Momentum curtain

Discovered by British engineer Christopher Cockerell, the momentum curtain is a unique and efficient way to reduce friction between a vehicle and its surface of travel, be it water or land, by levitating the vehicle above this surface via a cushion of air.

It is this principle of levitation upon which a hovercraft is based, and Christopher Cockerell set about applying his momentum curtain theory to hovercraft to increase their abilities in overcoming friction in travel.

John Thornycroft, in 1877, discovered that trapping air beneath a ship's hull, or pumping air beneath it with bellows, decreased the effects of friction upon the hull thereby increasing the ship's top attainable speeds.

Cockerell used the idea of pumped air under a hull (this then becoming a plenum, i.e. the opposite of a vacuum) and improved upon it further.

This theory was tried, tested and developed throughout the 1950s and 1960s until it was finally realised in full-scale in the SR-N1 hovercraft.