This came from a brainstorming on how to protect the entrance of a nuclear shelter without needed too much reinforcement material. Then I thought of a system that can resist a nuclear explosion at point-blank range : the pusher plate in the Orion project, the famous nuclear pulsed propulsion research program.

This concept uses two shock absorber assemblies in series to reduce the peak pressure generated by the outside explosion to manageable levels. The vertical assembly can act as a lift thanks to its hydraulic pistons, while the horizontal can slide inwards to form an airlock.