Overview of the “Solid Combustion” Experiment in the Japanese Experiment Module “Kibo” on the International Space Station

Fire safety in human-rated spacecraft or space station is one of the most important requirements for any human space mission. To prevent fires in space, material flammability tests such as NASA-STD-6001B standards have been widely employed. The tests are performed in a normal gravity environment. Previous research showed material flammability could be higher in microgravity environments for some conditions, so it is important to understand the impact of gravity-induced buoyant flow on material flammability. In 2010, the investigation titled “Quantitative Description of Gravity Impact on Solid Material Flammability as a base of Fire Safety in Space (Solid Combustion)” was selected by the Japan Aerospace Exploration Agency (JAXA) as an experiment candidate in the Japanese Experiment Module “Kibo” on the International Space Station (ISS). In the “Solid Combustion” experiment, three types of solid material (polyethylene insulated wires, thin PMMA sheets and thin filter papers) are selected as test samples. Flammability of these materials will be quantitatively determined in microgravity by evaluating the limits of two fundamental processes of solid combustion, which are (1) ignition limit of the solid material, and (2) flame spread limit (extinction limit) over the solid material. It is expected that the evaluation of the discrepancy between the data in normal gravity and microgravity will lead to improved understanding of the level of the conservatism of the existing material flammability tests. Also, a “material flammability map” for the selected samples will be produced as a fire safety database for spacecraft, which will be reference data to estimate the flammability of other solid materials. To date, a detailed consideration of the experimental plan in orbit and a conceptual design of the experiment specific hardware to be installed into the Multi-purpose Small Payload Rack (MSPR) in the Kibo, have been performed. In this paper, an overview of the “Solid Combustion” experiment and the current status of the project will be presented.