research Center

     Abstract Number: 584
     Working Group: Combustion

Abstract
A spacecraft fire represents a life- and mission-threatening scenario for any space flight or exploration mission. Due to the unique combustion and transport physics under reduced gravity and the need for rapid trace contaminant removal to conform to habitation requirements, spacecraft fire detection approaches must combine appropriate selection of detector technologies with their strategic placement within the spacecraft cabin. The most recent spacecraft fire detectors (abord the Shuttle and ISS) have relied on smoke particle detectors developed for terrestrial applications, and previous microgravity smoke studies have demonstrated that the efficacy of these detectors depends on aerosol size, composition, and morphology. Additionally, because spacecraft particle filtration rates may outpace smoke generation in early-fire scenarios, and because of disruptive false alarms due to nuisance cabin aerosol, a gas-phase detection target could ultimately supplement smoke particle sensors for a more robust detection strategy. Thus, particle and gas composition and concentration data from real reduced-gravity fires with relevant spacecraft materials are needed to optimize fire detection and ensure crew safety for future low-Earth orbit, Lunar, Martian, and deep space missions.

The Saffire series of experiments were conducted by NASA on Northrop Grumman Cygnus vehicles following completion of their primary ISS resupply missions. As Cygnus maintained low-Earth orbit, spacecraft-relevant materials were ignited to investigate flame behavior under different pressure and oxygen conditions. Although Saffire I-III focused primarily on obtaining flame spread and heat release information, Saffire IV-VI incorporated particle and gas sensors in the far field of the vehicle to track smoke transport and evolution over time. Here, we present particle and gas composition, concentration, and evolution results for fire experiments conducted during Saffire IV-VI. We also discuss implications for spacecraft detection strategies, including times to alarm and potential fire survivability.