The American space shuttle is still the world's only fully reusable space vehicle. Originally there were six members of the fleet: Enterprise, Columbia, Challenger, Discovery, Atlantis, and Endeavor. Enterprise was only built for test missions and was never flown into space. Columbia flew the first real missions, beginning in 1981. After the losses of Challenger in 1986 and Columbia in 2003, only three active shuttles remain in use. After the final voyage of Atlantis, there will be only two.
After the first Apollo missions to the moon, President Richard Nixon wanted to continue exploration, but wanted to reduce the costs of space travel. He reasoned that if the US had reusable space vehicles instead of the "one time use only" vessels like Apollo, it could afford to explore a lot more.
Today there are two main manned space vehicles: the American space shuttle and the three-stage Russian Soyuz rocket. The space shuttle missions have carried out a variety of experiments, transported satellites into orbit, and performed repairs and upgrades on the Hubble Telescope. Their most ambitious enterprise began in 1999: the construction of the ISS in cooperation with Japan, Russia, and the European Space Agency. Its symbolism of peace and cooperation between former enemies, America and the Soviet Union, cannot be overstated.
The shuttle program suffered a tragic setback on 28 January, 1986, when Challenger exploded minutes after launching, killing its entire crew, including a high school teacher, the first ordinary citizen to fly into space. Shuttle flights were suspended until 1988. Tragedy struck again in 2003 when Columbia was destroyed. This accident raised concerns for astronaut safety, and delayed construction of the ISS for several years.
President Barack Obama has not called for the construction of a new space fleet, but has a strategy for the exploration of space that will send man to an asteroid by 2025 and Mars by 2035.
With the space shuttle program entering its last year, many argue that manned space missions waste resources. Why send people into space when you can send probes for a fraction of the cost and with none of the risk to astronauts' lives? It might be wiser to use probes and deep space telescopes like Hubble to search space for someplace worthwhile to go before sending humans on dangerous and arbitrary missions. Plans to build a new manned space fleet and send humans to Mars remain in the embryonic stages.
There are lots of great books about outer space. My favorite is Astronomy: A Visual Guide, by Mark A. Garlick. It's filled with interesting information and lots of beautiful photographs.
For my previous posts on outer space, click here.