首页
登录
职称英语
[originaltext] The great advance in rocket theory 40 years ago showed that l
[originaltext] The great advance in rocket theory 40 years ago showed that l
游客
2023-09-17
64
管理
问题
The great advance in rocket theory 40 years ago showed that liquid-fuel rockets were far superior in every respect to the skyrocket with its weak solid fuel, the only kind of rocket then known. However, during the last decade, large solid-fuel rockets with solid fuels about as powerful as liquid fuels have made their appearance, and it is a favorite layman’s question to inquire which one is "better". The question is meaningless; one might as well as ask whether a gasoline or a diesel engine is "better". It all depends on the purpose. A liquid-fuel rocket is complicated, but has the advantage that it can be controlled beautifully. The burning of the rocket engine can be stopped completely; it can be reignited when desired. A solid-fuel rocket, on the other hand, is rather simple in construction, though hard to build when a really large size is desired. But once you have a solid-fuel rocket, it is ready for action at a very short notice. A liquid-fuel rocket has to be fueled first and can not be held in readiness for very long after it has been fueled. However, once a solid-fuel rocket has been ignited, it will keep burning. It can’t be stopped and reignited whenever desired. Because a solid-fuel rocket can be kept ready for a long time, most military missiles employ solid fuels, but manned space flight needs the fine adjustments that can only be provided by liquid-fuel rocket. It may be added that a liquid-fuel rocket is an expensive device; a large solid-fuel rocket is, by comparison, cheap.
选项
A、The rocket should be inexpensive to construct.
B、The rocket is capable of lifting heavy spacecraft into orbit.
C、The rocket should be easily controlled.
D、The rocket should be inexpensive to operate.
答案
C
解析
What’s the most important consideration for manned space flight?
转载请注明原文地址:https://tihaiku.com/zcyy/3020552.html
相关试题推荐
[originaltext]M:We’llcontinuewiththeworkofinvestigation.Laura,anident
[originaltext]M:Mm,it’snotabedsizableroom,isit?W:Oh,it’sgreat!It’
[originaltext]W:Ithinkifyouwanttogetsomeexcitementinyourlifeyouou
[originaltext]W:Ithinkifyouwanttogetsomeexcitementinyourlifeyouou
[originaltext]W:Ithinkifyouwanttogetsomeexcitementinyourlifeyouou
[originaltext]W:OurPresident,sinceleavingofficefiveyearsago,hasspent
[originaltext]W:OurPresident,sinceleavingofficefiveyearsago,hasspent
[originaltext]Investmentinthepublicsector,suchaselectricity,irrigat
[originaltext]Throughouthistorymanhaschangedhisphysicalenvironmenti
[originaltext]Throughouthistorymanhaschangedhisphysicalenvironmenti
随机试题
[originaltext]W:Didyoucookthesoupyourself,Mike?It’sdelicious.M:No.M
ARed,RedRosewaswrittenbyA、AlexanderPope.B、RobertBurns.C、WilliamBlake.
Wehavenotobtainedverymuchexperimentdata______conclusionbetweenthetwo
从企业开始招募员工到求职者完成入职手续,需要注意的问题不包括()。A.就业歧视
甲公司是国内唯一的一个100年前相传至今的大型首饰企业集团。目前,公司拥有职工1
关于保温工程质量的说法,正确的是()。A、屋面泡沫混凝土分层浇筑、终凝后应进行至
信号工资理论()。A.能解释薪酬水平的差异 B.认为应聘者心里都有一个
关于cDNA文库的叙述,哪些是正确的A.仅代表构建文库取材细胞当时表达的成套基因
关于髋关节结核的叙述,正确的是 A.儿童多见B.早期病变以单纯性骨结核多见
公民在法律面前一律平等,是我国()。A.社会主义法的基础 B.社会主义立法
最新回复
(
0
)