I've thought that if this idea is picked up it would have to be in space. Testing the rocket on the surface of the moon (point the plate straight up) would probably have been necessary anyway. Ordinary chemical rockets can be tested on the Earth's surface, this concept, not so much.This is among the reason I've thought nuclear waste should be disposed of in space. Send the stuff onto the moon; if future lunar inhabitants want to mine it for plutonium in the naturally radiation-soaked landscape that is the lunar surface, let them.