Introduction
There is currently considerable debate about whether or not the U.S. space program should continue, particularly bearing in mind its huge costs in these times of austerity, when budgets everywhere are subject to severe constraints, from government level down to individual households. Also, because manned space exploration is not without risk (witness the Challenger and Columbia disasters in 1986 and 2003 respectively that cost the lives of all seven crew members in each case), many question whether those risks are justified; what does humanity gain from space travel that can cause the risks to be considered worthwhile? This research ...