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
2024-06-16
35
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/3636818.html
相关试题推荐
[originaltext]GeneralizingabouteducationintheUnitedStatesinvolvesso
[originaltext]Yourprofessorhasaskedmetotalktoyoutodayabouttheto
[originaltext]Yourprofessorhasaskedmetotalktoyoutodayabouttheto
[originaltext]Inthe18thcenturyFrencheconomistsprotestedtheexcessive
[originaltext]Todaywearegoingtotalkaboutcopyrightingworksofart.A
[originaltext]Todaywearegoingtotalkaboutcopyrightingworksofart.A
[originaltext]Todaywearegoingtotalkaboutcopyrightingworksofart.A
[originaltext]Exportersaregoingtohavetochangeiftheyhopetopenetra
[originaltext]Exportersaregoingtohavetochangeiftheyhopetopenetra
[originaltext]M:Soyou’regoingtobewritingfortheschoolnewspaper?W:Yes
随机试题
Wefindthatbrightchildrenarerarelyheldbackbymixed-abilityteaching.
Insomecountries______aregettingricherandricher.A、richB、therichC、riche
Iwishmymemoryworkeddifferently.1dliketobeabletoconjureupanac
ABritishstudyfoundthatBvitaminscouldreducebrainshrinkageinolder
It’snosecretthatmanychildrenwouldbehealthierandhappierwithadopti
新生儿同种免疫性血小板减少性紫癜症(NAITP)的病因,下列哪项是正确的( )
下列关于煤气设备与管道附属装置的说法,正确的是( )。A.眼镜阀和扇形阀不宜单
Thechangeinthatvillagewasmiraculou
因支气管曲张静脉破裂所致咯血最常见于A.肺结核 B.肺脓肿 C.肺栓塞 D
甲公司为一家咨询服务提供商,与某客户签订了一项咨询服务合同。甲公司为取得该合同而
最新回复
(
0
)