American orbital launch vehicle. Shuttle-Z was Shuttle-C on steroids, the ultimate development of the shuttle to be used to put Mars expeditions into orbit. It would use 4 SSME's, and a third stage with 181,000 kg of propellant powered by 1 SSSME. But such designs would require new handling facilities due to the extra height of the vehicle.
Status: Study 1990. Payload: 87,500 kg (192,900 lb). Apogee: 407 km (252 mi).
LEO Payload: 87,500 kg (192,900 lb) to a 407 km orbit at 28.50 degrees.