Anastronautisrequiredtomakesomerepairstotheoutsideofthe...

栏目: 练习题 / 发布于: / 人气:2.35W

问题详情：

An astronaut is required to make some repairs to the outside of the International Space Station. After a successful repair, the astronaut finishes the task. Unfortunately, a tool flies off into space. The tool has now become space junk, high-speed pieces of objects(物体) going around the Earth at 17,000 kilometers per hour.

While humans produce an unbelievable amount of waste on Earth, we might not think too much about space junk. But NASA says there are probable millions of objects, both small and large, going around the Earth in a giant cloud of junk.

Space junk got its start in the middle of the twentieth century, at the very beginning of the space race, when satellite began to be launched to go into orbit (轨道) around the Earth. So far, space junks include waste spaceships and waste spaceship parts, rocket fuel containers and even pieces of paint. Believe or not, there are millions of tiny pieces of paint floating around Earth's orbit. Heat or crashes usually cut off paint from spaceship and turn them into space junk. Because there are so many objects flying around up there, there's concern that crashes between space junks will only produce more of them. Scientists are worried this is already happening.

Anything travelling at a high speed in space would cause a considerable amount of damage to a spaceship if a direct hit happened. Even a small piece of paint is capable of making a quarter-inch hole into the window of a space station. The good news for astronauts is that most space junk is located between 550 and 625 miles above the Earth——the International Space Station flies in orbit at 250 miles high, while spaceships usually only reach 375 miles above the Earth. Space programs are also working on rocket designs that limit the amount of space junk produced during a launch.

For those of us on the Earth, is there a possibility that space junk could fall back to the ground? Everything in orbit will finally be pulled back down by Earth's gravity—when that happens depends on how high the object is and how fast it's going. The higher the object is, the longer the object will take to fall. These objects could stay in orbit for thousands of years. As for the risks of getting hit on the head, fortunately, most objects burn up on their way back to the Earth, and no one has ever been killed by space junk.

44. Where is space junk from?

A. Pieces from satellites.

B. Fuel coming from rockets.

C. Waste from the space station.

D. Spaceships that no longer work.

45. What are scientists worried about space junk?

A. It may rub off the spaceship's outside paint.

B. It may be pulled back by gravity and hurt people.

C. More space junks will probably be produced in crashes.

D. The space station's windows may be blocked by space junk.

46. Where is the passage probably taken from?

A. Astronauts' travel diary.