Sussex close to Nasa deal

August 29, 1997

ELECTRICAL engineers at Sussex University were this week expected to sign a deal with Nasa to design a linear electric motor to help launch spacecraft. The technology could soon help Nasa save millions of pounds in launch costs.

Much of the credit for the motor's development rests with Eric Laithwaite, visiting professor at Sussex.

The device is a conventional motor that is split down the middle and laid out flat, enabling linear rather than rotational motion.

Linear motors are a type of induction motor in which the stationary and revolving parts are straight and parallel to each other rather than being circular and one inside the other as in ordinary induction motors. The first task for the Sussex engineers will be to build an experimental linear motor ten feet in length. The ultimate objective is to build one that stretches over a mile, which it is thought could lift and propel a spacecraft at high speed and shoot it into orbit.

Professor Laithwaite has been pushing the use of the technology to launch spacecraft since the 1960s. He said Nasa was now looking to intensify its launch programme and was keen to move on from the traditional "rocket" launch because of the sheer cost of the fuel they use to achieve orbit.

He said: "With a rocket you burn your fuel and you have lost it. Also you have to carry your fuel with you. Two thirds of the total weight of the rocket is burned up as fuel and half of that is simply used in getting the cargo up to 600 mph required to achieve orbit. All you have done to reach that speed is lift fuel."

A shuttle launch rocket weighs about 80 tonnes. Using a linear motor could eliminate the need for 60 tonnes of the fuel-laden first stage, leaving only 20 tonnes of cargo to be propelled into space.

In Professor Laithwaite's design the vehicle has no launch power itself. It would be the linear motor instead that is powered and this would come from safe and cheap mains electricity. The cost per launch would be about Pounds 1,000 compared with the millions of pounds needed to launch conventional rockets, he said.

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