Space Shuttles

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Space Shuttles

Overview

At the United States National Aeronautics and Space Administration (NASA), the space shuttle program goes by the name Space Transportation System (STS). The shuttle program, as it is commonly referred to, has enabled humans to travel to space on reusable craft, providing transportation to and from space stations, and allowing scientists and the public to begin thinking about regular transportation to moons and planets. The shuttle was originally envisioned as a fully reusable craft that would be both efficient and economical; the latter benefit is still argued by some politicians and others. As designed, the space shuttle is semi-reusable. The shuttle basically comprises two solid rocket boosters, an external fuel tank and three main engines for launching purposes, and the reusable airplane-like orbiter spacecraft. In operation since 1981, the space shuttle has become the foundation of NASA's space program.

Background

In fall 1969, shortly after Neil Armstrong (1930-) became the first human to walk on the Moon, a special Space Task Group, appointed by the president, recommended a plan for the future of the U.S. space program. NASA had lobbied the group during the preceding months, and the plan included NASA's requests for the development of a reusable space shuttle. President Richard M. Nixon accepted the group's report, but did not put a high national priority on the space program.

More than two years after the task group report, following meetings between Nixon and NASA Administrator James C. Fletcher, an announcement was made unveiling plans to build "an entirely new type of space transportation system designed to help transform the space frontier of the 1970s into familiar territory, easily accessible for human endeavor in the 1980s and '90s." By 1975, NASA had demonstrated that a shuttle-like craft could return from orbit and land safely on a runway, a key part of the Space Transportation System.

Tests continued, and on February 18, 1977, the first space shuttle was attached to the top of a Boeing 747 ferrying aircraft at NASA's Dryden Flight Research Center in southern California for its first flight test. The 747 jet still serves as the ferrying vehicle for shuttles, transporting them when necessary from the landing runway to the launch pad between missions. Named Enterprise after the spacecraft in the fictional television series "Star Trek," the space shuttle made its maiden free-flight tests six months later. Those tests demonstrated the craft's ability to glide to a safe landing.

By spring 1981, the shuttle was ready for its first extended flight. On April 12, astronauts John W. Young and Robert L. Crippin took the space shuttle Columbia into orbit for a flight lasting more than two days, and landed the craft safely at Edwards Air Force Base in southern California. Upon landing, the Columbia—named after one of the first U.S. Navy ships to circum-navigate the globe—was heralded as the first airplane-like craft to return from an orbital mission for reuse.

The next in NASA's series of shuttles was the Challenger, which had its first mission from April 4-9, 1983. In this flight and previous Columbia flights, the shuttles deployed a variety of communications and other satellites. Astronauts Crippin and Young continued to fly shuttle missions. In June 1983 Crippin was joined by an astronaut team that included Sally K. Ride (1951-), who became the nation's first female astronaut. On November 28, 1983, Young was part of a Columbia crew that included the U.S. space program's first non-American astronaut, Ulf Merbold of West Germany. The flight also made history by carrying Spacelab 1, an onboard research laboratory that allowed astronauts to conduct scientific experiments while in orbit. Unlike the U.S. space station Skylab, which was also used for scientific experiments, Spacelab 1 was not a space station since it was never deployed free of the orbiter.

Other "firsts" in the shuttle program included: the first black American astronaut, Guion S. Bluford (1942-), who flew aboard the Challenger after its August 30, 1983, launch; the first use of the Manned Maneuvering Unit (MMU), which allowed American astronauts to perform space-walks without being tethered to the shuttle, in February 1984; the first "on-orbit" satellite repair mission, which occurred during the April 1984 Challenger mission; and the inaugural flights of the space shuttles Discovery and At-lantis,launched on August 30, 1984, and August 8, 1985, respectively.

NASA's success with its shuttle program laid the groundwork for its decision to invite civilian school teacher Christa McAuliffe (1948-1986) to join its Challenger mission, which launched on January 28, 1986. The crew of seven also included Francis R. (Dick) Scobee, Michael J. Smith, Judith A. Resnik, Ronald E. McNair, Ellison S. Onizuka, and Gregory B. Jarvis. School children across the nation watched this highly anticipated launch live from their classrooms. However, the excitement gave way to disbelief and sorrow when the shuttle exploded just 73 seconds into the flight, killing all aboard.

Subsequent investigations concluded that the explosion was prompted by a faulty seal in one of the two solid rocket boosters. A review of photographic data showed a puff of smoke coming from the seal area. Several other puffs followed over the next two seconds. The smoke puffs indicated that hot propellant gases were burning and eroding the seal, including its rubber O-rings. A flame ignited on the solid rocket booster at 59 seconds into the flight, and five seconds later breached the external tank, which began to leak its liquid hydrogen fuel. At 73 seconds, various structural failures occurred, and the shuttle exploded into several sections that fell to Earth.

After the explosion, NASA ceased further shuttle missions and conducted internal investigations. These led to a redesign of the solid rocket booster seal, and several management changes, including the reappointment of Fletcher as NASA administrator (he had held the title from 1971- 77) and the selection of astronaut Richard H. Truly to lead the shuttle program. Truly and Daniel C. Brandstein piloted the Challenger on the August 1983 flight mentioned above. In addition, NASA initiated an Office of Safety, Reliability, Maintainability, and Quality Assurance.

More than two years passed after the illfated Challenger flight before NASA launched another shuttle mission. On September 29, 1988, the Discovery marked the return of the shuttle program and the 26th shuttle mission.

Impact

The space shuttle program has provided a reliable transportation vehicle for not only the U.S. space program, but the programs of other countries. Although the program experienced a major catastrophe and setback with the 1986 explosion, the shuttle has continued to be the workhorse driving the U.S. space program. Since the first orbital shuttle flight in 1981, shuttles have flown dozens of missions and have had major direct and indirect impacts on scientific endeavors as well as political efforts.

One of the shuttle program's major milestones came in April 1990 when the Discovery carried and launched the Hubble Space Telescope (HST). This Earth-orbiting observatory, which revolves around the planet once every 93 minutes, is able to collect data unavailable to telescopes on Earth because the HST is located beyond Earth's atmospheric distortion. A flaw in the Hubble's optics prompted a December 1993 flight by the shuttle Endeavour, a new shuttle that made its inaugural flight in May 1992. The Endeavour's astronauts were able to repair the optics, perform routine maintenance work, and release the telescope back into its orbit.

As the ferrying, and later the servicing, craft for the telescope, the shuttles are indirectly responsible for the wide variety of spectacular images that have been made available by the Hubble Space Telescope. In the decade since its launch, the Hubble has provided images and data about black holes, the birth of stars, previously unseen galaxies, and planets in our own solar system.

The shuttle was also an important part of space history when its American crew was joined by a Russian cosmonaut in February 1994. That initial U.S. space mission with a Russian on board opened the doors to later U.S.Russian missions, including the maiden link-up between the U.S. shuttle and the Russian space station Mir in the summer of 1995. Carrying two cosmonauts to replace the crew on Mir, the shuttle Atlantis docked with the space station. After several days of activities and experiments, the American crew, along with an American astronaut and two cosmonauts who had been stationed on the Mir since March, boarded Atlantis for a return voyage to Earth. Later missions to Mir ferried several astronauts to the station, including Shannon Lucid, the first American woman on the station. Lucid remained at the station for five months. United States involvement with the station ended in 1998, and the station is scheduled to be discontinued in early summer of 2000.

NASA points to numerous applications that have arisen from the myriad scientific research projects conducted during the shuttle-Mir missions. A cardio-muscular conditioner, for example, is a piece of exercise equipment designed hand-in-hand with experiments performed in a microgravity environment. The conditioner, which employs elastic cords and a kick plate, has potential uses for "athletes and heart disease patients by promoting cardiovascular fitness and muscular strength development," according to NASA's Shuttle-Mir web site. Other developments with potential Earth-bound applications are a heart rate monitor, a cardiac imaging system for use by cardiologists, and implantable and external pumps to help people with diabetes maintain insulin levels.

On the political side, the shuttle program has helped to cement a cooperative working arrangement between Russia and the United States. The shuttle program will also be a major part of the scheduled construction of an International Space Station. The station will involve cooperation between 15 countries in addition to the United States. Plans call for the shuttles to ferry component parts to the station at least through its completion, and later deliver food, water, and other supplies to station crews. With involvement in the International Space Station, NASA's shuttle program is likely to extend its role as the foundation of the U.S. space program and become a cornerstone of the combined world space program.

LESLIE A. MERTZ