transmitters located at 120 degree intervals in the geostationary orbit. The microwave link frequency was chosen to be 22 gigahertz to assure that the power beam did not penetrate the atmosphere while tracking the orbit transfer vehicle. The motivation for this concept is to sidestep the trapped radiation belt damage to onboard photovoltaic power supplies. Raytheon indicated during the discussion that thin film rectenna elements are possible with a specific weight of about 1 kg/kW. Mr. Preston Layton, an independent consultant to the DOE, gave the final presentation of this session. He presented the results of a three-day SPS transportation system workshop held at the Marshall Space Flight Center (MSFC) in late January of 1980. Fifty-seven space transportation specialists participated in this workshop. Although the report from this workshop has not yet been released, Mr. Layton paraphrased the conclusions as follows: 1. Space transportation system requirements are major cost and technological development elements of the SPS. 2. The first step in upgrading of the Space Shuttle launch system will be the Titan liquid boost module (LBM). The next step may be replacement of the current Shuttle solid rocket booster with a fully reusable liquid propellant booster system. 3. Although Space Shuttle growth concepts may suffice for the SPS research, engineering and demonstration phases, it is clear that an entirely new large HLLV will be required for the operational SPS. 4. The feasibility of and relative merits of a single-stage-to-orbit launch vehicle are not yet clear. 5. A considerable amount of research, development and technological development in the space transportation field is badly needed as an integral part of further exploration of the SPS. 6. The recurring cost of operating the HLLV dominates the cost of placing operational SPSs in geostationary orbit. 7. A suitable goal for cost to low Earth orbit for the first SPS is $30/kg. The goal for an average SPS and for other contemporary payloads should be $ 15/kg to low earth orbit. 8. A chemical orbit transfer vehicle compatible with the Space Shuttle needs to be given early “new start” authorization to enable the conduct of vital SPS development activities in geostationary orbit. Mr. Layton then displayed several engine approaches to the space transportation system and expressed the opinion that, for the chemical OTV, a small O2/H2 rocket engine is needed which utilizes an engine cycle other than the staged combustion cycle of the Shuttle main engines. He also stated that we need to emphasize early development of the MPD thruster because of its significant cost advantages over the ion bombardment device currently in the “Reference System." Due to a conflict in schedule between the environmental assessment sessions relevant to space transportation and the comparative assessment sessions, I was unable to hear most of the papers in this area. 1 did, however, hear most of the overview paper given by Argonne National Laboratory for DOE. My interpretation of this synopsis is that although more study and some experimental work is required, no massive adverse environmental impacts are predicted as a consequence of flight operations to put in place an SPS network. Argonne indicated that sulfur dioxide contribution was nil, that carbon dioxide production from 275 flights per year of the HLLV is only 1/4 that of a single 1,000 megawatt electrical power plant. NOj. formation may produce localized effects for a short time after each launch. These impacts are expected to be highly localized and transient in nature. An example given was
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