Mega Gauss Cannon

This weapon system was proposed several centuries ago as the basis for a space defence system. The plan to construct gigantic gauss cannons, firing scalable semi-solid projectiles of up to 200cm calibre at significant fractions of C. Such a system was calculated to have effective ranges against large targets of up to 3 million kilometres, and the destructive power to destroy a battleship with one or two hits. However, the power requirements and sheer size of the weapons made them only possible on a planet's surface.

These were never built because

a. the very high levels of lethal radiation leakage caused by the exceptionally high energies used in such a weapon make it impracticable on an inhabited world and too expensive to mount it, and the power supplies needed, on an automated asteroid platform (quite apart from the wider issues of the security of unmanned weapon systems).

b. The system would be ruinously expensive (costs in the 100s of SV level)

c. Whilst the weapon would have had an effective range that was orders of magnitude greater than anything else available, in order to hit - at range - relitively small targets such as warships in space, required exceptional computational power, suggesting that something approaching the computational power needed to create sentient AI would be needed to accurately fire the weapon. This would have had significant implications with regard to the Stickney Treaty.