COMBUSTION OF NOMEX® III FABRIC IN POTENTIAL SPACE HABITAT ATMOSPHERES: CYCLIC FLAME SPREAD PHENOMENON

Abstract

Upward flame spread over Nomex® III fabric was tested in enriched oxygen, reduced pressure atmospheres. These are potential conditions for future space habitat environments. Flammability boundaries as a function of oxygen percentage and pressure were determined experimentally. Upward spread is possible at 24% O₂ for pressures as low as 7 psia. For most cases, upward spread is cyclic in nature. A cycle consists of flame growth, flame split, blowoff of the downstream “secondary” flame and re-growth of the upstream “primary” flame. This article presents a detailed description of this interesting and unexpected phenomenon, and suggests that a two-stage solid pyrolysis is its cause.

Keywords:

• Flame splitting
• Nomex flammability
• Periodic upward flame spread
• Two-stage pyrolysis
• Upward flame spread limit

This research was carried out with support from NASA Grant #NNC04AA58A.