(c) The HLLV is approximately five times the size of the Space Shuttle, or comparable to a Boeing 747 airplane. The other vehicles are comparable or even larger in scale. Thus the (electrically propelled) Cargo Orbital Transfer Vehicle (COTV) is roughly 1 km in linear dimension and carries a 4000-ton payload from Low Earth Orbit (LEO) into Geostationary Earth Orbit (GEO). The Personnel Orbital Transfer Vehicle (POTV) carries some 160 passengers plus priority cargo from LEO to GEO; see Appendix B for details of the scenario. (d) The reference system design of RSR, 1978, as considered here has two options, based on the use of Si and GaAAAs solar (photovoltaic) cells, developed by Boeing and Rockwell, respectively. The Boeing/Si technology is more conservative and heavier than the Rockwell/GaA£As concept. (e) The injection of H20 and into the upper ionosphere can be very significant because these molecules produce molecular ions by charge transfer, or ion-molecule reactions with the ambient atmospheric 0+ ions, and molecular io^s recombine with electrons very much faster than atomic ions, by a factor 10 -ICr. The reason for this phenomenon is that dissociative recombination is very much faster than radiative recombination, or than three-body recombination at the low densities in question. Below 160 km the predominant atmospheric ions are 0^ and NO , which themselves recombine dissociatively with electrons, so that at these lower altitudes the change is not so obvious. However, the total electron content of the global ionosphere is of order 10J , and thus the injection of 10^32 - 10^33 H atoms, as H2O and (see Table 3), could have very significant effects on the ionosphere, depending on the rate of removal of the injected molecules and on how fast the ionosphere responds to such perturbations (see e.g., Mendillo, et al., 1975a, b, 1979; and Zinn, et al., 1978, 1979). (f) It is evident that the numerical values of the perturbation factor PF as quoted in Table 4 are not necessarily correct; however, the relative magnitudes are significant. The injection of water in Domain A is certainly important, and the potential importance of condensation in removing water from the ionsphere is evident. The characteristic time used in Domain C may not be appropriate, but the injection of hydrogen-containing species and of argon must be considered in this altitude region. (g) From Table 4 we see that even the very large energy deposition due to the kinetic energy of argon ions in the magnetosphere is not important on a global scale in that the PF is very much less than one. However, local effects can be important in a variety of altitude ranges. Some possible effects due to the HLLV second stage are examined briefly in Section 2.7. (Note that the ionospheric effects of microwaves, including ionospheric heating, are being considered elsewhere, under Task IV.) (h) Reference should be made to the early study of Kellogg, 1964. 1.3 APPROACH The approach adopted in the present study was the following. Technically, we began by identifying injectants in the different domains and characterizing their significance (see Section 1.2, especially Tables 1, 3, and 4). Then we outlined the relevant phenomenology to pinpoint areas needing
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