CONF-7906180 Proceedings of the Workshop on the Modification of the Upper Atmosphere by Satellite Power System (SPS) Propulsion Effluents La Jolla Institute La Jolla, California June 25-27,1979 Sponsored by: U.S. Department of Energy Office of Energy Research Satellite Power System Project Division Under Contract 31-109-38-5033 June 1980 DOE/NASA Satellite Power System Concept Development and Evaluation Program
CONF-7906180 Dist Category UC-13 Proceedings of the Workshop on the Modification of the Upper Atmosphere by Satellite Power System (SPS) Propulsion Effluents La Jolla Institute La Jolla, California June 25-27,1979 Prepared for: U.S. Department of Energy Office of Energy Research Satellite Power System Project Division Washington, D.C. 20585 Prepared by: Ernest Bauer La Jolla Institute La Jolla, California Under Contract 31-109-38-5033 June 1980 DOE/NASA Satellite Power System Concept Development and Evaluation Program
FOREWORD The Satellite Power System (SPS) is a concept for obtaining baseload, i. e., continuous, electric power from the sun. It involves placing large arrays of photovoltaic cells in geostationary earth orbit, where they would receive continuous illumination by the sun, except for periods of as much as 40 minutes per night near the equinoxes, when the arrays would be in the earth's shadow. The power would be transmitted to the ground using microwave beams, according to the reference system concept. The scale of the reference system is very large, involving 5-GW power units in space (by comparison, a present day nuclear power reactor produces about 1 GW). One 5-GW power satellite would have a solar collector array of area 5 x 10 km and a mass of 37,000 - 50,000 metric tons in orbit; the microwave receiving antenna on the ground would cover a 10 x 13 km ellipse. The reference concept presumes that two satellites would be built each year between 2000 and 2030 to provide some 25% of total U. S. electric power needs at that time. Environmental impact studies are divided into five major tasks, namely: 1 - Health and ecological effects of microwave radiation 2 - Other effects on health and the environment 3 - Effects on the atmosphere 4 - Effects on communication systems that use the ionosphere 5 - Electromagnetic compatibility and radio frequency interference. The present study is part of Task III. The main effects considered result from space transportation operations -- in particular the injection by rocket engines of water and hydrogen between 70 km altitude and geostationary earth orbit (36,000 km radius) -- and with the injection of argon ion beams into the plasmasphere at the higher altitudes. The object of the present study is to identify atmospheric research needs, including both theory and experiment, for the evaluation of upper atmospheric environmental effects due to SPS construction and deployment. A list of participants in the workshop is given in Appendix A.
TABLE OF CONTENTS FOREWORD................................................ Hi ABSTRACT .............................................................. 1 ACKNOWLEDGEMENT........................................................ 2 SUMMARY...................................... .......................... 3 1 INTRODUCTION........................................................ 7 1.1 The Context of the Present Study......... 7 1.2 The Significance of Different Injections....................... 7 1.3 Approach....................................................... 10 2 EFFECTS OF INJECTANTS IN THE 70-120 km RANGE........................ 21 2.1 Introduction...................... 21 2.2 Injectants..................................................... 22 2.2.1 H2O/H2 Injections...................................... 22 2.2.2 NO Production on Reentry (Park)........................ 22 2.2.3 Construction Debris (Whitten).......................... 22 2.3 Water Vapor in the Mesosphere and Lower Thermosphere (Ellsaesser)............................................ 23 2.4 High-Altitude Clouds........................................... 25 2.4.1 Noctilucent Clouds (Ellsaesser, Turco) ................. 25 2.4.2 Nacreous Clouds (Elsaesser)............................ 26 2.5 Condensation and Re-evaporation in Rocket Exhausts............. 27 2.5.1 Prefatory Comments (Bauer) ............................ 27 2.5.2 The Overall Problem (Mendillo) ....................... 27 2.5.3 Experimental Studies, Mainly in Domain B (Pongratz). . . 31 2.5.4 The Current Status (Bernhardt — prepared after the Workshop................................... 32 2.6 Spreading of Rocket Exhaust Clouds: Local, Regional, Zonal and Global Effects (Bernhardt)................................ 33 2.7 Energy and Momentum Transfer Due to Rocket Exhaust Plumes (Forbes)................................................ 36 2.8 Photochemical Effects (Turco) ................................ 36 2.9 Ionospheric Conductivity and Atmospheric Electricity (Vondrak).................................................... 38 2.10 Potentially Important Phenomena (Vondrak) .................... 39 2.11 Atmospheric Experiments ...................................... 40 2.11.1 Water Vapor in the Mesosphere (Sundararaman).......... 40 2.11.2 Noctilucent Clouds (Sundararaman, Turco).............. 40 2.11.3 NO Production on Reentry (Whitten).................... 42 2.11.4 Rocket Observations (Mendillo)........................ 42 2.11.5 Airglow (Zinn)........................................ 43 2.11.6 Cloud Dispersion (Bernhardt).......................... 46 2.11.7 Mesospheric NO (Turco)................................ 46 2.11.8 Conductivity Experiments (Vondrak)..................... 49
3 EFFECTS OF HYDROGEN AND WATER INJECTIONS ON THE IONOSPHERE.......... 51 3.1 Phenomenology of Hydrogen in the Upper Atmosphere ............ 51 3.1.1 The Overall Problem.................................... 51 3.1.2 The Fate of ^O/H? Injected in the Thermosphere (Zinn) . 51 3.1.3 Some Details of the Distribution of Propulsion Effluents (Park) ............................... 52 3.1.4 Effect of H2O/H2 Injections on Geocoronally Scattered Lyman-a and Lyman-0 Radiation (Prasad and Forbes). ... 55 3.2 Morphology of Perturbed Ionospheric Regions (Fedder).......... 55 3.2.1 Ionospheric Depletion due to a Single Burn............ 55 3.2.2 Ionospheric Depletion due to the Multiple Launches during SPS Construction......................... 57 3.2.3 Dissociative Recombination of and 0H+ (Bernhardt — prepared after the Workshop) ..... 58 3.2.4 Verification of the Extent of the Depleted F-Region of Section 3.2.2............................... 60 3.2.5 Possible Experimental Verification: Some Relevant Natural Phenomena (Carlson — prepared after Workshop) . 60 3.2.6 Effects of the Reduced Ionization on HF Propagation (Bauer)......................................... 61 3.2.7 Ionospheric Irregularities Associated with the Depleted Regions ............................... 62 3.3 Effects on Satellite Drag (Curtis)............................ 63 3.4 Airglow (Turco).............................................. 64 3.5 Potentially Important Phenomena (Vondrak) .................... 66 3.6 Atmospheric Experiments ...................................... 67 3.6.1 Rocket Experiments (Pongratz).......................... 67 3.6.2 LAGOPEDO-Type Releases (Fedder)........................ 68 3.6.3 Ionospheric Irregularities (Bernhardt) ................ 68 3.6.4 Other Experiments (Aikin).............................. 69 4 MAGNETOSPHERIC EFFECTS............................................. 71 4.1 Introduction.................................................. 71 4.2 Phenomenology of H2O/H2 Injection in the Plasmasphere and Magnetosphere (Zinn).................................... 71 4.3 Injection of keV Plasma (Palmadesso).......................... 72 4.3.1 Potential Consequences........... 72 4.3.2 Phenomenology Issues to be Resolved.................... 73 4.4 Some Possible Effects...................... 73 4.4.1 Enhancement of Trapped Radiation (Chiu)................ 73 4.4.2 Dumping of the Radiation Belts (Aikin, Cladis) ........ 74 4.4.3 Depletion versus Enhancement of the Radiation Belts (Curtis)................................. 75 4.4.4 Phenomenology Associated with Large Space Structures (Vondrak)....................................... 76 4.4.5 A Ring of Neutral Gases Associated with the Satellite (Garrett)....................................... 76 4.5 Synthesis of Magnetospheric Effects and Possibly Important Phenomena (Chiu)........................................ 77
4.6 Conceivable Atmospheric Experiments ............ ....... 78 4.6.1 High-Altitude Injection of Gases, Plasmas, and Electron Ion Beams (Pongratz)................... 78 4.6.2 Relevance of SCATHA (P78-2) to SPS (Chiu).............. 78 4.6.3 Cameo, Firewheel and Other Experiments (Chiu).......... 79 4.6.4 Starfish and Other Past Nuclear Explosions (Palmadesso) ................................... 80 5 CONCLUSIONS AND RECOMMENDATIONS .................................... 82 5.1 Introduction. ......................... 82 5.2 Permanent Depletion of F-Region Ionization..................... 82 5.3 Problems Involving ^0, H2, and NO............................. 83 5.4 Problems Involving Argon Ion Injections in the Plasmasphere and Magnetosphere (Carlson and Vondrak) ................ 84 APPENDIX A: List of Workshop Participants ............................ A.l APPENDIX B: Scenario for SPS Construction ............................ B.l APPENDIX C: Abbreviations and Acronyms.................................. C.l APPENDIX D: Ambient Atmospheric Loadings for Different Species..........D.l APPENDIX E: References.................................................. E.l APPENDIX F: Supplementary Material...................................... F.l LIST OF FIGURES No. Title Page 1 SPS Heavy Lift Launch Vehicle Trajectory and Exhaust Products Data......................................................... 9 2 Mesospheric Water Vapor Measurements............................ . 24 3 Horizontal Dispersion of a Function of Travel Time — Data for the Upper Stratosphere and Mesosphere ....................... 35 4 Mesospheric Nitric Oxide Measurements ............................ 47 5 POTV Effluent Deposition.......... 56 B .l Scenario for Construction of Two 5 GW Satellites/year...........B.2 D.l Atmospheric Species Concentrations........................ D.2 LIST OF TABLES No. Title Page S .l Propulsion Injectants into the Upper Atmosphere ....... ..... 4 S .2 Recommendations for Research....................................... 5 1 SPS Injections into the Upper Atmosphere............................ 12 2 Atmospheric Domains ............................................... 14 3 Atmospheric Injection Rates for each Domain ....................... 15
4 Perturbation Factor, PF of Eq. 1, for each Domain ........ .... 16 5 Task Assignments for the Workshop................................. 17 6 Time Schedule for Study...................... 20 7 Sketch of Cloud Dispersion in the Mesosphere....................... 34 8 POTV Effluents..................................................... 55 B.l Space Transportation Vehicles for SPS Project ..................... B.3 B.2 Emission of the Main Burn of the HLLV Second Stage. .................B.5 D.l Representative Values of the Global Energy Flow in Geospace .... D.5
ABSTRACT This report presents results of a workshop held in June, 1979, to identify research needs for evaluating environmental impacts on the upper atmosphere (here defined as greater than 70 km) due to Satellite Power System (SPS) transport, i.e., propulsion and reentry. The substantial injections of water and hydrogen therefrom may lead to global-scale regions of reduced ionization in the ionospheric F-Region that may have a serious impact on worldwide HF radio communications; and the resulting possibly significant increases in mesospheric humidity and probable cloudiness could affect climate and remote sensing from satellites. The large injections of argon ions of kilovolt energy between low earth orbit and geostationary orbit may alter substantially the trapped radiation environment of the magnetosphere and thus the hazard for personnel and electronic equipment. During the workshop it became clear that the highest priority for SPS environmental assessment goes to theoretical studies needed before acceptable atmospheric experiments can be designed. Problems to be addressed include: the extent, magnitude, and variability of the predicted depletion in F- region ionization together with descriptions of water and hydrogen injections into the atmosphere characteristic of SPS vehicles and flight profiles; the long-term variations in mesospheric humidity and cloudiness with and without SPS operations; and the description of condensation and evaporation processes of water exhausted from high-altitude rockets in order to predict mesospheric contrail formation and dissipation. Furthermore, in considering argon ion rocket transport to geosynchronous orbit, the stopping and lifetime of the argon ion beams and consequent changes in the radiation belts, especially as they affect spacecraft, should also be addressed.
ACKNOWLEDGEMENT It gives me great pleasure to thank everybody who participated in this workshop for their enthusiastic and effective work. The participants not only cooperated during the initial telephone phase of the study and put in the long hours needed during the workshop but also provided a better than 90% response to the review draft which was circulated to them.
SUMMARY In the context of reviewing the potential environmental impact of SPS construction and deployment on the upper atmosphere, the present study was designed to identify particular atmospheric experiments and theoretical studies which should be given high priority for support; it also served as a follow-up to the initial environmental impact workshops held at Argonne National Laboratory in August and September of 1978 (Brubaker, 1979; and Rote, 1978) *. The present study deals only with effects above 70 km where worldwide rather than localized effects are anticipated. The study was conducted by a panel of 27 scientists and engineers who met in La Jolla, CA, on 25-27 June 1979; the membership is listed in Appendix A. The approach used was to identify the injectants in different altitude regions and to review the anticipated impact of each (see Table S.l) in order to identify critical research requirements (see Table S.2). While emphasis was originally placed on the design of atmospheric experiments, it quickly became apparent that considerable theoretical study effort is needed before one designs dedicated atmospheric experiments. *References are listed in the bibliography, Appendix E. **See Appendix C for a definition of abbreviations, acronyms, and specific technical terms used here. The single most critical problem identified in the present study is the impact on global HF ** radio propagation of a band of permanently depleted ionization in the F-region as a result of launch operations. Some of the hydrogen and water emitted from the exhaust of the second stage of the HLLV rocket in the 70-120 km altitude region diffuses upward and leads to the replacement of atomic 0+ ions with molecular ions H2O and 0H+. Molecular ions recombine with electrons much more rapidly than do atomic ions, and thus replacing atomic with molecular ions leads to a reduction in effective ionization. This effect is significant above 160-180 km only, as at+lower altitudes the main natural atmospheric ions are molecular, NO and O2 The physical extent of the region could cover a band at the latitude of launch (28.5° for Cape Canaveral) of north-south extent of several thousand kilometers, extending around the globe at the latitude of injection. The effective ionization may be reduced by a factor of two at night and by 10-20% in the daytime. The critical consequence of such a reduction in ionization is that it drastically reduces the available HF band that can be used for long-range radio communication at a time when this frequency band is already heavily overcommitted internationally (see Section 3.2.6 for a discussion, Section 5.2 for research recommendations, and item F.3 of Appendix F for a brief account of this problem). Other problems associated with water and hydrogen releases involve the general enhancement in mesopheric humidity and cloudiness with, as opposed to without, SPS operations, including the possible production of long-lasting contrails. These changes may have some climatic impact and could impact
Table S.l Propulsion Lnjectants into the Upper Atmosphere
Table S.2 Recommendations for Research.
remote sensing from satellites. Studies called for in this context include long-term measurements of water vapor concentrations and cloudiness in the mesosphere, and the description of condensation and evaporation of water vapor emitted in high-altitude rocket exhausts. The injection of water and hydrogen, as well as that of nitric oxide (NO) due to atmospheric heating from reentering spacecraft, may enhance the airglow and may also affect the long-range propagation of relatively low frequency radio waves (VLF and ELF) by changing the ion chemistry in the ionospheric D-region. Enhancing the hydrogen concentration in the upper atmosphere will increase the drag on low-altitude orbiting satellites; the significance of this effect is not yet established. In going from a low-altitude parking orbit to geosynchronous orbit, the current SPS concept calls for the use of argon ion engines. The quantity of argon injected into the atmosphere above 500 km is very large indeed, relative to the ambient atmospheric mass, and it is not yet established how rapidly the ion beams will be stopped or what the lifetime and energy loss and gain processes of the ions are. The injection could lead to significant changes in the earth's radiation belts, possible changing the radiation environment of spacecraft in orbit. The structure of the report is the following. Section 1 reviews the injections of different materials in different altitude ranges, amplifying Table S.l and attempting a quantitative estimate of the relative significance of the different injectants. It also reviews how the study was conducted. Section 2 treats problems due to the very large propulsion injections in the 70-120 km altitude region. Section 3 discusses the general problem of hydrogen and water injections due to SPS in the ionosphere. Section 4 reviews effects on the magnetosphere in the passage from the parking orbit (LEO = Low Earth Orbit, at 500 km) to geosynchronous orbit (GEO at 36,000-km altitude, or 6.5 earth radii away). Section 5 presents the conclusions and recommendations of the study. Appendix A lists the membership of the present workshop, Appendix B gives a brief summary of the SPS transportation system, Appendix C defines abbreviations and acronyms used here, and other appendices furnish various technical details.
1 INTRODUCTION 1.1 THE CONTEXT OF THE PRESENT STUDY The Satellite Power System (SPS) implies a very large space construction project, involving the annual construction in orbit over a 30-year period of two arrays of solar cells, each roughly 5 x 10 km in dimension and weighing 35,000-50,000 metric tons. Each array would provide 5 GW of baseload electric power, which would be beamed to the ground, using 2.45 GHz microwaves. Over a 30-year construction period this effort would provide 60 such satellites, supplying some 20-25% of U.S. anticipated electric power needs by the year 2030. The total propulsion effluents injected into the upper atmosphere per year would include 140,000 metric tons of hydrogen, 800,000 of oxygen and 25,000 of argon, and 6 x 101 joules of energy. In the context of reviewing environmental impacts on the upper atmosphere, the present study is designed to identify research needs, in particular for atmospheric experiments as a part of currently ongoing research, and to follow up on workshops held at Argonne National Laboratory in August and September, 1978 (Rote, 1978, and Brubaker, 1979). Effects of microwaves, effects due to launch and construction operations on the surface, and effects on communication systems are not addressed here. It became apparent during the workshop that under the constraints of present understanding and the time requirements for the current SPS assessment program, certain critical questions in phenomenology must be analyzed in more detail, which will require a lot of time and funds, before one can design and execute useful atmospheric experiments. Thus the orientation of the study changed to emphasize these analytical requirements. 1.2 THE SIGNIFICANCE OF DIFFERENT INJECTIONS The atmospheric disturbances considered cover a wide range of materials and of altitudes; see Table 1* for the injection due to each element of the system and Appendix B for more details of the scenario; also RSR, 1978. The principal material injectants in the upper atmosphere are H2O and H2 from chemical rocket exhausts, NO due to reentry heating of air, and argon ions in the keV energy range with their neutralizing electrons from electrical propulsion. Material injections, but not necessarily their atmospheric effects, occur in three general atmospheric domains that are described in Table 2. Domain A, 70-120 km, corresponds to the main burn of the Heavy Lift Launch Vehicle (HLLV) second stage, and to reentry heating. Domain B corresponds to Low Earth Orbit (LEO), approximately 500 km, the circularization and deorbit burns of the HLLV, while Domain C corresponds to transport from LEO to Geostationary Earth Orbit (GEO), at approximately 36,000 *Tables appear consecutively at the end of this section.
km from the surface of the earth. Figure 1 shows the altitude distribution of injectants from HLLV, and Table 3 gives the overall injection rates in each domain. To estimate the importance of a given injectant in a specific domain requires not just the injection rate and the ambient burden in the domain but also a characteristic residence time for the different injectants in the various domains. Some initial estimates of residence times are listed in Table 2. For water they are typically characteristic times for transport out of the domain (note the large effects of condensation!), while for NO where photochemical destruction of odd nitrogen (N, NO, NO2) is more rapid than transport, this sets the limit. In Domain C the energy equilibration time may be used, but here in particular there are large uncertainties because the phenomenology is not well understood (see Sections 4.3 and 4.4). Both the concepts and the numerical values must be examined and modified as necessary (see also Kellogg, 1964). Table 4 represents an initial attempt to describe the loading of the atmospheric injections in each domain in terms of a dimensionless "Perturbation Factor" or PF which is defined as pp _ (expected concentration change) (ambient concentration) In order to estimate a numerical value for the PF, some estimate of the expected concentration change resulting from the specified injection must be made. To lowest order, the concentration change may be estimated by the expression: (injection rate) x (residence time), in which the injection rate is given in units of mass/unit volume/unit time. An equivalent expression for the lowest-order PF is easily seen to be (total mass injection rate into domain) x (residence time in domain)/(total ambient loading in domain); this latter expression is used throughout the remainder of this report. The concept of a PF is useful in the limited context of suggesting the general areas in which problems may be expected. (Thus the same methodology shows that at altitudes below 70 km or so, only local rather than global effects may be expected; see Brubaker, 1979). Values of PF as large as a few percent indicate that effects of a given injection should be looked for, while PF values in excess of unity raise a warning flag. The detailed numerical values are generally not significant, partly because the numerical value of the characteristic or residence time is generally not well known and partly because details of the chemistry, etc., limit the applicability of the concept. (Thus we do not list separate PF values for 1^0 and I^.) The following points should be noted in connection with Tables 1-4: (a) The ambient loadings of injectants as used here are presented in Appendix D. (b) The atmospheric injections are large on an absolute scale because of the overall scale of a 5-GW SPS unit system, which corresponds to an orbital mass of 35,000-50,000 metric tons. Note that the overall effect of injectants tends to be significant on a global, rather than on a regional or local scale only above 75 km because of the very large mass of the lower atmosphere.
Figure 1. SPS Heavy Lift Launch Vehicle Trajectory and Exhaust Products Data
(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
further study in order to reduce uncertainties in the environmental impact of the SPS transportation system to acceptable levels. The initial object was to identify atmospheric experiments in this context, but many current questions first need theoretical answers before one goes to the complication of atmospheric experiments. The organizational plan was the following, designed to produce results quickly and with optimum input from a wide range of experts. A strawman draft (Bauer, 1979) was prepared to set up the structure of the study and to define questions to be addressed. The document was circulated to the panel a month before the workshop, and during the workshop the various experts were asked to revise specific sections of the draft. Immediately afterwards a review draft was prepared and sent to the participants and to the other people listed in Appendix A. The final report was based on the responses received, which include a number of additional contributions. Table 5 lists the final task assignments as they were carried out, and Table 6 outlines the overall schedule of the study.
SPS INJECTIONS INTO THE UPPER ATMOSPHERE TABLE 1
TABLE 1 - SPS INJECTIONS - Continued. Structural debris: if 1% of total mass brought into GEO is lost per year, either from LEO or from GEO, taking the amount and proportions from RSR,1978,p.59 , some AxlCr kg/year will result from reentry burnup and presumably be deposited in the mesosphere. This is small compared with the natural meteoroid infall of order 4x10? kg/year. Microwaves. 2% increase in heating rate in the mesosphere and 3% in the stratosphere, both locally over the rectenna (Brubaker & Rote, Oct. 1978). Small on a global basis. Ionospheric heating being studied under Task IV. See Appendix B for more details of the scenario. Note that the figures in this scenario are slightly different from the Boeing/Si scenario used in Table 4. The present Si (heavy) scenario of COTV + POTV flights calls for annual use of 2400 metric tons of hydrogen (vs 2100 for Boeing) and 20,00l) metric tons of argon (vs 25,00'0).
TABLE 2 ATMOSPHERIC DOMAINS
TABLE 3 ATMOSPHERIC INJECTION RATES FOR EACH DOMAIN
TABLE 4 PERTURBATION FACTOR, PF OF EQ. 1, FOR EACH DOMAIN*
TABLE 5 TASK ASSIGNMENTS FOR THE WORKSHOP Park*, Whitten Whitten*, Park, Vondrak Ellsaesser*, Sundararaman Ellsaesser*, Sundararaman, Turco Ellsaesser*, Sundararaman, Turco Ellsaesser*, Sundararaman, Turco Mendillo*, Park, Bernhardt, Zinn Bernhardt*, Brubaker, Forbes, Bauer Forbes*, Brubaker, Sundararaman Turco*, Prasad, Garrett Vondrak*, Fedder, Garrett Vondrak*, Rote, Aikin, Whitten Sundararaman , Ellsaesser, .Turco Sundararaman , Ellsaesser, Turco Whitten*, Park Mendillo*, Pongratz Zinn*, Turco, Prasad Bernhardt*, Brubaker, Forbes 2.2.2 NO Production on Reentry 2.2.3 Construction Debris 2.3 Water Vapor in the Mesosphere and Lower Thermosphere 2.4 High-Altitude Clouds 2.4.1 Noctilucent clouds 2.4.2 Nacreous Clouds 2.5 Condensation in Rocket Exhausts 2.6 Spreading of Exhaust Clouds: Local, Regional, Zonal, Global Effects 2.7 Energy & Momentum Transfer due to Rocket Plumes 2.8 Photochemical Effects 2.9 Atmospheric Electricity: Conductivity in the Lower Ionosphere 2.10 Listing of Potentially Important Phenomena 2.11 Atmospheric Experiments: A. Water Vapor in the Mesosphere B. Noctilucent Clouds C. NO Production on Reentry D. Rocket Observations E. Airglow F. Cloud Dispersion
TABLE 5 - TASK ASSIGNMENTS FOR THE WORKSHOP - Continued Turco*, Prasad, Park Vondrak*, Fedder. Garrett Aikin*, Whitten, Forbes, Rote Zinn*, Aikin, Rote» McCormac Zinn*, Aikin, Rote Park, Bauer (prepared after the workshop) Prasad, Forbes Fedder*, Richmond, McCormac, Zinn Curtis*, Forbes, Garrett Turco*, Forbes, Zinn, Prasad Pongratz*, Mendillo, Prasad Vondrak*, Rote, Mendillo, Zinn Pongratz*, Mendillo, Simmons, Prasad Fedder*, Pongratz, Bernhardt, McCormac. Bernhardt*, Mendillo, Palmadesso, Richmond Aikin*, Whitten, Forbes, Rote Zinn*, Aikin, Chiu, Rote McCormac, Carlson G. Mesospheric NO H. Electric Conductivity I. Other Experiments 3.1 Phenomenology of Hydrogen in the Upper Atmosphere 3.1.2 Fate of H^O/H^ injected in the Thermosphere 3.1.3 Some Details of the Distribution of Propulsion Effluents 3.1.4 Effect of H2O/H2 Injections on Geocoronally Scattered Lyman -a and Lyman -B Radiation 3.2 Morphology of Perturbed Ionospheric Regions 3.3 Effects on Satellite Drag 3.4 Other Phenomenology: 3.4.1 Airglow 3.4.2 Condensation and Re-evaporation in Rocket Exhausts 3.5 Listing of Potentially Important Phenomena 3.6 Atmospheric Experiments: A. Rocket Observations B. Lagopedo-Type Releases C. Ionospheric Irregularities D. Other Experiments 4.2 Phenomenology of H 0/H 2 2
TABLE 5 - TASK ASSIGNMENTS FOR THE WORKSHOP - Continued Palmadesso*, Chiu, Curtis, Garrett, Cladis Chiu*, Carlson, Vondrak, Palmadesso , Cladis Aikin*, Curtis, Fedder, Carlson Curtis Vondrak*, Garrett Chiu*, Vondrak, Rote, Richmond Pongratz*, Fedder Chiu*, Garrett, Carlson, Palmadesso , Pongratz, Cladis Chiu*, Carlson, Garrett Palmadesso*, Zinn, McCormac Bauer, Carlson, Vondrak 4.3 Injection of a kev Argon Plasma 4.4 Some Possible Effects 4.4.1 Enhancement of Trapped Radiation 4.4.2 Dumping of the Radiation Belts 4.4.3 Depletion vs. Enhancement of the Radiation Belts 4.4.4 Phenomenology associated with large space structures 4.5 Synthesis of Effects, and Possibly Important Phenomena 4.6 Conceivable Atmospheric Experiments: A. Injection of Gases, Plasmas and Beams B. The Relevance of SCATHA to SPS C. Firewheel and other relevant Experiments D. Starfish, and other past nuclear explos ions 5. Recommendations
TABLE 6 TIME SCHEDULE FOR STUDY A. Overall Schedule 1 April 1979 - Work began 1 May 1979 - Panel established 1 June 1979 - Straw man draft report to Panel Members 25-27 June 1979 -■ 3-day Workshop 30 July 1979 - Revised Report to Panel Members 30 August 1979 - Comments received from Panel Members by this date 4 September - Final report preparation begun 14 September - Report to Reviewers (very quick turnaround needed ) 30 November 1979 - Final Report due at Argonne National Laboratory B. Outline of Workshop 1/2 day - General Introduction 1 day - Working groups (see Table 5) met separately to prepare their briefings to the panel as a whole, and their revised write-ups 3/4 day - Working group chairmen reported to the group as a whole (since there were some 30 separate presentations, this part of the program was very tight and over-ran its allocated time) 1/4 day - Summary of conclusions and recommendations
2 EFFECTS OF INJECTANTS IN THE 70-120-km ALTITUDE RANGE 2.1 INTRODUCTION The injectants are discussed in Section 2.2. The ambient levels of water vapor and of noctilucent clouds are reviewed in Sections 2.3 and 2.4, respectively, since the predicted enhancement as described by PF = 0.07 (see Table 4) is so large that possible changes in both water vapor and clouds must be evaluated. We must know both the mean levels of these quantities and also their fluctuations, so as to be able to evaluate potential impacts. Condensation has been observed in rocket exhausts in this altitude range (see Benech and Dessens, 1974) as well as at high altitudes, which could give rise to a significant enhancement in mesospheric cloudiness, as discussed in Section 2.5. The whole issue of condensation and re-evaporation in rocket exhausts is important from the standpoint of the absorption and, in particular, scattering of sunlight and earth shine, which affects the global climatology as well as optical remote sensing. Additionally, the issue is also critical for the overall effect of water injections, especially at the higher altitudes, near LEO; reference to Table 4 shows that water sediments out of Domain B much more rapidly if deposited in the atmosphere as an aerosol than as a gas, giving rise to a very much smaller perturbation factor or PF. The problem of condensation and re-evaporation was addressed by two groups (see items 2.5 and 3.4.1 of Table 5). A discussion also was given by P. Bernhardt after the workshop. These three discussions are presented verbatim as Section 2.5. Section 2.6 treats the spreading of rocket exhausts, on various scales, which could be very important both as far as the impact and the experimental simulation of an injection are concerned. Rocket exhausts deposit a large amount of energy in the atmosphere: Would this activity be expected to produce any observable effects? This question is raised in Section 2.7. Photochemical effects, including enhancement or reduction in ionization, possible changes in ozone and other neutral species, and changes in airglow, are reviewed in Section 2.8, and changes in atmospheric conductivity related to these changes in ionization are treated in Section 2.9. One very important effect of H2 injections from the HLLV second stage burn is the ionospheric depletion associated with the formation of H20+ and OH ions in the F-region as a consequence of the upward diffusion of hydrogen from the 70-120-km altitude region. This problem is discussed in Sections 3.1 and, especially, 3.2. The topics discussed above relate to phenomenology. The overall significance of these possible changes is reviewed in Section 2.10, and in the light of the phenomenology and of the significance of the effects a listing of atmospheric experiments that merit consideration is given in Section 2.11.
2.2 INJECTANTS 2.2.1 H2O/H2 Injections The amounts and altitude profiles of injections are shown in Fig. 1 (see also Appendix B, Table B.2) and also in Tables 1, 3, and 4. To maximize the thrust per unit propellant from a rocket engine, many rocket engines are run fuel rich so that the effective molecular weight of the exhaust is relatively low. In the present case, approximately 30% of the hydrogen atoms in the exhaust are emitted as H2 rather than as H2O. 2.2.2 NO Production on Reentry (Park) Every object reentering the earth's atmosphere is slowed down by friction, and the kinetic energy lost by the reentering body goes to heat up air to rather high temperatures. The amount of air heated depends upon the projected area of the body, its speed, the reentry time, and the ambient air density. Temperatures in excess of 2000 K are achieved, and at these temperatures some nitric oxide is produced, and "freezes in" as the air cools. For an entry vehicle of the size, mass, and shape of the HLLV, the amount of nitric oxide expected to be produced is approximately 22% of the mass of the vehicle. The NO produced will be distributed between 55 and 100 km in altitude, the peak being around 70 km (Rakich, Bailey, and Park, 1975; Park, 1979, to be published). 2.2.3 Construction Debris (Whitten) During construction of the SPS satellites in space, there will certainly be some waste material or lost items. Even though a serious effort will be made to minimize any losses, yet, presumably, some of this material will reenter the earth's atmosphere. Small pieces will burn up on reentry, producing fine (micron or submicron sized) particles analogous to meteoritic dust, as well as a small amount of NO due to reentry heating. Large objects, such as Cosmos 954 or Skylab, may maintain their integrity during reentry, producing NO and a possible ground-level hazard. Other objects, such as large, light sheets of material with appropriate aerodynamic characteristics, could be expected to reach the earth's surface without ablation, giving rise to troublesome effects. The structural material for the satellites will be largely graphite composite (see RSR, 1978, p. 58ff), which will burn up on reentry, but there will be a certain amount of Al and Si/SiO? that will presumably form small oxide particles. Regarding the quantity of material involved, lacking other information, it will be assumed here that 1% of the total mass of a 5-GW system is lost each year. From RSR, 1978, p. 59, this loss gives a mass injection rate of (3-5) x 10^ kg/yr, perhaps half metal (Fe, Cu, etc.) and half stony (SiC^, A^O^). This quantity is small compared with the annual mass injection of meteoritic material, which is of the order of 4 x 10' kg/yr (see Park and Menees, 1978, p. 4033); thus the effect of such structural debris is probably negligible unless some exotic material such as teflon,
which is present in the debris but not in meteors, is deposited in the ablation region. The probable deposition of such materials and their possible effects are not known. A recent paper (Kessler and Cour-Palais, 1978) estimated the potential for the formation of a permanent belt of satellite debris around the earth. As visualized in their study, it is highly probable that debris fragments may strike a large satellite in the next decade) some evidence indicates that this may already have occurred). Such an impact would produce many more fragments in a variety of orbital inclinations. According to their calculations, given the present launch rate and estimated population of existing satellites and debris, the near-earth orbital environment could be approaching a critical point around the year 2000 wherein such debris collisions would lead to a chain reaction type of process. The end result would be the creation of an artificial debris cloud around the earth. Not only would such a belt be a very real threat to an SPS and other satellites, but an SPS could exacerbate the situation. Although the conclusions of Kessler and Cour-Palais are somewhat tentative, they must be taken seriously as a possible environmental effect of global significance. 2.3 WATER VAPOR IN THE MESOSPHERE AND LOWER THERMOSPHERE (Ellsaesser) At present there are very few measurements of the water vapor concentration in the mesosphere, most of which are rocket measurements at high latitudes (Arnold and Krankowsky, 1977; Rogers et al., 1977; and data from the AFGL SPIRE flight [J. S. Garing, AFGL, private communication]), suggesting a water vapor mixing ratio of 5 ppmv. Radford et al. (1977) using groundbased microwave radiometry, obtained a mixing ratio as high as 15 ppmv, but this seems much too high to understand on physical grounds. Figure 2 shows all presently available data. The longest and most generally accepted series of ^0 observations above the tropopause are those of the MRF (British Meteorological Research Flights) and of Mastenbrook (1968, 1971, 1974). These indicate a decrease in mixing ratio for the first 1-3 km above the tropopause, both polar and tropical, to values of 3-5 ppmv (parts per million by volume, i.e., molecular rather than mass mixing ratio) near 19-20 km. Above 20 km there is a fairly consistent tendency toward both higher mixing ratios and greater uncertainty in the data. Mastenbrook (1974), Harries (1976), and Penndorf (1978) have all interpreted these and other observations as showing a constant mixing ratio from the lower stratosphere up to 28-35 km, with the suggestion of an increase at higher levels. Below 20 km these two series of observations show seasonal cycles decreasing in amplitude with distance above tropopause, and a tendency for a biomodal distribution. Most soundings are of the "dry" type showing mixing ratios 3 ppmv, while perhaps 20% of the soundings are of the "wet" type showing mixing ratios above 10 ppmv. These series also support a long-term trend with almost a doubling between 1952 and 1973 and a decrease since then of at least twice the rate of the earlier increase. Beyond these variations, these data series show remarkably little variability.
Figure 2. Mesospheric Water Vapor Measurements
Current theory suggests that the only variation in H20 mixing ratio to be expected above 20 km is that due to oxidation of CH^, methane. Since CH^ probably enters the stratosphere through the tropical tropopause at a mixing ratio of approximately 1.6 ppmv, it could at most add 3.2 ppmv to the HgO mixing ratio passing through the tropical tropopause "cold trap." At -80 C and 100 mb this is 5.5 ppmv and would lead to ~ 9 ppmv as a maximum possible F^O mixing ratio in the upper stratosphere. However, as indicated above, current data indicates a decrease in mixing ratio from the tropical tropopause to a value near 4.5 ppmv, near 19-20 km. This decrease suggests a stratospheric sink for ^0, but in the absence of an identified sink it must be regarded as currently unexplained. Since the methane concentration also decreases between the tropopause and 20 km, it can no longer add as much as 3.2 ppmv of H20 by oxidation at higher levels. Thus one can arrive at a value of ~ 8 ppmv as a maximum possible mixing ratio for water at any level above 20 km. Similarly, from the minimum temperatures observed over the winter poles at 25-30 km and over the summer poles at the mesopause, one can arrive at a minimum possible water mixing ratio for the upper atmosphere. The numbers obtained from this exercise are near 3 ppmv. Any observations of upper atmospheric water vapor concentrations outside the range of 3-8 ppmv must be regarded as due to observational error or to unknown H20 sources, sinks, or redistribution mechanisms. During the last year (1978), limited satellite measurements of water vapor have been made with an earth limb scanner on Nimbus VI (Gille and Russell) and with a pressure-modulated radiometer (PMR) on Nimbus VII (Houghton) . Both of these measurements (neither of which has yet been reported fully) have been made in the infrared at 6.3 micron wavelength. For the 1980s, there are plans to measure atmospheric water vapor using a variety of instruments, and thus it is hoped that ten years from now the situation will be much better than it is at present, when not even an adequate global mean value exists for mesopheric water vapor, to say nothing of variations with time and latitude. 2.4 HIGH-ALTITUDE CLOUDS 2.4.1 Noctilucent Clouds (Ellsaesser, Turco) These are thin clouds observed occasionally at the high latitude summer (cold) mesopause, where the temperature drops so low (below 150 K) that condensation can occur even though water vapor mixing ratios are no greater than several ppmv. These mesopheric clouds have been the subject of scientific investigation for nearly a century. Noctilucent clouds (NLCs) have been observed from the ground (Fogle and Haurwitz, 1966), from satellites (Donahue et al., 1972), and have been sampled in situ (Hemenway et al., 1964). Current theories favor a crystalline ice composition (Reid, 1975) covering a meteoritic dust nucleus, although hydrated metallic ions have also been suggested as the nucleating agent (Goldberg and Witt, 1977). D'Angelo and Ungstrup (1976) recently reported an anticorrelation between NLCs and ionospheric electric fields (which lead to ohmic heating of the mesosphere), suggesting that NLCs are composed of a condensible substance such as H20. This theory tends to confirm the idea that the conditions necessary for NLC
formation are an extremely cold mesopause (Theon et al., 1967) and sufficient ambient water vapor and numerous condensation nuclei (Witt, 1969). If these conditions are met anywhere in the upper atmosphere, it is at the high latitude summer mesopause where they would be expected to be most likely. And it is here that NLCs were observed by satellite (Donahue et al., 1972). By contrast, NLCs are not seen at latitudes below 45° except for artificial NLCs correlated with SCOUT missile launches from Pt. Mugu (Meinel et al., 1963) and with French sounding rockets (Benech and Dessens, 1974). A detailed discussion of NLC sightings and morphology can be found in Fogle and Haurwitz (1966). By depositing water vapor and exhaust particles near the mesopause and thereby enhancing two of the three conditions believed necessary for NLC formation, rockets can apparently form artificial mesospheric clouds (Meinel et al, 1963; Benech and Dessens, 19/4) and might presumably increase the frequency or extent of natural NLCs. Rocket injections of water vapor may also lower the temperature at or near the mesopause. Chenurnoy and Charina (1977) studied variations in hydroxyl (OH) band emissions before, during, and after an NLC display. As a result they suggested that higher concentrations of ^0 before formation lead to enhanced OH emission causing local cooling; after formation of the NLC, H2O vapor is condensed into cloud particles leading to reduced emission. Despite the observed production of artificial mesospheric clouds following rocket launches, as cited above, two direct mesospheric releases each of 2 kg H2O over Ft. Greeley, Alaska, on 5 and 8 August 1964, failed to produce observable cloud (Fogle et al., 1965). However, since the water was released in bulk at heights that could not be clearly determined, these failures may not be significant. Liquid water would not have much time to evaporate and condense into particles of sufficient size to make a visible cloud. (See also the discussion of Section 2.5.3 concerning several additional high altitude water release experiments, and the discussion in item F.2 of Appendix F on the specific enthalpy of different water releases). Novozhilov (1979) has suggested that the formation of NLCs is probably facilitated by the presence of a deep cyclonic vortex in the mesosphere, and Scott (1974) reports that NLC sighting occur earlier in summers following major sudden stratospheric warmings. 2.4.2 Nacreous Clouds (Ellsaesser) Nacreous clouds form in the stratosphere (~ 25 to 30 km) in the region of temperatures below —80°C that develop within the polar winter vortices, particularly over Antarctica. As such they are indicative of (high) stratospheric water vapor mixing ratios and (low) temperatures, and of year-to-year variations in atmospheric circulation. In view of the dearth of information of this type, they offer an additional source of information for interpreting or inferring conditions at high levels in the atmosphere. The catalog of sighting by Stanford and Davis (1974) shows periods of maximum frequency in the 1880s to 1890s and in the 1930s to 1940s. There was also a 30-year period from 1895 to 1926 during which almost no sighting were done. These data suggest long-period cycles of variation in stratospheric
water vapor mixing ratios and/or temperatures that exceed anything we have seen since observations of stratospheric water vapor and temperature were begun. Stratospheric cycles of such long periods must also have an impact on the mesosphere. 2.5 CONDENSATION AND RE-EVAPORATION IN ROCKET EXHAUSTS 2.5.1 Prefatory Comments (Bauer) The problem of condensation and re-evaporation of water vapor is significant for rocket exhausts in all altitude ranges considered here, and for a variety of applications. Two subpanels, chaired respectively by M. Mendillo and M. Pongratz (see items 2.5 and 3.4 in Table 5) addressed the problem at the workshop, and P. Bernhardt wrote a discussion afterwards. These three contributions are all presented here. There is, of course, some redundancy, but it seems preferable to present the whole of the discussion in view of the importance of the problem. Mendillo reviews the problem as a whole, Pongratz makes specific suggestions for experiments, and Bernhardt summarizes the problem as it appeared after the workshop (he participated in both Mendillo's and Pongratz' subpanels). 2.5.2 The Overall Problem (Mendillo) A. Introduction The exhaust gases from a rocket cool adiabatically on expanding through the nozzle and into the low-density ambient environment. At high altitudes, temperatures below the saturated vapor temperature of ^0 are reached and thus condensation and the formation of ice crystals are expected to occur. Ample evidence exists from laboratory experiment to show that under a wide variety of conditions condensation occurs rapidly once supersaturation is reached. However, the condensation mechanism is not always well defined or understood. Thus Wegener (H. G. Wolfhard, private communication) demonstrated that the concept of homogeneous condensation did not explain the Apollo-8 lunar injection effects, but Castleman (private communication, June 1979) points out that hydrated protons lead to the formation of clathrate structures involving some 20 H2O molecules that form nuclei for condensation. The mass fraction of the condensed phase is not well known. However, laboratory experiments indicate that under many conditions at least half the water condenses. Since condensation is enhanced by longer residence time in the rocket nozzle, there is a tendency for more condensation to occur as the size of the rocket engine increases. Condensation in the exhaust of a hydrogen-oxygen rocket was observed in the Apollo-8 lunar orbit injection burn. Molander and Wolfhard (1969) analyzed the observations made by Smithsonian Astrophysical Observatory personnel at Mt. Haleakala of a "cloud as bright as the moon" photographed during the
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