Trying to remember Scifi book title

[tuxxj]

Trying to remember a book title I read back in the late 50's or early 60's. I thought it was was "Superman Jones" not Heinlein's "Starman Jones". The main thing I remember about it was the idea of rearanging the equation E=mc squared to create mass by compressing energy.

[wolfpackjeeper]

Heinlein has a couple of books that go by that theme, that is how his torch ships worked, but I don't know of any specific titles of hand without more clues.

[tuxxj]

The created matter was used to make an enormous wall in the path of home world of condemmed evil bad guys to obliterate their planet.