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Science and technology
科學技術
Reusable spacecraft
可重復使用的航天器
Jet-set rocket-man
乘噴氣式火箭的乘客
A small British firm is working on a nifty new jet-rocket hybrid engine
英國一家小公司正在研發一款輕巧的新型噴氣式火箭混合引擎
ROCKETS are a spectacular way to get into space.
火箭是進入太空的一種壯觀的方法，
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.
它不像噴氣式引擎，能將大氣層中的氧和儲存的燃料混合以獲取推動力。火箭必須在真空中工作，因此必須攜帶自己的氧。
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.
那就增加了它們的重量。其結果就是火箭的很大一部分燃料被用來將其余的燃料送離發射塔。
Now Reaction Engines, a small British firm, reckons it has a way around the problem.
現在英國的一家小公司反應引擎認為他們已經找到了解決這一問題的方法。
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日該公司說他們已對其軍刀引擎完成了一系列測試，這是一種火箭和噴氣式飛機的高科技結合體。
At low altitudes and speeds, SABRE would operate as a powerful, lightweight form of jet engine.
在低海拔和低速度，軍刀靠一架強大的輕型噴氣式引擎推動。
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時，它將切換使用內部攜帶的氧，像火箭一樣工作。
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.
通過減少航天器需要攜帶的用氧量，這種引擎最終或許可以讓航天公司建造一種真正可以重復使用的有翼航天飛機，它既能飛入太空，又能滑回地面，在普通跑道上著陸。
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.
這將會是一個巨大的進步：所有的現代火箭都是單次使用的機械，而反應引擎認為自己的天龍概念航天器與此不同，它們可以每隔幾天飛行一次，大大降低了太空飛行的費用。
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.
這種引擎的關鍵在于一個小型、輕質而強大的熱交換器，用來將進入的空氣冷卻。在高速狀態下，這些空氣由于摩擦溫度會升高到1000左右。
The heat exchanger will bring the air down to around 150.
這種熱交換器將把這些空氣的溫度降到零下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.
這會帶來很多好處，其中包括不再需要建造用來防止引擎熔化的高負荷結構，從而減輕了重量，而重量對一個航天器來說非常關鍵。
Space cadets may object that they have heard this all before.
航天新手們也許會反駁說他們之前已經聽說過這些。
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.
航天飛機很久以來就是航天工程師們的一個夢想，而軍刀引擎是從被放棄了的英國航飛天機項目HOTOL發展而來。該項目1980年代由勞斯萊斯和英國航天承擔。
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.
但是軍刀已經通過了歐洲航天局的嚴格審查，他們并未發現任何大問題，并且在更多的地面測試中表現良好。
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應用：該公司談到對一種5馬赫噴氣式飛機的軍事和民事應用，以及小型的、超輕型的熱交換器在地面項目中的應用。
