How a space shuttle lands?
When a mission is over, to land following operations are performed
The bay door is closed. If the space shuttle is flying upside down (nose first), reaction control system thrusters fire to turn the tail first.
Then the crew fires the OMS engines to slow the space shuttle. It takes space shuttle 25 minutes to reach the upper atmosphere.
During that period, reaction control system thrusters are fired to pitch the shuttle over so that the bottom of the shuttle faces the atmosphere and it is moving nose first again.
Finally, the leftover fuel is burnt as a precautionary measure as the shuttle encounters maximum heat at the point of re-entry.
The space shuttle enters the earth at a speed greater than 28,000-km/h. The shuttle will heat air molecules and friction is built up. The friction due to air raises the temperature to 1500 0 C. To protect from this heat spacecrafts are constructed of insulating ceramic materials.
Reinforced carbon- carbon material is used for the wings and underside.
High temperature black surface insulation tiles are used for the upper forward fuselage and around the windows
White nomex blankets make up the upper payload bay doors, upper portion of the wings and mid/aft fuselage
Low temperature white surface tiles are used for the remaining area.
The above materials are designed to absorb large quantity of heat. These materials have high heat capacity.
The hot ionized gases present in the atmosphere prevent radio communication with earth for about 12 minutes. This is referred to as “ ionization blackout”.
When the shuttle enters successfully into the earth's atmosphere, it flies like an airplane. It is designed in such a way that it can generate lift with a small wing area. A series of s-shaped turns are made to slow the speed as it approaches the runway.
At 25 miles above, the shuttle's computer give the control to the commander. The commander flies the shuttle around an imaginary cylinder to line the orbiter with the runway and drop the altitude. During final approach, the commander steepens the angle of descent to minus 20 degree.
When the shuttle is 610m above the ground, the commander pulls the nose to slow the rate of descent. The pilot deploys the landing gear and the shuttle touches down. The commander applies brakes and the speed brake on the vertical tail opens up. A parachute is deployed from the back to stop the shuttle. The parachute and speed brakes increase the drag and stops the shuttle about the midway to three quarters down the runway.
After landing, the crew goes through the shutdown procedures. This process takes about 20 minutes. During this time, the shuttle is cooled and noxious gases, which were produced during re-entry, blow away. Once the shuttle is powered down, the crew exits the vehicle.