Space Shuttle

Last updated: June 22, 2006.

The development of NASA's reusable space-plane, the Space Shuttle, has launched a whole new age of space exploration. Previous spacecraft had lasted only for one mission, but the Shuttle, which took off like a rocket and flew back like a plane, could be reused up to 100 times. Since its maiden flight in 1981, the Shuttle has successfully launched and repaired numerous satellites and the Hubble Space Telescope, and future missions will concentrate on assembling a giant international space station.

Photo: Relaunch of Space Shuttle (mission STS-26) in 1988. Picture courtesy of Great Images in NASA

The main component of the Shuttle is a spacecraft about two thirds the size of a 747 airplane ("Jumbo Jet") called the orbiter. This is launched by two solid rocket boosters (SRBs) fixed to its underside, which burn solid fuel inside them. In between the SRBs, a giant external tank (ET) feeds around 528,000 gallons (2 million liters) of liquid fuel to the orbiter's three engines. This vast amount of fuel is needed to accelerate the Shuttle to a speed of roughly 17,500 mph (28,000 km/h) to reach an orbit of 190-330 miles (304-528 km) above Earth. During liftoff, the Shuttle's main engines burn fuel so quickly that they could drain a family-sized swimming pool in just 25 seconds! Each orbiter costs roughly $2 billion to build and each Shuttle mission costs roughly $450 million.

Life in the Shuttle

Each Space Shuttle mission lasts up to two weeks, so the orbiter has a comfortable-but-compact, two-storey living area. On the top storey are the pilot's seats and cockpit controls. A ladder leads down to a large sleeping area, galley kitchen, storage lockers, gym—and a vacuum toilet that works even in space. The astronauts eat their food with metal knives and forks held to metal trays with magnets; this stops them floating away in the Shuttle's near-zero gravity.

Shuttle missions

Space Shuttle missions often make headline news around the world. The maiden voyage on April 12, 1981, confirmed the Shuttle could successfully return from space. Another notable flight in April 1984 involved astronauts repairing a crippled satellite in the Shuttle's cargo bay before returning it successfully to space. Two years later, the orbiter Challenger exploded shortly after takeoff killing all seven crew members. Flights resumed in late 1988 and the Hubble Space Telescope was launched in 1990. Disaster struck again in February 2003, when the Space Shuttle Columbia was destroyed as it returned to Earth.

From takeoff to landing

During a typical one-week voyage, the Shuttle launches from its base at Kennedy Space Center (KSC), Florida, and carries out its mission several hundred miles above Earth's surface. When the mission is complete, it returns to Earth's atmosphere and makes an unpowered landing, like a glider, either at KSC or at Edwards Airforce Base in California. At 15,000 ft (4572 m) long, the landing strip is roughly twice the length of a typical airport runway.

Liftoff stages

At liftoff, three engines on the orbiter burn liquid fuel from the large brown tank underneath. Two SRBs either side burn solid fuel and make over 70 per cent of the liftoff thrust. Together, these five engines produce some 7.3 million pounds of thrust—150 times as much as a single Jumbo Jet engine! During this part of the flight, the temperature inside the Shuttle's engine is two thirds as hot as the surface of the Sun.
Two minutes later and 32 miles (48 km) into the sky, the empty SRBs are detached.
When the Shuttle reaches its orbit, the ET is detached and burns up on its way back to Earth.
A typical mission lasts 4-7 days.
The orbiter flies backward for the first part of its descent.
As the orbiter turns, its nose is raised so its heat-resistant undercarriage meets Earth's atmosphere first.
During descent, the orbiter slows from 17,500 mph (28,000 km/h) to 220 mph (350 km/h) and a parachute brings it completely to rest.

Inside the cargo bay

Astronaut Bruce McCandless walking above the cargo bay of the Space Shuttle (mission STS-41B) in 1984. Picture courtesy of Great Images in NASA.

At 60 ft (18.3 m) long and 15 ft (4.6 m) wide, the orbiter's cargo bay is big enough to hold a a satellite or a couple of trucks parked side by side. It contains a variety of sensors and scientific instruments and a 50 ft (15 m) grabber arm, used for launching and retrieving satellites. The reflective inside doors of the cargo bay double up as heat shields to protect the cargo from solar radiation. Bigger picture from the NASA website.

The Shuttle cannot launch a satellite directly into geostationary orbit (a fixed orbit over a certain place on Earth). Instead, it spins the satellite slowly out of the cargo bay. When the satellite is clear, its own rocket motors fire and power it into position.

Reentry

Testing a model of the space shuttle in a wind tunnel. Picture courtesy of Great Images in NASA.

The Shuttle's unique feature is its ability to venture into space and return to Earth intact. However, friction can heat up the orbiter to nearly 3500°F (1927°C) as it passes into Earth's atmosphere, so it is coated with about 20,000 heat-resistant ceramic tiles to stop it burning up on reentry. A tough material called reinforced carbon-carbon is used in the tiles on the wing edges, the nose, and other areas where temperatures exceed 2300°F (1260°C). Black high-purity silica tiles 1-5 inches (2.5-12.7 cm) thick are individually cemented to the underside of the orbiter to protect it from temperatures of 1200-2300°F (649-1260°C). Less heat reaches the upper surface of the craft, so it is protected either by white tiles or by a blanket made from a silica composite. Bigger picture from the NASA website.