larly in orbit-to-orbit transportation, even though the weight of the solar collectors involved drives them to rather low thrust/weight ratios. Both solar and nuclear energy can be used to drive electrical rockets which get around the temperature restrictions in normal rocket combustion chambers by using electrical means to accelerate the exhaust stream. This, unfortunately, requires electrical power supplies and processing equipment to be carried onboard the rocket. Since all these processes must be limited to temperatures which will not melt the materials involved, the weight of such equipment becomes extremely large. All such rockets designed to date have very low accelerations. In almost all rocket performance analysis, the extremely low accelerations of either solar or nuclear electric rockets have usually nullified their advantages of high exhaust velocity. Their gains have not been high enough to justify their development cost. Spectacular breakthroughs in power supply weight are required to change this situation. The essence of the use of nuclear energy from the sun to power rockets is to use a source of energy at a remote location with the energy transferred to the accelerating transport vehicle by electromagnetic radiation. Thus a remotely powered rocket is created. The remote power supply can be of tremendous weight without affecting the rocket performance since the power supply need not be moved. This type of system is certainly worthy of investigation. Another form of this class of system would be a miniature man-made version — a power station which would transmit energy to the rocket by means of electromagnetic radiation. Although one can conceive of doing this with incoherent light or microwave radiation, the odds-on favorite candidate for transmitting such radiation is the laser. This option was not available to Goddard or Tsiolkovskiy. Such a laser power station transmitting coherent light will have an extremely
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