Note that in an actual intercept, this thing is in space and going like 10km/s. It's job is to slam directly into an incoming Ballistic Missile re-entry craft before it can deploy nukes and decoys.
The giant nozzle pointed downwards is simulating 0-gravity, and probably does not exist on live fired craft.
Those thrusters must be extremely precision controlled too. At that flight profile, having a nozzle open an extra millisecond means missing the intercept by hundreds of feet.
