Two Aspects of the Time Element in Interplanetary Flight

Abstract

Ion rockets do not suffer from some of the limitations imposed by the high fuel consumption of chemical rockets. They allow us to consider, therefore, the use of non-minimal orbits to the inner planets and the use of reasonable transfer times on flights to the outer planets. In the former connection it is shown that even when rockets of very high characteristic velocity are used, there are still long periods during which transfers between Earth and Mars cannot be made. In the latter connection some design characteristics of very high powered ion rockets are derived and applied in the case of a flight between Earth and Neptune. It is shown that this requires power conversion units having a power output per unit mass of the order of ten times that of a unit that is adequate for an Earth-Mars rocket.