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Broadcast: May 10, 2003
By Cynthia Kirk
This is the VOA Special English program, In the News.
Investigators say they now believe they know what caused the American space shuttle Columbia to break apart as it re-entered the earth's atmosphere. The chairman of the Columbia Accident Investigation Board, Admiral Harold Gehman, announced the committee's "working" theory during a news conference Tuesday in Houston, Texas.
Columbia broke apart February first as it flew two-hundred-thousand kilometers over the state of Texas. It was flying toward a landing at the Kennedy Space Center in Florida. All seven astronauts were killed when the shuttle came apart. Since then, all space shuttle flights have been grounded while investigators search for the cause of the accident.
Investigators have studied evidence2 from almost fifty-thousand pieces of the shuttle. Most of it fell over east Texas and Louisiana. Thousands of people helped in the recovery effort.
After three months of investigating, the board members say they have a better understanding of the events leading up to the accident. Evidence recovered so far supports the belief that the spacecraft was damaged during lift-off on January sixteenth. Photographs taken during the launch show that a piece of foam3 insulation4 fell off the external fuel tank5 and struck Columbia's left wing. Investigators believe that the foam struck heat-resistant carbon panels6 on the front edge of the wing, opening a hole. They noted that an object that came off of the shuttle during its second day in orbit7 also suggests evidence of a hole.
Investigators believe that shortly after re-entry, extremely hot gas entered through the hole in the wing. A recording device tied to hundreds of sensors within the spacecraft helped investigators follow the path of the hot gas inside the wing. The gas melted the wing frame within seconds, causing it to bend. Finally, the shuttle rolled and spun out of control, breaking up high above Earth. Within fifteen minutes, all communication with Columbia stopped.
The board is examining many possible reasons for what may have weakened the strong carbon panels along the shuttle's wing. They are considering manufacturing problems, the age of the shuttles and poor administration of the shuttle program.
NASA officials have begun planning for the return to shuttle flights, possibly early next year. Board members say repeated incidents of foam insulation breaking away from the external fuel tanks must be fixed before the shuttles can fly again.
Board chairman Harold Gehman says they may never prove the wing was damaged by the foam insulation. He says more tests need to be done before any final conclusions can be made. Investigators will suggest ways to make the shuttle program safer in their final report in a few months.
This VOA Special English program, In the News, was written by Cynthia Kirk.
1. shuttle [5FQtl] n. 航天飞机
2. evidence [5evId[ns] n. 明显，迹象，证物
3. foam [f[um] n. 泡沫，水沫，泡沫材料
4. insulation [7InsjJ5leIF[n] n. 绝缘
5. fuel tank n. 燃料水槽
6. panel [5pAnl] n. 面板，嵌板，仪表板
7. orbit [5CbIt] n. 轨道 |