The Space Shuttle
The world's first reusable spacecraft launched like a rocket, maneuvered in Earth orbit like a spacecraft and landed like an airplane. It was comprised of the orbiter, the main engines, the external tank, and the solid rocket boosters.
The Space Shuttle was the world’s first reusable spacecraft, and the first spacecraft in history that can carry large satellites both to and from orbit. The Shuttle launches like a rocket, maneuvers in Earth orbit like a spacecraft and lands like an airplane. Each of the three Space Shuttle orbiters now in operation—Discovery, Atlantis and Endeavour—is designed to fly at least 100 missions. So far, altogether they have flown a combined total of less than one-fourth of that.
Columbia was the first Space Shuttle orbiter to be delivered to NASA’s Kennedy Space Center, Fla., in March 1979. Columbia and the STS-107 crew were lost Feb. 1, 2003, during re-entry. The Orbiter Challenger was delivered to KSC in July 1982 and was destroyed in an explosion during ascent in January 1986. Discovery was delivered in November 1983. Atlantis was delivered in April 1985. Endeavour was built as a replacement following the Challenger accident and was delivered to Florida in May 1991. An early Space Shuttle Orbiter, the Enterprise, never flew in space but was used for approach and landing tests at the Dryden Flight Research Center and several launch pad studies in the late 1970s.
The Space Shuttle consists of three major components: the Orbiter which houses the crew; a large External Tank that holds fuel for the main engines; and two Solid Rocket Boosters which provide most of the Shuttle’s lift during the first two minutes of flight. All of the components are reused except for the external fuel tank, which burns up in the atmosphere after each launch.
The longest the Shuttle has stayed in orbit on any single mission is 17.5 days on mission STS-80 in November 1996. Normally, missions may be planned for anywhere from five to 16 days in duration. The smallest crew ever to fly on the Shuttle numbered two people on the first few missions. The largest crew numbered eight people. Normally, crews may range in size from five to seven people. The Shuttle is designed to reach orbits ranging from about 185 kilometers to 643 kilometers (115 statute miles to 400 statute miles) high.
The Shuttle has the most reliable launch record of any rocket now in operation. Since 1981, it has boosted more than 1.36 million kilograms (3 million pounds) of cargo into orbit. More than than 600 crew members have flown on its missions. Although it has been in operation for almost 20 years, the Shuttle has continually evolved and is significantly different today than when it first was launched. NASA has made literally thousands of major and minor modifications to the original design that have made it safer, more reliable and more capable today than ever before.
Since 1992 alone, NASA has made engine and system improvements that are estimated to have tripled the safety of flying the Space Shuttle, and the number of problems experienced while a Space Shuttle is in flight has decreased by 70 percent. During the same period, the cost of operating the Shuttle has decreased by one and a quarter billion dollars annually—a reduction of more than 40 percent. At the same time, because of weight reductions and other improvements, the cargo the Shuttle can carry has increased by 7.3 metric tons (8 tons.)
Main Engines
The three Space Shuttle Main Engines, in conjunction with the Solid Rocket Boosters, provide the thrust to lift the Orbiter off the ground for the initial ascent. The main engines continue to operate for 8.5 minutes after launch, the duration of the Shuttle’s powered flight.
After the solid rockets are jettisoned, the main engines provide thrust which accelerates the Shuttle from 4,828 kilometers per hour (3,000 mph) to over 27,358 kilometers per hour (17,000 mph) in just six minutes to reach orbit. They create a combined maximum thrust of more than 1.2 million pounds.
As the Shuttle accelerates, the main engines burn a half-million gallons of liquid propellant provided by the large, orange external fuel tank. The main engines burn liquid hydrogen—the second coldest liquid on Earth at minus 423 degrees Fahrenheit (minus 252.8 degrees Celsius)—and liquid oxygen.
The engines’ exhaust is primarily water vapor as the hydrogen and oxygen combine. As they push the Shuttle toward orbit, the engines consume liquid fuel at a rate that would drain an average family swimming pool in under 25 seconds generating over 37 million horsepower. Their turbines spin almost 13 times as fast as an automobile engine spins when it is running at highway speed.
The main engines develop thrust by using high-energy propellants in a staged combustion cycle. The propellants are partially combusted in dual preburners to produce high-pressure hot gas to drive the turbopumps.
Combustion is completed in the main combustion chamber. Temperatures in the main engine combustion chamber can reach as high as 6,000 degrees Fahrenheit (3,315.6 degrees Celsius).
Each Space Shuttle Main Engine operates at a liquid oxygen/liquid hydrogen mixture ratio of 6 to 1 to produce a sea level thrust of 179,097 kilograms (375,000 pounds) and a vacuum thrust of 213,188 (470,000 pounds).
The engines can be throttled over a thrust range of 65 percent to 109 percent, which provides for a high thrust level during liftoff and the initial ascent phase but allows thrust to be reduced to limit acceleration to 3 g’s during the final ascent phase. The engines are gimbaled to provide pitch, yaw and roll control during the ascent.
Solid Rocket Boosters
The Solid Rocket Boosters (SRBs) operate in parallel with the main engines for the first two minutes of flight to provide the additional thrust needed for the Orbiter to escape the gravitational pull of the Earth. At an altitude of approximately 45 km (24 nautical miles), the boosters separate from the orbiter/external tank, descend on parachutes, and land in the Atlantic Ocean. They are recovered by ships, returned to land, and refurbished for reuse. The boosters also assist in guiding the entire vehicle during initial ascent. Thrust of both boosters is equal to 5,300,000 lbs.
Propellant Properties
16% Atomized aluminum powder (fuel)
69.8% Ammonium perchlorate (oxidizer)
.2% Iron oxide powder (catalyst)
12% Polybutadiene acrylic acid acrylamide (binder)
2% Epoxy curing agent
In addition to the solid rocket motor, the booster contains the structural, thrust vector control, separation, recovery, and electrical and instrumentation subsystems.
The solid rocket motor is the largest solid propellant motor ever developed for space flight and the first built to be used on a manned craft. The huge motor is composed of a segmented motor case loaded with solid propellants, an ignition system, a movable nozzle and the necessary instrumentation and integration hardware.
Each solid rocket motor contains more than 450,000 kg (1,000,000 lb.) of propellant, which requires an extensive mixing and casting operation at a plant in Utah. The propellant is mixed in 600-gallon bowls located in three different mixer buildings. The propellant is then taken to special casting buildings and poured into the casting segments.
Cured propellant looks and feels like a hard rubber typewriter eraser. The combined polymer and its curing agent is a synthetic rubber. Flexibility of the propellant is controlled by the ratio of binder to curing agent and the solid ingredients, namely oxidizer and aluminum. The solid fuel is actually powdered aluminum — a form similar to the foil wraps in your kitchen — mixed with oxygen provided by a chemical called ammonium perchlorate.
External Tank
The External Tank, or ET, is the “gas tank” for the Orbiter; it contains the propellants used by the Space Shuttle Main Engines.
The tank is also the “backbone” of the Shuttle during the launch, providing structural support for attachment with the solid rocket boosters and orbiter.
The tank is the only component of the Space Shuttle that is not reused. Approximately 8.5 minutes into the flight, with its propellant used, the tank is jettisoned.
At liftoff, the External Tank absorbs the total (7.8 million pounds) thrust loads of the three main engines and the two solid rocket motors.
When the Solid Rocket Boosters separate at an altitude of approximately 45 kilometers (28 miles), the orbiter, with the main engines still burning, carries the external tank piggyback to near orbital velocity, approximately 113 kilometers (70 miles) above the Earth. The now nearly empty tank separates and falls in a preplanned trajectory with the majority of it disintegrating in the atmosphere and the rest falling into the ocean.
The three main components of the External Tank are an oxygen tank, located in the forward position, an aft-positioned hydrogen tank, and a collar-like intertank, which connects the two propellant tanks, houses instrumentation and processing equipment, and provides the attachment structure for the forward end of the solid rocket boosters.
The hydrogen tank is 2.5 times larger than the oxygen tank but weighs only one-third as much when filled to capacity. The reason for the difference in weight is that liquid oxygen is 16 times heavier than liquid hydrogen.
The skin of the External Tank is covered with a thermal protection system that is a 2.5-centimeter (1-inch) thick coating of spray-on polyisocyanurate foam. The purpose of the thermal protection system is to maintain the propellants at an acceptable temperature, to protect the skin surface from aerodynamic heat and to minimize ice formation.
The External Tank includes a propellant feed system to duct the propellants to the Orbiter engines, a pressurization and vent system to regulate the tank pressure, an environmental conditioning system to regulate the temperature and render the atmosphere in the intertank area inert, and an electrical system to distribute power and instrumentation signals and provide lightning protection.
The tank’s propellants are fed to the Orbiter through a 43-centimeter (17-inch) diameter connection that branches inside the orbiter to feed each main engine.
Orbiter Discovery
Discovery (OV-103) was NASA’s third space shuttle orbiter to join the fleet, arriving for the first time at the Kennedy Space Center in Florida in November 1983.
After checkout and processing, it was launched on Aug. 30, 1984, for its first mission, 41-D, to deploy three communications satellites.
Since that inaugural flight, Discovery has completed more than 30 successful missions, surpassing the number of flights made by any other orbiter in NASA’s fleet. Just like all of the orbiters, it has undergone some major modifications over the years. The most recent began in 2002 and was the first carried out at Kennedy. It provided 99 upgrades and 88 special tests, including new changes to make it safer for flight.
Discovery has the distinction of being chosen as the Return to Flight orbiter twice. The first was for STS-26 in 1988, and the second when it carried the STS-114 crew on NASA’s Return to Flight mission to the International Space Station in July 2005.
The choice of the name “Discovery” carried on a tradition drawn from some historic, Earth-bound exploring ships of the past. One of these sailing forerunners was the vessel used in the early 1600s by Henry Hudson to explore Hudson Bay and search for a northwest passage from the Atlantic to the Pacific.
Another such ship was used by British explorer James Cook in the 1770s during his voyages in the South Pacific, leading to the discovery of the Hawaiian Islands. In addition, two British Royal Geographical Society ships have carried the name “Discovery” as they sailed on expeditions to the North Pole and the Antarctic.
Destined for exploring the heavens instead of the seas, it was only fitting that NASA’s Discovery carried the Hubble Space Telescope into space during mission STS-31 in April 1990, and provided both the second and third Hubble servicing missions (STS-82 in February 1997 and STS-103 in December 1999).
During its many successful trips to space, Discovery has carried satellites aloft, ferried modules and crew to the International Space Station, and provided the setting for countless scientific experiments.
https://www.nasa.gov/reference/the-space-shuttle/