The Hajile project was undertaken by the British Admiralty’s Directorate of Miscellaneous Weapons Development or DMWD, founded in 1941 as an offshoot of the Inspectorate of Anti-Aircraft Weapons and Devices. In true cheeky British fashion, this name was soon corrupted to the “Instigator of Anti-Aircraft Wheezes and Dodges”, creating the DMWD’s enduring nickname of the “Wheezers and Dodgers.”
In any event, the DMWD was one of many similar groups established by the British early in the war, leveraging the unique talents of a ragtag group of scientists, engineers, and other eccentric misfits to develop creative and often bizarre solutions to difficult wartime problems. Over its brief 4-year history, the DMWD would employ a number of colourful characters, including motor racing photographer Louis Kemantaski; engineer Barnes Wallis, inventor of the “bouncing bomb” used in the famous 1943 Dambusters raid; and engineer Nevil Shute Norway, later to become famous as the author of novels like On the Beach and A Town Like Alice. Headed by Canadian chemist Charles Goodeve and headquartered at HMS Birnbeck – a converted pier at Weston-super-Mare in Somerset – DMWD tackled all sorts of unconventional projects, including radar countermeasures and ship camouflage, amphibious assault techniques, anti-submarine weapons, and – of course – Hajile.
The concept behind Hajile was straightforward enough: instead of a parachute, air-dropped payloads were fitted with a set of downward-facing cordite solid-fuel rockets which were fired just before impact, quickly slowing the payload and delivering it safely to the ground. This would allow the payload to free-fall for most of its descent, allowing it to be more accurately dropped onto landing zones and protecting it from enemy fire. In practice, however, this scheme proved anything but simple to pull off. One of the key technical difficulties of the Hajile concept was how to reliably trigger the rockets at the exact right moment– too late and the payload would either plough into the ground at terminal velocity or bounce back into the air, while too early and it would pick up enough additional speed after to be damaged on impact. To solve this problem, the boffins at the DMWD developed a plumb-bob that hung a certain distance below the payload, and which would fire the rockets as soon as it touched the ground.
Initial trials were conducted by simply dropping a concrete block fitted with rockets from a tall crane. Unfortunately the project got off to an inauspicious start as the first block, fitted with too few rockets, simply buried itself in the ground, while also being dramatically engulfed in a wreath of flame and smoke. Witnessing this impressive spectacle, one of the observers, Captain G.O.C. Davies, exclaimed: “Look at it! It’s Elijah in reverse!” – referring to the biblical prophet who ascended to heaven in a chariot of fire. The comment resulted in the project being officially dubbed Hajile – literally Elijah in reverse.
Moving on to the second drop, this ended much like the first, while in the third the engineers fitted the block with too many rockets, causing it to launch itself several dozen feet into the air before crashing back to the ground.
These early tests also revealed the difficulties inherent in designing a reliable triggering device, for the plumb-bob had to be simultaneously heavy enough not to be blown upwards by strong winds during descent and sensitive enough to detect soft terrain like long grass.
Following these disappointing trials, the Hajile team decided to conduct all further experiments over the sea, which would not only provide an ideal flat surface to test triggering devices, but also hopefully allow test rigs to be recovered intact. For these water based tests, rather than a crane, the test articles were dropped from a Lancaster heavy bomber – much as they would once Hajile entered service. Unfortunately, the first few drops landed too far away to be successfully recorded, so the engineers asked the Lancaster pilot to drop the next payload closer to the pier…. What could go wrong?!?
To their horror, the pilot took their request a little too literally, as team member Gerald Pawle later recalled:
“As [Hajile] came screaming through the air the watchers on the pier gazed open-mouthed. Then, suddenly realizing that it was going to score a direct hit, every one started running for dear life down the long plank roadway. The concrete “bomb” landed squarely on the roof of D.M.W.D.’s engineering shop. It sheared through a massive steel joist and then demolished the covered way leading to the steamer jetty. Happily there were no casualties, though the Wren [WRNS – Women’s Royal Naval Service] cooks preparing lunch a few feet from the wrecked shelter thought the end of the world had come.”
Whoopsa-doodle!
Following this hair-raising incident, the Hajile team finally began to make some progress when they increased the number of rockets from four to eight. In this configuration, the test blocks came to a complete stop just a few feet above the water before sinking slowly beneath the surface. Buoyed by this encouraging success, the Hajile team decided to move on from concrete blocks to actual payloads, and attended to convince the Royal Navy to provide them with a number of jeeps for testing. Understandably, the Navy was skeptical about risking perfectly good vehicles on such an unproven and potentially destructive device, and the DMWD was forced to procure its jeeps from the United States Navy instead. Unfortunately, the Royal Navy’s fears proved well-founded as the first test drop ended in spectacular failure. Snowfall had dampened the rocket fuses, causing the rockets to fail and the jeep to hit the ground at terminal velocity, completely destroying it. After two weeks of tinkering, the team was ready to try again. This time, the rockets fired right on cue, but when the smoke cleared the team discovered the jeep lying upside-down.
Further tests were no more successful, with the system proving maddeningly difficult to get working reliably. As for the flipping issue, one major problem was the difficulty of getting the primitive cordite rockets to ignite simultaneously, a shortcoming that caused many test articles to flip over or tumble end-over end. Moving on from there, matching the thrust of the rockets to the weight of the payload also proved tricky, leading to many payloads crashing to the ground at high speed or being launched erratically back into the air.
Ultimately while the team ultimately came tantalizingly close to perfecting the system, the end of Hajile finally came on June 6, 1944 – the day of the D-Day landings – when an electrician accidentally triggered the rockets on a test rig while the engineering team was gathered around it. The resulting blast injured several people, including photographer Louis Kemantaski who was blinded for several days after receiving a blast of sand to the eyes. With the strategic need for Hajile quickly fading, the project was temporarily shelved and then abandoned completely as the war – and the DMWD – came to an end.
The hilarious failure of Hajile aside, the DMWD did make a great many useful contributions to the war effort, developing such successful devices as the Hedgehog and Squid anti-submarine mortars, methods for protecting ships against magnetic mines, and the Mulberry floating harbours used during the D-Day landings. However, on the other end of things, the Hajile was not that only of the DMWD’s bizarre misfires. Among the group’s more eccentric undertakings was a scheme called “Kentucky Minstrels”, which sought to disguise reflective rivers and canals – used by German bombers as navigation aids at night – as roads by coating them in a substance derived from coal dust. While the actions of wind and tide ultimately made the scheme impractical, on at least one occasion the effect proved remarkably convincing, when a man out walking his dog at night mistook a camouflaged canal for an asphalt road and ended up unexpectedly soaked.
But perhaps the “Wheezers and Dodgers’s” most bizarre creation was the “Great Panjandrum” – a giant rocket-propelled explosive wheel designed to be launched from a landing craft, rapidly roll up an invasion beach, and destroy coastal defences with a bang. Like Hajile, Panjandrum was a spectacular failure – but that is a subject for another video.
Another, related wartime project was the “Jumping Tank”, an attempt to use rockets to make light armoured vehicles like the Valentine tank and Universal Carrier leap over obstacles like canals or anti-tank ditches. Needless to say, this insane concept proved completely unworkable and the project was quickly scrapped.
Interestingly, while Hajile proved an abject failure, the concept of slowing air-dropped payloads using retro-rockets was later revived and successfully implemented – albeit as an enhancement rather than a replacement for parachutes. For example, ever since the first manned spaceflight by Yuri Gagarin in 1961, the Soviet Union and later the Russian Federation have opted to recover their space capsules on land rather than at sea like the American space program. There are several reasons for this; firstly, unlike the Americans, the Russians do not possess a large enough naval surface fleet to perform efficient ocean recoveries. Secondly, during the Cold War, having spacecraft land within Russia’s vast territory made them less likely to be captured by the enemy.
However, this recovery method brought with it a key safety issue: achieving a ground landing soft enough to prevent the cosmonauts from being injured required a parachute far larger than could be carried in the cramped capsule. The Vostok capsule flown by Gagarin solved this problem by having the cosmonaut eject and land separately from the spacecraft. However, the later Voskhod and Soyuz capsules landed with their crew still inside and used a system of solid-fuel retro-rockets to lessen the impact speed. On the Voskhod capsule, these rockets were mounted on the parachute shroud lines, while on the Soyuz – which is still in use today – they are located under the heat shield which is jettisoned just prior to landing. These six rockets are triggered by a gamma ray altimeter codenamed Kaktus-2V between 1.1 and 0.8 metres from the ground, slowing the capsule from around 10 metres per second to around 2.5 – resulting in a relatively light impact cosmonauts describe as a “light thump.” However, as it is possible that the retro-rockets may fail, the crew couches are designed to withstand the impact of landing under only a parachute – though this is a decidedly less comfortable experience.
In the 1970s, the Soviets also developed a Hajile-like landing system for the BMD-1, a lightweight armoured fighting vehicle designed for use by airborne troops. Weighing only 7.5 tons, the BMD-1 can be carried by nearly any Russian transport aircraft and a handful of heavy-lift helicopters, and airdropped using a large multi-canopy cargo parachute. As this parachute lowered the vehicle at a bone-crunching 15-20 metres per second (about 65 km/h or 40 mph), the original operation doctrine called for the BMD-1 and its crew to be dropped separately onto the battlefield. In practice, however, the two tended to drift and land far apart, making it difficult for the crew to find and reach their vehicle. The Soviets thus began experimenting with dropping the BMD-1 with the driver and gunner aboard, using a system of retrorockets mounted on a drop pallet to slow the vehicle’s impact speed to a more reasonable 7 metres per second. Other crew members, who dropped separately, were given radio receivers tuned to a beacon on the vehicle, allowing them to easily locate their mount after landing. The system entered service in 1975 and its still in use today – validating the Hajile principle some 30 years after the fact.
Expand for References
Directorate of Miscellaneous Weapons Development (DMWD), Nevington War Museum, https://ift.tt/4LSYGEU
Infantry Tank Mk.III, Valentine, The Online Tank Museum, November 27, 2014, https://tanks-encyclopedia.com/ww2/gb/tank_infantry_mkiii_valentine.php
“Hajile”, https://ift.tt/ZaL3QOB
Here is How Soyuz Returns to Earth, Russian Space Web, https://www.russianspaceweb.com/soyuz-landing.html
Soyuz Landing, NASA, September 15, 2011, https://www.nasa.gov/mission_pages/station/structure/elements/soyuz/landing.html
The post That Time the British Military Tried to Replace Parachutes with Rockets appeared first on Today I Found Out.
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