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[7] 金属氢是氢在超高压下变成的导电体,导电性类似于金属,故称金属氢。——译注
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[8] Ranga P.Dias and Isaac F.Silvera,“Observation of the Wigner-Huntington Transition to Metallic Hydrogen,” Science 355(2017):715-718,doi:10.1126/science.aal1579.
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[9] Isaac Silvera,private communication,March 20,2018.
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[10] 第二次世界大战后,冯·布劳恩和他的许多同事被秘密转移到美国,此为回形针行动(Operation Paperclip)的一部分。他们为美国陆军的中程弹道导弹项目工作。NASA聘请冯·布劳恩担任在亚拉巴马州亨茨维尔新成立的马歇尔航天飞行中心的主任。他在那里成为“土星5号”(Saturn Ⅴ)运载火箭的总设计师。正是该火箭将阿波罗宇航员送上了月球。
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[11] 航天飞机的主燃料箱,即中间那个锈色的大燃料箱将在接近轨道时被抛弃,它将在再次进入地球大气层时燃烧殆尽。然而每个燃料箱的体积都比整个ISS的体积还大。如果NASA选择把这100多个燃料箱留在轨道上,在太空中收集并焊接起来,那么我们今天就会在近地轨道上有一个低成本的环形设施,能够产生人造重力,容纳1000多人。科学家兼作家大卫·布林(David Brin)在他虚构的短篇小说《油罐发电机》(Tank Farm Dynamo)中经过计算写下了这个设想。
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[12] Roger A.Pielke Jr.,“The Rise and Fall of the Space Shuttle,” American Scientist 96(2008):432-433.
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[13] Traci Watson,“NASA Administrator Says Space Shuttle Was a Mistake,” USA TODAY ,September 27,2005,https://usatoday30.usatoday.com/tech/science/space/2005-09-27-nasa-griffin-interview_x.htm.
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[14] Michael Griffin,Leadership in Space:Selected Speeches of NASA Administrator Michael Griffin,May 2005-October 2008 (Washington,DC:NASA,2008),328.
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[15] Sagdeev,Making ,213-214.
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[16] Andrew Chaikin,“Is SpaceⅩ Changing the Rocket Equation?” Air & Space Magazine ,January 2012,https://www.airspacemag.com/space/is-spacex-changing-the-rocket-equation-132285884/.
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[17] Christian Davenport,The Space Barons:Elon Musk,Jeff Bezos,and the Quest to Colonize the Cosmos (New York:PublicAffairs,2018)
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[18] Davenport,Space Barons.
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[19] Cristina T.Chaplain,“The Air Force’s Evolved Expendable Launch Vehicle Competitive Procurement,” letter to US Congress,GAO-14-377R Space Launch Competition,March 4,2014,https://www.gao.gov/assets/670/661330.pdf.
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[20] Loren Grush,“Elon Musk’s Tesla Overshot Mars’Orbit,But It Won’t Reach the Asteroid Belt as Claimed,” The Verge ,February 8,2018,https://www.theverge.com/2018/2/6/16983744/spacex-tesla-falcon-heavy-roadster-orbit-asteroid-belt-elon-musk-mars.
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[21] Hamza Shaban,“Elon Musk Says He Will Probably Move to Mars,” Washington Post ,November 26,2018,https://www.washingtonpost. com/technology/2018/11/26/elon-musk-says-he-will-probably-move-mars.
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[22] Kenneth Chang,“Space Launch Firms Start Small Today to Go Big Tomorrow,” New York Times ,November 12,2018,B2.
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[23] 有一些卫星被称为微卫星、纳卫星、皮卫星和飞卫星,体积依次递减,但是它们的名字更加口语化,而并非真正严格的分类。立方星(CubeSat)是一种大小为10厘米×10厘米×10厘米的皮卫星。
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[24] Gary Martin,“NewSpace:The‘Emerging’Commercial Space Industry,” undated NASA presentation,circa 2014,https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140011156.pdf.
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[25] NASA Fact Sheet,“Advanced Space Transportation Program:Paving the Highway to Space,” 2008,https://www.nasa.gov/centers/marshall/news/background/facts/astp.html(retrieved March 21,2018).
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[26] Sagdeev,Making.
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[27] W.David Compton and Charles D.Benson,Living and Working in Space:A History of Skylab (Washington,DC:NASA 1983),271.
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[28] Compton and Benson,Living and Working in Space ,324.
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[29] Paul Martin,“Extending the Operational Life of the International Space Station Until 2024,” NASA Office of Inspector General,Audit Report,IG-14-031,September 18,2014.
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[30] Jeff Foust,“NASA Sees Strong International Interest in Lunar Exploration Plans,” Space News ,March 6,2018,http://spacenews.com/nasa-sees-strong-international-interest-in-lunar-exploration-plans.
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[31] Robert M.Lightfoot Jr.,“Return to the Moon:A Partnership of Government,Academia,and Industry,” symposium,Washington,DC,March 28,2018.
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