The danger from fire aboard spacecraft is immediate with only moments for detection and suppression. Spacecraft are unique high-value systems where the cost of failure is measured in lives and dollars. Space crews have little or no chance to escape vessels on fire. It is imperative to detect the onset of combustion in microgravity at the earliest possible moment. Present fire detectors onboard spacecraft are inadequate due to sensitivity, time response, or both. Smoke detectors are insufficient for detecting the early stages of combustion, sensors are needed to detect the products of combustion directly. These sensors must meet stringent size, weight and power requirements. Vista Photonics proposes to develop rugged, compact fire detection instrumentation capable of selectively and simultaneously measuring the combustion species HCN, acetylene, carbon dioxide and carbon monoxide at parts-per-million (ppm) or better sensitivities in a 1 Hz bandwidth. The enabling technology for meeting NASA's stringent mission requirements is a new rugged, compact, and lightweight optical path length enhancement cell that recovers the theoretical sensitivity of proven high-performance optical absorption detection techniques.