“Radian’s solution is a rocket-powered sled that runs along a two-mile rail and accelerates up to Mach 0.7 — 537 mph (864 kilometers per hour) — before releasing the space plane”.

Once released from the rail track (a flat track at ground level, I assume), won’t air drag hit it like a ton of bricks?

Maybe if they put the track on top of a 20,000 foot mountain, and/or somehow released the spacecraft at a 45 degree angle?