首页
登录
职称英语
Since ancient times, people have dreamed of leaving their home planet and exp
Since ancient times, people have dreamed of leaving their home planet and exp
游客
2023-12-18
13
管理
问题
Since ancient times, people have dreamed of leaving their home planet and exploring other worlds. In the later half of the 20th century, that dream became reality. The space age began with the launch of the first artificial satellites in 1963. A human first went into space in 1963. Since then, astronauts and cosmonauts have ventured into space for ever greater lengths of time, even living aboard orbiting space stations for months on end. Two dozen people have circled the moon or walked on its surface. At the same time, robotic explorers have journeyed where humans could not go, visiting all but one of the solar system’s major worlds. Unpiloted spacecraft have also visited a host of minor bodies such as moons, comets, and asteroids. These explorations have sparked the advance of new technologies, from rockets to communications equipment to computers. Spacecraft studies have yielded a bounty of scientific discoveries about the solar system, the Milky Way Galaxy, and the universe. And they have given humanity a new perspective on the earth and its neighbors in space.
The first challenge of space exploration was developing rockets powerful enough and reliable enough to boost a satellite into orbit. These boosters needed more than brute force, however; they also needed guidance systems to steer them on the proper flight paths to reach their desired orbits. The next challenge was building the satellites themselves. The satellites needed electronic components that were lightweight, yet durable enough to withstand the acceleration and vibration of launch. Creating these components required the world’s aerospace engineering facilities to adopt new standards of reliability in manufacturing and testing. On Earth, engineers also had to build tracking stations to maintain radio communications with these artificial "moons" as they circled the planet.
Beginning in the early 1920s, humans launched probes to explore other planets. The distances traveled by these robotic space travelers required travel times measured in months or years. These spacecraft had to be especially reliable to continue functioning for a decade or more. They also had to withstand such hazards as the radiation belts surrounding Jupiter, particles orbiting in the rings of Saturn, and greater extremes in temperature than are faced by spacecraft in the closeness of Earth. Despite their great scientific returns, these missions often came with high price tags. Today the world’ s space agencies, such as the United States National Aeronautics and Space Administration (NASA. and the European Space Agency (ESA), strive to conduct robotic missions more cheaply and efficiently.
It was inevitable that humans would follow their unpiloted creations into space. Piloted space flight introduced a whole new set of difficulties, many of them concerned with keeping people alive in the hostile environment of space. In addition to the vacuum of space, which requires any piloted spacecraft to carry its own atmosphere, there are other deadly hazards: solar and cosmic radiation, micrometorites (small bits of rock and dust) that might puncture a spacecraft hull or an astronaut’s pressure suit, and extremes of temperature ranging from frigid darkness to broiling sunlight. It was not enough simply to keep people alive in space -- astronauts needed to have a means of accomplishing useful work while they were there. It was necessary to develop tools and techniques for space navigation, and for conducting scientific observations and experiments. Astronauts would have to be protected when they ventured outside the safety of their pressurized spacecraft to work in the vacuum. Missions and hardware would have to be carefully designed to help insure the safety of space crews in any foreseeable emergency, from liftoff to landing.
The challenges of conducting piloted space flights were great enough for missions that orbited Earth. They became even more daunting for the Apollo missions, which sent astronauts to the moon. The achievement of sending astronauts to the lunar surface and back represents a summit of human space flight.
After the Apollo program, the emphasis in piloted missions shifted to long-duration spaceflight, as pioneered aboard Soviet and U.S. space stations. The development of reusable spacecraft became another goal, giving rise to the U.S. space shuttle fleet. Today efforts focus on keeping people healthy during space missions lasting a year or more w the duration needed to reach nearby planets -- and in lowering the cost of sending satellites into orbit. [br] What have given mankind a new viewpoint on the earth and its neighbors in space?
选项
A、Those explorations.
B、The advance of new technologies.
C、Spacecraft studies.
D、Scientific discoveries.
答案
D
解析
答案在第一段,此问题是第一段最后一句,该段指出,技术进步导致的科学发现使人们对地球和其他星球的看法发生变化,选D。
转载请注明原文地址:https://www.tihaiku.com/zcyy/3284993.html
相关试题推荐
Inourlooks-obsessedsociety,manypeoplethinkthatbeingoverweightisan
Inourlooks-obsessedsociety,manypeoplethinkthatbeingoverweightisan
Inourlooks-obsessedsociety,manypeoplethinkthatbeingoverweightisan
Inourlooks-obsessedsociety,manypeoplethinkthatbeingoverweightisan
Inourlooks-obsessedsociety,manypeoplethinkthatbeingoverweightisan
Inourlooks-obsessedsociety,manypeoplethinkthatbeingoverweightisan
Inourlooks-obsessedsociety,manypeoplethinkthatbeingoverweightisan
Inourlooks-obsessedsociety,manypeoplethinkthatbeingoverweightisan
Inourlooks-obsessedsociety,manypeoplethinkthatbeingoverweightisan
Inourlooks-obsessedsociety,manypeoplethinkthatbeingoverweightisan
随机试题
[originaltext]M:IamreallygettingworriedaboutMary.She.willsitinfora
片剂溶出度检查时,必须进行复试的结果是A.6片均不低于规定限度(Q) B.平均
某公司的部分财务状况如下表(一年按365天计算):则两年的应收账款周转天数分别为
免疫胶乳比浊法的特点不包括A.敏感性可达ng/LB.操作简便,易于自动化C.Ig
某县筹备县庆,园林部门决定利用现有的3490盆甲种花卉和2950盆乙种花丼搭
某企业试验用两种新材料生产产品。现从每种材料生产的产品中各随机抽取5个进行检验,
解决委托代理问题的微观经济政策包括()。A.明晰产权 B.强化企业的外部竞争
以下关于基金会监事的规定,正确的是()。A.监事任期与理事任期不同 B.
社区工作者小王一直在介入张大爷精神健康的服务工作。张大爷在退休之后,没有事情干,
面谈过程中,调查人员可以采用国际通行的信用“6C”的标准原则,以下不属于该原则内
最新回复
(
0
)