A team of British scientists are developing plans for a spacecraft that could stop large asteroids² from destroying the Earth.

一组英国科学家正在研究可以阻止大块行星毁灭地球的宇宙飞船方案。

steer³ asteroids away from the Earth" width="226" border="0" src="/upimg/090901/4_031900_1.jpg" />
The tractor would steer asteroids away from the Earth

The 10 tonne "gravity tractor" would deflect⁴（打歪，使偏） any orbiting rocks years before any potential collision could happen.

The device, which would rely on the force of gravity, is being developed by Stevenage space company, EADS Astrium.

However the idea is still in its early stages and the company admits a prototype（原型） has not yet been made.

NASA's Near Earth Object Programme reports on its website that it has recorded 1068 known "Potentially Hazardous⁵（危险的） Asteroids（小行星）", however there are thousands more estimated to be present in space.

Dr Ralph Cordey, who is EADS Astrium's head of exploration and business told the BBC that the concept of a tug⁶（用力拉，拖船） was actually first mooted⁷（讨论） by two Nasa astronauts, Edward Lu and Stanley Love, a few years ago.

He said: "Frankly⁸ I thought it was crackers⁹. I thought it would never work."

But he said after reconsidering the idea and focusing on specific engineering issues, including the size of the spacecraft, and long-term propulsion（推进，推进力） methods, it was considered by the team to be potentially feasible（可行的，可能的）.

The tractor would intercept¹⁰（拦截，阻止） the asteroid¹ from just 48 metres away and exert a small gravitational force on it, pulling the rock towards it. The pair would then embark¹¹ on a different orbit, away from the Earth.

It could possibly be powered using solar panels.

However the device would have to be launched at least 15 years before any predicted collision and would need a team to monitor it from the ground during this time.

Dr Cordey said the company had worked with a number of space authorities on other methods of protecting the Earth from asteroids but this one would be able to target a wider range.

He said: "We have done quite a lot of design work on this with the European Space Agency and we believe this would work just as well on a big solid iron asteroid as well as other types."

But the high cost implications mean that before the device could be made, it would have to be commissioned by a government or a group of governments working together.