[Taniwha]

so to put something in orbit you have to do 2 things:

- get it high out of the atmosphere - give it a sideways kick so that it's going fast enough as it falls back that it misses the earth

Going straight up minimises the velocity lost by drag, but means you have to pull a right angled turn, going straight sideways grossly increases drag but makes the energy for insertion less

A railgun can only put one velocity vector on a launch, you still need a rocket of some sort to pull that turn

[whatshisface]

All unthrusted orbits eventually return to their starting points - so without a rocket on the payload there would be absolutely no way for a railgun to orbit anything. (Even if the railgun was on a tower on the moon, the satellite would eventually hit the back of the railgun.)

[toomanybeersies]

Unless you gain enough velocity that your projectile is trapped in the gravity well of another planet.