0191-9067/83 $3.00 + .00 Copyright ® 1983 SUN SAT Energy Council TRANSPORTATION: OPTIONS AND HIGH PAYOFF CHOICES MAXWELL W. HUNTER II Advanced Systems Division Lockheed Missiles & Space Company, Inc. Palo Alto, California 94304, USA Abstract — In recent years, nonrocket ideas have proliferated. Various electromagnetic acceleration schemes, energy transfer by laser from power stations to accelerating vehicles, and momentum transfer devices consisting of structures of vast proportions have been suggested. It is a complex array of possibilities, many of which potentially apply from low Earth orbit to interstellar propulsion. This paper relies on the simple relations between energy and momentum which are fundamental to the various possible space propulsion systems. Energy transmission by new techniques, such as a laser power station, and the various limitations on its conversion to momentum are covered. Momentum storage and direct momentum transfer are also treated. INTRODUCTION At the time of Sputnik, space transportation was viewed, with a few minor exceptions, as strictly the province of chemical rocket propulsion. The exceptions were nuclear rockets, which still had to carry working fluid on board, air-breathing chemical systems which had dubious payload capabilities, and some occasional speculation on magnetic accelerators. Direct momentum transfer was used first in Lunik III in 1958, and later in planetary swingbys, but it was not widely considered as a subset of propulsion methods. In recent years, nonrocket ideas have proliferated. Various electromagnetic acceleration schemes, energy transfer by laser from power stations to accelerating vehicles, and momentum transfer devices consisting of structures of vast proportions have been suggested. It is a complex array of possibilities, many of which potentially apply from low Earth orbit to interstellar propulsion. This paper ignores mass drivers and other electromagnetic acceleration schemes. This is not to say that such things will not be useful in limited situations, but rather that any really useful space transportation system must carry human beings and other soft cargo. We should not redesign humans and most of their accoutrements just to satisfy some simplified transportation design ideas. Space transportation is a high-velocity proposition, and the accelerations must be at most only a few g’s to accommodate the cargo. Mass drivers suffer on two points. To attain reasonable dimensions, they require high accelerations. They consequently are large, fixed installations aimed at only one, or a few limited, point(s) in space. There is a whole solar system out there. Nothing of interest yet exists at L5, and precious little in geostationary orbit unless you are a communication freak.
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