With the curtailment of manned space flights now that the Apollo mission is completed, the emphasis will be on unmanned exploration similar to the Mariner Mars series. Strong, a space development enthusiast (Flight to the Stars, 1965) and employee of Hawker Siddeley Dynamics (Guided Weapons Division), discusses in relatively accessible language various systems which have been developed and, most intriguing, the possibilities for future probes of hot as opposed to cold (the Moon) targets, including the asteroids between Mars and Jupiter. Most of this is high level speculation -- Strong openly concedes ""I have deliberately suggested ideas which may seem outrageous"" and in like manner he admits the potential dangers as yet unencountered (solar storms, meteor streams, etc.). But on the other hand there is nothing here which is not supported by scientific evidence or logic; as he says, ""There is only one answer -- to get out there and find out."" This small booster for that effort will appeal to anyone concerned with the space program, professional or amateur.