Rail guns would greatly reduce the expense of launching items, vehicles, satellites, and so on, into space. Possibly down to the magic level that would allow privatization of space travel, finally putting advocates of such to put up or shut up. Allow me to explain.
A railgun is an engineered device that, using two electrically charged rails, exerts an enormous force on the object placed between those two rails. Aligning the currents with the right spin, this direction is "up." Yes, it uses a lot of energy to reliably produce a space launch, but less with this method because the energy will be provided at ground level. The launch vehicle will not require its own fuel, as the rail gun will be providing the energy. It can launch thousands of vehicles a day, if need be. (Though need will not be unless we're evacuating the Earth or something.)
Now space travel is expensive, because anything you want to get even into earth orbit must be sped to 11 km/s, or it will just fall back down again. 11 km/s is absurdly fast. To accelerate even, say, my car, to this kind of speed, some 19,958 Kilo-newtons must be applied. This would easily consume the entire output of a medium sized power plant, all charged in a bank of capacitors the size of a skyscraper.
Existing space travel uses massive hydrogen-oxygen bombs that, when
detonated, provide all that thrust and more. Of course, this means
carrying thousands of kilograms of those materials with you, which will further throw off calculations by being used up. Heavier thing, more fuel required. More fuel means even more weight. Any space mission will easily cost a billion dollars, leaving it solely in the reach of national governments.
With a rail gun setup, a very rich person could afford to send themselves and a Soyuz-type space station into orbit, for about $10 million. Plus maybe another $50 million in startup costs. Further advances might further reduce the expenses, bringing space travel to the masses.
Now at this time, there are people who complain that space travel is a misuse of government resources, and that space travel should be privatized. Very well. For $60 million, I offer you more material resources than the entire mining output of the earth. For $400 million, a consistent trade route could be developed, earning that sum back within 20 years time and employing a staff equal to the current population of Utah. I dare you to.