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
2023-09-14
15
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 if or 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-fund 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?文中提到“manned space flight needs the fine adjustments that can only be provided by liquid-fuel rocket.”故选C。
转载请注明原文地址:https://www.tihaiku.com/zcyy/3014337.html
相关试题推荐
[originaltext]WilliamShakespearewaschristenedinthemarkettownofStrat
[originaltext]WilliamShakespearewaschristenedinthemarkettownofStrat
[originaltext]Theworldisnotonlyhungry;itisalsothirstyforwater.Th
[originaltext]Theworldisnotonlyhungry;itisalsothirstyforwater.Th
[originaltext]M:Hello,Ann.Ihaven’tseenyouinawhile.Whatseemstobeth
[originaltext]M:Hello,Ann.Ihaven’tseenyouinawhile.Whatseemstobeth
[originaltext]M:Hello,Ann.Ihaven’tseenyouinawhile.Whatseemstobeth
_______________(我订阅这份杂志的主要原因)istokeepabreastofadvancesinscience.Mymain
[originaltext]Weknowthenthatinthe,US,it’sthejobofCongresstoprop
[originaltext]TheAmericansbelievethatanybodycanbecomePresidentofthe
随机试题
IntroductiontoGeographyCourse1.ThescopeofgeographyProcessesaffect【
据Frank-Starling定律()A.心室收缩力与心室收缩末期容积正相关
M企业属于小规模纳税人,2011年6月25日销售产品100件,开出的普通发票上注
互联网规定的A类私网IP地址为()。A.10.0.0.0/8 B.172.
教师布置学生搜集整理描写四季景物的诗句,依春、夏、秋、冬的时序排列,正确的是(
中性粒细胞的主要功能是A:产生抗体 B:产生肝素 C:参与过敏反应 D:吞
A.自杀 B.学校恐怖症 C.遗尿 D.违拗 E.溺水学龄前期常见的心理
全脊椎麻醉的严重性主要在于A:损伤脊髓致瘫痪 B:麻醉时间持久 C:长时间低
57、线路保护应直接采样,经GOOSE网络跳断路器。
义务教育的学制,通常有( )。A、 “六三”学制 B、 “五四”学制 C、
最新回复
(
0
)