That violates physics as we know it, but there might be effects we don't know about just yet. Marginal improvements are boring. And besides, having to carry pr

That violates physics as we know it, but there might be effects we don't know about just yet. Marginal improvements are boring. And besides, having to carry propellant is a significant limitation to the travel distance and one of the biggest nuisances of spaceflight. If you only needed electricity or other form of energy, but not matter, it would be much, much easier.