Nuclear space guns have been proposed. Aside from the manhole cover: http://nextbigfuture.com/2010/03/150-kiloton-nuclear-verne-gun.html http://nextbigfuture.com/2010/12/sea-based-launch-option-for-nuclear.html
(This appears in Hannu’s Quantum Thief trilogy, incidentally.)
Nuclear space guns have been proposed. Aside from the manhole cover: http://nextbigfuture.com/2010/03/150-kiloton-nuclear-verne-gun.html http://nextbigfuture.com/2010/12/sea-based-launch-option-for-nuclear.html
(This appears in Hannu’s Quantum Thief trilogy, incidentally.)