ally give values between 0.5 x IO6 and 2 x IO6 m2/s as averages for Kuu in the lower stratosphere. Bauer (13) uses a collection of atmospheric measurements to show that for lengths greater than 1000 km, Kuu is no longer scale- or time-dependent. For this study, Kuu was chosen to be 2 x 106 m2/s. From scaling arguments (Appendix A), it is shown that L can be approximated by 2H(Kuy/Kzz)m, where H is the scale height. The values of Kzz used in the calculations varied from 2 m2/s at 60 km to 30 m2/s above 70 km. Ebel (14) gives values of Kzz that vary from 10 to 1000 m2/s over that altitude range. The use of values of K„ greater than 30 m2/s would decrease the predicted corridor effect in proportion to the square root of Kzz. However, even the largest values of Kzz given by Ebel would not be sufficient to eliminate the predicted corridor effect for H2 and H2O. In order that the fractional increase be readily detectable, 17 will be set equal to 0.2 and the minimum injection rate calculated from Comparison of Analytic and Numerical Model Predictions In this section, the predicted altitudes for which a detectable corridor effect can be expected for the hypothetical case of 400 HLLV launches per year for 10 years, as predicted by Eq. 9 and by the two-dimensional model, will be compared. The principal emissions from the HLLV that can be expected to modify atmosphere composition are water vapor, hydrogen, and carbon dioxide effluents in the rocket-engine exhaust, and nitric oxide formed during reentry. Water vapor and hydrogen deposition profiles are presented in Fig. 1; note the discontinuity at an altitude of 56 km, where the first stage, which uses methane as fuel, cuts off the second stage, which uses hydrogen as fuel, begins. Also note the large increase of the deposition rates as the vehicle approaches an altitude of 120 km; it results from the nearly horizontal character of the trajectory at the 120-km burnout. Figure 2 shows Q/Qmin as a function of altitude calculated from Eq. 9 for the injection of water vapor, hydrogen, and nitric oxide. From an examination of Fig. 2 it can be seen that no corridor effect is expected for water vapor or molecular hydrogen below 80 km, but above 85 km the corridor effect for both should be quite pronounced. The corridor effect for nitric oxide is predicted to be significant for altitudes between 60 and 90 km. The effects of the injection of water vapor and nitric oxide were also simulated in a modified version of the Ames Research Center's two-dimensional stratospheric model; see Borucki et al. (15) and the companion papers for H2O by Whitten et al. (16) for the descriptions of the model. Model predictions at seven altitudes are given in Fig. 3. The figure shows that at altitudes below 70 km, a general increase in the abundance of water vapor is predicted, but no corridor effect is expected. At 75 km, the water-vapor abundance peaks at latitude 30° N, the latitude at which the water vapor is assumed to be injection. At 85 km, the predicted corridor effect is quite pronounced; the peak is about 50% above the ambient value and about 35% above the abundance at lower latitudes. It is clear that results obtained with the Ames two-dimensional model and from Eq. 9 agree in predicting that a corridor effect for H2O should occur at altitudes above 75 km. There are, however, uncertainties in the model predictions that must be considered. These will be discussed in a later section.
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