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Landing Summary
Entry phase begins 5 minutes before the shuttle re-enters the atmosphere at an altitude of 169,773 meters (557,000 feet).
Between the altitudes of 80,772 meters (265,000 feet) and 49,377 meters (162,000 feet) the shuttle generates intense heat. Radio communications are maintained, however, via the NASA Tracking, Data and Relay Satellite System (TDRS).
During re-entry, guidance software manages the shuttle's trajectory, while protecting against overheating and excessive pressure.
The shuttle coasts till the atmosphere is reached at 121,920 meters (400,000 feet).

IMAGE: Space Shuttle Endeavour lands
Concluding its world-mapping mission, the Space Shuttle Endeavour lands at Kennedy Space Center Tuesday, February 22, 2000. (Media Player Format - 28K / 56K; Real Video Format - 28K / 56K)

IMAGE: Mission Basics

Space Shuttle Basics


When it is time to return to Earth, the shuttle is rotated tailfirst into the direction of travel to prepare for another firing of the orbital maneuvering system engines, a firing called the deorbit burn. This engine firing, usually about three minutes long, slows the shuttle by only a couple of hundred miles per hour, but it is enough that it begins to descend toward the atmosphere. The engine firing takes place usually half a world away from the intended landing site: for example, the firing may take place above the Indian Ocean to put the shuttle on course toward a landing at the Kennedy Space Center. The three-minute firing is the only active brake the shuttle will use as it heads toward a landing. The rest of its descent toward Florida and trip halfway around the world is devoted to slowing down using only the drag produced by the atmosphere.

IMAGE: shuttle landing
The Space Shuttle Endeavour lands at the Kennedy Space Center.

After the firing takes place, it is about another 25 minutes before the shuttle will descend to a point that it first encounters the effects of the atmosphere, usually at an altitude of about 129 kilometers (80 miles) and a range of more than 8,047 kilometers (5,000 miles) from the landing site. Before the shuttle encounters the atmosphere, leftover fuel is burned from the forward reaction control system steering jets as a safety precaution. Before it reaches the upper atmosphere, the shuttle is oriented with the nose angled up about 40 degrees from horizontal and its wings level, an orientation that keeps the black thermal tiles on the underside facing the majority of the heat generated by its encounter, heat that can range as high as 1,648.9 degrees Celsius (3,000 degrees Fahrenheit) on the leading edges of the wings and nose.

The aft steering jets are used to control the shuttle's orientation as it descends into the atmosphere. As it descends, however, it begins a transition from spacecraft to aircraft, and its aerosurfaces -- the wing flaps and rudder -- gradually become active as air pressure builds. As those surfaces become usable, the steering jets turn off automatically.

IMAGE: typical shuttle groundtrack
Typical shuttle groundtrack for a landing at Kennedy Space Center.

During its descent, the shuttle performs a series of four steep banks, rolling over as much as 80 degrees to one side or the other, to slow down. The series of banks gives the shuttle's groundtrack toward landing an appearance similar to a highly elongated letter "S".

As the shuttle approaches the landing site, it incorporates several aids to navigation. The first, a radio beacon from the Tactical Air Navigation System, or TACAN, is received when the shuttle is about 225 kilometers (140 miles) from the landing site and at an altitude of about 45,720 meters (150,000 feet). The TACAN provides updated bearing information to the shuttle to aid in steering toward the runway.

As the shuttle continues toward landing and its speed drops to less than three times the speed of sound, or Mach 3, two air data probes are deployed from either side of the nose of the spacecraft. These probes provide supplemental information on the airspeed and altitude derived from the outside barometric pressure and wind speed.

For a normal entry and landing, the shuttle's flight control computers are in control of the spacecraft until it is about 40 kilometers (25 miles) from touchdown. At that time, as the shuttle's speed drops below the speed of sound and it is at an altitude of about 15,240 meters (50,000 feet), the commander takes over manual control of the approach and landing. Using an approach aid called the Microwave Scanning Beam Landing system that is installed at shuttle landing sites, the commander normally flies the shuttle around an imaginary cylinder to align with the runway, sometimes completing almost a full 6.4-kilometer- (4-mile-) diameter circle of one end of the runway.

IMAGE: space shuttle being serviced after landing
The space shuttle being serviced immediately after landing.

During the circle, the shuttle's altitude drops from 15,240 meters (50,000 feet) to about 3,048 meters (10,000 feet) as it begins to align with the runway. As it aligns with the runway, the shuttle then begins a steep descent with the nose angled as much as 19 degrees down from horizontal, a glide slope that is seven times as steep as the average commercial airliner landing. During the final approach, the shuttle drops toward the runway 20 times faster than a commercial airliner as its rate of descent and airspeed increase. When it is less than 610 meters (2,000 feet) above the ground, the commander pulls up the nose and slows the rate of descent in preparation for touchdown.

At this point, the pilot deploys the landing gear. As the shuttle's main landing gear touches down, it is dropping at less than 8 kilometers per hour (5 miles per hour) and has a forward speed of about 354 kilometers per hour (220 miles per hour). After touchdown, the pilot deploys a drag chute from a compartment located just below the tail and the commander begins to drop the shuttle's nose gear slowly toward the runway. The drag chute is then jettisoned before the wheels come to a stop to ensure that it falls clear of the shuttle.

Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 03/17/2003
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