Experimental Needs For Spacecraft Risk Assessment

Abstract

Due to the closed environment of a spacecraft and the lack of egress, fire on-board may pose a significant risk. There are many differences between a fire on-board the spacecraft and one in a terrestrial facility that must be accounted for in any risk assessment. Both the risk assessment methodology and the phenomena-based models for terrestrial applications must be modified. This paper discusses some of the methodology modifications, as well as several experimental results. Multiple experiments have been conducted in terrestrial and microgravity environments in order to construct and validate models required for the assessment and management of risk on-board spacecraft. Past Shuttle experience with electrical overheating events supports the belief that these types of events may pose a serious threat to any human-crewed spacecraft and/or the crew. Experiments have been performed to simulate these events and quantify several damage modes. A preliminary set of experiments at the 2.2 second NASA Lewis Drop Tower has led to several conclusions. First, the production of damage causing elements depends on temperature. Second, the wire insulation involved can have a significant impact on the risk of the event. Third, the smoke particle size distribution is shifted towards larger sizes in microgravity, which may prove important in designing a smoke detector or selecting a sensitivity.