Railgun progress
Rail guns are increasing in power and robustness: Navy Railgun and Laser Projects still on track – nextbigfuture.com.
Interesting that they are already at lunar escape velocity. Not that one would use a Navy railgun as a lunar mass driver (need bigger projectiles and can accelerate them over longer distances) but it’s good to know that the technical/industrial infrastructure is being built up that is capable of developing such a system.