The early antigravity craft TR-3B used a spinning vortex of mercury plasma. One of the problems with this type of engine was that it slowly converted the mercury to gold so the engine efficiency was reduced. Periodic stripping of the gold was necessary, together with replacement of the mercury.

The early antigravity craft TR-3B used a spinning vortex of meercury plasma. One of the problems with this type of engine was that it slowly converted the mercury to gold so the engine efficiency was reduced. Periodic stripping of the gold was necessary, together with replacement of the mercury.