Inert projectiles and inert propellant, no elaborate armored weapons elevators and no magazines to blow up are not “useless.”
I don’t know what voltages this needs. The gunner could get a nasty shock or electrocuted if there is an insulation failure.
But this might not be too hard to automate.
With a Mach 6 muzzle velocity, that is a heck of a lot of kinetic energy!
1.Huge wonking generators/monster capacitors to gin up and store the megawattage required to launch the projectiles. Not ideal in vessel operating in a saltwater environment/could be punctured by the enemy. Which has been known to happen.
2. Ultrahigh velocity projectiles of indifferent accuracy. Ultrahigh velocities in air at sea level equals gigantic air friction/heating and projectile degradation. Think "meteorite". That's why there is all that flame in the videos.
3. High air friction loads equal high drag loads, so the projectile loses velocity very rapidly when fired against a flat trajectory target (such as another ship on the horizon). Firing at long distance against indirect targets equals throwing a cannon-projectile-sized weight at the target but without the explosive fill. By the time the projectile reaches its maximum ordinate (apogee) it will have retained only a portion of its initial velocity and it will be driven primarily by gravity. Think "thrown brick".
4. No explosive fill and no fuze and no guidance because none of those components can survive the high launch accelerations/electromagnetic pulse at launch.
5. No guidance means near uselessness at any significant range from the launch platform. For those new to the art of ballistics, errors increase with range and there are many, many sources of error. With only a slight chance of the initial firing direction/elevation being within a mil or so, the further the projectile flies, the more inconsistencies in projectile weight, initial velocity, wind direction(s), coreolis effect, etc. will play hob with actually hitting what was aimed at.
6.Remember that EMP at launch? Huge RF signature which will be interesting with the shipboard electronics and will give the entire planet the firing platform's location when the trigger is pulled.
We can add launch rail erosion issues to the pile, but you get the picture by now, I hope.
BAE Systems and a host of parasitic contractors are deeply thankful for all that defense funding and gosh, those great videos help the Navy look all modern and such - but I am saddened that we haven't chased down better solutions than this turkey for long-distance fire support.