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What does speed have to do with sound?
速度和声音有什么关系?
And if there’s no wall in the sky, how exactly do you break a sound barrier?
如果天空中根本就没有墙，那么怎样才能打破音障呢?
Hey guys, Amy here with you on DNews today talking speed!
朋友们，大家好，我是艾米，欢迎大家收看今天的DNews，我们今天的主题是速度!
Fast things. Not drug things.
也就是非常快的东西。不是什么毒品啦。
Most of us will probably never go supersonic.
我们中的大多数人可能永远都不会体验到超音速。
Though the idea of cutting travel times in half is so appealing,
尽管将旅行时间减半的想法非常吸引人，
it’s not something likely to become common place anytime soon.
但这样的旅行方式在短期内还是不太可能成为普遍现象。
But let’s start with a bit of a history lesson.
不过，我们还是先来了解点儿历史吧。
In the 1880s, Austrian physicist Ernst Mach was studying the supersonic flow of gases using a shadowgraph,
19世纪80年代，奥地利物理学家恩斯特·马赫用阴影图研究气体的超音速流动的时候，
when he successfully photographed a bullet traveling faster than the speed of sound.
他成功地拍摄到了一颗子弹以超音速前进时的景象。
What his images showed was a bullet with a shock wave in front of it and another one trailing behind it,
图像显示的是一颗子弹前面出现了一条冲击波，后面也拖着一条冲击波的瞬间。
clear proof of the phenomenon of compressibility.
这张图片由此成了压缩性效应的明证。
This research eventually led to the measurements that bear his name:
这项研究最终得出了以他的名字命名的测量结果：
a Mach number is the ratio of the speed of an object traveling through a gas to the speed of sound in that gas.
马赫数的定义为物体穿过气体时的速度与气体当地声速的比值。
Because while we don’t think about it, air is made up of molecules,
因为，虽然我们不用想也知道空气是由分子组成的，
and like any other physical substance, those air molecules can compress,
而且，和其他物理物质一样，这些空气分子也是可以压缩的，
and when they compress they form shock waves.
压缩时就会形成冲击波。
It’s these shock waves that make flying faster than the speed of sound such a challenge,
正是这些冲击波让飞行速度突破音速成了一个挑战，
and in the 1940s, pilots were coming face to face with this challenge.
一个20世纪40年代就困扰着飞行员们的挑战。
These shock waves vibrate the air molecules they’re made of,
这些冲击波会引起其组成分子的震动，
and when those molecules vibrate they vibrate whatever is compressing them.
这些分子一振动，就会跟着振动压缩它们的任何物质。
In the case of a fast-flying airplane, the shock waves can shake an airplane hard enough to rip it apart.
就快速飞行的飞机而言，冲击波能使飞机发生剧烈摇晃，甚至将其撕裂。
It was clear to engineers in the 1940s that the future of aviation lay beyond the sound barrier,
20世纪40年代就工程师们已经清楚地知道，航空的未来在音障的另一面，
so someone would have to build an airplane solid enough and fast enough to break through that wall.
所以，必须有人造出一架足够坚固而且速度足够快，能够突破音障的飞机。
It was the Bell Aircraft corporation working on a contract with the US Army Air Force that devised the solution.
最终设计出了解决方案的是当时正在完成和美国陆空军签订的一份合同的贝尔飞机公司。
Taking design inspiration from a bullet,
从一颗子弹中获得了设计灵感后，
Bell engineers designed the X-1 aircraft specifically to break through that wall of compressed air in the sky.
贝尔的工程师们设计了专门用来打破空中的空气被压缩时形成的音障的X-1飞机。
The advent of supersonic flight opened a whole new era of aviation,
超音速飞行的面世开启了一个全新的航空时代，
and though higher Mach numbers don't come with the same “barriers”,
尽管更高的马赫数并不会带来相同的“障碍”，
every increase in speed is nonetheless a major technological hurdle.
但速度的每一次提高都称得上是一个大型技术难关。
The fastest manned flight on record was set in 1967 with the NASA-Air Force X-15,
有记载的最快的载人飞行记录是1967年美国航空航天局和空军共同研制的X-15，
a rocket-powered dart of an aircraft that hit a top speed of Mach 6.7, which is about 4,519 mph!
一架火箭驱动的逐电追风的飞机，最高速度为6.7马赫，约4519英里/小时!
But the X-15 was a hypersonics research vehicle.
但X-15是超音速研究用的飞机。
Most fighter jets today aren’t nearly that fast, though there are supersonic fighters.
当下的战斗机大多都远达不到这个速度，虽然已经有超音速战斗机了。
Air Force planes like the F-15 Eagle and the F-22 Raptor are both supersonic fighter jets,
空军的F-15老鹰和F-22猛禽都是超音速战斗机，
and the F-22 can even hit Mach 2 using afterburners.
F-22还能靠加力燃烧器将速度提到2马赫。
But there’s another challenge associated with supersonic flight and that’s the sonic boom.
但是超音速飞行还有另一个挑战，那就是音爆。
The sonic boom is the sound an airplane makes when it smashes through that wall of compressed air that builds up in front of it.
音爆就是飞机撞穿在它前面形成的压缩空气墙时发出的声音。
But the boom doesn’t just come once when the plane goes supersonic;
但是当飞机超音速飞行时，这种现象不会只出现一次；
it keeps going in the wake of that supersonic aircraft.
它会一直跟在那架超音速飞机后面。
This is exactly why the Concorde, the world’s only supersonic passenger plane that flew from 1976 to 2003, only ever flew over oceans.
这也是协和式飞机——世界上唯一一架超音速客机，从1976年一直服役到了2003年——为什么只跨海飞行的原因。
In fact, the Federal Aviation Administration prohibited domestic civil supersonic flight over land in 1973.
事实上，1973年，联邦航空管理局就明令禁止国内的民用超音速飞机在陆地上飞行了。
But all is not lost!
不过也不用绝望!
NASA and its aviation partners are looking into identifying an acceptable loudness level and working on so-called “low boom” aircraft designs
美国宇航局及其航空合作伙伴已经在研究，确定一个可接受的响度水平，并已经在致力于所谓的“低爆”飞机设计，
to reduce sonic boom levels and maybe bring back supersonic passenger flights.
以降低音爆水平了，也许还能让超音速客机重新投入使用喔。
But that’s still something to look forward to down the line.
但这也是需要我们继续期待的事。
And the U.S. Air Force always has its eye on the future, too, and it’s a big supporter of DNews!
美国空军也一直是着眼于未来的，也是我们节目组的一个很大的后援喔。
The United States Air Force is powered by Airmen and fueled by innovation.
美国空军有飞行员提供动力，还有创新的加持。
Every day American Airmen go above and beyond to break barriers both professionally and personally.
每天，美国空军都在突破职业和个人障碍。
Whether it’s overcoming poverty to become a nurse and officer or becoming the first female Thunderbird pilot,
无论是克服贫困成为一名护士和军官，还是成为第一位女雷鸟飞行员，
these Airmen are known for doing what was once thought to be impossible.
这些飞行员都以完成一度被认为是不可能完成的任务著称。
Have any of you flown supersonically?
你们有人体验过超音速飞行吗?
If so, tell us what it was link in the comments below because I’m dying to know what it’s like!
如果有的话，请在下方的评论里告诉我们那是怎样的一种体验，因为我对此非常非常好奇！
And if you haven’t, do you want to?
如果没有，那你想体验吗?
Let us know in the comments below and don’t forget to subscribe for more DNews every day of the week.
也请在下面的评论中告诉我们，不要忘记订阅，观看更多的DNews视频喔。
