未来月球将不再担心用电问题：美国将把核反应堆送上天

　　If all goes as planned, sometime in the next decade an American robotic lander will arrive at a burgeoning moon base toting a small nuclear reactor. Inside the reactor a boron control rod will slide into a pile of uranium and start a nuclear chain reaction, splitting uranium atoms apart and releasing heat. Next that warmth will be piped to a generator. Then the lights will come on—and stay on, even through long, cold lunar nights.

　　如果一切顺利的话，未来十年里的某个时间一艘美国登陆器将携带一个小型核反应堆抵达月球基地。在这种反应堆内部，一根硼控制棒将伸入一堆铀中开启核连锁反应，分裂铀原子并且释放热量。接下来，这些热量将传输到一台发电机中，这样就会给月球基地带来光明。

　　After a half-century struggle to develop a nuclear power plant for use in space, NASA just completed a successful test of a brand-new design. The next milestone for the new reactor, called Kilopower, could be an inaugural spaceflight sometime in the 2020s. Developed with the Department of Energy (DoE), Kilopower marks the first new nuclear reactor of any kind in the U.S. in 40 years. It could transform energy production for space exploration, especially for permanent human outposts elsewhere in the solar system.

　　美国宇航局经历了半个世纪的努力来打造一种能够在太空中使用的核反应堆，而且刚刚完成了一次新设计的测试。这台新反应堆名为Kilopower，它的下一个里程碑有可能是在2020年代的某个时间开启太空飞行。Kilopower是由美国能源部协助研发的，它标志着美国40年来打造的第一个全新的核反应堆。它有可能改变太空探索，尤其是太阳系中永久性人类前哨基地的能源制造方式。

　　Current space missions use fuel cells, nuclear batteries or solar power. But a night on the moon lasts two weeks, and the strength of sunlight on Mars is only about 40 percent that of Earth. “When we go to the moon and eventually on to Mars, we are likely going to need large power sources not dependent on the sun, especially if we want to live off the land,” says Jim Reuter, NASA’s acting associate administrator for space technology.

　　目前的太空任务使用的是燃料电池、核电池或者太阳能。但是月球的夜晚持续两个周时间，而且火星上的阳光强度只有地球上的40%。美国宇航局太空技术部门的副行政助理Jim Reuter称：“当我们前往月球或者最终前往火星时，我们很可能需要大量无法依赖于太阳的能源，特别是如果我们想要生活在那里。”

　　Kilopower is a small, lightweight fission reactor that can provide up to 10 kilowatts of electricity. NASA says four 10-kilowatt Kilopower units would provide enough electricity to power a human outpost on Mars or the moon. For comparison, 40 kW is enough to power three to eight typical American houses, says Claudio Bruno, an engineering professor at the University of Connecticut who studies nuclear energy. He adds that 40 kilowatts would be roughly equivalent to 60 horsepower. “You get a sense that it is very modest power. In truth, if you want to do anything useful, especially if missions to the moon or Mars are crewed missions, you need lots more than that,” he says. “But this said, every time this research was done in the past, there were hues and cries about the mortal danger of nuclear power. This is the first time [in decades] they are talking about powering an electricity generator with a nuclear reactor, so it is a first, positive signal.”

　　Kilopower是一种小型的轻量级裂变反应堆，能够提供多达10千瓦的电量。美国宇航局称，4台10千瓦的Kilopower反应堆就能够为火星或者月球上的一座人类基地提供足够的电能。核能研究领域专家，美国康涅狄格大学工程学教授Claudio Bruno称，40千瓦电足能够满足3到8户美国正常家庭的使用。他补充道：“40千瓦电大约相当于60马力，你或许会认为有点不够用。事实上，如果你想要做什么有用的事情，特别是如果月球或者火星任务是载人任务时，你需要的能量会更多。但是过去每一次研究都会有人抗议核动力存在致命危险。这是人们数十年来首次谈论借助核反应堆为发电机提供能量，因此这也是首次出现的积极信号。”

　　In space exploration nuclear energy can be used in two main ways: for generating electricity or for propulsion. Kilopower would be used to produce electricity, much like a power plant on Earth. It would likely produce more than a single spacecraft would need, making it a better fit for larger surface outposts. Kilopower could also be used to drive a spacecraft, primarily by powering an ion engine, although NASA presently has no definitive plans to use it in this way.

　　在太空探索中，核能的使用主要有两种方式：制造电能或者产生推进力。Kilopower将用于产生电能，就像地球上的发电站一样。它所产生的电能很可能要超过单艘太空飞船的需要，这就使它更适合于更大的星球前哨。Kilopower也将用于驱动飞船，主要为离子发动机提供能量，但是美国宇航局目前还没有决定这样利用这项技术。

　　Kilopower has been in development since 2012, but its legacy reaches much farther back, to NASA’s Systems for Nuclear Auxiliary Power (SNAP) program of the 1960s. The SNAP project developed two types of nuclear power systems: The first was radioisotope thermoelectric generators, or RTGs, which capture heat from radioactive decay to provide warmth and electricity. Dozens of deep-space spacecraft have used RTGs, including the Curiosity rover on Mars and the New Horizons Pluto probe now exploring dwarf planets of the outer solar system. The second SNAP project was for a fission reactor, which splits atoms to produce energy. This is the same type of technology that powers nuclear submarines. NASA launched one nuclear power plant, called SNAP-10A, in April 1965. It worked for 43 days and produced 500 watts of electricity before a part failed; it remains in Earth orbit today and is considered space junk.

　　Kilopower自2012年就开始研发，但是它的效果远超过美国宇航局上世纪60年代的辅助核动力系统项目(简称SNAP)。SNAP项目研发出了两种核动力系统，一种是放射性同位素热电发生器(简称RTG)，它能够从放射性衰变中捕获能量提供热能和电力。数十艘深太空飞船已经使用了RTG系统，其中包含火星上的好奇号漫游车和正在外太阳系探索矮行星的新视野号冥王星探测器。SNAP项目的另外一种动力系统就是裂变反应堆系统，通过原子分裂产生能量。这项技术与核潜艇使用的动力系统相同。美国宇航局在1965年4月发射了一台名为SNAP-10A的核电站。这座核电站工作了43天时间，并且在出现故障前产生了500瓦的电量。它现在仍然在地球轨道中，而现在变成了太空垃圾。

　　During the 1960s and ’70s NASA also researched nuclear power for rocket propulsion under the Nuclear Engine for Rocket Vehicle Application (NERVA) program. This would have used nuclear reactors to heat hydrogen and expel it through a nozzle, much like a chemical rocket burning fuel to push a rocket forward. But this program ended in 1973.

　　在上世纪60年代和70年代，美国宇航局也在火箭核动力应用(NERVA)项目中对核动力火箭推进技术进行了研究。这项技术使用核反应堆对氢气进行加热，并且通过喷嘴排出气体，与常规火箭燃烧燃料产生推力相似。但是这个项目在1973年结束。

　　Russia has flown more than 30 fission reactors in space, according to the World Nuclear Association. But after Pres. Richard Nixon canceled NASA’s nuclear propulsion research in 1973, Russia backed down from its program, too, Bruno says. “Everything went basically on the back burner or was frozen by 1973,” he adds. “By 2018, most of the people working on this are either retired or passing away. We don’t have firsthand knowledge of what they did. We have reports, sure, but reports don’t speak to you. Humans speak to you.”

　　据世界核能委员会的数据，俄罗斯已经向太空发射了超过30个裂变反应堆。在美国总统尼克松1973年取消美国宇航局的核动力推进技术研究之后，俄罗斯也放弃了自己的项目。Bruno称：“所有的研究在1973年都被叫停。到2018年，曾经参与那个项目的大多数人或者退休或者离世。虽然我们还有报告，但是报告不会讲话，研究人员才会。”

　　The thaw began in 2012, when NASA and the DoE performed a preliminary test of Kilopower’s progenitor, the Demonstration Using Flattop Fissions (DUFF) experiment, producing 24 watts of electricity. DUFF used a heat pipe to cool its reactor and demonstrated the first use of a Stirling engine to convert reactor heat into electricity. (Stirling engines use external heat to drive a piston, which turns a crankshaft to produce power.) Following the DUFF test, NASA’s Game Changing Development program endorsed Kilopower and the project received its first funding in 2014.

　　这项研究在2012年解冻，美国宇航局和美国能源部对Kilopower的前身(DUFF实验)进行了初步测试，并且产生了24瓦的电能。DUFF借助一根热导管来为反应堆降温，并且首次展示了斯特林发动机将反应堆热量转变成电能的应用。在DUFF测试之后，NASA授权开始进行Kilopower项目，这个项目在2014年首次获得研究资金。

　　The latest NASA and DoE Kilopower tests occurred from November 2017 through March of this year. Dubbed Kilowatt Reactor Using Stirling Technology—KRUSTY, which like DUFF pays homage to The Simpsons—the tests put the Kilopower reactor through its paces, culminating in a 28-hour run where the reactor was turned on, operated at full power, then cooled and shut down. Operating at temperatures of 800 degrees Celsius the reactor produced more than 4 kilowatts, says Marc Gibson, Kilopower lead engineer at NASA Glenn Research Center where KRUSTY took place.

　　美国宇航局和能源部对Kilopower进行的最新测试开始于2017年11月，并且一直持续到今年3月。测试中，Kilopower反应堆进行了长达28小时的全功率测试，随后关闭并且进行了降温。美国宇航局格伦研究中心Kilopower项目首席工程师Marc Gibson称，反应堆在800摄氏度的温度中运行，并且产生了超过4千瓦的电能。

　　David Poston, chief reactor designer at Los Alamos, says a similar reactor could provide electricity to power ion thrusters, which could in turn propel a spacecraft. But the amount of material required to start the chain reaction would likely mean a reactor too large and too heavy for practical use, according to Bruno. NASA is separately developing a new uranium-based nuclear thermal engine concept, which would work much like current chemical rockets to accelerate fuel out the back end of a thruster. But the Nuclear Thermal Propulsion project started in August 2017 is not as far along as Kilopower.

　　洛斯阿尔莫斯国家实验室的首席反应堆设计师David Poston称，一种类似的反应堆能够为离子推进器提供电能，从而为飞船提供飞行动力。但是据Bruno称，启动裂变连锁反应所需要的原料量很可能意味着反应堆会很大而且很重，无法得到实际应用。美国宇航局单独提出了一种全新的铀核热力发动机概念，它与目前的化学燃料火箭所使用的技术相似。但是2017年8月启动的核热力推进系统项目并未像Kilopower一样获得这样的进步。

　　Most nuclear-powered spacecraft use RTGs, which simply harness heat from plutonium decay to make electricity. But RTG efficiency is extremely low—and what’s more, plutonium dioxide fuel is in short supply. The DoE resumed plutonium 238 fuel production in 2015 after a 30-year gap, but currently there is only enough in the nation’s stockpile to power NASA’s 2020 Mars rover and maybe one or two other potential missions to the outer solar system.

　　大多数核动力飞船使用了RTG系统，通过收集钚衰变产生的热量来产生电能。但是RTG的能效极低，此外，二氧化钚原料供应不足。在经历了30年的空白之后，美国能源部从2015年开始恢复钚238的生产，但是目前美国的库存只足够为美国宇航局的2020火星漫游车提供能量，而且或许能够支持一到两个前往外太阳系的潜在任务。

　　Kilopower could serve as an alternative—but that’s a big maybe, officials and experts warn. “We kind of start where RTG stops, from a power standpoint. We are kind of taking [up] where they are leaving off and trying to give us a power range for things like human exploration, where you need tens to hundreds of kilowatts,” Gibson says. In other words, human activities on the moon or Mars would require 10 to 100 times more power than what a single Kilopower reactor or even a handful of reactors is projected to produce. But Poston says the reactor’s modular design can easily be scaled up to meet those needs.

　　Kilopower能够作为一种替代品，但是政府官员和专家们都认为可能性很大。Gibson称：“从能量的角度来看，我们是从RTG项目开始的。我们希望这个项目能够让我们实现更多的用途，比如说深太空探索，那样你就需要成千上万瓦的电能供应。”换句话说，人类在月球或者火星上活动所需要的能量要超过单台Kilopower反应堆产生量的十到百倍。但是Poston称，反应堆的标准化设计能够轻易实现规模化来满足那些需要。

　　Nevertheless, Kilopower is an important step toward a workable nuclear power plant for use in space, Bruno adds. The next step would likely be a test of the reactor in space. NASA has not yet approved such a mission, but at a press conference earlier this month Reuter says the next 18 months will be devoted to figuring out how such a test flight would work. One possibility is to fly a small Kilopower reactor on a lunar lander, which may be developed under NASA’s newly moon-focused exploration mission.

　　Bruno补充道，Kilopower反应堆是打造太空中可用核电站的重要一步。接下来很可能是在太空中对反应堆进行测试。美国宇航局尚未许可进行这样的项目，但是在本月月初的一场新闻发布会上，路透社称未来18个月时间里将致力于如何进行这样的测试飞行。其中一种可能性是，使用登月飞行器运送一台小型Kilopower反应堆，而这种小型反应堆或许将在美国宇航局最新的月球探索任务中研发出来。

　　Poston says the successful ground tests are an important step in the next phase of human space exploration. “We demonstrated a concept NASA can use right now. To me, the most exciting thing is the potential. This really is the first step in using fission power in space,” he says.

　　Poston称：“成功的地面测试对于未来的人类太空探索阶段有着重要意义。我们验证了这个技术概念是美国宇航局现在能够利用的。对于我来说，最令我激动的事情是它的潜在应用。从真正意义上将，这是我们在太空可用裂变能技术的研究领域跨出的第一步。”