London, Nov 16 : A aerospace company has successfully tested a rocket thruster, which might be used to power the engine of the Apollo 11 lunar lander on its next mission to the moon.

Devised by the Northrop Grumman aerospace company, the thruster runs on a mix of liquid methane and liquid oxygen, which has never been used before to power or steer a spacecraft.

Missions such as landing on and taking off from the Moon put stringent requirements on engines. Importantly, rockets must be liquid-fuelled so they can be shut down and restarted if needed.

Scientists say that the previously unused fuel can prove to be more efficient than other engines and could be a candidate for powering the liftoff vehicle NASA is developing to return astronauts from the lunar surface.

The earlier Appollo lunar landers used mixtures called 'hypergolic' fuels, which ignite when they come into contact with a matched oxidizer.

A major disadvantage of hypergolic fuels is that it uses compounds such as nitrogen tetroxide and hydrazine, which are extremely toxic for astronauts and ground crews.

Also, though these fuels can be stored longer than liquid hydrogen and liquid oxygen (LOX) without boiling away, the specific impulse (a measure of propulsion power) in the hypergolic engines is only 260 to 310 seconds. This is quite low compared to 425 to 455 seconds from liquid hydrogen and LOX.

Liquid methane, on the other hand, is denser than liquid hydrogen. This can help the fuel tanks to be smaller than those for liquid hydrogen.

The new test engine has already beaten the specific impulse of hypergolic fuels, although it can't match that of a liquid-hydrogen engine.

The Northrop tests are also a step toward answering NASA concerns about the ease of igniting methane, crucial for engine function.

"The engine far exceeded performance requirements," said Northrop programme manager Mark Trinidad.

It was fired more than 50 times, a key capability for thrusters, which are used repeatedly.

Other teams are also working on more powerful methane/LOX engines suitable for lunar liftoff. (ANI)