SCIENCE AND SPACE

Entry And Landing Procedures Of A Space Shuttle : Some Facts

1. Deorbit Burn : During this phase of the Space Shuttle's return to earth, its velocity is 27,875 kph. It is marked by the firing of two manoeuvring engines so as to reduce the speed of the orbiter by approximately 330 kph. Thereafter, the shuttle begins to descend.

2. Entry Interface : At this point, the Space Shuttle's velocity is 27,545 kph. The shuttle's entry into earth atmosphere takes place almost 25 minutes after the deorbit burn. During this phase, some parts of the Space Shuttle's exterior record a temperature up to nearly 1,648 degree c.

3. Communication Blackout : During this phase of the Space Shuttle's return to earth, its velocith comes down to 26,874 khp. Heat from re-entry creates pocket of ionised air around the sides and bottom of orbiter. There is a temporary loss of communication with ground control.

4. S-Turn Manoeuvres : Due to atmospheric pressure, the orbiter turn into a high-speed glider and performs a series of four steep 'S' turn to slow down.

5. Terminal Area Energy Management : This phase of landing is marked by a rise in the temperature up to 2,734 kph. It offers the last chance to correct speed if orbiter descends too quickly. Computers steer shuttle toward two imaginary circular heading alignment cylinders 11 km from runway. Eventually, the speed of the shuttle decreases to 1,082 kph.Shuttle commander takes over control of orbiter five minutes before landing. Rate of descent is nearly 22,000 ft per minute.

6. Autoland Sequence : Speed of the shuttle comes down to 684 kph. It descends at about 22 degree toward runway;17 seconds before landing, pilot reduces angle to 1.5 degree.

7. Wheel's Down : At a speed of 430 kph, landing gear is lowered at an altitude of 90 ft, and orbiter touches down at 346 kph. Drag parachute is released and shuttle rolls to stop.