Flammability of Combustible Solids in Spacecraft Environments
The flammability of combustible materials inside a spacecraft environment is of importance for fire safety applications because the conditions in this type of environments can greatly differ from those on earth, and a fire could have catastrophic consequences. Moreover, experimental testing in space can be difficult and expensive, and ground-based microgravity facilities such as drop towers or parabolic flights are limited to a few second duration. Additionally, future space missions may require spacecraft cabin environments different than those currently used in the International Space Station, 21% O2 by volume and 101.3 kPa, moving to reduced cabin pressure and increased oxygen concentration. These new conditions may result in an increased fire risk of the materials used due to the higher flame temperatures and the reduction in the convective losses from the heated solid surfaces. In particular, the influence of low pressure on material flammability and flame spread behavior is emphasized here because of the similarities existing in between the flow field produced in reduced pressure environments and microgravity.
Chapter 1 presents an introduction to material flammability and flammability testing, focusing particularly on flame spread over solid fuels and previous related research. Chapter 2 presents a description of the experimental setups used for the normal gravity and the microgravity tests presented as part of this work. Chapter 3 is an experimental study covering flammability boundaries for flame spread of fire resistant fabrics exposed to different environmental conditions. In Chapter 4 and 5, an experimental study is presented along with a phenomenological analysis to simulate the burning behavior of thin and thick solids in microgravity conditions by using reduced pressure environments. Then, in Chapter 6 a similar approach is presented to study the flame spread behavior under the effect of external radiant heating, making comparisons with low pressure and microgravity environments.