Bob Lazar is a known nutjob who ignores the laws of physics, preferring to make them up as he goes. Element 115 is a synthetic element with a half life of seconds. You can't use it as a fuel because even assuming it was combustible (we don't yet know because we haven't been able to make more than 1 or 2 atoms of it at a time) it would degrade almost instantly. Even Area51 "investigators," themselves subject to wild flights of paranoid fancy, dismiss Lazar as not credible.
http://www.serve.com/mahood/lazar/lazarmn.htm
We're not talking about ununpentium here, we're talking about unobtanium. When I asked for references showing that aliens have been here and that this gravity drive exists, I didn't mean from already discredited sources.