8.1.2 Piggy-back Options & Small Launch Vehicles For the first space solar power demonstration mission in the 1990s, the mass of the satellite could be below 1000 kg, so there are piggy-back and small rocket options to launch it. The principle of piggyback launch system is based on the fact that most launch vehicles do not charge precisely on the basis of the satellite mass. Excess capability can be used to launch secondary small satellites without modification of the launcher. The available mass depends on the mass of the main passenger and the performance of the launcher. The secondary payloads are placed into the same orbit as the primary payload. The number of launch opportunities is limited. To date there are 15 to 25 commercial launches per year with expendable launchers (US and Europe) and about 6 to 8 flights for the US Shuttle. For an inexpensive and near term space solar power demonstrator we need the combination of minimum launch costs and maximum launch opportunities so piggy-back options appear to be very attractive. In this case the mass of the satellite is between 50 and 500 kg. If the mass is higher, small launch vehicles can be used. They are capable of lifting payloads ranging from 100 to 1000 kg into low Earth orbits. Review and Analysis of Piggy-back Options Here is a list of piggy-back options: Ariane 4 - ASAP (Ariane Structure for Auxiliary Payloads) ASAP (Ariane Structure for Auxiliary Payloads) is a small payloads carrier below the prime passenger of the European Ariane 4 launch vehicle. It can carry up to six small payloads up to a total of 200 kg, with a maximum of 50 kg for any one particular satellite. This circular plate extends into
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