首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Someday, in【C1】______ the outer planets of our solar system, humankind will want to do【C2】______ send small probes that merely
Someday, in【C1】______ the outer planets of our solar system, humankind will want to do【C2】______ send small probes that merely
admin
2013-06-02
47
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.
【C15】
选项
A、slowing
B、decreasing
C、boosting
D、simulating
答案
C
解析
动宾搭配题。本处意思是:以利用该行星的引力来拉动飞船前行,提高速度。故选C boosting“提高”。
转载请注明原文地址:https://kaotiyun.com/show/B2n7777K
0
大学英语六级
相关试题推荐
Itisnotthe"somedayIwillwinthelottery"kindofdaydream,butthekindthattapsintothehidden,partofyourbrain.Tha
Itisnotthe"somedayIwillwinthelottery"kindofdaydream,butthekindthattapsintothehidden,partofyourbrain.Tha
Fromthechildtooldage,wealluselanguageasameansof【B1】______ourknowledgeofourselvesandtheworldaroundus.When
A、ItwaseasytoshipfromEngland.B、Horsesoccasionallyateitiftherewasnograinavailable.C、Peopletookitwiththemwhe
TheAmericanideaofrespectinghumanrightscamefromseveralsources.First,thecolonistshadbeen【36】oftheirfightsinthe
A、Becauseshecouldgraspthecustomers’feeling.B、Becauseshehasestablishedsuccessfulbrands.C、Becausesheisaskillfulw
A、Onehour.B、Threehours.C、Twohours.D、Fourhours.B对话中二次听到expresstrain,听到saveanhour,taketwohours,而问句是localtrain,因此,只需进
Scotlandisauniqueplace.IthassomeofthemostbeautifulcitiesinEurope,alivingevidenceofasplendidandproudpast.
A、HewasborninNewEngland.B、HeonceworkedforHarvardUniversity.C、HewasEdwardThomas’friend.D、Hewasn’tawardedanyp
A、Herillness.B、TheCivilWar.C、HertriptoEngland.D、Hergrandmother’sdeath.B推断题。文章结尾处提到,南北战争期间(theCivilWar),Dorothea在联盟
随机试题
因为在体检过程中被查出感染艾滋病病毒,青年小吴虽然在2010年度某省A市市直属学校招聘考试中连过笔试、面试两关,但最终仍被拒之门外。2010年10月13日,小吴诉A市教育局案开庭。11月12日下午,A市人民法院对此案作出一审判决,认定被告作出的不予录用决定
肺下界降低常见于()
格林一巴利综合征常见的病因为
铸造时铸件应位于铸圈内径的中心,蜡型至铸圈内壁的距离至少
Ⅱ类土壤适用于()。
和解和调解都是自愿性的。()
利息保障倍数主要说明公司( )。
每个合格境外机构投资者可分别在上海、深圳证券交易所委托5家境内证券公司进行证券交易。()
下列关于资本监管的说法,不正确的是()。
教学过程阶段的中心环节是()。
最新回复
(
0
)