In 1910, two Army officers, Second Lieutenant Bowle-Evans and Lieutenant Cammell independently put forward a new idea for an anti-aircraft weapon: the vortex ring gun.

In principal, it involved the formation of a vortex in the air, by the firing of an explosive charge inside a conical 'gun' which, if it were pointed upwards, would propel the vortex towards the intended airborne target on which, it was suggested, the violent air movement within the vortex would have a sufficiently destructive effect. Some practical support for the theory was provided firstly by a Dr Pernter of Germany who had some years earlier carried out some experimental firings which were said to have torn apart birds and other objects, and secondly by the farmers of a large region ranging from Hungary to northern Italy, who appeared to use such guns routinely in the belief that they could disperse hailstorms.¹

These proposals seem to have been made to the War Office; in any case a year later the Secretary of State for War, Richard Haldane, was corresponding on the subject with Sir Oliver Lodge, the eminent physicist. Lodge told Haldane that 'I really think the thing is worth a trial', but although he proposed acquiring a vortex ring gun from Piedmont for testing purposes it's unclear whether this ever happened.

The idea of using a vortex ring gun for air defence was aired in public at an Aeronautical Society lecture given on 3 December 1913 by Captain C. M. Waterlow, Royal Engineers, on the topic of the 'The coming airship'. In a discussion of the potential for aerial combat between aeroplanes and airships, Waterlow thought the former would be disadvantaged because of its inferior weight-carrying capacity: the airship could afford to be much better armed. This is perhaps not surprising since he was himself an airship pilot. When it came to the weapons which would be used, he suggested vortex rings:

The question of a suitable weapon had hardly been considered, but he would remark that there were great possibilities in the use of vortex rings, such as had been used in France in connection with vineyards. To show the destructive effects that they can produce, he stated that when fired horizontally they were capable of breaking up a wooden fence at a distance of 100 yards.²

The basic principle behind vortex ring guns is quite sound: a smoke ring is a common form of vortex ring, and toy vortex guns can bought or even made at home. Practical uses are a bit more dubious. The use of vortex ring guns (or hail cannon) to disperse hailstorms has a long history but little scientific evidence to back it up. More recently, militaries have looked at vortex ring guns as non-lethal weapons, to knock people down, but they don't seem to be able to do this even over a distance as short as 30 metres.

So the utility of vortex rings in air defence seems doubtful -- to us. It wasn't as clear a century ago. Pernter was a respected scientist who demonstrated vortex rings at the British Association in 1903 (and apparently eventually concluded that they didn't work for weather modification, so he wasn't simply a crank). There was at least widespread anecdotal evidence, from the United States as well as Europe, for the effectiveness of hail cannon. And in the era of wood and wire the idea of knocking an aeroplane out of the sky by, more or less, pushing some air at it wasn't as silly as it would have been a decade or two later. They hardly needed any encouragement to crash as it was. (I read Waterlow's reported comment about vortex ring guns in aeroplane vs airship combat as referring to the aeroplane's armament but it seems to me it would profit the airship more.)

However. If we step back and take a broad overview of ideas for anti-aircraft weapons in the first few decades of the twentieth century then, taken as a whole they do look rather mad ('wildly creative' was how I put it in my thesis). Setting aside spiritual forms of air defence, at one extreme there was the death ray, which I've discussed here several times, which had varied proposed applications but was most desired for its ability to stop engines and bring bombers down. At the other are what we would consider mundane anti-aircraft weapons, because they actually existed and were effective to some degree: anti-aircraft guns and balloon barrages. Even these could have some odd ideas attached to them, such as the giant Lee-Enfield rifle described by the Daily Express in 1935. It was sometimes suggested that the cables used to tether Britain's barrage balloons were enhanced somehow, to make them more dangerous beyond the physical damage caused to a colliding aeroplane. Shaw Desmond, in his 1938 novel Chaos, imagined London defended by a balloon apron with 'Lethal wires [...] suspended which, upon contact, could wipe out the enemy bombers automatically'.³ This was somewhat science-fictional, but around the same time two more serious and well-informed writers, J. M. Spaight and C. C. Turner, also used the word 'lethal' to describe barrage balloon cables: it could just mean 'electrified'.⁴

That was far from the end of the barrage's potential. Desmond also proposed explosive balloons, detonated either by radio or by proximity.⁵ Again, he wasn't alone: Stefan Possony, a Czech diplomat Air Ministry official, proposed 'a barrage of bombs suspended either from balloons or some type of machine built on the principle of the helicopter'.⁶ He also thought that helicopters or autogyros could be used to replace barrage balloons and fighter interceptors, as they could be armed with guns, bombs and searchlights: any 'aeroplanes, which manage to pierce the wall of ropes, can easily be destroyed by dropping bombs fitted with time fuzes on them'.⁷

Another variation on the barrage used rockets. Arch Whitehouse, writing during the Phoney War, attributed to Harry 'Death Ray' Grindell Matthews the idea of the 'torpedo-rocket', which would explode at a set height 'and release a whole slew of 6-ft. diameter parachutes from which two-pound bombs will dangle at the end of long lengths of entangling steel wires'.⁸ J. F. C. Fuller cut out the middleman and proposed using large (anything up to twenty tons) liquid-fuelled rockets to shoot down aircraft directly:

The first nation which discovers how to build a practical rocket of one ton in weight will have at its disposal a most powerful anti-aircraft weapon which, acting like a depth-charge, may render flight in formations highly dangerous.⁹

This too was something Grindell Matthews had been working on in the mid-1930s.¹⁰

As a last example, J. M. Kenworthy, a Labour MP, past lieutenant-commander in the Royal Navy and the future Lord Strabolgi, claimed in 1927 that 'we now have improved projectiles and improved guns, with gas shells capable of producing a gas barrage in the air'.¹¹

Despite the frequent claims, like Kenworthy's, that these weapons were in development or even in service, very few of them ever seem to have been given serious official consideration. But government scientists did sometimes work along the same lines. Experiments with anti-aircraft rockets, though much smaller than Fuller's, eventually bore some fruit, though more for ground attack than air defence.¹² The case of the aerial mine programme is fairly well known, which had the support of Frederick Lindemann, Churchill's confidant and scientific advisor. Aerial mines consisted of a long length of cable with a parachute on one end and a small bomb on the other: bombers would lay these in the path of an oncoming air raid. The idea got a pretty fair run during the Blitz, but was found wanting.¹³ Research was also conducted into ways to increase the 'lethality' (there's that word again) of balloon barrage cables by attaching bombs to them.¹⁴ Like the rockets this seems to have been turned into an offensive weapon, as deployed in Operation Outward, Britain's anticipation of the Japanese Fu-Go balloons: 99,000 balloons were released between 1942 and 1944 to drift across the North Sea, about half trailing cables to wreck the German electrical grid and half with incendiaries to start forest fires.¹⁵

No other form of response to the threat of a knock-out blow from the air elicited such 'wildly creative' technological thinking as did anti-aircraft defences. Many of the ones discussed here do look mad, but the same desire for a defensive superweapon which made the vortex ring gun appealing led to radar (itself inspired by the death ray) and the proximity fuze. It also led, much later, to the Strategic Defense Initiative, of which Possony was an early advocate. Blind alleys are inherent in blue sky research (to mix metaphors); perhaps the price of vigilance is eternal freedom.

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1. Malcolm Hall, From Balloon to Boxkite: The Royal Engineers and Early British Aeronautics (Stroud: Amberley, 2010), 204. [↩]
2. '"The coming airship"', Flight, 13 December 1913, 1362. [↩]
3. Shaw Desmond, Chaos (London: Hutchinson & Co., 1938), 385-6. [↩]
4. J. M. Spaight, Air Power in the Next War (London: Geoffrey Bles, 1938), 24; C. C. Turner, How the Air Force Defends Us (London: George Allen & Unwin, 1940), 28. [↩]
5. Desmond, Chaos, 384-5. [↩]
6. Stephen Th. Possony, To-morrow's War: Its Planning, Management and Cost (London, Edinburgh and Glasgow: William Hodge & Company, 1938), 121. [↩]
7. Ibid., 120. [↩]
8. A. G. J. Whitehouse, Hell in Helmets: The Riddle of Modern Air Power (London: Jarrolds, n.d. [1940]), 198. This was evidently in 1937 or 1938: see the account in E. H. G. Barwell, The Death Ray Man: The Biography of Grindell Matthews, Inventor and Pioneer (London, New York and Melbourne: Hutchinson & Co., n.d. [1943], 136-8. [↩]
9. J. F. C. Fuller, Towards Armageddon: The Defence Problem and its Solution (London: Lovat Dickson, 1937), 187. [↩]
10. Barwell, The Death Ray Man, 139. [↩]
11. J. M. Kenworthy, Will Civilisation Crash? (London: Ernest Benn, 1927), 255. [↩]
12. David Zimmermann, Britain's Shield: Radar and the Defeat of the Luftwaffe (Stroud: Sutton, 2001), 147-8. [↩]
13. Zimmermann, Britain's Shield, 145-7, 150-1; but see also David Edgerton, Britain's War Machine: Weapons, Resources and Experts in the Second World War (London: Allen Lane, 2011), 107-8. [↩]
14. Zimmermann, Britain's Shield, 150. [↩]
15. Edgerton, Britain's War Machine, 111. [↩]