Nuclear Rockets and Ramjets

Abstract

Abstract The objective of this article is to describe the design concepts of and the programs to develop our nuclear rocket propulsion capability for spaceflight and the nuclear ramjet systems intended for missile delivery and to describe the mission capabilities they could provide. In both systems, the nuclear reactor replaces the combustion chamber as the source of high‐temperature energy used to provide the thrust in place of their chemical alternatives. The nuclear rocket was, and still is, considered for deep space missions, including missions, such as human flight to Mars, whereas the stimulus for the nuclear ramjet was its potential performance as a high‐speed, almost limitless range, low‐altitude and, therefore, almost undetectable missile delivery system. In the early phases of research on the nuclear rocket, it too had been considered as a possible missile system. The hardware weight of the entire system must be limited so that the various mission benefits resulting from the nuclear energy source are not counterbalanced by that total weight. Major design and development requirements include selecting materials that have high‐temperature strength and are compatible with hydrogen propellant in the rocket and air in the ramjet, appropriate neutronic characteristics, controlled and stable start‐up and operation, component design and reliability, and are safe. All of these matters must be and were comprehensively researched and developed to provide systems that could achieve the desired performance. These were all high priority tasks in both the nuclear rocket and nuclear ramjet programs, and they are discussed in this article, as are the important management organizations and technical capabilities established to carry them out. Though significant progress was made in these programs, neither the nuclear rocket nor the nuclear ramjet program was carried to actual application in its proposed and anticipated missions. In the nuclear rocket case, the space program has not yet committed to mission objectives that require the high payload and deep space capability of that system. However, nuclear rocket propulsion continues to be recognized as necessary for large, deep space missions. In the nuclear ramjet case, existing chemical rocket systems provide all of the military missile requirements that are foreseen. Similar to the nuclear ramjet development, the extensive work that had been done on nuclear‐powered turbojet engines, that is mentioned here, was also discontinued because chemically fueled turbojets provide all of the capability that was required.