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A lot of our ideas about the future come from popular works of science fiction,
人类关于未来的很多构想都来自知名科幻小说，
like how the Star Trek communicators of the 1960s became the cell phones of the 90s.
比如《星际迷航》中用于上世纪60年代的通讯器是如何演变为90年代的手机的。
But go back to the 1800s and some of the most important stories about space travel had nothing to do with rockets, like you'd think they should.
但是早在19世纪的时候，一些关于太空旅行的最为重要的作品都与火箭没什么关系，这与我们想象得不太一样。
Instead, authors like Jules Verne and H. G. Wells thought we'd get things into space with guns.
那时候，一些作家在作品里描述的景象是：我们会用枪将物品携带到太空中。这样的作家有儒勒·凡尔纳和赫伯特·乔治·威尔斯。
Really big guns. If you think about it, it makes a lot of sense.
是很大的枪哦！细思的话，确实不无道理。
Things need to go very fast to reach space, and bullets are very fast. So, voila!
物体的运动速度要非常快才能进入太空，而子弹的速度就很快。就是这么简单！
Unfortunately, the physics don't really work that way.
不幸的是物理学里可没有这样的规矩。
But that definitely hasn't stopped us from trying to build space guns of our own.
不过，这当然并没有阻止人类试图建造属于自己的太空枪。
Obviously, guns differ from rockets in a bunch of important ways. They're an example of what's called ballistic flight, which means that,
显然，枪都与火箭的不同表现在很多方面，枪和火箭都是弹道飞行的具体例子，所谓弹道飞行就是，
once a projectile's launched, only external forces like gravity and drag can affect its trajectory.
一旦发射物发射出去了，那么只有重力和拉力这样的外力才能影响其轨道。
Guns are an advanced form of creating ballistic flight, but the basic idea goes back to the days of things like trebuchets and,
枪是弹道飞行的一种高级表现形式，但其基本原理还是以前的投石机，
you know, just, like, throwing rocks. All of that is different than something like a rocket, which can be steered in flight.
就是那种投掷石头的装置，这些都与火箭的飞行方式不同，因为火箭在飞行过程中也是可以操纵的。
What guns have going for them, though, is simplicity.
而用枪发射的整个流程就非常简单了。
We've been using the same basic design for hundreds of years and, by now, we understand pretty well how to build something efficient and reliable.
数百年来，我们一直在使用这种简单的设计，而现在，我们非常了解怎样构建得有效可靠。
They're also pretty cheap, since you get to reuse the barrel and just replace the propellant, like gunpowder, after each shot.
而且成本也十分低廉，因为枪管可以重复利用，只需要在每次射击后更换推进剂就可以了，比如火药。
Still, guns do have some major downsides as a launch tool.
不过，如果把枪作为发射工具的话，也是有一些明显的缺点的。
To get to space, you need to go really, really fast, and the payload in a gun just gets one shove to get it going that quickly.
要抵达太空，速度就要非常之快，然而枪只为其有效载荷提供一次推力。
So the acceleration experienced is incredible.
那么，要实现巨大的加速过程就是不可能的了。
We're talking about thousands of times more g forces, or thousands of times the regular force of Earth's gravity, than when riding on a rocket.
这里说的是比乘坐火箭还要高出数千倍的重力加速度，是地球正常情况下重力的数千倍。
Which is not great if you're an astronaut who suddenly doesn't have a skeleton.
这对于在太空里不受重力的宇航员来说当然不是什么大事。
Reaching those speeds so quickly also really heats things up, meaning your payload needs to be basically fireproof.
但要在短时间内将提高到这么大的速度会产生热量，也就是说，枪上的有效载荷得是防火的材料。
The real kicker, though, is all the pesky physics.
而要设法研制具备如此性能的材料就是物理学需要绞尽脑汁做的事了。
At the end of the day, it's actually impossible to fire something from the surface directly into orbit around the Earth.
就算弄一整天，要把物体从地球表面直接运送到地球轨道上也是不可能的。
See, you can think of an orbit like a closed loop around the planet.
这里可以将轨道看成地球周围的一个闭环。
If you fire a projectile from the surface, that loop is guaranteed to intersect the Earth, meaning your projectile will crash into the ground.
如果将发射物从地球表面发射出去的话，这个闭环一定会地球相交，也就是说，发射物还是会坠落到地面上。
Meanwhile, after a rocket launches, it fires its engines to create a new loop, and an orbit, that doesn't intersect with the surface.
而火箭发射后，会启动发动机以创造一个新的闭环和轨道，这样就能保证不与地球表面相交。
Because they don't have a propulsion system of their own, ballistic projectiles just can't do that.
而由于没有自己的推进系统，弹道抛射体是做不到这一点的。
Of course, none of this has actually stopped us from building enormous guns to try it out.
当然了，这些都没能阻挡人类构造巨型枪支的尝试。
Because, pff, who needs science? In the 1960s, Project Harp, or the High Altitude Research Program, was our first attempt to reach space with a gun.
毕竟在娱乐至上的年代，谁需要科学呢？20世纪60年代，竖琴项目（高空研究计划）是我们首次尝试用枪来抵达太空。
The U.S. military was racing to improve early intercontinental ballistic missiles,
美国军队正在紧锣密鼓地提升初期的洲际弹道导弹，
and they needed a cost-effective way to test how designs reentered the atmosphere.
因此他们需要划算的方式来检测重新进入大气层的方式。
With Project HARP, they aimed to reuse the leftover barrels of battleship cannons to launch payloads high into the sky.
竖琴项目的目标是重新利用战舰枪炮遗留的枪管，以将物体发射到高空中去。
These massive guns were eventually built in Arizona and Barbados, and they were used to fire more than 200 payloads, each weighing about 180 kilograms.
最终，这些大型枪支在亚利桑那州和巴巴多斯进行了建造，用于给发射200多个有效载荷，其中每一个都有近180公斤重。
At peak efficiency, a HARP gun launched one of these objects at more than 2100 meters per second, fast enough to reach an altitude of about 180 kilometers.
在最高效率的状态下，该项目中的枪支可以给物体加速到2100多米/秒的速度。这个速度足以抵达近180千米的高度了。
That's about the same height as Alan Shepard's historic Mercury mission and is definitely into space.
这与艾伦·谢泼德在水星计划里抵达的高度近乎相同，而且绝对可以进入太空了。
But that gun also had a heck of a kick.
不过，这种枪型也是只能提供一次推力。
The payload experienced around 25,000 g's at launch, so its electronics had to be encased in solid plastic blocks to avoid breaking apart.
其有效载荷在发射时会受到25000g的推力，所以其固体塑胶叠层板中必须设置电子系统，以防止其分崩离析。
Unsurprisingly, it wasn't a sustainable idea, but these guns did help us study the Earth's upper atmosphere, so it wasn't a complete waste.
意料之内的是，虽然这个想法也不够持久，但这些枪确实帮助我们研究了地球的高空，所以也不算是完全的浪费。
Some tests released objects that left smoke trails and that helped scientists track the movement of high-altitude air currents.
一些测试里还放出了自带烟迹的物体，这样就能帮助科学家追寻高空气流的运动。
After that, the space gun idea was continued in California in the 80s with Project SHARP, or Super HARP.
在那以后，太空枪的想法在80年代加州的超高空研究计划(SHARP)里得以延续。
The regular HARP guns used gunpowder, but Project SHARP was a light gas gun, meaning it propelled objects using hydrogen compressed by a piston.
竖琴项目里的枪用的都是火药，而超高空研究计划里用的是轻气炮。也就是说，该计划是通过活塞压缩氢气来推进物体的。
Its goal was to launch small projectiles into space, for real this time, but the projectiles only got about a quarter of the velocity they needed.
这样做的目的是将小型发射物切切实实地送往太空，但发射物只能得到其所需速度的1/4左右。
Still, that was good enough for them to plan the final version, which would've had a barrel about 3.5 kilometers long.
不过，这已经足够让他们计划最终版了：近3.5千米长的枪管。
Unfortunately, the planned gun cost more than a billion dollars and was never approved.
不幸的是，这版的计划成本达10多亿美元，所以审批从来就没过过。
And, although some companies have tried to resurrect the idea over the years, we never really got serious about trying again.
而虽然这么多年来还是有一些公司尝试再提这个点子，却从来没人想过真地尝试。
With enough money, determination, and propulsion systems, maybe someday we could build a functioning space gun.
有了充足的资金、决心、推进系统，或许有一天我们可以建造一个可用的太空枪。
But all told, ballistic flight just hasn't proven to be an effective way to get to space, and its opportunity might be gone forever.
但是目前为止，太空枪这种弹道飞行的方式还不是一种有效抵达太空的方式，而这个机会可能永远不会重来了。
The great promise of a space gun has always been that it launches things cheaply,
太空枪最大的好处一直都是发射成本低廉，
but with the advent of reusable rockets like SpaceX's Falcon 9, even that advantage is disappearing.
但像太空探索技术公司猎鹰9号这样的可重复利用火箭面世后，这个优势也荡然无存。
Modern rockets can carry more stuff, do more kinds of missions, and offer a gentle ride to space, all without breaking the bank.
现代火箭的运载量更大，可承担的任务类型更多，发射过程更加平稳，就是成本太高。
So space guns might be out. But hey, we'll never stop shooting for the stars.
所以虽然太空枪的想法可能就此湮灭了，但我们是不会停止进军太空的想法的。
Thanks for watching this episode of SciShow Space!
感谢收看本期的《太空科学秀》！
Over the years, people have thought up all kinds of wacky ways to get to outer space, including space guns and even giant elevators.
多年来，人们想尽了各种稀奇古怪的办法来进入外太空，包括太空枪甚至是巨型升降舱。
And believe it or not, we've looked at the science behind that one, too.
不过，或许难以置信的一点是，我们也在研究其背后的科学。
You can learn all about space elevators, and whether they'd work, over at the main SciShow channel.
您可以通过《太空科学秀》的主频道来了解太空升降舱是否好使。
