I assume its a closed room because the acceleration isn't done in normal atmosphere - so you are going to literally explode out of this thing into normal air at 2100m/s?
Earth escape velocity is 11.1 km/s, which is Mach 32 at sea level. They have some more engineering to do, maybe even invent something better than carbon fibers.
Exactly. I don't think their scale demonstrator demonstrates much beyond the possibility of making a propulsion stage that survives the launch at 10000G's