Project Orion Nuclear Pulse Rocket

Project Orion was a study of a starship intended to be directly propelled by a series of explosions of atomic bombs behind the craft (nuclear pulse propulsion)

The project was eventually abandoned for multiple reasons such as the Partial Test Ban Treaty which banned nuclear explosions in space as well as concerns over nuclear fallout.

The biggest design was the "Super" Orion design; at 8 million tons, 7250000000 Kilograms it could easily be a city. thanks