(Ref. 3.38) and taking into account the number of rocket engines to be used in the HLLV first stage, NO-injection rates have been estimated and are given in Table 3.3. Estimated nitric oxide perturbation ratios at these altitudes are also given in Table 3.3. The calculations were based upon observed odd nitrogen concentrations as given by Oliver et al. (Ref. 3.35) and Hudson (Ref. 3.17). These estimates indicate that, as in the case of carbon dioxide, nitric oxide injections from SPS-related spaceflight activity do not appear to be cause for concern at this time. Nitric oxide production due to reentry heating may be significant, however, and should be examined, but has not been considered in this preliminary analysis. The discussion in this section has centered on the potential for significant chemical perturbations in the stratosphere and mesosphere. Water vapor emissions have been identified as a potential cause for concern, particularly at altitudes above 50 km. The effects of increases in the water vapor content of the atmosphere at these altitudes are not clearly understood at this time. In addition to the potential effect on the ozone concentration distribution alluded to previously, the possibility of significant climatic effects due to increased cloud formation, for example, deserves serious consideration, particularly in view of our present lack of understanding of the overall water budget. The need for additional research in this regard is particularly acute; until our understanding in this area is advanced beyond Table 3.3. Estimated Nitric Oxide Injection Rates and Perturbation Ratios
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