Cotton Protective Apparel for the Space Shuttle

Abstract

All the materials for use either in a manned space flight or in a flight experiment, including materials of the spacecraft, crew provision, and equipment, must be evaluated and meet certain performance criteria as established during the Mercury, Gemini, Apollo, and Skylab programs. In addition to testing for the primary requirements of flame-resistance, odor, offgassing products, flash- and fire-point temperatures, cotton textile items were also considered as candidate space-shuttle, in-flight apparel on the basis of skin sensitivity, comfort, electrieal resistivity, colorfastness, and general protective features exhibited under certain conditions of flame and heat exposure.

Chemically-treated flame-resistant cotton fabries that have been approved for space-shuttle apparel include a two-ply sateen (244 g/m²), a filling sateen (153 g/m²), and a two-ply, mercerized, single-knit jersey (187 g/m²). These fabrics are being used to fabricate the total flight ensemble from underwear to coverall and outer jacket. Fabrics for the outer garments were dyed to NASA-specified shades of blue with stable vat dyestuffs, compatible with the flame resistant treatment.

These cotton fabrics were treated first with commerciat phosphonium salts and subsequently cured with gaseous ammonia. The process is more commonly referred to as the tetrakis(hydroxymethyl)phosphonium hydroxide/ammonia (THPOH/NH₃) method. A second finishing application was required in order for the finished textile items to meet the slightly oxygen-enriched environment of the spacecraft crew bay area. The final finishing process comprised adding on diammonium phosphate (DAP)/urea, drying, curing (90 s @177°C), and afterwashing. DAP is a more efficient flame inhibitant than the phosphonium polymer, thus the combination treatment served to impart higher resistance to ignition and sustained combustion, as required by NASA test standards.