On good day, `exhilarating' glide on brick

Usually, a shuttle lands after fiery toboggan ride to touchdown in Florida

The Loss Of Columbia

February 03, 2003|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

A space shuttle gliding into the Kennedy Space Center may look like a beefed-up airliner ending its milk run from Cleveland. But astronauts say the ride home from space is a fiery toboggan ride on a vehicle they liken to a plummeting brick.

A shuttle landing in Florida typically begins 45 minutes earlier, high over the Pacific Ocean. The shuttle at that point is 150 miles or more above the Earth, orbiting from west to east at 17,500 miles per hour.

The astronauts are still weightless as the commander turns the shuttle's tail toward the direction of flight and fires its two large maneuvering engines.

For three or four minutes, the engines fire, slowing the shuttle. It is only a slowing of 1 percent, but enough to begin to drop the shuttle from orbit, and begin its long, irreversible fall to Earth.

It's a smooth, silent slide at first, said former astronaut Tom Jones, who has done it four times. "It's some quiet time when we can enjoy the ride. It's a pretty tremendous, exhilarating feeling," he said.

The pilot and commander sit up front, with a view out the front windows. The flight engineer sits between them and slightly behind. The rest of the crew is seated at the rear of the flight deck, with views out the shuttle's top windows, or on the mid-deck, with no view at all. All wear fireproof suits and flight helmets, a precaution instituted after the Challenger disaster in 1986.

After the re-entry rockets shut down, the pilot turns the shuttle around again to face in the direction of flight and lifts the nose to a 45-degree angle, its heat shield facing the approaching atmosphere.

About a half-hour before landing, the shuttle is racing eastward, just off the West Coast of the United States, and 400,000 feet high. That's where it begins to strike the atmosphere, beginning the most spectacular part of the ride home.

"The vehicle ... starts to glow, and you can't see out the front window," said former astronaut Charles Bolden Jr., who has piloted the shuttle home twice. "It's as though you're seated inside a light bulb, trying to look out."

The shuttle's fall through the atmosphere heats the gases around the shuttle until it becomes a fiery, glowing plasma.

"There was a plume of orange fire trailing behind us, a transparent orange-yellow," Bolden said.

Outside, the shuttle's skin heats to 3,000 degrees Fahrenheit at the nose and the leading edges of the wings. Tiles on the underside of the craft reach 2,000 to 2,500 degrees.

Inside, however, the cabin remains a comfortable 73 degrees. The astronauts can sense Earth's gravity again and feel deceleration forces up to 3 times the pull of gravity at sea level. Bolden likened the sensation to that of having "a couple of gorillas on your shoulders."

Jones said the hand-held video camera he used during one re-entry "had turned into a 25-pound sack of sand."

The fall through the air causes the shuttle to vibrate and shake. Jones said it was "like driving a heavy truck down a dirt road."

The returning shuttle is now entering the most dangerous phase of its flight home, when high speed and increasing atmospheric forces on the spacecraft reach their peak.

"We understand that you can be killed doing this," said former astronaut Jack Lousma, "but it is something that comes with the turf."

When the shuttle reaches about 250,000 feet, flying over the western United States, the plasma glow dissipates. The shuttle is moving at more than 24 times the speed of sound and falling at a rate of 400 feet per second.

Here, it begins a series of six- or seven-minute automatic banking maneuvers. The right and left turns, precisely controlled by onboard computers, are designed to shed speed and altitude much like skiers turn their skis across the slope to slow descent on a mountain.

The computers calculate how much speed and altitude the spacecraft must lose in the distance remaining to the landing strip to enable the shuttle to touch down safely.

The flight crew monitors the shuttle's systems, making adjustments as needed.

It was during the second of these turns, at about 207,000 feet, that Columbia went silent and vanished from radar.

When things go right, the shuttle finishes the turns below 100,000 feet, and speeds of 2 1/2 times the speed of sound, and flies on toward Kennedy.

Just minutes from landing, the crew can hear the wind rushing by.

"You get a lot of shrieking of wind outside," Jones said. "That's part of the exhilaration factor, that, `Hey, we're really going fast.'"

With no engines, the crew's only option is to land. The shuttle's computers continue to guide the spacecraft until it is within five minutes of landing and begins circling to line up with the runway.

It is still falling "like a brick," Jones said, descending from more than 40,000 feet at 19 degrees - an angle seven times steeper than that of a landing airliner. It is a pitch so steep that Jones, a former B-52 bomber pilot, said he found it "very disconcerting."

"Literally, just before the shuttle reaches the runway, the commander will pull the nose up, to cause it to glide over the runway for touchdown," said Ed Campion, a NASA spokesman at the Johnson Space Center in Houston.

"Because this is nothing more than a giant glider, he can't go around for a second attempt."

Wire services contributed to this article.

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