Hajile

Last updated April 05, 2019

Hajile was an experimental project developed by the British Admiralty's Directorate of Miscellaneous Weapons Development (DMWD) during the final years of Second World War for slowing the landing of air-dropped supplies with retrorockets.

The United Kingdom, officially the United Kingdom of Great Britain and Northern Ireland but more commonly known as the UK or Britain, is a sovereign country lying off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state, the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world. The Irish Sea lies between Great Britain and Ireland. With an area of 242,500 square kilometres (93,600 sq mi), the United Kingdom is the 78th-largest sovereign state in the world. It is also the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017.

The Admiralty, originally known as the Office of the Admiralty and Marine Affairs, was the government department responsible for the command of the Royal Navy first in the Kingdom of England, later in the Kingdom of Great Britain, and from 1801 to 1964, the United Kingdom and former British Empire. Originally exercised by a single person, the Lord High Admiral (1385–1628), the Admiralty was, from the early 18th century onwards, almost invariably put "in commission" and exercised by the Lords Commissioners of the Admiralty, who sat on the Board of Admiralty.

World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries. The major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China. It included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, and the only use of nuclear weapons in war.

Development

The project was initiated by a request from the Army for a method of dropping heavy equipment and vehicles from aircraft at high speed, retaining the materiel's terminal velocity for as long as possible in order to minimise drift and damage from anti-aircraft gun batteries. It was further required that the materiel suffer only minimal or no damage from landing, and once dropped be ready to deploy within minutes.

The British Army is the principal land warfare force of the United Kingdom, a part of British Armed Forces. As of 2018, the British Army comprises just over 81,500 trained regular (full-time) personnel and just over 27,000 trained reserve (part-time) personnel.

Materiel, refers to supplies, equipment, and weapons in military supply chain management, and typically supplies and equipment only in a commercial supply chain context.

Terminal velocity is the highest velocity attainable by an object as it falls through a fluid. It occurs when the sum of the drag force (F_d) and the buoyancy is equal to the downward force of gravity (F_G) acting on the object. Since the net force on the object is zero, the object has zero acceleration.

The high falling speed ruled out parachutes, so the DMWD came up with the idea of loading the drops onto a platform surrounded with cordite rockets. These would fire at the last instant to decelerate the materiel to a safe landing speed. The initial test produced the project's codename; as the rockets' exhaust engulfed the apparatus in a plume of smoke and fire, an attending officer, Captain G. O. C. "Jock" Davies, remarked "Look at it! It's Elijah in reverse", referring to the biblical prophet's ascension to Heaven in a "chariot of fire".^[1]

A parachute is a device used to slow the motion of an object through an atmosphere by creating drag. Parachutes are usually made out of light, strong fabric, originally silk, now most commonly nylon. They are typically dome-shaped, but vary, with rectangles, inverted domes, and others found. A variety of loads are attached to parachutes, including people, food, equipment, space capsules, and bombs.

Cordite is a family of smokeless propellants developed and produced in the United Kingdom since 1889 to replace gunpowder as a military propellant. Like gunpowder, cordite is classified as a low explosive because of its slow burning rates and consequently low brisance. These produce a subsonic deflagration wave rather than the supersonic detonation wave produced by brisants, or high explosives. The hot gases produced by burning gunpowder or cordite generate sufficient pressure to propel a bullet or shell to its target, but not so quickly as to routinely destroy the barrel of the gun.

Testing

Initial tests

Once testing began, a number of problems became apparent. The most immediate was that of how to get the rockets to fire at exactly the right instant. Too early and the platform would pick up enough speed again to cause damage to the load. Too late and the deceleration would be ineffective. The solution settled upon was a plumb-bob, which would dangle below the platform and activate the rockets when it hit the ground. However, the implementation of this idea was complicated by the fact that the weight of the plumb-bob would have to be carefully calibrated, heavy enough not to be blown back into the underside of the platform by the extreme upward winds during the fall, yet still sensitive enough to react immediately on hitting "fuzzy" terrain such as heather or long grass.

The earliest tests were made by simply dropping a concrete block from a tall crane (surviving film was shown in the BBC documentary series "The Secret War" in 1978). The first two tests used insufficient rocket fuel, resulting in the concrete block embedding itself firmly into the ground. On the third and final test the technicians filled the rockets with too much fuel, and the block launched itself several dozen feet back into the air again before plummeting to the ground.

The British Broadcasting Corporation (BBC) is a British public service broadcaster. Its headquarters are at Broadcasting House in Westminster, London, and it is the world's oldest national broadcasting organisation and the largest broadcaster in the world by number of employees. It employs over 20,950 staff in total, 16,672 of whom are in public sector broadcasting. The total number of staff is 35,402 when part-time, flexible, and fixed-contract staff are included.

Documentary film nonfictional motion picture

A documentary film is a nonfictional motion picture intended to document some aspect of reality, primarily for the purposes of instruction, education, or maintaining a historical record. "Documentary" has been described as a "filmmaking practice, a cinematic tradition, and mode of audience reception" that is continually evolving and is without clear boundaries. Documentary films were originally called 'actuality' films and were only a minute or less in length. Over time documentaries have evolved to be longer in length and to include more categories, such as educational, observational, and even 'docufiction'. Documentaries are also educational and often used in schools to teach various principles. Social media platforms such as YouTube, have allowed documentary films to improve the ways the films are distributed and able to educate and broaden the reach of people who receive the information.

The Secret War was a seven–part television series produced by the BBC in conjunction with the Imperial War Museum (IWM) that documented numerous key secret technical developments during the Second World War. It first aired during 1977 and was presented by William Woollard, drawing on the first-hand recollections of participants from both sides. The principal interviewee was Reginald Victor Jones, whose autobiography informed much of the research before its publication.

A prototype device was constructed for use over water, since the relatively flat and smooth surface of the water would work as an idealised ground-target and with luck the rig wouldn't sustain any damage from the fall. The weight for the plumb-bob was worked out experimentally, and so the first full-scale tests began. A large concrete block was strapped to the top of the Hajile platform, and the rig loaded into a Lancaster bomber. After a number of attempts to drop the device ended with hits too far from shore to capture on film, the bomber's crew were instructed to aim as close to the testing facility as possible from a height of 2,000 ft (610 m). Gerald Pawle, a member of the DMWD at the time, recalls (Pawle 1972: 173):

The Avro Lancaster is a British four-engined Second World War heavy bomber. It was designed and manufactured by Avro as a contemporary of the Handley Page Halifax, both bombers having been developed to the same specification, as well as the Short Stirling, all three aircraft being four-engined heavy bombers adopted by the Royal Air Force (RAF) during the same wartime era.

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 cooks preparing lunch a few feet from the wrecked shelter thought the end of the world had come.

On further testing, the initial four-rocket design proved slightly ineffective. The addition of another four rockets spaced evenly around the platform increased the deceleration enough to bring the block to a complete stop a few feet above the water, and Hajile quietly sank beneath the surface rather than thunderously crashing into the water as it had done while using the four-rocket design.

The DMWD attempted to procure a number of jeeps to load onto Hajile for testing the prototype over land, but it proved difficult to convince the Royal Navy to provide working vehicles to jettison from a plane at 2,000 ft (610 m) strapped to an experimental, and potentially explosive, device. Eventually two jeeps were provided by the United States Navy and trials began in earnest. The first test was a spectacular failure, as snowfall on the day dampened the rocket fuses. The rockets didn't fire and the whole rig crashed to the ground slowed only by a small pilot parachute, hitting the ground at around 40 ft/s (12 m/s) and causing extensive damage to the jeep. Hajile underwent a further two weeks of tinkering before another test was performed. This time the rockets fired successfully and when the smoke cleared, the jeep was relatively intact – but had ended up upside-down, with the platform's rockets pointed skyward.

Further testing showed Hajile to be incredibly unreliable: Rockets on some tests misfired and sent the platform into a spin, while on others the weight of the load was misjudged and the platform shot back up into the air for a distance before crashing back to ground with enough force to tear the fittings apart.

One of the last times the rockets on the rig fired was on the morning of the Normandy landings. Hajile was on the ground surrounded by its crew, when an electrician, unaware the device was live, began to test the wiring – and accidentally connected the firing circuit. All eight rockets immediately fired and the platform shot forty feet into the air before lurching sideways and crashing back to earth, injuring a number of the crew and blinding one for several days.

Aftermath

The testing of Hajile ran on long enough that the device was still not working reliably by the time the war drew to a close, and with no chance to put the project into action, it was shelved. The dissolution of the DMWD following the war led to the shelving becoming permanent. As with many such research projects the details of Hajile were kept secret for many years, and very little interest was aroused once the documents describing the project became public.

Notes

↑ Gerald Pawle (1957), Secret Weapons of World War II (original title, The Secret War), 1967 reprint, New York: Ballantine, Part II, "The Enemy under the Waters", Ch. 15, "The Mantle of Elijah", pp. 202-203.

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References

Pawle, G. The Secret War, White Lion, 1972. ISBN 0-85617-120-4
Johnson, B. The Secret War, BBC Publications, 1978. ISBN 0-09-920790-7

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[1] Gerald Pawle (1957), Secret Weapons of World War II (original title, The Secret War), 1967 reprint, New York: Ballantine, Part II, "The Enemy under the Waters", Ch. 15, "The Mantle of Elijah", pp. 202-203.