2. 外语
  3. As in the field of space travel, so in undersea exploration new technologies continue to appear. They share a number of similar

As in the field of space travel, so in undersea exploration new technologies continue to appear. They share a number of similar

admin2012-09-10  47
问题 As in the field of space travel, so in undersea exploration new technologies continue to appear.  They share a number of similarities with each other — as well as some important differences.
   Manned submersibles (潜水器), like spaceships, must maintain living conditions in an unnatural environment. But while a spaceship must simply be sealed against the vacuum of space, a submersible must be able to bear extreme pressure if it is not to break up in deep water.
   In exploring space, unmanned vehicles were employed before astronauts. In undersea exploration, on the other hand, men paved the way, only recently have unmanned remote-operated vehicles (ROVs) been put to use.
   One reason for this is that communicating with vehicles in orbit is much easier than talking to these underwater. A vacuum am ideal medium for radio communications, but underwater communications are limited to much slower sound waves. Thus, most undersea vehicles—particularly ROVs— operate at the end of long ropes.
   For a similar reason, knowing where you are undersea is much more difficult than in space. A spaceship’s position can be located by following its radio signal, or by using telescopes and radar. For an undersea vehicle, however, a special network of sonar (声纳) must be laid out in advance on the ocean’ floor in the area of a dive to locate the vehicle’s position.
   Though undersea exploration is more challenging than outer space in a number of respects, it has a distinct advantage: Going to the ocean depths doesn’t require the power necessary to escape Earth’s gravity. Thus, it remains far less expensive.
选项 A、the communication problem
B、the ocean depths
C、the movement of waves
D、the problem of vacuum
答案A
解析 参阅第四段第一句。
转载请注明原文地址:https://jikaoti.com/ti/14JsFFFM
本试题收录于： 职称英语理工类A级题库职称英语分类
0

职称英语理工类A级

职称英语

相关试题推荐
随机试题
最新回复(0)