Abstract
This paper is an attempt to place in correct perspective the current considerable speculation regarding the problem of interplanetary travel.
The concept and importance of “escape velocity” is dealt with first, and then the elementary mass-ratio equations for the motion of a space vehicle under various conditions are derived.
Available energy sources are considered next, the operational parameter being jet velocity. It is indicated that the maximum jet velocity conceivably attainable with chemical fuels is of the order of 20,000 ft. per sec. Nuclear fuels are dealt with and it is shown that, while energy potentials are very high, the problem of practical utilization is formidable. A thermodynamic type of atomic rocket motor employing an inert reaction mass to absorb the fission energy is postulated, and it is demonstrated that the heat transfer and materials requirements present a problem of the first magnitude.
The influence of propellent density on the performance characteristics of both chemical and atomic rockets is discussed, and it is shown that propellents giving high jet velocities may not necessarily be the best to use.
Orders of magnitude for the mass ratios required for various interplanetary flights are established, and it is indicated that only an atomic drive will render them small enough to be attainable in practice.
It is concluded that, unless nuclear energy can be suitably harnessed, economical space-travel will not be feasible.
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