(单词翻译:单击)
There have been plenty of successful space missions over the years, and they've accomplished some amazing things.
过去这些年间，人类实现过多次成功的空间任务，做出了令人惊奇的发现。
We've been to the Moon, we've sent rovers to Mars, and we've even done a flyby of Pluto.
我们去过月球，向火星发射过探测器，甚至还曾在冥王星做过飞近探测。
Not to mention the International Space Station orbiting Earth right now.
更不用说目前已经有环绕地球飞行的国际空间站了。
But there were more missions that could have happened.
但还有更多任务有待完成。
Ones that were researched and developed and could have had a huge impact on the history of space travel.
其中一项任务已经经过研究和开发，本来可以对太空旅行的历史造成巨大影响。
If they hadn't been canceled, that is.
不过，这项任务被取消了。
Take Mars, for example.
以火星为例。
Lately, NASA's been working on plans for the first manned mission to Mars.
最近，美国宇航局一直在着手规划飞往火星的第一次载人航空任务。
But what if we'd gone there in the 1980s?
但如果我们在上世纪80年代就去过火星了呢？
Once NASA had sent humans to the Moon, sending people to Mars seemed like the natural next step.
美国宇航局将人类送往月球后，再送往火星也就自然成了下一步。
But our rockets weren't really up for the job.
但我们的火箭条件还不够。
Most of the rockets at the time burned chemicals like kerosene and oxygen.
目前，大多数火箭的燃料都是煤油和氧气。
Even though these rockets were great for orbital or lunar missions, they just didn't have enough power for a trip to Mars, which is more than 50 million kilometers longer than the journey to the moon.
即便火箭满足条件，可以进行环绕飞行和探月任务，但能量也不足以支撑其飞往火星，毕竟火星与地球的距离比地月距离长5000万公里。
So NASA started Project Rover, to create rockets powered by nuclear reactors.
鉴于此，美国宇航局发起了探测器项目，用核反应堆为火箭提供能量。
Project Rover would use a reactive fluid like hydrogen — which combines easily with most other elements — and use a reactor to heat it into an ionized gas, aka plasma.
探测器项目会用到像氢一样的作用流体——这样的流体可以毫不费力地与其他元素结合——同时也用到了反应器，从而将其加热为电离气体，也就是等离子体。
The plasma would then be ejected from the rocket, creating thrust to push the rocket forward.
这样，等离子体在从火箭射出的时候，就会为火箭产生推力。
Traditional chemical rockets also eject gas for thrust, but with much less force than a nuclear reactor.
传统的化学火箭也会通过喷射气体来提供推力，但这样的推力不如核反应堆提供的推力大。
In 1961, this nuclear rocket research became part of a new program that came this close to taking us to Mars: the NERVA engine.
1961年，对核火箭的研究成了一个新项目的部分内容，而这个新项目让我们离载人去往火星的目标如此接近：火箭飞行器用核引擎。
Early NERVA tests were so successful that a mission to send 12 people to Mars was suggested for 1981.
早期对火箭飞行器用核引擎的测试非常成功，所以有人提出1981年的时候就可以送12个人去往火星。
The mission would split crew between two rockets, each powered by three NERVA engines, and would take nine months to reach the planet.
这项任务可以将两节火箭间的宇航员分开，每一节火箭都由3个火箭飞行器用核引擎提供动力。这样，用9个月就可以抵达火星。
Engine tests continued to go really well, and soon the NERVA engine could meet almost every NASA requirement!
对引擎的测试依然进展顺利。不久后，火箭飞行器用核引擎就满足了几乎所有美国宇航局的要求。
...but then the project was canceled.
但该项目就在这时遭停。
In 1972, Congress decided that a Mars mission would be too expensive and would extend the pricey space race between the United States and the Soviet Union.
1972年，国会决定，火星任务成本高昂，会加剧美苏之间昂贵的太空竞赛。
So, almost 50 years later, we're still waiting for the first people to land on Mars.
所以，就在近50年后的今天，我们依然在等待第一批人抵达火星的喜讯。
Also during the 1960s, the Soviet Union started working on a huge rocket to send crews to Mars and Venus: the N1.
此外，上世纪60年代，苏联开始研制一个巨型火箭，从而将宇航员送往火星和进行，该火箭名为N1。
The N1 would launch the TMK, which stands for a Russian phrase that basically means Heavy Interplanetary Spaceship — a very accurate name.
N1可以发射重型星际飞船(TMK)。
The TMK was supposed to take three cosmonauts to fly by each of our next-door neighbor planets.
重型星际飞船可以将3名宇航员送往地球附近的行星。
Besides having crew quarters, the TMK would also have an instrumental module that doubled as a radiation shield.
除了设置有宇航员舱之外，重型星际飞船还有一个功能性的模块，可以起到双倍辐射防护屏的作用。
It was even supposed to have artificial gravity caused by the ship's rotation.
重型星际飞船甚至还能通过船体旋转而产生人造重力。
It was way ahead of its time!
这在上世纪可是很先进的东西了！
A 2-3 year mission to Mars was planned for 1971, with a Venus mission some time afterward.
美国宇航局计划于1971年发射飞船进行为期2-3年的任务，然后隔一段时间再送往金星。
Cosmonauts wouldn't land or anything, but they'd fly by the planets and drop unmanned probes to the surface.
宇航员不会降落到行星表面或者出舱活动之类的，但他们会低空飞过，并将无人探测器投掷在行星表面。
But the TMK, and its potential missions were abandoned once NASA became more involved in the Apollo program.
但一旦美国宇航局更多地着手到阿波罗的项目中，他们就放弃了重型星际飞船以及其他可能的任务。
Instead of aiming for Mars and Venus, the Soviet Union started using the N1 to try and land on the moon, and plans for TMK were canceled by 1966.
苏联反其道而行之：以火星和进行为目标，用N1来尝试着陆于月球。因此，美国宇航局在1966年之前就暂停了重型星际飞船的计划。
Unfortunately, the N1 wasn't too successful either, with four failed launches before the program was canceled in the 1970s.
不幸的是，N1也不是很成功，先是四次发射失败，然后又于上世纪70年代被取消了项目。
Now, even though we haven't sent a crew another planet yet, Americans first started living in space aboard NASA's Skylab, which launched in the 1970s.
现在，虽然我们还未曾向另一个星球传送过人类，但美国是第一个在太空实验室里安置了人类居住。这个太空实验室是上世纪70年代建造的。
Skylab was pretty small and could handle only three astronauts at a time.
太空实验室很小，一次只能容纳3名宇航员。
So it wasn't like the International Space Station, which, since 2000, has typically had 3-6 people living on board at a time.
所以，太空实验室和国际空间站不一样，后者自2000年以来就能一次性容纳3-6个人。
But something like the ISS could have existed a lot sooner.
但国际空间这样的东西本来可以在2000年之前就出现的。
In the 1980s, after Skylab, there were plans for a much larger, all-American space station named Space Station Freedom.
上世纪80年代，继太空实验室之后，美国宇航局计划建造名为自由号空间站的美国国家空间站，其容纳空间更大。
Because what else do you call an American space station?
这是属于美国的空间站。
The plan was to build the station from 1994 to 1997, with a crew living there and doing scientific research starting in 1995.
他们的计划是：在1994-1997年间建造这个空间站，让一名宇航员从1995年开始住在那里，做科学研究。
But when NASA sent their first budget proposal to Congress, the government was pretty upset about the $14.5 billion price tag.
但美国宇航局将第一份预算提案送交国会后，美国政府被高达145亿美元的成本吓到了。
So the plans were downsized, but the conflicts continued.
所以计划遭到了删减，冲突依然在继续。
In 1987, the “all-American” idea was dropped to help lower costs, and the European Space Agency was brought in to add a module to the station.
1987年，这个计划因为想要降低成本的原因而弃置了这个计划，欧洲太空总署也参与进来，为空间站的规划增添了一个模块。
But NASA and the ESA had a hard time agreeing on what Europe's role was.
但美国宇航局和欧洲太空总署曾苦苦纠结于欧洲在这项计划中的角色。
On top of that, scientists disliked the new plans for Freedom because the budget cuts had reduced its science capabilities.
最重要的是：一些科学家不喜欢这项新计划，因为经费缩减得已经无法发挥其科学价值了。
By 1988, they'd finally seemed to reach an agreement:
1988年的时候，他们似乎终于达成了一项协议：
The U.S., Canada, Europe, and Japan would all share lab space on Freedom, and the station would have a rotating crew of six American and two international astronauts.
美国、加拿大、欧洲、日本共享这个空间站，站内宇航员由6名美国人和2名国际宇航员轮流值班。
But more logistics and budgetary problems came up, and despite years of planning and development, Space Station Freedom was canceled in 1990.
但这样一来就出现了更多的物流问题和预算问题，虽然经过了多年的筹划和研发，这项计划还是在1990年的时候夭折了。
The International Space Station was approved just a few years later, though, so we did get a brand-new space station.
仅在其后数年，国际空间站的计划得到审批，所以我们确实建造了崭新的空间站。
The history of space travel could've been a lot different if the 1980s Mars mission, TMK, and Freedom had succeeded.
上世纪80年代重型星际飞船的成功会改写太空旅行的历史。
But that's okay. Even without them, we've launched hundreds of other amazing missions, explored strange new worlds, and boldly gone where no one has gone before.
不过也没关系。即便没有重型星际飞船，我们也完成了很多其他令人叹为观止的任务，探索了怪异新奇的世界，也大胆地探索了未曾有人涉足的地方。
And we have plenty more missions to look forward to!
未来依然可期！
Thank you for watching this episode of SciShow Space!
感谢收看本期的《太空科学秀》！
And a very special thanks to our patrons on Patreon for helping us make this show possible.
尤其要感谢我们的忠实粉丝支持节目。
If you'd like to help make SciShow Space, just go to patreon.com/scishow, and don't forget to go to youtube.com/scishowspace and subscribe.
如果大家想为我们的节目出一份力，可以访问patreon.com/scishow。不要忘记订阅youtube.com/scishowspace哦！
