首页
登录
职称英语
The great advance in rocket theory 40 years ago showed that liquid-fuel rocke
The great advance in rocket theory 40 years ago showed that liquid-fuel rocke
游客
2025-05-10
14
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 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 re-ignited when desired. In addition, the thrust can be made to vary by adjusting the speed of the fuel pumps. 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 very short notice. A liquid-fuel rocket has to be fueled first and cannot 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 cannot be stopped and re-ignited whenever desired (it could conceivably be stopped and re-ignited after a pre-calculated time of burning has elapsed) and its thrust cannot be varied. 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 fuels. It may be added that a liquid-fuel rocket is an expensive device; a large solid-fuel rocket is, by comparison, cheap. But the solid fuel, pound per pound; costs about 10 times as much as the liquid fuel. So you have, on the one, hand, an expensive rocket with a cheep fuel and on the other hand a comparatively cheap rocket with an expensive fuel. [br] Which of the following statements is not characteristic of liquid-fuel rockets?
选项
A、The fuel is cheap.
B、They are cheap to build.
C、They can be stopped and re-ignited.
D、They must be used soon after fueling.
答案
B
解析
文中指出a liquid-fuel rocket is an expensive device,选项B说其造价低,与文意不符。
转载请注明原文地址:https://tihaiku.com/zcyy/4069693.html
相关试题推荐
Advancementinthearmyisoftengiventothepersonwho______.A、callsattentio
Thegreatadvanceinrockettheory40yearsagoshowedthatliquid-fuelrocke
Thegreatadvanceinrockettheory40yearsagoshowedthatliquid-fuelrocke
Thegreatadvanceinrockettheory40yearsagoshowedthatliquid-fuelrocke
Perhapsallsocieties(aresignificantlymoreadvanced)thanourownhaveachiev
Oneoutcomeoftherapidadvanceoftechnologyisthebreakdownofthetradition
Thecarpollutes,butadvancesinfuelqualityandefficiency,andinmicropro-c
Dr.Thompsongaveanexpositionofthetheoryandpracticeofsocialism.A、accoun
Ourtheoryandpracticeintheareaofsentencinghaveundergoneagradualb
Ourtheoryandpracticeintheareaofsentencinghaveundergoneagradualb
随机试题
[originaltext]Didyoucallme,Mary?[/originaltext][audioFiles]2016m8s/audio_e
[originaltext]M:Hello,thisisLandTransportInformationatTorontoAirport.
WhichofthefollowingEnglishsoundsisNOTbilabial?A、[b]B、[m]C、[p]D、[f]D考
测试用例的三要素不包括()。A.输入 B.预期输出 C.执行条件 D.实
A.预防性矫治 B.暂时性错 C.功能性矫治器 D.个别正常验 E.阻断
肾炎性肾病与单纯性肾病相比最主要的特点是A.血浆白蛋白<3g/dl B.血尿,
教师义务是指法律对教师从事教育活动的一定行为的约束。( )
我国2007全年普通高等教育招生566万人,在校生1885万人,毕业生448万人
为落实党中央、国务院推进政府职能转变、深化“放管服”改革和优化营商环境的要求,现
患者,女性,38岁。在工作中中毒,但不清楚中毒的原因。正常情况下,以洗胃方式解救
最新回复
(
0
)