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Hajile was an experimental project developed by the
British
British may refer to:
Peoples, culture, and language
* British people, nationals or natives of the United Kingdom, British Overseas Territories, and Crown Dependencies.
** Britishness, the British identity and common culture
* British English, ...
Admiralty
Admiralty most often refers to:
*Admiralty, Hong Kong
*Admiralty (United Kingdom), military department in command of the Royal Navy from 1707 to 1964
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's
Directorate of Miscellaneous Weapons Development
Directorate may refer to:
Contemporary
*Directorates of the Scottish Government
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* Directorate-General for External Security, the French external intelligence a ...
(DMWD) during the final years of
Second World War
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
for slowing the landing of air-dropped supplies with
retrorocket
A retrorocket (short for ''retrograde rocket'') is a rocket engine providing thrust opposing the motion of a vehicle, thereby causing it to decelerate. They have mostly been used in spacecraft, with more limited use in short-runway aircraft land ...
s.
Development
The project was initiated by a request from the
Army
An army (from Old French ''armee'', itself derived from the Latin verb ''armāre'', meaning "to arm", and related to the Latin noun ''arma'', meaning "arms" or "weapons"), ground force or land force is a fighting force that fights primarily on ...
for a method of dropping heavy equipment and vehicles from aircraft at high speed, retaining the
materiel
Materiel (; ) refers to supplies, equipment, and weapons in military supply-chain management, and typically supplies and equipment in a commercial supply chain context.
In a military context, the term ''materiel'' refers either to the specifi ...
's
terminal velocity
Terminal velocity is the maximum velocity (speed) attainable by an object as it falls through a fluid (air is the most common example). It occurs when the sum of the drag force (''Fd'') and the buoyancy is equal to the downward force of gravit ...
for as long as possible in order to minimise drift and damage from
anti-aircraft
Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...
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 high falling speed ruled out
parachute
A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, who ...
s, so the DMWD came up with the idea of loading the drops onto a platform surrounded with
cordite
Cordite is a family of smokeless propellants developed and produced in the United Kingdom since 1889 to replace black powder as a military propellant. Like modern gunpowder, cordite is classified as a low explosive because of its slow burni ...
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
Elijah ( ; he, אֵלִיָּהוּ, ʾĒlīyyāhū, meaning "My God is Yahweh/YHWH"; Greek form: Elias, ''Elías''; syr, ܐܸܠܝܼܵܐ, ''Elyāe''; Arabic: إلياس or إليا, ''Ilyās'' or ''Ilyā''. ) was, according to the Books of ...
in reverse", referring to the biblical prophet's ascension to Heaven in a "chariot of fire".
[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.]
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
A plumb bob, plumb bob level, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical reference line, or plumb-line. It is a precursor to the spirit level and used to establish a vertic ...
, 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 #REDIRECT BBC #REDIRECT BBC
Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board exam. ...
...
documentary series
Television documentaries are televised media productions that screen documentaries.
Television documentaries exist either as a television documentary series or as a television documentary film.
*Television documentary series, sometimes called d ...
"The Secret War" in 1978). The first two tests used insufficient
rocket fuel
Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical ...
, 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
The Avro Lancaster is a British 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 ...
. 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 . Gerald Pawle, a member of the DMWD at the time, recalls (Pawle 1972: 173):
As ajilecame 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
Wrens are a family of brown passerine birds in the predominantly New World family Troglodytidae. The family includes 88 species divided into 19 genera. Only the Eurasian wren occurs in the Old World, where, in Anglophone regions, it is commonly ...
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
jeeps
Jeep is an American automobile marque, now owned by multi-national corporation Stellantis. Jeep has been part of Chrysler since 1987, when Chrysler acquired the Jeep brand, along with remaining assets, from its previous owner American Moto ...
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 strapped to an experimental, and potentially explosive, device. Eventually two jeeps were provided by the
United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
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 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
The Normandy landings were the landing operations and associated airborne operations on Tuesday, 6 June 1944 of the Allied invasion of Normandy in Operation Overlord during World War II. Codenamed Operation Neptune and often referred to as ...
. 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
*
Retrorocket
A retrorocket (short for ''retrograde rocket'') is a rocket engine providing thrust opposing the motion of a vehicle, thereby causing it to decelerate. They have mostly been used in spacecraft, with more limited use in short-runway aircraft land ...
*
Soviet air drop technique similar to Hajile
*
Curiosity descent stage
Notes
References
* Pawle, G. ''The Secret War'', White Lion, 1972.
* Johnson, B. ''The Secret War'', BBC Publications, 1978. {{ISBN, 0-09-920790-7
World War II military equipment of the United Kingdom
Rocketry