Waterhole that should provide an opportunity for optical ice cloud diagnostics. This experiment will be conducted in March/April 1980 and may be useful for the future. The ideal Domain B experiment would involve a rocket exhaust simulator making releases with varying speeds above and below the terminator for the ice crystals. The rocket exhaust simulator should produce F^O vapor with the same specific enthalpy as the SPS rockets used for the circularization, deorbit, and POTV burns) see Item F.2 in Appendix F). From a single sounding rocket launch during sunrise, many of the sublimation parameters could be varied, and the ice crystal size and inventory determined. Because of the critical impact of the sublimation question on the issue of ionospheric depletion, we would recommend that such an experiment be conducted. 2.5.4 The Current Status (Bernhardt — prepared after the workshop) Rapid vapor expansion produces cooling that may lead to condensation. The amount of condensation will depend on (1) the initial specific enthalpy (i.e., CpT/p) of the vapor, (2) the expansion geometry (such as a spherical versus a rocket plume release), and (3) the constituents of the exhaust. The amount of condensation also depends on whether condensation nuclei are formed by the vapor molecules themselves or by some foreign particles such as smoke, dust, salt, ions, etc. With these factors in mind, several vapor releases which have produced (or will produce) ionospheric modification are considered. The first release is the Saturn V/Skylab burn that produced the ionospheric depletions measured by Mendillo et al. (1975a,b). There seem to be good theories and measurements of the condensation in these rockets. The Saturn V ionospheric hole was produced by the second-stage burn. The second- stage propulsion systems consist of five J-2 LO2/LH2 rocket engines. This type of engine (J-2) was the same that is used by the Saturn IVB. The translunar injection burn of the Saturn IVB during the Apollo 8 mission produced a visible plume that was attributed to scattering of sunlight off of ice clusters. Analysis of photographs of the plume indicate that 5-10% of the exhaust condensed (Kung, Cianciolo, and Myer, 1975). The particle radius is estimated to be 70-100 A. The visible cloud lasted for more than two hours (Lundquist, 1970). A purely theoretical calculation of this effect by Wu (1975), using nonequilibrium condensation theory, gives 10.5% condensation with 17 A (radius) clusters. Using a simple model described in Bernhardt (1976), with modifications for rocket plumes, we calculate 12.2% condensation with a final cluster temperature of 200 K. Based on this research, it seems that the Saturn V condensation should be taken as 10%. Cluster size should be 70-100 A and the cluster lifetime is greater than 2 hours. The second release of interest is LAGOPEDO. Much more water vapor is expected to condense because of the high initial density of the Lagopedo release. For instance, the Lagopedo vapor density is 526 kg/ni at 1000 K temperature, while its Saturn V density is only 0.0146 kg/m'^ at that temperature. Our calculations indicate that 54% of this I^O vapor will be nucleated. The heat of vaporization released for H2O ice will prevent any of the CO2 from freezing.
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