released by an explosive rupture of the storage tanks in the lower ionosphere. A large amount of material exists on thee experiments, almost all of it in the form of contractor reports, in-house memoranda, and partially reduced data (Lundquist, private communication, 1979). A preliminary examination of that information suggests that the major result of interest to the ionspheric hole question concerns the degree of condensation experienced by the released water. Debus et al. (1964) estimated that approximately 85% of the water formed a cloud of fine ice crystals. Photographic records exist of the early development of the resultant ice cloud. Similar records of various fuel dump scenarios carried out during several Apollo missions (Lundquist, 1970) document cases of substantial condensation percentages at higher altitudes. As an ionospheric modification experiment, the Saturn High Water dumps were of little value. This shortcoming is due both to the altitudes of the releases and to the lack of appropriate ionospheric diagnostics. If the injections had occurred at F-region heights, the 15% of water vapor produced would have caused a large-scale ionospheric hole comparable to the Skylab effect. At 105 km and 165 km, no ill effects were produced as predicted in the preliminary planning document (Debus et al., 1964). It is possible that a more detailed examination of the photographic record of the ice cloud could lead to a better understanding of the condensation problem or to such atmospheric questions as the formation of high altitude noctilucent clouds. These were in fact considered at the time and, as described by Debus et al. (1964), "Noctilucent clouds were not observed, or if observed, went unrecognized." C. Current Status Participants in the June, 1979, SPS workshop re-examined the question of condensation in rocket exhausts in the light of past experiments and new theoretical calculations. Evidence taken from the High Water experiments of 1963 and the LAGOPEDO experiments of 1977 suggest that 80-100% of water deposited in the upper atmosphere (via explosives or ruptured storage tanks) quickly condenses. The water vapor resulting from a rocket exhaust plume, which has a significantly higher specific enthalpy (see item F.2 in Appendix F), may experience a significantly lower fraction of condensation, but uncertainties in this area suggest that 50-100% may still be the range of possibilities. Since the condensation process occurs very close to or in the rocket nozzle (in a time much less than 1 second), the degree of condensation would not be expected to exhibit appreciable diurnal or altitude dependence. Thus little difference should occur between Domains A, B, and C with respect to condensation. While the molecules that escape condensation are available for immediate aeronomic processes, the frozen component must still be considered. Translational processes (diffusion, gravitational settling, suborbital and/or orbital motions, and atmospheric escape) will obviously transport the
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