8. Assessment of Post-flight Materials

The low Earth orbit (LEO) environment is defined as that region of space between 200 and 1000 km (124 and 621 miles) above the Earth. It was reasonably well characterized in the 1950s, during the prelude to the race into space, by means of sounding rockets equipped with monitoring devices for recording air pressure, temperature, and gaseous composition. Many of the data obtained from those early space flights are suitably accurate for today’s calculations and have been discussed in Chap. 2 and compiled into Table 2.​3. In just one decade, the 1960s, human beings began to extend their physical boundaries by initially venturing into LEO and then progressing to explore the mountains and valleys of the Moon. The first human to orbit the Earth was cosmonaut Yuri Gagarin in the Vostok 1 spacecraft on the 12th April 1961. Since then, manned spaceflight included the Mercury (Atlas ELV) missions, the Gemini (Titan ELV) missions, and the Apollo (Saturn ELV) missions that gave 12 human beings the opportunity to walk on an extraterrestrial surface, with the first manned landed on the Moon in 1969 with Apollo 11, and the final Moon-landing in 1972 with Apollo 17. The 1970s saw the launch of several Salyut space stations and three Skylabs, followed in the 1980s and 90s with the Mir station, the Kvant module, and the many Space Shuttle launches (for the placement of satellites into orbit, ejection of probes into space, retrieval of spacecraft, and utilization of Spacelab which remained attached to the Shuttle’s cargo bay). At the time of writing, it is the International Space Station (ISS) that continues to be the most newsworthy space activity. This is the biggest construction to fly in space and can be readily seen from the ground as it completes 16 orbits per day. Huge solar panels, totaling approximately one acre are attached to the central truss of ISS—the dimensions are equivalent to the length of a football field, the habitable volume is as large as a six-bedroom house and the total mass is just over 450 metric tons (tonnes). Awe-inspiring, as ISS was built by astronauts and cosmonauts, 216 have lived there, bringing each part of the construction from Earth by Shuttles and various other cargo-vehicles (2015 data).