Space Shuttle

Before the invention of the space shuttle, the world's first reusable spacecraft, rockets were used to put a tiny capsule carrying human space travelers into orbit. Stage by stage, booster segments would fall away during the launch as their fuel ran out. The spacecraft would go into orbit around Earth, and then the multi-stage rocket would plunge into the ocean. At that point the rocket would become space rubbish.

In the late 1960s the federal government ordered the National Aeronautics and Space Administration (NASA) to cut costs because of the lagging economy. On January 5, 1972, after suspending several other space programs, President Richard M. Nixon gave NASA the authority to proceed with the development of the shuttle in hopes that the cost of future space travel would be reduced.

The first space shuttle orbiter, known as OV-101, rolled out of a Rockwell assembly facility in Palmdale, California on September 17, 1976. The shuttle was originally to be named Constitution, but fans of the television show Star Trek started a write-in campaign urging the White House to choose the name "Enterprise" instead.

The Enterprise had no engines and was built to test the shuttle's gliding and landing ability. Early glide tests that began in February 1977 were done without astronauts and with the orbiter attached to the back of a converted Boeing 747 jet airplane. This vehicle was referred to as a Shuttle Carrier Aircraft (SCA).

The Enterprise took to the air on its own on August 12, 1977, when astronauts Fred W. Haise and C. Gordon Fullerton flew the 68,000-kilogram (75-ton glider) around a course and made a flawless landing. They had separated the shuttle from the SCA at 6,950 meters (22,800 feet) and glided to a runway landing at Edwards, California. The Enterprise was retired after its fifth test.

On April 12, 1981, Columbia became the first shuttle to actually fly into space. Four sister ships joined the fleet over the next ten years: Challenger, arriving in 1982 but destroyed four years later; Discovery, arriving in 1983; Atlantis, arriving in 1985; and Endeavour, built as a replacement for Challenger in 1991.

The Space Shuttle's Mission

The shuttle has many capabilities unprecedented in human spaceflight, including the ability to retrieve or repair a satellite, house a laboratory for weeks in orbit, and deploy satellites or planetary probes.

Through its reusability, the shuttle was initially intended to provide low-cost frequent access to space. But according to NASA, the shuttle has not been able to fly often enough (only four to eight missions a year) to significantly lower launch costs. In the fiscal year 2001, the operating cost of the shuttle program was $3.165 billion, which is approximately 25 percent of NASA's entire budget.

The Structure of the Space Shuttle

The most complex machine ever built, the space shuttle has more than 2.5 million parts, including four major components: (1) the orbiter, (2) three main engines, (3) an external fuel tank, and (4) two solid rocket boosters. Combined, the weight at launch is approximately 2.1 million kilograms (4.5 million pounds). About the size of a DC-9 commercial airliner, the orbiter, which typically carries a five-to seven-person crew, is the main part of the space shuttle. Constructed primarily of aluminum, it has a length of 37 meters (121 feet) and a wingspan of 23 meters (78 feet).

The orbiter is divided into two parts: the crew cabin and the cargo bay. The crew cabin contains the flight control center and living quarters for the crew. The long middle part of the shuttle is the cargo area and contains the payload bay. Whatever is stored in this area represents the purpose for the mission and "pays" for the flight. The payload bay is 18.3 meters (60 feet) long by 4.6 meters (15 feet) in diameter and can carry 29,500 kilograms (65,000 pounds) into space.

Because the United States could not afford to construct a space workshop on its own, NASA partnered with the European Space Agency (ESA). On August 14, 1973, 14 nations contributed $500 million to build the Space-lab module, which is a portable science laboratory that could be loaded into the cargo bay.

In June 1993 the Spacehab Space Research Laboratory made its debut aboard the STS-57. Spacehab modules, which are leased to NASA by Space-hab, Inc., of Arlington, VA, provide extra space for crew-tended experiments. Spacehab is in the forward end of a shuttle orbiter's cargo bay and increases pressurized experiment space in the shuttle orbiter by 31 cubic meters (1100 cubic feet), quadrupling the working and storage area. During shuttle-Mir, Spacehab modules were used to carry supplies and equipment up to Mir. Spacehab also provides shuttle experiments with standard services such as power, temperature control, and command-data functions.

To get the orbiter into space, the main engines and the booster rockets ignite simultaneously to lift the shuttle. About 2 minutes after launch the boosters complete their firing sequence, separate from the external tank (ET), and by parachute fall into the Atlantic Ocean, where they are recovered and used in a later shuttle launch.

The orbiter continues its flight into space with the main engines furnishing ascent power for another 8 minutes before they are shut down just before achieving orbit. The empty ET separates and falls back to the atmosphere, where friction causes it to break up over the ocean. This is the only major part of the shuttle that is not reused after each flight.

In orbit, the shuttle circles Earth at 28,157 kilometers (17,500 miles) per hour. Each orbit takes about 90 minutes, and the crew sees a sunrise or sunset every 45 minutes.

When the mission ends and the orbiter begins to glide back through the atmosphere, special exterior insulating tiles prevent the vehicle from burning up. The 15.2-centimeter (6-inch) silica tiles shed heat so well that one side is cool enough to hold in the bare hands while the other side is red-hot and withstands temperatures of 2,300°F. Tiles occasionally get damaged during launch or landing and need to be replaced.

Spinoff Benefits of the Space Shuttle

Although it is a U.S. national asset, the shuttle has had a very international presence, flying astronauts, cosmonauts, and experiments from dozens of countries. Many benefits have come from the research and technologies developed as a result of the shuttle.

The same rocket fuel that helps launch the space shuttle has been used to save lives by destroying land mines. A flare device that uses leftover fuel donated by NASA is placed next to an uncovered land mine and is ignited from a safe distance by using a battery-triggered electric match.

Space shuttle technology has also led to medical benefits. The technology used in space shuttle fuel pumps led NASA and the heart surgeon Doctor Michael DeBakey to develop a miniaturized ventricular assist pump. The tiny pump, which has been implanted into more than 30 people, is 5.1 centimeters (2-inches) long and 2.5 centimeters (1-inch) in diameter and weighs less than 0.11 kilogram (4 ounces). Another development has been the spinoff of special lighting technology developed for plant growth experiments on space shuttle Spacelab missions. This technology has been used to treat brain tumors in children. In addition, a non-surgical and less traumatic breast biopsy technique based on technology developed for NASA's Hubble Space Telescope saves women time, pain, scarring, radiation exposure, and money. Performed with a needle instead of a scalpel, it leaves a small puncture wound rather than a large scar.

Preparing the Space Shuttle for the Future

In 1988, when Discovery returned the fleet to space following the Challenger accident, more than 200 safety improvements and modifications had been made. The improvements included a major redesign of the solid rockets, the addition of a crew escape and bailout system, stronger landing gear, more powerful flight control computers, updated navigational equipment, and several updated avionic units.

Shuttle improvements did not stop with Discovery. Endeavour's first flight in 1992 unveiled many improvements, including a drag chute to assist braking during landing, improved steering, and more reliable power hydraulic units. Further upgrades to the shuttle system occurred when Columbia was modified to allow long-duration flights. The modifications included an improved toilet and a regenerative system to remove carbon dioxide from the air.

Future enhancements planned by NASA could double the shuttle's safety by 2005. New sensors and computer power in the main engines will detect trouble a split second before it can do harm, allowing a safe engine shutdown. A next-generation "smart cockpit" will reduce the pilot's workload in an emergency, allowing the crew to focus on critical tasks. Other improvements will make steering systems for the solid rockets more reliable.

Besides increasing safety and cutting costs, another objective in the next generation of spacecraft is to reduce the amount of preparation time and work required between launches. The shuttle currently takes an average of four months to be readied for launch. Goals for future spacecraft call for turnaround times of only a few weeks, if not days.

The space shuttle is prepared to fly until at least 2012 and perhaps as long as 2020. Each of the four shuttle vehicles was designed for 100 flights. In 2001, Discovery led the fleet with 30 completed flights. Over two-thirds of the shuttle fleet's lifetime is ahead of it. However, continuous upgrades and modifications will be required to ensure improved safety and protect against obsolete parts.

SEE ALSO ASTRONAUTS, TYPES OF (VOLUME 3); CHALLENGER (VOLUME 3); CHALLENGER 7 (VOLUME 3); EXTERNAL TANK (VOLUME 3); HISTORY OF HUMANS IN SPACE (VOLUME 3); HUMAN SPACEFLIGHT PROGRAM (VOLUME 1); LAUNCH VEHICLES, REUSABLE (VOLUME 1); REUSABLE LAUNCH VEHICLES (VOLUME 4); SOLID ROCKET BOOSTERS (VOLUME 3).

Lisa Klink

Bibliography

Kallen, Stuart A. Giant Leaps: Space Shuttles. Edina, MN: Abdo and Daughters, 1996.

Kerrod, Robin. Space Shuttle. New York: Gallery Books, 1984.

Smith, Carter. One Giant Leap for Mankind. Morristown, NJ: Silver Burdett, 1985.

Smith, Melvyn. Space Shuttle. Newbury Park, CA: Haynes Publishing Group, 1989.

Internet Resources

"Human Space Flight: Fiscal Year 2001 Budget Summary." Integrated Financial Management Program. <http://www.ifmp.nasa.gov/codeb/budget2001/HTML/fy01_shuttle.htm>.

The 21st Century Space Shuttle: Upgrade History. NASA Human Spaceflight. <http://www.spaceflight.nasa.gov/shuttle/upgrades/upgrades4.html>.

Upgrades. NASA Human Spaceflight. <http://www.spaceflight.nasa.gov/shuttle/upgrades3.html>.