Landing the STS120 Space Shuttle: one hour before touchdown

Landing-60 minutes

At approximately 12:00 p.m. (ET) today, Mission Control will give the “go” for deorbit burn. Its flight path upon entering the atmosphere and approaching the landing site varies depending on the inclination of launch. Low-inclination missions typically begin the re-entry process over the Indian Ocean, then cross the Pacific, Mexico, southern Texas and the Gulf before reaching Florida.

During reentry and landing, the orbiter is not powered by engines. Instead, it flies like a high-tech glider, relying first on its steering jets and then its aerosurfaces to control the airflow around it.

Landing-30 minutes

Roughly half an hour after the deorbit burn, the orbiter will begin to encounter the effects of the atmosphere. Called Entry Interface, this point usually takes place at an altitude of about 80 miles, and more than 5,000 statute miles from the landing site.  The shuttle begins entering the atmosphere at an altitude of around 400,000 feet.

Early in reentry, the orbiter’s orientation is controlled by the aft steering jets, part of the Reaction Control System. But during descent, the vehicle flies less like a spacecraft and more like an aircraft. 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.

To use up excess energy, the orbiter 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 track toward landing an appearance similar to an elongated letter “S.”

As the orbiter slices through the atmosphere faster than the speed of sound, the sonic boom — really, two distinct claps less than a second apart — can be heard across parts of Florida, depending on the flight path.

Landing-Minus 45,000 feet

At approximately 45,000 feet, the orbiter starts to maneuver into the landing approach corridor.

As it nears the landing site, the commander takes manual control of the vehicle.

Landing-5 minutes
The orbiter’s velocity eases below the speed of sound about 25 statute miles from the runway. As the orbiter nears the Shuttle Landing Facility, the commander takes manual control, piloting the vehicle to touchdown on one of two ends of the SLF.

As it aligns with the runway, the orbiter begins a steep descent with the nose angled as much as 19 degrees down from horizontal. This glide slope is seven times steeper than the average commercial airliner landing. During the final approach, the vehicle drops toward the runway 20 times faster than a commercial airliner as its rate of descent and airspeed increase. At less than 2,000 feet above the ground, the commander raises the nose and slows the rate of descent in preparation for touchdown.

Landing-15 seconds
The main and nose landing gear are deployed and locked in place.

The orbiter’s main landing gear touches down on the runway at 213 to 226 miles per hour. As the nose pitches down and makes contact with the runway, a 40-foot drag chute is deployed from the vehicle’s aft end, and the orbiter rolls to a stop.

Text and image credit: compiled from NASA’s web sites

Watch the landing of STS-121 below.


~ by tellinghistory on November 7, 2007.

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