RELEASE OF LIQUID WATER FROM THE SPACE-SHUTTLE

Groundbased and onboard video images of a sunlit Shuttle Orbiter water dump are interpreted as showing that the continuous ∼1 mm diameter liquid stream quickly breaks up in near‐vacuum to form ice/snow particles of two characteristic sizes. Discrete large droplets (shown from laboratory measurements, to have diameters comparable with that of the initial coherent quasicylinder) are most evident in the close‐in photographs, and unresolved submicron “fog” from recondensation of overexpanded evaporated water appears to dominate the ground‐telescope photographs of the ∼2½ km long optically detectable trail. We estimated the mean diameter of the smaller particles from the spatial distribution of visible radiance using a model of their energy balance, (small) surface roughening as they sublime, and Mie scattering of pre‐dawn sunlight. The results are consistent with those from recent space‐tank simulations. © 1990 by the Chinese Geophysical Society