SPACECRAFT: DECENT AND LANDING

SPACECRAFT: DECENT AND LANDING:

The outside of the Shuttle heats to over 1,500 °C during re-entry. The vehicle begins re-entry by firing the OMS engines opposite to the orbital motion for about three minutes. The deceleration of the Shuttle lowers its orbit perigee down into the atmosphere. This OMS firing is done roughly halfway around the globe from the landing site. The entire re-entry, except for the lowering the landing gear and deploying the air data probes, is then under complete computer control. However the re-entry can be and has (once) been flown manually. The final landing can be done on autopilot, but is typically hand flown.

Endeavour deploys drag chute after touch-down. In the lower atmosphere the Orbiter flies much like a conventional glider, except for a much higher descent rate, over 10,000 feet per minute (roughly 20 times that of an airliner). It glides to landing with a glide angle of 4:1. At approximately Mach 3, two air data probes, located on the left and right sides of the Orbiter's forward lower fuselage, are deployed to sense air pressures related to vehicle's movement in the atmosphere.

When the approach and landing phase begins, the Orbiter is at 10,000 ft (3048 m) altitude, 7.5 miles (12.1 km) to the runway. The pilots apply aerodynamic braking to help slow down the vehicle. The Orbiter's speed is reduced from 424 mph (682.3 km/h) to approximately 215 mph (346 km/h), (compared to 160 mph for a jet airliner), at touch-down. The landing gear is deployed while the Orbiter is flying at 267 mph (429.7 km/h). In additional to applying the speed brakes, a 40 ft (12.2 m) drag chute is deployed once the nose gear touches down at about 185 knots. It is jettisoned as the Orbiter slows through 60 knots.

After landing the vehicle stands on the runway to permit the fumes from poisonous hydrazine that was used as propellant for attitude control to dissipate.