10.2 Space to Space Demonstration Several concepts have been proposed for a near-term demonstration project within a total budget of $80 million (see Appendix A for a complete list). The work group for this near term demonstrator had a closer look at the following projects: A. Beaming microwave power from a Viking-like platform (Swedish platform designed into the Ariane 3rd stage adapter). In a first experiment the target could be a rectenna mounted on the Ariane 3rd stage (Ariane Structure for Auxiliary Payloads (ASAP). The second experiment could be to beam power from the Viking platform to an experimental rectenna in Arctic regions. B. Beaming laser power to a satellite in GEO or the GEO graveyard orbit. C. Beaming microwave power from the Mir space station to the Progress service vehicle. Proposal A has been discarded due to severe orbital mechanics constraints when using the spinning Viking platform. The experiments would have needed a permanent change of the spacecraft's spin axis thus leading to an excessive propellant demand. A redesign of the Viking platform to use another stabilization principle was not considered to fit into the cost and schedule constraints. The quite short experiment duration in the range of some minutes due to visibility constraints would have been another problem. The second proposal (B) has been abandoned mainly because of technology and budget problems: no laser has been found to be compatible with the requirements of wavelength (to use existing solar arrays for back conversion), power and system mass. All considered laser design options exceeded the given envelopes in cost and project time significantly (see Appendix E for more details). Proposal C has been retained. The experiment demonstrates key issues of microwave power beaming. It represents a major milestone with respect to the other design examples as well as to a long term power beaming application. This proposal will be presented and discussed in the following sections. 10.2.1 Mission Objectives The aim of the mission is to beam power from the Mir space station to a Progress transport spacecraft over a distance of about 80 m and more. With this mission the following objectives can be met. First of all the experiment would demonstrate in space a complete microwave power beaming system transmitting a significant amount of power. Since the mission time would be in the range of several days, the experiment would be the next step in terms of beaming time and transmission power compared with the proposed sub orbital demonstration projects such as the METS experiment. [Kaya, 1991] So an important feature of the experiment would be to demonstrate target acquisition and locking the beam on the target in various emitter/receptor constellations over a longer period of time. The Progress vehicle as a beaming target could demonstrate the potential of a future microgravity laboratory without solar panels. This would possibly reduce weight and aerodynamic drag effects. The mission incorporates a range of scientific experiments, chiefly investigating the nature of the interactions between the microwave beam and plasmas. This interaction is in two regimes. Firstly, the ambient medium through which the spacecraft travels will be analyzed and its characteristics when heated examined—ionization, thermal profile, energy distribution, charge and composition analysis. Secondly, the lower levels of the atmosphere will be examined while the beam is pointing toward the Earth. These experiments will be performed by an on-board mass (retarding potential) spectrometer and a multi-band electromagnetic spectrometer. Finally, a matrix of probes will investigate the surface charge characteristics of the beaming antenna, both while beaming and during passive phases of operation. 10.2.2 Mission Scenario The Progress spacecraft will be launched by a Soyuz launcher into a circular orbit with a 51.6 degrees inclination, at an altitude of approximately 320 km. The Progress transport vehicle will carry all equipment for the experiment to the Mir station. The transmitting and receiving antennae are initially fitted to the Progress vehicle at the attachment points of the solar arrays, as shown in Figure 10.2.1.
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