be sent anywhere, although if they are, their time between missions would be increased and more will be required. The operating cost of such a large fleet of space transports is difficult to estimate. It depends very strongly on whether the vehicles must be handled with current rocket launching systems, or whether it is possible to approach air transport operational methods. The latter might be facilitated by using a large air transport “zero stage” which carried the orbital transport to high altitudes but only subsonic speeds. Its purpose would be both to place the orbiter above the cloud cover so that it could receive laser energy from space and to act as a mobile launch platform which could use normal airports and obviate the need for vertical launch facilities. The direct operating cost, minus fuel, of large commercial transports is shown in Fig. 12. These data are old (circa 1967) (16), but most of the recent cost increases have been far more associated with petroleum cost than normal inflation. Heavy transport rockets would operate at $1000 to $2000 per hour if the air transport analogy held. Fuel costs of the advanced systems described would not be great since the fuel load is small. The cost of buying energy from the laser power station is a complete mystery, and would depend strongly on the policy of the nation or consortium which created it. Since the basic energy is free, and the transport quite efficient, it is conceivable that such a system would be very economical at high throughput. CONCLUSIONS The search for convenient and economical space transportation is still vexing even when nonstandard ideas are considered.
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