orbital missions, these events seemed anticlimactic. The second space era, initiated about 1970 and continuing in the present, has been funded at approximately 10% of the level of Apollo era funding and has generated relatively few joyous headlines. Yet it has been marked by three major developments that are critical for a permanent move into space. First immense experience has been gained living and working in low Earth orbit. Although the distances involved between Earth and Salyut, Skylab, shuttle, and Mir orbits may seem trivial compared to the distance between the Earth and the Moon, the fact is that the space habitats of the 1970s and 1980s are characterized by reduced gravity, cramped and austere living conditions, isolation from normal social contacts, confinement with a limited number of other individuals, and most of the other conditions that will be prevalent during the next 100 years or so of life in space. Using two and three person crews, the Russians set record after record in the area of spaceflight duration. From 1971 through mid-1985, 34 Soviets spent 3300 man-days in space; individual cosmonauts have spent up to six months per mission and have accrued up to a year's time in space in the course of multiple missions [4]. The USA, in the meantime, gained experience with orbital missions of up to three months on Skylab, and, later on, with many different shuttle crews consisting of up to seven members. During the ‘quiet' 15 years or so that followed Apollo, approximately 75 new astronauts and cosmonauts visited space, the average length of their stay in space increased, and these spacefarers learned how to perform routinely, the everyday selfmaintenance, recreational, and work activities that will be necessary to establish permanent bases. There were plans for approximately 300 shuttle flights by the mid- 1990s, and it is estimated that approximately 1000 people will have ventured into space by the year 2000 [5]. Unfortunately, the Challenger tragedy may set back that timetable, but expanded manned flights will occur in the decades ahead. A second significant event of the 1970s and 1980s has been that identifiable and attainable financial profits may now be added to scientific gain and national prestige as justifications for space exploration and settlement. Since the early days of science fiction, writers have identified unparalleled wealth in the skies. What has happened in the past few years is that these potential rewards have become real and immediate. Present day orbiters are useful as pharmaceutical and metallurgy labs, and the shuttles have proven invaluable for the deployment, repair, and redeployment of military, scientific, and commercial satellites. Detailed and sound analyses are making it increasingly clear that space settlements will be commercially profitable for energy collection and distribution, for mining, and for manufacturing [6, 7, 4]. The third relatively recent development is the emergence of coherent long-term strategies for the phased exploration and settlement of Space [7]. These plans recognize that society has many different needs, and that space programmes cannot be based on staggering government expenditures. These strategies are evolutionary rather than revolutionary, with each step following from the preceding and leading to the next: shuttle, low earth orbit space station, geosynchronous orbit space station, lunar base, and Mars outpost. Budgeting has been such that while most resources are focused on the immediately following step, some funds remain available for subsequent projects. Certainly the details and dates are somewhat imprecise, particularly in the wake of the Challenger explosion. Space professionals should not get sidetracked by such issues as whether or not the first permanently occupied lunar base will preceed the first Mars touch-down, or
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