Evaluating Material Flammability in Microgravity and Martian Gravity Compared to the NASA Standard Normal Gravity Test

Abstract

Drop tower tests are conducted at Martian gravity to determine the flammability of three materials compared to previous tests in other normal gravity and reduced gravity environments. The comparison is made with consideration of a modified NASA standard test protocol. Material flammability limits in the different gravity and flow environments are tabulated to determine the factor of safety associated with normal gravity flammability screening. Previous testing at microgravity and Lunar gravity indicated that some materials burned to lower oxygen concentrations in low gravity than in normal gravity, although the low g extinction limit criteria are not the same as 1g due to time constraints in drop testing. Similarly, the data presented in this paper for Martian gravity suggest that there is a gravity level below Earth's at which materials burn more readily than on Earth. If proven for more materials, this may indicate the need to include a factor of safety on 1g flammability limits.

Experimental study on downward/opposed flame spread and extinction over electric wires in partial gravity environments

“…The underlying mechanism of the flame spread over solid fuels in different gravitational fields can be primarily explained by the effect of the gas flow velocity under varied gravitational force as a buoyancy-induced flow nearby the flame. Several previous studies [2,6,20] have reported well-known U-shaped flammability limit curve versus gravity levels for flame spreading over solid fuels which consists of the radiation extinction branch in low gravity conditions, where the flame temperature is reduced by radiation heat loss from the gas phase and solid surface, and blowoff branch in high gravity conditions, where the flame temperature is reduced by reactant leakage due to the finite rate chemistry. It has been also reported that 𝑉 shows a peak value at moderate gravity levels due to the competition between the radiation heat loss from the system and the reactant leakage caused by the finite rate chemistry [2,20].…”

“…Most recently, Ferkul and Olson [5] and Olson and Ferkul [6] have performed drop-tower experiments using a centrifuge apparatus to measure the LOCs of the flame spreading over solid materials in the upward configuration under partial gravity environments. They have reported that flames spreading in Lunar and Martian gravity levels are sustained at lower oxygen concentrations than in normal gravity environments.…”

A historical overview of experimental solid combustion research in microgravity

“…NASA has recently expanded its capabilities to produce Martian and Lunar gravity levels in their drop tower. A centrifuge (drop bus system) can be allocated inside the 5.2 seconds drop tower [60,61]. As a result, Lunar and Martian gravity levels can also be achieved in the drop tower and parabolic flights.…”