[frithguild]

Turbofans to get it off the ground. Existing technology.

Scrams to get it above the atmosphere. Amount of thrust it produces is classified. You don't know how much hydrogen produces how much thrust. No moving parts. Not much more than a specially shaped tube. Simple to produce.

Chemical rockets to achieve escape velocity. Existing technology.

[jpsb]

"Existing technology."

Propulsion yea, but I bet the airframe design is a nighmare! Imagine dsigning an air frame that can takeoff on a runway and accelerate to 25,000 mps switching populsion systems as it goes. Thank God for computers.