The specter of fire in a man-carrying spacecraft has long haunted NASA scientists. In the pure-oxygen cabin atmospheres of U.S. craft, it seemed all too probable that a random spark from electrical equipment or insulation overheated by a short circuit might touch off fires that would blaze with explosive fury.
That fear now seems to have been exaggerated. Recent NASA tests at Wright-Patterson Air Force Base showed that all orbiting spacecraft carry a built-in fire fighter: weightlessness.
To simulate fires in orbit, the scientists loaded test chambers containing high concentrations of oxygen into KC-135 jet transports and flew them through parabolic...