STS 129: Atlantis Prepares For Landing

It's all been too quick, mission STS-129 is nearly over. Atlantis and her crew have completed all of the necessary tasks and prepared the orbiter to re-enter the atmosphere and glide home as an aircraft. Astronauts Charles Hobaugh, Barry Wilmore and Leland Melvin tested Atlantis’ flight control surfaces, the flaps and rudders, and test fired the thruster jets that control its orientation.

Orbit 171 landing track

Orbit 172 landing track

There are two landing opportunities at Kennedy tomorrow, when the rotation of the Earth below the Shuttle's orbital track is optimal for de-orbit and re-entry. The process is pretty cool and involves lowering the perigee of the Shuttle's elliptical orbit on the other side of the world from Kennedy, then guiding the vehicle through the atmosphere to a precise landing. All that energy that was put into Atlantis at launch to accelerate her up to 17,500mph has to be taken out again, but this time there isn't a huge rocket stack and fuel tank attached, so it has to be done by a carefully choreographed series of events.

First contact with the Earth's atmosphere at such high speed creates incredible friction and temperatures that would melt the spacecraft if it weren't covered in protective thermal tiles. Thrusters are used at this stage to maintain the orientation of the vehicle. After slowing down enough to permit aerodynamic interaction, the wings and rudder take over and Atlantis performs a series of side to side rolls to lose even more speed. As it approaches the cape it is still traveling supersonic, and as it drops to subsonic speeds the classic dual sonic booms are heard. With the runway looming, one final 270 degree turn bleeds off the final excess speed and Atlantis flares up her nose to touch down at regular aircraft speed.

If all goes well, the first landing is scheduled for 9:44am EST. The second 90 minutes later.


Images credit: NASA
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