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Over the past quarter of a century there has been a significant amount of work on modification of internal combustion (IC) engines to operate on hydrogen. However, comparisons are difficult because of large variation in designs, engine parameters, and test conditions. A comparative summary of the recent work on hydrogen-powered engines is presented under a unifying format. This summary includes material extracted from published reports and obtained by private communication. It is intended that this survey be of value to those beginning work in the field, and will provide some guidance in determining the direction of future research. Included are the following: engine parameters, modifications, operating conditions, running characteristics, performance, and related comments. More detailed discussion is included on the manpower and material costs associated with the modification of one of the engines listed.

It is concluded that the direct effects of an ideal form of fusion technologies would be socially more desirable than those of the alternatives. This is particularly true of the second generation fusion power plant. However, given our technological inputs, this was a trivial result. Less trivial was consideration of the negative effects that might accrue through the availability of potentially unlimited supplies of low cost energy. It is concluded that while there may be reasonable humanist argument both for and against such abundance, in a democratic society control of energy development for its own sake is likely to be unacceptable. However, if the indirect effects of pollution, despoilment, and resource depletion through ever expanding energy use become sufficiently disturbing to the well-being of the majority, unlimited energy may come to be seen as undesirable by the society. To this extent successful research and development for unlimited sources such as the fusion or mixed solar alternatives might be judged from some point far in the future to have been a mistake. This could occur even though advances in the technology of pollution control and resource use greatly reduce the pollution and hazard accompanying a much higher rate of energy utilization.