These days, flying saucers are most commonly associated with sci-fi films and conspiracy theories, but in the 1950s, some saw them as the future of aviation.

Documents published by the US National Archives give new information about a craft commissioned by the US air force, which if successfully developed would have achieved speeds of 2,600mph and flown at around 100,000ft.

Details of the proposed craft have been around for years. But the declassified papers include new diagrams and documents that demonstrate the scale of the project’s ambition.

The US air force contracted the work to a now-defunct Canadian company, Avro. In one document, Avro envisaged a “top speed potential between Mach 3 and Mach 4, a ceiling of over 100,000ft and a maximum range with allowances of about 1,000 nautical miles”. That would have sent the flying saucer spinning into the Earth’s stratosphere.

Language in a report labelled “final development summary” was optimistic: “It is concluded that the stabilization and control of the aircraft in the manner proposed – the propulsive jets are used to control the aircraft – is feasible and the aircraft can be designed to have satisfactory handling through the whole flight range from ground cushion take-off to supersonic flight at very high altitude.”

Such lofty ambitions were never achieved; video footage of other disc-shaped crafts constructed by Avro show a machine wobbling uncertainly around 3ft off the ground.

The cost for the endeavour is listed as $3,168,000, which Wired estimates at $26.6m in today’s money.

Sadly, the project was cancelled and the craft were never built.

They sounded good at the time …

Flying tanks

“Imagine those two formidable weapons of modern warfare, the airplane and the armored tank,combined into one terrible machine of destruction!”

Hurrah! Stick some wings on your tank and watch it fly. Apparently “initial tests were successful“, but clearly flying tanks did not become the ‘terrible machine of destruction’ envisaged in the 1930s. More robust aeroplanes meant tanks were placed inside aircraft, rather than strapped underneath.

Massive ‘gas-shooting’ riot car

Apparently this vehicle was designed to control crowds ”and put a stop to riots at any cost”. The concept, which was patented by a Brooklyn based-company, would have spurted poisonous gas at any ne’er-do-wells, or alternatively soaked them with water. Or just shot them with machine guns. Options.

Bell rocket belt

After it was built for the US army in the 1960s, John F Kennedy was treated to a rocket-belt display in October 1961. The device used hydrogen peroxide as fuel – the belt-wearer was advised to wear insulating trousers – and could carry a man over 9m high obstacles at speeds of up to 10mph. Unfortunately it could only do so for about 20 seconds, and it was not put into widespread use by the military.