Tuesday, September 21, 2010
We Fly The Space Shuttle (Simulator, That Is)
What’s it like to reenter the atmosphere from Earth’s orbit?
Senior Editor Bill Cox (left) and Flight Director Paul Dye (right) fly a series of landings in the motion-based Shuttle simulator at NASA’s Johnson Space Center in Houston, Texas.
The flight deck is familiar yet foreign, with eight flat-panel, PFD/MFD displays that offer graphical presentations of many standard aviation parameters—airspeed, altitude, attitude, heading, rate of climb, plus a number of other instruments you probably wouldn’t recognize. Still, there’s enough that’s friendly so that those of us confined to the bottom 10 miles of sky don’t feel lost.
Climbing into either of the pilot seats is exactly that, a climb, and I was doing it in comfortable street clothes with the cockpit conveniently straight and level as opposed to lying on its back. It’s hard to imagine how difficult the task would be wearing a full David Clark pressure suit with the aircraft pointed vertically up.
The pilot flies the Shuttle with a short-throw, fly-by-wire hand controller mounted on a pedestal. It looks fairly conventional, but it has at least one function you may not recognize. It incorporates a third direction of travel in addition to pitch and roll. In space, without the benefit of an atmosphere, the Shuttle can be maneuvered thru its yaw axis, and the pilot commands thrusters to accomplish a lateral yaw roll by simply twisting the stick. This fires thrusters that rotate the spacecraft as if it were balanced on the head of a pin. Pretty obviously, that function isn’t operative during an approach to landing.
Launch From Cape Canaveral
Everyone aboard the Shuttle is a passenger during the launch, as the entire process—liftoff to orbit—is computer controlled. Flight director Paul Dye nevertheless gave us a taste of the launch. The first step in a simulated launch is to rotate the sim to the aforementioned vertical position. This is, after all, a motion-based simulator, so we were given an idea of the real starting position, lying on our backs.
The simulator re-creates the experience of launch fairly accurately, though Gibson comments that the vibration of an actual launch is more violent than the sim experience. Considering that the sim is primarily an electric device with hydraulic assist, repeated shaking wouldn’t be conducive to long life.
You feel the rumble of the engines seven seconds before launch, and when the countdown reaches zero and the explosive bolts release the Shuttle, the launch becomes a numbers game, and all the numbers are BIG. You can watch the tower begin to flash by as the 4.4 million-pound “stack” starts its climb with the assistance of about 7.5 million pounds of thrust. (The stack consists of the orbiter itself, two solid rocket boosters—SRBs—and the huge external tank.) Gibson commented that the real Shuttle comes off the ground with what seems like a tidal wave of power. Acceleration is reminiscent of riding the thrust of a giant rubber band, subjecting the crew to an eventual three G’s of vertical acceleration. Meanwhile, the massive thrust of five rocket engines creates a level of vibration similar to a giant, berserk paint-shaking machine.
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