solar-pumped lasers. They did not cover free electron lasers which, should they work, are possibly better than any of the other types. The minimum weight laser power station designs were about 8000 kg/MW of power. It is desirable to have the laser power station system bootstrap itself to space. The first station will obviously have to be emplaced by conventional rocketry. But afterward, since the system will use little or no Earth energy and should have low operating cost, the first small power station should spend much of its time driving transport rockets which expand the power system. The one MW needed per kg of payload has to be applied for 600 s to achieve orbit. If continually driving rockets, 1 MW could hence place 52,596 kg on orbit per year. The power supply is potent, but another factor driving this self-expansion is how many rocket flights provided by a station are required for self-replication. Since we have determined that 1 MW is required per kilogram of payload, and power station’s weight is 8000 kg per MW, then, regrettably, 8000 flights are required for replication. There is hope that more refined analysis of these systems, particularly the laser- driven air-breather rocket hybrid, will substantially improve the power/payload ratio. This paper is supposed to speculate on the next 50 years, and it is reasonable to expect to lower this to 1000 flights per replication. As mentioned, the power station must deliver power for only about 600 s to the transport until it reaches orbit. Thus, the total power station employment for replication is 600,000 s or about 1 week! It is quite clear that the problem will not be the power station. The problem will be to feed transport rockets to it fast enough to satisfy its capabilities.
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