Visionary projects: a viable rationale for human space-flight?

Today's prevailing geo-political and socio-economic climate is proving unfavourable towards justifying on-going and future human space-flight programmes. Traditionally cited benefits, such as scientific and aconomic progress or political advantages, are widely deemed insufficient reasons for spending considerable amounts of public funds. A rationale for human space-flight, evoking visions such as exploitation of extraterrestrial resources or human exploration of space, has to cope with an unavoidable dilemma: attractive as they may appear, these projects are fraught with many grave uncertainties and risks. This paper attempts to answer the question over what, if any, significance such visionary projects may assume in justifying the continuation of human space-flight activities. We argue that, despite as yet unanswerable technological and economical questions, and despite the extremely long time-frames involved, it seems reasonable and, hence, justified to keep the option of being able to solve by means of humans in space the impending energy crisis in the coming century.