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
23
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.
【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://kaotiyun.com/show/n2n7777K
0
大学英语六级
相关试题推荐
ThisyearthecombinedadvertisingrevenuesofGoogleandYahoo!willrivalthecombinedprimetimeadrevenuesofAmerica’sthre
ThisyearthecombinedadvertisingrevenuesofGoogleandYahoo!willrivalthecombinedprimetimeadrevenuesofAmerica’sthre
Fromthechildtooldage,wealluselanguageasameansof【B1】______ourknowledgeofourselvesandtheworldaroundus.When
TheAmericanideaofrespectinghumanrightscamefromseveralsources.First,thecolonistshadbeen【36】oftheirfightsinthe
TheAmericanideaofrespectinghumanrightscamefromseveralsources.First,thecolonistshadbeen【36】oftheirfightsinthe
TheAmericanideaofrespectinghumanrightscamefromseveralsources.First,thecolonistshadbeen【36】oftheirfightsinthe
A、Peoplecanusenearly75percentofit.B、Peoplecanuseabout97percentofit.C、Peoplecanuseexactly3percentofit.D、P
A、Waitandseehowshefeelsin24hours.B、Gohomeimmediatelyandtakesomemedicine.C、Returntothegrocerystoretopickup
A、One.B、Two.C、Three.D、Four.C
A、NewEngland.B、Britain.C、Newfoundland.D、Alaska.C
随机试题
人民团体、企业事业单位等社会组织对公安机关及其人民警察执法活动的监督,主要通过批评、建议、控告、检举等方法进行。()
护士自发形成的志愿者为
高分辨率CT技术条件不正确的是
52岁,月经不规则,月经过多,子宫如孕50天大小,无贫血,诊断为子宫肌瘤。需采用下列哪项措施
蛋白质对紫外线的最大吸收波长是
A.Na+内流B.Cl-内流C.Ca2+内流D.K+内流E.K+外流骨骼肌细胞动作电位降支形成的原因是
女,18岁。皮肤反复紫癜和瘀斑、月经量多2年。既往经常关节痛,并因此经常服用保泰松等药物。家中无类似疾病的患者。10岁起经常刷牙出血。本患者的诊断,不应考虑哪种情况
2010年4月,某市劳动行政部门在对甲公司进行例行检查时,发现甲公司存在以下问题:(1)2009年9月1日,张某发现甲公司未依法为其缴纳社会保险费,当日通知甲公司解除劳动合同。张某自2001年1月1日起开始在甲公司工作,张某的月平均工资为5000元。
A、Sheforgotthetime.B、Shedidn’ttakeenoughlessons.C、Shewassonervousthatshecouldn’tconcentrate.D、Theinstructorla
【B1】【B10】
最新回复
(
0
)