Operation Outward

Operation Outward was the name given to the British World War II program to attack Germany by means of free-flying balloons. It made use of cheap, simple balloons filled with hydrogen. They carried either a trailing steel wire intended to damage high voltage power lines by producing a short circuit, or incendiary devices that were intended to start fires in fields, forests and heathland.

A total of 99,142 Outward balloons were launched; about half carried incendiaries and half carried trailing wires.

Compared to Japan's better known fire balloons, Outward balloons were crude. They had to travel a much shorter distance so they flew at a lower altitude – 16,000 feet (4,900 m), compared with 38,000 feet (12,000 m) – and had only a simple mechanism to regulate altitude by means of dropping ballast or venting lifting gas. This meant the balloons were simple to mass-produce and only cost 35 shillings each (approximately equivalent to £86 in 2017).

The free flying balloon attacks were highly successful. Although difficult to assess exactly, they had an economic impact on Germany far in excess of the cost to the British government.

In 1937, the British carried out a study on the damage that may be caused by a balloon-carried wire hitting power lines, as there was concern over what could happen if a barrage balloon accidentally got loose. Early in the year 1940, the Air Vice Marshal of the Balloon Command, the organisation responsible for the barrage balloons, wrote that "Since the outbreak of the war, I have had constant complaints from the electricity distributors regarding the damage done in this country by [barrage] balloons that have broken away from their moorings. [...] advantage might be taken of this to impede and inconvenience the enemy." It was proposed that balloons, launched from France, would carry transmitters and their position would be tracked by radio triangulation. The bomb would be released by radio control when the balloon drifted over a worthwhile target. This plan was never put into action, objections included that "attacks of this nature should not be originated from a cricketing country" and a concern that the enemy might retaliate with similar weapons. The idea became redundant when defeat in the Battle of France put possible launch sites out of British control.

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Wikipedia