Orion Saturn V

American nuclear pulse orbital launch vehicle. The final iteration of the Orion design was a nuclear pulse propulsion module launched into earth orbit by a Saturn V. The 100 metric ton unit would have had a diameter of 10 m to match that of the booster. This would limit specific impulse to 1800 to 2500 seconds, still two to three times that of a nuclear thermal system.

A second launch would put a 100 metric ton Mars spacecraft with a crew of eight into orbit. After rendezvous and checkout, the combined 200 metric ton spacecraft would set out on a round trip to the Mars - total mission duration as little as 125 days!

Payload: 100,000 kg (220,000 lb) to a Mars and back.