经济学人下载:发射飞机 让电磁感应来验证

Science and technology
科学技术

Launching aircraft
发射飞机

Proof by induction
让电磁感应来验证

In the future, airliners could be catapulted into the sky by electric motors
将来，会用电动机将客机弹射到天空中

READERS of a certain age may remember Fireball XL5, a children's television programme devised by Gerry Anderson about a spacecraft of that name.
某个年龄段的读者可能还记得《雷霆机》这个儿童电视节目，这个节目是由格里安德森制作的，讲的是一艘叫做雷霆机的宇宙飞船的故事。

Instead of taking off vertically, as real spacecraft do, Fireball XL5 sat on a rocket-propelled trolley that accelerated it horizontally to launch speed.
与现实中的宇宙飞船垂直起飞不同，雷霆机是架在一个由火箭推动的滑车上，水平加速到发射速度。

And that, in effect, is what engineers at Airbus, Europe's largest civil-aviation company, are proposing in their latest bout of blue-sky thinking.
实际上，这是空中客车公司的工程师们在其最近一次天马行空的想法中提出的建议。

Apart from the fact that the trolley would be powered by linear-induction motors rather than rockets, they are suggesting that the fantasy of 1962 might become the reality of 2050.
滑车由线性感应电动机提供动力，而非火箭，除此之外，他们认为1962年的幻想会在2050年成为现实。

Mindful that many passengers are already nervous about the whole process of getting a plane airborne, the engineers prefer to call their proposal Eco-climb.
考虑到飞机离开地面的整个过程中已经够让许多乘客紧张了，工程师更喜欢将他们的提议称为环保型起飞。

But the idea is straight out of Fireball.
但这一想法是直接来自于雷霆机的。

The aircraft to be launched would sit on a platform that ran along a track where the runway would otherwise be.
待发射的飞机会架在一个沿轨道滑行的平台上，而这轨道可说是跑道的另一种形式。

The platform would accelerate to take-off speed, at which point the plane would lift into the air powered by its own engines.
平台会加速到起飞速度，到达这一速度点后，飞机便可以通过自己的引擎升上天空。

Taking off in this way would both save fuel and make life more pleasant for those who live near airports.
以这种方式起飞既可以节约燃料，又能够让住在机场附近的人过的更舒心些。

Aircraft engines are optimised for level flight at cruising speed in the stratosphere.
飞机引擎最适合在平流层以巡航速度水平飞行。

Using them to accelerate a plane on the ground wastes a lot of fuel.
在地面上用它们为飞机加速会浪费很多燃料。

An induction-motor-powered platform, by contrast, would be optimised for the job at hand.
相比之下，由感应电动机提供动力的平台最适合手头的这个工作，

It could launch the plane at higher speed, letting it climb faster.
它能以更快的速度发射飞机，让飞机爬升更快，

That would save fuel, too.
还能节约燃料，

It would also mean fewer people on the ground suffered aircraft noise.
还意味着地面上要经受飞机噪音的人更少了。

And it could do all this from a track that was a third shorter than a conventional runway.
所有这些在一条比传统跑道短三分之一的轨道上即可完成。

Altogether, according to Airbus's back-of-the-envelope calculations, Eco-climb would reduce fuel consumption by 3% on a typical 900km flight, even with existing aircraft designs.
总而言之，很据空中客车的粗略计算，按一次典型的900公里的飞行算，即使按照现在的飞机设计，环保型起飞也能将其油耗减少3%。

But it would also allow for the design of lighter aircraft, with smaller engines, which would cut fuel consumption, noise and emissions further.
而且它还为设计引擎更小，重量更轻的飞机留下了空间，可以进一步降低油耗，噪声及排放。

Nor is the idea complete fantasy. General Atomics, an American military contractor, has already built and tested a linear-induction-motor-based system of this sort at an airbase at Lakehurst, New Jersey.
这个想法并不完全是幻想。通用原子公司是一家美军的承包商，其已经在一座位于新泽西州莱克赫斯特的空军基地建造了一个这类基于线性感应电动机的系统，并进行了测试。

The General Atomics system is now being scaled up to be fitted on a new generation of aircraft carriers for the American navy.
目前通用原子正在对该系统进行放大，以便能装备到美国海军的新一代航空母舰上。

A launcher powered by a linear-induction motor has several advantages over the steam-driven catapults used on existing aircraft carriers, according to General Atomics.
据通用原子公司称，与现在航空母舰上使用的蒸汽动力弹射器相比，由线性感应电动机提供动力的发射台有多个优点。

Whereas a steam catapult lets rip with a constant force, the speed and power of a linear motor can be controlled to provide smooth acceleration.
恒定的力使蒸汽弹射器难以控制；而线性电动机的速度和力量都可以控制，可带来平缓的加速，

That extends the life of an aircraft by subjecting it to less stress.
因为承受的压力更小，所以能够延长飞机的寿命，

It also makes for a more comfortable take off.
并且能让起飞时更舒服一些。

And the launch shuttle can brake quickly once the plane has lifted off by reversing the current running through the motor.
飞机一旦起飞，通过反转电动机中的电流，发射装置能够快速制动，然后返回原位准备下一次发射。

What works in a military context might not, of course, be appropriate for civil aviation—one reason why nobody has considered equipping airports with steam catapults.
当然，在军事中使用的技术不一定适合民用航空，这也是为什么没人会考虑在机场配备蒸汽弹射器的一个原因。

But the smooth operation of a linear motor means the take-off force could be kept within the 2.5g typically felt in a modern airliner dashing along a runway.
但是线性电动机的平缓运行意味着起飞的力会在2.5倍重力加速度之内，与一架现代的客机沿着跑道加速时的感觉一样。

Passengers need not be subjected to Top Gun levels of acceleration.
乘客们不需要去承受《壮志凌云》那种级别的加速度。

It might be possible to use linear motors for landings, too.
将线性电动机用于着陆也是有可能的。

Carrier-style arrester wires would cause too much damage and would hardly be comfortable for passengers.
航母式的拦截索会是飞机产生很多损伤，而且乘客也不会舒服。

But if an incoming aircraft landed on a moving platform equipped with a linear motor, the current in the motor could then be reversed to slow it down.
但如果一架准备降落的飞机在一个装有线性电动机的移动平台上着陆，电动机中的电流会反转，使飞机减速。

That might mean planes could do without landing gear, saving still more weight. Even Mr Anderson didn't think of that one.
这或许意味着飞机没有起落架也行，能让飞机再轻一些。

Fireball XL5 landed vertically, on retro-rockets.
安德森先生都没有想到这种方法，雷霆机是靠制动火箭垂直着陆的。