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
2024-05-05
12
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] 【C18】
选项
A、in contrast to
B、in addition
C、with regard to
D、contrary to
答案
A
解析
逻辑衔接题。本处意思是为:与化学燃料火箭相比,核能火箭…。故选A in contrast to“与…对比”。
转载请注明原文地址:https://tihaiku.com/zcyy/3585599.html
相关试题推荐
Someday,in【C1】______theouterplanetsofoursolarsystem,humankindwil
Someday,in【C1】______theouterplanetsofoursolarsystem,humankindwil
Someday,in【C1】______theouterplanetsofoursolarsystem,humankindwil
Someday,in【C1】______theouterplanetsofoursolarsystem,humankindwil
Someday,in【C1】______theouterplanetsofoursolarsystem,humankindwil
Someday,in【C1】______theouterplanetsofoursolarsystem,humankindwil
Someday,in【C1】______theouterplanetsofoursolarsystem,humankindwil
Someday,in【C1】______theouterplanetsofoursolarsystem,humankindwil
Someday,in【C1】______theouterplanetsofoursolarsystem,humankindwil
Someday,in【C1】______theouterplanetsofoursolarsystem,humankindwil
随机试题
There’sgoodnewsandbadnewsaboutlifeinmoderncities—first,theba
[originaltext]Childrenhavetheirownrulesinplayinggames.Theyseldomn
治疗风湿性心脏炎的首选药物是A.阿司匹林 B.青霉素 C.布洛芬 D.糖皮
幼儿的基础代谢率低于成年人。( )
A.苯乙肼 B.氯氮平 C.氟西汀 D.碳酸锂 E.马普替林属于单胺氧化
一名中学生晚自习时玩手机,被老师发现后没收。这名学生心怀不满,在老师走后吐了一口
技术分析为基础的投资战略是在否定()市场的前提下,以历史交易数据为基础的调查研究
基金份额不固定,基金份额可以在基金合同约定的时间和场所进行申购或者赎回的基金运作
下列关于审判监督程序的表述不正确的有:A.被告人及其法定代理人对已经发生法律效力
叠加定律不适用于( )。A.电阻电路 B.线性电路 C.非线性电
最新回复
(
0
)