经济学人下载:可重复使用的航天器 乘喷气式火箭的乘客

Science and technology
科学技术

Reusable spacecraft
可重复使用的航天器

Jet-set rocket-man
乘喷气式火箭的乘客

A small British firm is working on a nifty new jet-rocket hybrid engine
英国一家小公司正在研发一款轻巧的新型喷气式火箭混合引擎

ROCKETS are a spectacular way to get into space.
火箭是进入太空的一种壮观的方法，

But they are also inefficient.
但是效率不高。

Unlike jet engines, which combine atmospheric oxygen with stored fuel to obtain thrust, rockets must work in a vacuum, and so must carry their oxygen with them.
它不像喷气式引擎，能将大气层中的氧和储存的燃料混合以获取推动力。火箭必须在真空中工作，因此必须携带自己的氧。

That increases their weight, with the result that a large fraction of a rocket's fuel is expended just lifting the rest of the fuel off the launch-pad.
那就增加了它们的重量。其结果就是火箭的很大一部分燃料被用来将其余的燃料送离发射塔。

Now Reaction Engines, a small British firm, reckons it has a way around the problem.
现在英国的一家小公司反应引擎认为他们已经找到了解决这一问题的方法。

On November 28th it said it had completed a series of tests of its SABRE engine, a high-tech hybrid of a rocket and a jet.
11月28日该公司说他们已对其军刀引擎完成了一系列测试，这是一种火箭和喷气式飞机的高科技结合体。

At low altitudes and speeds, SABRE would operate as a powerful, lightweight form of jet engine.
在低海拔和低速度，军刀靠一架强大的轻型喷气式引擎推动。

At higher speeds and altitudes, it would switch to internal oxygen and act as a rocket.
在更高的速度和高度时，它将切换使用内部携带的氧，像火箭一样工作。

By cutting the amount of oxygen a spacecraft needs to carry, this engine may at last allow aerospace firms to build a truly reusable winged space-plane that can fly into orbit and then glide back to land on an ordinary runway.
通过减少航天器需要携带的用氧量，这种引擎最终或许可以让航天公司建造一种真正可以重复使用的有翼航天飞机，它既能飞入太空，又能滑回地面，在普通跑道上着陆。

That would be a big advantage: all modern rockets are single-use machines. Reaction Engines reckon that its Skylon concept vehicle could, by contrast, undertake a flight every couple of days, slashing the cost of space flight.
这将会是一个巨大的进步：所有的现代火箭都是单次使用的机械，而反应引擎认为自己的天龙概念航天器与此不同，它们可以每隔几天飞行一次，大大降低了太空飞行的费用。

The key to the engine's performance is a small, light and powerful heat exchanger, designed to cool incoming air, which, at high speeds, will be heated by friction to around 1,000.
这种引擎的关键在于一个小型、轻质而强大的热交换器，用来将进入的空气冷却。在高速状态下，这些空气由于摩擦温度会升高到1000左右。

The heat exchanger will bring the air down to around 150.
这种热交换器将把这些空气的温度降到零下150度左右。

Among other benefits, that removes the need for the sort of heavy-duty construction that would otherwise be required to stop the engine from melting, helping to save precious weight.
这会带来很多好处，其中包括不再需要建造用来防止引擎熔化的高负荷结构，从而减轻了重量，而重量对一个航天器来说非常关键。

Space cadets may object that they have heard this all before.
航天新手们也许会反驳说他们之前已经听说过这些。

Spaceplanes are a long-held dream of aeronautical engineers, and the SABRE engine is a development of an abortive British spaceplane project called HOTOL, undertaken in the 1980s by Rolls-Royce and British Aerospace.
航天飞机很久以来就是航天工程师们的一个梦想，而军刀引擎是从被放弃了的英国航飞天机项目HOTOL发展而来。该项目1980年代由劳斯莱斯和英国航天承担。

But SABRE has survived close scrutiny by the European Space Agency, which could find no show-stopping problems, and has performed well in extensive ground tests.
但是军刀已经通过了欧洲航天局的严格审查，他们并未发现任何大问题，并且在更多的地面测试中表现良好。

Nor is space travel the only possible application: the firm talks of the military and civilian uses of a Mach five air-breathing aircraft, as well as the potential usefulness of its compact, ultra-light heat exchangers for earthbound applications.
太空旅行并不是唯一可能的应用：该公司谈到对一种5马赫喷气式飞机的军事和民事应用，以及小型的、超轻型的热交换器在地面项目中的应用。