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British female military auxiliaries handle a barrage balloon.

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 gas balloons filled with hydrogen. They carried one of two types of payload: a trailing steel wire intended to damage high voltage power lines by producing a short circuit, or three incendiary devices - 6-pound (2.7 kg) flexible socks filled with flammable material - that were intended to start fires in forests and heathland.

A total of 99,142 Outward balloons were launched: 53,343 carried incendiaries and 45,599 carried steel wires.[1] 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 (£85 when adjusted for inflation).

History and development

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. The idea of using balloons to carry bombs was proposed in the winter of 1939-1940. The 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.[2] The idea became redundant after defeat in the Battle of France put possible launch sites out of British control.

On the night of 17–18 September 1940, a gale broke loose a number of British barrage balloons and carried them across the North Sea. In Sweden and Denmark, they damaged power lines, disrupted railways and the antenna for the Swedish International radio station was knocked down, bearing out the findings of the 1937 report. Five balloons were reported to have reached Finland.[3] A report on the damage and confusion reached the British War Cabinet on 23 September 1940. Winston Churchill then directed that the use of free-flying balloons as weapons against Germany should be investigated.[3]

The Air Ministry initially produced a negative report, possibly because the Ministry of Aircraft Production felt balloons would be ineffective weapons and would use up too many resources. However, the Admiralty took up the idea with more enthusiasm. They concluded balloons had the advantages of being low cost and not placing British personnel at risk. The design of the German power grid made it vulnerable to damage by short-circuit. Large areas of pine forest and heathland in Germany made the countryside vulnerable to random incendiary attack and the Germans would be forced to assign large numbers of people to the task of fire watching, possibly diverting them from more productive war-work. Furthermore, winds above 16,000 feet (4,900 m) tend to blow from west to east, making it harder for the Germans to retaliate with similar balloons.[4]


The balloons had no guidance control and operated only on a timing fuse. Balloon were made from white latex rubber[5] and were about 2.4 metres (7.9 ft) in diameter when inflated. They carried a simple timing and regulating mechanism. A double-walled can contained mineral oil in an inner chamber and a roll of hemp cord and piano wire in an outer chamber. At deployment, a slow-burning fuse was lit, calibrated to the estimated time to arrive over German-controlled territory. At launch the balloon rose and expanded in size until an internal cord tightened, releasing some gas and preventing further increase in altitude beyond 25,000 feet (7620 m); the balloon would begin a slow descent. After several hours, the fuse would burn through the cord holding the trailing wire. The payload consisted of about 200 metres of light hemp cord secured to the balloon at one end and tied to about 90 metres of steel wire at the other. This would unroll as the balloon sank to working altitude of about 300 metres. A stopper on the canister of mineral oil was also released, so that it would slowly drip out and lighten the load on the balloon, to assist in maintaining altitude.[6]

The plan was that the wire tail would be dragged for many miles (kilometers) across the countryside, eventually encountering a high-voltage transmission line. A phase-to-phase short circuit would be initiated; during trials, arcs 4 metres (13 ft) long were initiated by the piano wire. The arc would burn for some time before the transmission line protection operated; there was a good chance the circuit breaker itself would be damaged, and the line conductors might burn through due to arcing, causing a line to collapse and require repairs. German efforts to protect transmission lines from attack were unsuccessful; neither a new type of line conductor clamp, nor different overcurrent protection settings had any useful effect. Just fewer than half of the Operation Outward balloons carried wire; the rest carried an incendiary bomb intended to set fires in forests.


After a lengthy bureaucratic struggle between the opponents in the Air Ministry and proponents in the Admiralty, the British Chiefs of Staff gave the go-ahead in September 1941 and a launch site was set up, based at HMS Beehive, a Royal Navy shore establishment near Felixstowe in Suffolk. The actual balloon releases took place at the Felixstowe Ferry Golf Club.[7] The first launches took place on 20 March 1942. Within days, the British were receiving reports of forest fires near Berlin and Tilsit in East Prussia.[8]

Intercepts of Luftwaffe communications soon showed German fighters were trying to shoot down balloons. This encouraged the British as it was felt that the harassment value on German air defences alone justified Operation Outward. It cost the Germans more, in terms of fuel and wear and tear on aircraft, to destroy each balloon than it cost the British to make them. The crews that launched the balloons were primarily from the WRNS, with up to 140 women being employed with assistance from a small number of personnel from the RAF Regiment. The balloons were inflated using hydrogen from pressure cylinders that were brought to the launch site by truck. They were inflated inside three-sides tents or windbreaks. It was necessary to keep the latex wet with a water spray during inflation, otherwise friction between the balloon and the tent canvas might have caused the hydrogen to ignite. The inflated balloons were conveyed by hand to a dispersal point, where their payload was attached. Balloon operations could be hazardous, and there were many incidences of launch crew requiting hospital treatment for burns caused by exploding balloons or by mishandling incendiary payloads.[9] For security reasons, the Felixstowe launch crews were referred to as a "Boom-defense" unit, a cover story that was partly true as they were put to work maintaining Anti-submarine nets when weather conditions were not right for balloon launches. The Felixstowe golf club site had a number of Lewis Guns for anti-aircraft defense, which the WRNS women were trained to operate, occasionally releasing balloons for the purpose of target practice.[10] In July, a second launch site was set up at Oldstairs Bay near Dover.[8] On 12 July 1942, a wire-carrying balloon struck a 110,000-volt power line near Leipzig. A failure in the circuit breaker at the Böhlen power station caused a fire that destroyed the station;[1] this was Outward's greatest success.[6] In August 1942 launches reached 1000 per day. Balloon launches continued, though they were frequently suspended when there were large air-raids on Germany as it was feared the balloons might damage Allied bombers. Also, they continued to cause damage in neutral countries - on the night of January 19–20, 1944, two trains collided at Laholm in Sweden after an Outward balloon knocked out electrical lighting on the railway.[1] Changing winds could also blow balloons back to the United Kingdom. On one occasion, a balloon knocked out the electricity supply to the town of Ipswich.[11]

In the lead-up to D-day invasion, balloon launches became more sporadic. The last balloons were launched on 4 September 1944.[1]

See also


  1. 1.0 1.1 1.2 1.3 Peebles, p56.
  2. Peebles, p52.
  3. 3.0 3.1 Peebles, p53.
  4. Peebles, p54.
  5. Porter (2005), 21 min
  6. 6.0 6.1 Raoul F. Drapeau, Operation Outward Britains World War II offensive ballons, IEEE Power&Energy Magazine, September/October 2011 pp. 94-105
  7. Cornwall, Richard (26 October 2001). "Revealed: Secret of the balloon blitz". Ipswich Star. Retrieved 20 August 2013. 
  8. 8.0 8.1 Peebles, p.55
  9. Porter (2005), 22 min
  10. Bywater (2005), Reel 2, 20 min. 10 sec.
  11. Bywater (2005), Reel 2, 9 min. 30 sec.
Bibliography, Sources

External links

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