The COVENANT won't be pleased that we humans are developing our own 'Ring'. [HALO ranting off]
Two undesirable things would be happening as the launch sled circled for hours: heat would build up; and increasing amounts of energy would be wasted on overcoming air resistance.
Perhaps a more optimal design would incorporate a larger sled, and a larger rocket and more rocket fuel. This would enable a quicker launch, at lower speeds & lower g forces. The rocket could provide the final boost at very high altitudes, where there is very little air resistance.
The lateral g-forces would be enormous. Most satellites are designed with a single direction high g-load in mind for launch.
Not sure how this would play out. The Moon is a different animal though. For years, there have been proposed designs for a mass driver to lift payloads to space.
Air resistance is the major problem. First it will bleed energy off the projectile, and second it will cause extreme aerodynamic heating. A solution would be a hollow tube reaching at least five miles high that could hold a vacuum, ten miles even better. The tube could be built along the side of a mountain, but it would have to go even higher than any mountain. This project is somewhat similar to the space elevator as far as technology.