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  3. The 10th launch of the space shuttle Challenger was scheduled as the 25th space shuttle mission. Francis R. (Dick) Scobee was th

The 10th launch of the space shuttle Challenger was scheduled as the 25th space shuttle mission. Francis R. (Dick) Scobee was th

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问题    The 10th launch of the space shuttle Challenger was scheduled as the 25th space shuttle mission. Francis R. (Dick) Scobee was the mission commander. The crew included Christa McAuliffe, a high-school teacher from New Hampshire. The five other crew members were Gregory B. Jarvis, Ronald E. McNair, Ellison S. Onizuka, Judith A. Resnik, and Michael J. Smith.
   After several launch delays, NASA officials overruled the concerns of engineers and ordered a liftoff on a cold morning, Jan. 28, 1986. The mission ended in tragedy. Challenger disintegrated into a ball of fire. The accident occurred 73 seconds into flight, at an altitude of 14020 meters and at about twice the speed of sound.
   Strictly speaking, Challenger did not explode. Instead, various structural failures caused the spacecraft to break apart. Although Challenger disintegrated almost without warning, the crew may have briefly been aware that something was wrong. The crew cabin tore loose from the rest of the shuttle and soared through the air. It took almost three minutes for the cabin to fall to the Atlantic Ocean, where it smashed on impact, killing the seven crew members.
   All shuttle missions were halted while a special commission appointed by President Reagan determined the cause of the accident and what could be done to prevent such disasters from happening again. In June I986, the commission reported that the accident was caused by a failure of O rings in the shuttle’s right solid rocket booster. These rubber rings sealed the joint between the two lower segments of the booster. Design flaws in the joint and unusually cold weather during launch caused the O rings to allow hot gases to leak out of the booster through the joint. Flames from within the booster streamed past the failed seal and quickly expanded the small hole. The flaming gases then burned a hole in the shuttle’s external fuel tank. The flames also cut away one of the supporting beams that held the booster to the side of the external tank. The booster tore loose and ruptured the tank. The propellants (火箭燃料) from the tank formed a giant fireball as structural failures tore the vehicle apart.
   The commission said NASA’s decision to launch the shuttle was flawed. Top-level decision makers had not been informed of problems with the joints and O rings or of the possible damaging effects of cold weather.
   Shuttle designers made several technical modifications, including an improved O-ring design and the addition of a crew bail-out system. Although such a system would not work in all cases, it could save the lives of shuttle crew members in some situations. Procedural changes included stricter safety reviews and more restrictive launching conditions. The space shuttle resumed flying on Sept.29, 1988, with the launch of the redesigned shuttle Discovery. (465 words)
Which of the following is mentioned as an improvement on the launch of Discovery?
选项 A、a special examination of the O ring
B、greater safety design of the crew cabin
C、redesign of the booster system
D、careful consideration of the effects of weather
答案D
解析 根据最后一段，宇航飞机的设计者做了几方面的技术改进，包括改进了O形圈的设计，增加了跳伞 (bail-out)系统，虽然跳伞系统不可能是万能的，但在某些情况下却可以拯救宇航员的性命。程序上也做出了改进，包括更严格的安全检查，更严格的升空条件。根据上下文，这里所说的launching conditions包括天气情况。1988年9月29日，改进后的航天飞机(“发现者”号)成功升空。从以上分析来看，改进内容不包括A、B、C所提到的内容。
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