The Emissivity and Absorptivity of Parachute Fabrics

Abstract

The use of parachutes for recovery of information and equipment from high-speed vehicles has directed attention to the heating problem which in some instances may be so severe as to cause destruction of the parachute. Consequently, the parachute engineer requires sufficient information on the heat-transfer characteristics of geometries resembling those of parachutes and on the heat-transfer properties of the materials used to allow a calculation of the temperature history of a descending parachute. In particular, the radiation properties of the parachute materials must be known since the parachute is receiving radiant energy from the sun and loses energy by radiation to the surroundings. The measurement of radiation properties for such parachute materials is more complicated than for solid surfaces since an appreciable amount of energy is transmitted by such fabrics. It is the purpose of this paper to describe the equipment which was used to measure the absorptivity for solar radiation and the long-wave-length emissivity for such parachute materials and to report these data for a number of important parachute materials.