Or possibly just pseudoscientific rubbish which has somehow managed to attract government funding, perhaps via powerful magnetic fields:

The theoretical engine works by creating an intense magnetic field that, according to ideas first developed by the late scientist Burkhard Heim in the 1950s, would produce a gravitational field and result in thrust for a spacecraft.

Also, if a large enough magnetic field was created, the craft would slip into a different dimension, where the speed of light is faster, allowing incredible speeds to be reached. Switching off the magnetic field would result in the engine reappearing in our current dimension.

Don’t get me wrong. Nobody is more eager to see three-hour trips to Mars and 80-day trips to Alpha Centauri than yours truly. I’m just not holding my breath, is all.

UPDATE FROM STEPHEN: Here’s a New Scientist article on the same subject.

[Dröscher] and Häuser have suggested an experiment to prove it.

This will require a huge rotating ring placed above a superconducting coil to create an intense magnetic field. With a large enough current in the coil, and a large enough magnetic field, Dröscher claims the electromagnetic force can reduce the gravitational pull on the ring to the point where it floats free. Dröscher and Häuser say that to completely counter Earth’s pull on a 150-tonne spacecraft a magnetic field of around 25 tesla would be needed. While that’s 500,000 times the strength of Earth’s magnetic field, pulsed magnets briefly reach field strengths up to 80 tesla. And Dröscher and Häuser go further. With a faster-spinning ring and an even stronger magnetic field, gravitophotons would interact with conventional gravity to produce a repulsive anti-gravity force…

Why not try it?

And here’s the Wikipedia article on Burkhard Heim. He’s the eccentric scientist who came up with the theory behind these proposed experiments. This theory is weirdly accurate at predicting particle masses.

Or possibly just pseudoscientific rubbish which has somehow managed to attract government funding, perhaps via powerful magnetic fields:

The theoretical engine works by creating an intense magnetic field that, according to ideas first developed by the late scientist Burkhard Heim in the 1950s, would produce a gravitational field and result in thrust for a spacecraft.

Also, if a large enough magnetic field was created, the craft would slip into a different dimension, where the speed of light is faster, allowing incredible speeds to be reached. Switching off the magnetic field would result in the engine reappearing in our current dimension.

Don’t get me wrong. Nobody is more eager to see three-hour trips to Mars and 80-day trips to Alpha Centauri than yours truly. I’m just not holding my breath, is all.

UPDATE FROM STEPHEN: Here’s a New Scientist article on the same subject.

[Dröscher] and Häuser have suggested an experiment to prove it.

This will require a huge rotating ring placed above a superconducting coil to create an intense magnetic field. With a large enough current in the coil, and a large enough magnetic field, Dröscher claims the electromagnetic force can reduce the gravitational pull on the ring to the point where it floats free. Dröscher and Häuser say that to completely counter Earth’s pull on a 150-tonne spacecraft a magnetic field of around 25 tesla would be needed. While that’s 500,000 times the strength of Earth’s magnetic field, pulsed magnets briefly reach field strengths up to 80 tesla. And Dröscher and Häuser go further. With a faster-spinning ring and an even stronger magnetic field, gravitophotons would interact with conventional gravity to produce a repulsive anti-gravity force…

Why not try it?

And here’s the Wikipedia article on Burkhard Heim. He’s the eccentric scientist who came up with the theory behind these proposed experiments. This theory is weirdly accurate at predicting particle masses.