The key is to understand that you are applying very large amounts of power, to large masses, driving them to ultra-high velocities in short distances. (even ten miles is short.) And, if you are to do so in a series of short pushes or pulls, as with most electric motors, some method must be found to switch on or off that high power quickly and repeatedly. It might be too strong to say the quench launcher is the only approach that will work, but it is the one that is regarded as feasible by experts in the field. Future discoveries may make other methods workable or further research may leverage hybrid approaches. Each of the other launcher approaches is described below.
The simplest of all the designs, it is just a projectile (armature) located between two rails. As power flows from one rail, through the projectile, into the other rail, a force, known as the Lorentz Force, pushes the projectile forward.
Critically, and unfortunately, the rails and the projectile have to be in physical contact for the system to work. At high power levels and high speeds, the arcing, plasma and wear creates limits on the number of times such a launcher can be used without needing to be rebuilt.
In fact, the DoD quietly shuttered their research effort into high power and high-speed rail guns as the issues with robustness at high power levels and high speeds do not appear to be resolvable.
There are experts of the view, once freed of tactical constraints such as short barrel length, the rail gun could still possibly produce a workable space launch system. Careful attention to managing the plasma, and power introduced along the full length of the launcher rather than solely at the base, could possibly produce a workable way forward.
Further, there are proprietary hybrid designs combining rail gun simplicity with novel magnetic levitation methods that could also help with the fundamental difficulties of the rail gun approach.
This is a wonderful technology and the basis of most electric motors today.
Unfortunately, there is no known way to switch very high current levels required at very high frequencies necessary to reach high velocities.
In a general way, this is known as “the switching problem” and is common to all the non-contact methods.
A series of coils, in theory, could push or pull a launch package forward, each giving another boost to higher and higher velocities. Power needs to be stored so that it can quickly dump into each coil when needed. Batteries do not release power quickly enough, but many thousands of giant capacitors could suffice.
As with the Induction Launcher, the switching problem is a significant concern. A good way has yet to be found to release power, exactly when needed, with the speed and precision required to each coil.
A method to switch the drive coils at the speed and power necessary is the Quench Switch. High-Temperature Super Conductors in the Quench Launcher makes it a form of a multi-coil launcher. Importantly, the drive coils are then both an energy storage device and a solution to “the switch problem.”