A Fire Suppression Analysis for the Altair Project 2009-01-2511

This paper presents a fire suppression analysis for the Altair project. The architecture of the Altair systems relevant to fire safety is briefly reviewed. This is followed by an outline of a fire safety analysis of the spacecraft including an outline of a probabilistic risk analysis (PRA). The particular emphasis of this analysis is the change in risk as the vehicle moves to lower pressure, higher operating voltage and increased oxygen mole fraction. The analysis shows that all of these changes increase the likelihood and intensity of a fire. The paper then outlines the options for a suppression system followed by a trade analysis of the different options. The candidate systems include inert gas agents (nitrogen, carbon dioxide and helium), water-based systems (spray, mist and foam) and chemically active agents. Chemically active agents are included for reference purposes since they are not likely candidates for the Altair vehicles.