Hajile
Encyclopedia
Hajile was one of a number of highly experimental projects, including the Hedgehog
and Panjandrum
, that were developed by the British
Admiralty
's Directorate of Miscellaneous Weapons Development
(DMWD) during the final years of World War II
. 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 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 high falling speed ruled out parachute
s, so the DMWD came up with the idea of loading the drops onto a platform surrounded with cordite
rocket
s. 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 remarked "Look at it! It's Elijah
in reverse", referring to the biblical prophet's ascension to Heaven in a similar manner.
, 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.
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 feet. Gerald Pawle, a member of the DMWD at the time, recalls (Pawle 1972: 173):
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.
s 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 2000 ft 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. Since the fuses wouldn't light, the whole rig crashed to the ground slowed only by a small pilot parachute, hitting the ground at around 40 ft/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 D-Day
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.
Hedgehog (weapon)
The Hedgehog was an anti-submarine weapon developed by the Royal Navy during World War II, that was deployed on convoy escort warships such as destroyers to supplement the depth charge. The weapon worked by firing a number of small spigot mortar bombs from spiked fittings...
and Panjandrum
Panjandrum
Panjandrum, known also as The Great Panjandrum, was a massive, rocket-propelled, explosive-laden cart designed by the British military during World War II. It was one of a number of highly experimental projects, including Hajile and the Hedgehog, that were developed by the Admiralty's Directorate...
, that were developed by the British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
Admiralty
Admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...
's Directorate of Miscellaneous Weapons Development
Directorate of Miscellaneous Weapons Development
The Directorate of Miscellaneous Weapons Development , known colloquially as the Wheezers and Dodgers, was a department of the Admiralty responsible for the development of various unconventional weapons during World War II...
(DMWD) during the final years of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. The project was initiated by a request from the Army
British Army
The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...
for a method of dropping heavy equipment and vehicles from aircraft at high speed, retaining the materiel
Materiel
Materiel is a term used in English to refer to the equipment and supplies in military and commercial supply chain management....
's terminal velocity
Terminal velocity
In fluid dynamics an object is moving at its terminal velocity if its speed is constant due to the restraining force exerted by the fluid through which it is moving....
for as long as possible in order to minimise drift and damage from anti-aircraft batteries
Anti-aircraft warfare
NATO defines air defence as "all measures designed to nullify or reduce the effectiveness of hostile air action." They include ground and air based weapon systems, associated sensor systems, command and control arrangements and passive measures. It may be to protect naval, ground and air forces...
. 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 high falling speed ruled out parachute
Parachute
A parachute is a device used to slow the motion of an object through an atmosphere by creating drag, or in the case of ram-air parachutes, aerodynamic lift. Parachutes are usually made out of light, strong cloth, originally silk, now most commonly nylon...
s, so the DMWD came up with the idea of loading the drops onto a platform surrounded with cordite
Cordite
Cordite is a family of smokeless propellants developed and produced in the United Kingdom from 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...
rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
s. 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 remarked "Look at it! It's Elijah
Elijah (prophet)
Elijah also Elias ; , meaning "Yahweh is my God";Arabic:إلياس, Ilyās), was a prophet in the Kingdom of Samaria during the reign of Ahab , according to the Books of Kings....
in reverse", referring to the biblical prophet's ascension to Heaven in a similar manner.
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-bobPlumb-bob
A plumb-bob or a plummet is a weight, usually with a pointed tip on the bottom, that is suspended from a string and used as a vertical reference line, or plumb-line....
, 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
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
documentary series
Documentary film
Documentary films constitute a broad category of nonfictional motion pictures intended to document some aspect of reality, primarily for the purposes of instruction or maintaining a historical record...
"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.
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
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
block was strapped to the top of the Hajile platform, and the rig loaded into a Lancaster bomber
Avro Lancaster
The Avro Lancaster is a British four-engined Second World War heavy bomber made initially by Avro for the Royal Air Force . It first saw active service in 1942, and together with the Handley Page Halifax it was one of the main heavy bombers of the RAF, the RCAF, and squadrons from other...
. 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 feet. Gerald Pawle, a member of the DMWD at the time, recalls (Pawle 1972: 173):
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 WrenWomen's Royal Naval ServiceThe Women's Royal Naval Service was the women's branch of the Royal Navy.Members included cooks, clerks, wireless telegraphists, radar plotters, weapons analysts, range assessors, electricians and air mechanics...
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.
Refinement
The DMWD attempted to procure a number of jeepJeep
Jeep is an automobile marque of Chrysler . The first Willys Jeeps were produced in 1941 with the first civilian models in 1945, making it the oldest off-road vehicle and sport utility vehicle brand. It inspired a number of other light utility vehicles, such as the Land Rover which is the second...
s 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 2000 ft strapped to an experimental, and potentially explosive, device. Eventually two jeeps were provided by the United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
and trials began in earnest. The first test was a spectacular failure, as snowfall on the day dampened the rocket fuses. Since the fuses wouldn't light, the whole rig crashed to the ground slowed only by a small pilot parachute, hitting the ground at around 40 ft/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 D-Day
D-Day
D-Day is a term often used in military parlance to denote the day on which a combat attack or operation is to be initiated. "D-Day" often represents a variable, designating the day upon which some significant event will occur or has occurred; see Military designation of days and hours for similar...
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.See also
- RetrorocketRetrorocketA retrorocket is a rocket engine providing thrust opposing the motion of a spacecraft, thereby causing it to decelerate.-History:...
- Soviet air drop technique similar to Hajile