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Orbit Summary
Orbit Insertion
Orbital maneuvering system fires to place shuttle in circular orbit about two minutes after main engine cutoff.
Guidance, navigation and control systems ensure proper position, velocity and attitude.
Payload bay doors open for heat rejection.
Orbit flight control software regulates reaction control system and orbital maneuvering system firings.
On-Orbit Checkout
Checkout performed day before deorbit.
Left and right main engine nozzles repositioned, hydraulic system activated and checked, all cockpit displays and controls checked.
Payload bay doors closed.
The orbiter rotates 180 degrees and the orbital maneuvering system fires to slow the orbiter down -- deorbit burn.
The reaction control system fires to maneuver the shuttle to entry attitude -- nose first, angled up 40 degrees.
The shuttle coasts till the atmosphere is reached at 121,920 meters (400,000 feet).
IMAGE: Mission Basics

Space Shuttle Basics


After the main engines shut down, the shuttle is in an egg-shaped orbit that, if nothing changed, would cause it to re-enter the atmosphere above the Pacific Ocean, the same as what happens to the external fuel tank. But, about 35 minutes after the main engines have shut down, usually when the shuttle has reached the highest point of the egg-shaped orbit, the two orbital maneuvering system engines, located on the left and right side of the shuttle's tail, are fired for about three minutes. The orbital maneuvering system engines use two propellants that automatically burn whenever they contact one another, and the three-minute firing circularizes the shuttle's orbit at a safe altitude, one that will keep it above the atmosphere.

IMAGE: Orbital maneuvering system engine firing
An orbital maneuvering system engine firing caused this bright glow at the aft end of the shuttle during STS-7.

The shuttle is the only spacecraft ever built that can retrieve large satellites from orbit and bring them back to Earth. Using the Canadian-built robotic arm, called the Remote Manipulator System, mounted on the left-hand edge of the cargo bay, shuttle crews can move large objects into or out of the payload bay. The arm also can maneuver spacewalking astronauts into positions for satellite repairs and maintenance, as have been performed on the Hubble Space Telescope, or space construction, as is being conducted for the International Space Station.

The largest shuttle crew ever flown numbered eight people, but the average crew ranges from five to seven people. Crew members include pilot astronauts, called the commander and pilot who fly the shuttle, and mission specialist astronauts who are scientists and engineers trained to conduct the experiments onboard or perform specific tasks in orbit. Occasionally, the crew also may include payload specialist astronauts in charge of the operations of a specific cargo. The shuttle can launch as much as 28,803 kilograms (63,500 pounds) of cargo into orbit. It has remained in orbit for as long as 17 days before returning to Earth.

IMAGE: Upfiring of the shuttle's reaction control system
Upfiring of the shuttle's reaction control system.

Eating, sleeping and personal hygiene equipment are located on the lower deck of the shuttle, called the middeck. The top deck, called the flight deck, is the shuttle cockpit, with flight controls located on both the front and back walls. A small lower "deck," called the equipment bay, is inaccessible unless the floor panels of the middeck are lifted up. This under-floor area houses avionics equipment, electronics equipment and a trash compartment. The crew cabin's total pressurized volume is about 74.3 cubic meters (2,625 cubic feet). The cabin includes a circular side hatch, about a meter (3 feet) in diameter, that is used for entry and exit from the shuttle before launch and after landing.

The shuttle's airlock, used to seal spacewalkers off from the rest of the cabin and depressurize to begin an extravehicular activity, is located in the payload bay just aft of the main cabin and attached to the middeck by a short tunnel. An inner airlock hatch can be closed to seal the lock from the rest of the cabin. An outer hatch can be opened to exit into space. The airlock's volume is about 4.24 cubic meters (150 cubic feet). A docking mechanism to attach to the International Space Station is located atop the airlock.

IMAGE: crew portraits
Flight portrait and post-flight portrait of the STS-82 crew. The solar arrays of the Hubble Space Telescope are visible behind the STS-82 crew in their flight portrait. The shuttle Discovery is directly behind the crew in their post-flight portrait.

Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 10/22/2002
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