首页
登录
职称英语
Someday, in【C1】______ the outer planets of our solar system, humankind wil
Someday, in【C1】______ the outer planets of our solar system, humankind wil
游客
2023-08-30
44
管理
问题
Someday, in【C1】______ the outer planets of our solar system, humankind will want to do【C2】______ send small probes that merely fly rapidly by them. In time, we will want【C3】______ spacecraft that will go【C4】______ orbit around these alien planets, land robots on their moons, and even return rock and soil sample back to Earth.【C5】______ , we will want to send humans to their moons, on at least【C6】______ which liquid water—the fundamental requirementfor life【C7】______ we know it—is believed to be【C8】______ .
For missions such as these, we will need rockets powered by a nuclear reaction【C9】______ igniting chemicals. Chemical rockets have served us well. But the【C10】______ low amount of energy that they can deliver for a given mass of fuel is a severe【C11】______ when dispatching spacecraft【C12】______ long distances. To reach the outer planets, for example, a chemically-powered space vehicle must【C13】______ fuel by having a very small mass and making【C14】______ use of gravity "assists", in which the craft maneuvers close enough to a planet for the planet’s gravity to propel the craft forward,【C15】______ its speed.
In technical term, chemical rockets have low【C16】______ velocity growth, which means that their exhaust velocities are not high enough to【C17】______ very high speed to the rocket. Nuclear rockets,【C18】______ their chemical counterparts, could impart a maximum velocity of【C19】______ about 22 kilometers a second. Such a high velocity would make possible a direct path to Saturn (土星), reducing travel time from about seven years to as【C20】______ as three. [br] 【C13】
选项
A、conserve
B、consume
C、exploit
D、contain
答案
A
解析
动词辨义题。本处意思是:…以化学燃料为动力的宇宙飞船不得不保存很少的燃料。故选A conserve“保存”。
转载请注明原文地址:https://tihaiku.com/zcyy/2969330.html
相关试题推荐
TheAmericaneconomicsystemisorganizedaroundabasicallyprivateenterpri
Humanity’sprimal(原始的)effortstosystematizetheconceptsofsize,shapes,
TheUnitedStatescourtsystem,aspartofthefederalsystemofgovernment,
TheUnitedStatescourtsystem,aspartofthefederalsystemofgovernment,
TheUnitedStatescourtsystem,aspartofthefederalsystemofgovernment,
TheUnitedStatescourtsystem,aspartofthefederalsystemofgovernment,
TheUnitedStatescourtsystem,aspartofthefederalsystemofgovernment,
TheUnitedStatescourtsystem,aspartofthefederalsystemofgovernment,
Americanculturehasbeenenrichedbythevaluesandbeliefsystemsofvirtu
Americanculturehasbeenenrichedbythevaluesandbeliefsystemsofvirtu
随机试题
Thewindowisdirty.______Icleanitforyou?A、DoB、WillC、ShallCdo意为“做,实行”;w
SalesWhenastoresells【T1】______atacostlowerthanusual,itiscall
Lookingbackonmychildhood,Iamconvincedthatnaturalistsarebornandn
Alloftheinformationthatyouneedtoapplyforyourvisaisavailable-freeo
我国24万成人数据汇总分析表明,我国人群血压水平和高血压患病率北方高于南方,与人
表面白色或灰白色,质硬,吸湿性强,舔之粘舌,无臭无味的药材是A.滑石 B.
教育心理起源论认为教育起源于( )。 A.生产劳动 B.模仿 C.语言
在2010年上海世博会中,丹麦馆名为“梦幻城市”。丹麦馆展出的“小美人鱼”雕像,
根据《民事诉讼法》和相关司法解释,有关简易程序的说法哪一项是不正确的:()
(2018年真题)脾肾阳虚,水饮内停,常见的舌形是( )A.胖嫩舌 B.齿痕
最新回复
(
0
)