I have been interested in, and sometimes professionally involved with, electromagnetic launchers since I was a teenager. A few years ago, one of the scientists that I had worked with bragged about a rail gun his team had built that he said was capable of launching "one pound to Jupiter!" At the time I sort of brushed his remark off because this individual was a known drama king... he once bragged about a certain precision optical metrology system that, according to him, was so well designed it could be assembled on orange crates, this when we were spending thousands of dollars for air-suspended granite optical tables. But he sure could sell R&D research projects to the government. He once brought an Australian scientist to work in the States because the Aussy was an expert in homopolar generators. I spent a few years working for him trying to build a flash xray motion-capture camera for underground nuclear tests. The goal was one million frames per second and at least nine high-resolution frames. I failed at this task because I couldn't magnetically deflect the image to nine different positions on a cathode ray tube with sufficient speed and stability to achieve both the resolution and the speed required. The project went away, but I later learned that the image capture problem was accomplished with a different technology than the one I was asked to use. There's always more than one way to skin a cat, assuming you can catch and skin it at all.
In case you don't know what a
homopolar generator is, it's something Michael Faraday dreamed up in 1831 while "messin' 'round with magnets." Basically, it's a copper disk rotating on an axle with an external magnetic field applied parallel to the axle (perpendicular to the rotational plane of the disk). When the disk is rotated, a DC electrical field is produced radially between the axle and the outer edge of the disk, polarity depending on direction of disk rotation and orientation of the external magnetic field, voltage depending on how fast you spin the disk.
Now take this simple description and hand it to an engineer who will scale it up to industrial strength: two copper disks rotating in opposite directions so their angular momentum cancels, each disk weighing in at about a ton or so and several feet diameter, a monster electromagnet to apply a one or two tesla magnetic field, electrical contacts at the axle and on the two rims capable of handling several million amperes, a prime mover in the form of a rather largeish three-phase induction motor and you now have a rail-gun power supply. You need only add the rail-gun and a suitable switch capable of passing a mega-ampere or so of current.
IIRC this research occurred in the late 1970s and continues to this day. There is a machine shop here in Dayton that builds rail guns for the U.S. Navy, and also machines test projectiles made from aluminum block cubes about eighteen inches on a side. These weigh considerably more than a pound, so the "one pound to Jupiter!" quote was probably referring to another rail gun in an earlier stage of development. AFAIK the homopolar generator was never built for a rail gun application. I personally thought it would have been a great thing to use in an Army tank, spun up with gas turbines. The Navy powers their rail gun from capacitor banks, conventionally charged from ship electrical power and switched with thyristors.
