In military munitions , a fuze (sometimes fuse ) is the part of the device that initiates its function. In some applications, such as torpedoes , a fuze may be identified by function as the exploder . The relative complexity of even the earliest fuze designs can be seen in cutaway diagrams .
82-455: A fuze is a device that detonates a munition 's explosive material under specified conditions. In addition, a fuze will have safety and arming mechanisms that protect users from premature or accidental detonation. For example, an artillery fuze's battery is activated by the high acceleration of cannon launch, and the fuze must be spinning rapidly before it will function. "Complete bore safety" can be achieved with mechanical shutters that isolate
164-587: A microphone , or hydrophone , or mechanically using a resonating vibratory reed connected to diaphragm tone filter. During WW2, the Germans had at least five acoustic fuzes for anti-aircraft use under development, though none saw operational service. The most developmentally advanced of the German acoustic fuze designs was the Rheinmetall-Borsig Kranich (German for Crane ) which
246-449: A sea mine , spring-loaded grenade fuze, pencil detonator or anti-handling device ) as opposed to a simple burning fuse . The situation of usage and the characteristics of the munition it is intended to activate affect the fuze design e.g. its safety and actuation mechanisms. Time fuzes detonate after a set period of time by using one or more combinations of mechanical, electronic, pyrotechnic or even chemical timers . Depending on
328-460: A 52% success against a water target when tested in January, 1942. The United States Navy accepted that failure rate. A simulated battle conditions test was started on 12 August 1942. Gun batteries aboard cruiser USS Cleveland (CL-55) tested proximity-fuzed ammunition against radio-controlled drone aircraft targets over Chesapeake Bay . The tests were to be conducted over two days, but
410-500: A German neon lamp tube and a design of a prototype proximity fuze based on capacitive effects was received by British Intelligence as part of the Oslo Report . In the post-World War II era, a number of new proximity fuze systems were developed, using radio, optical, and other detection methods. A common form used in modern air-to-air weapons uses a laser as an optical source and time-of-flight for ranging. The first reference to
492-552: A certain threshold, various ground-triggered means using radio signals, and capacitive or inductive methods similar to a metal detector . All of these suffered from the large size of pre-WWII electronics and their fragility, as well as the complexity of the required circuitry. British military researchers at the Telecommunications Research Establishment (TRE) Samuel Curran , William Butement , Edward Shire, and Amherst Thomson conceived of
574-553: A development effort at Pye Ltd. to develop thermionic valves (electron tubes) capable of withstanding these much greater forces. Pye's research was transferred to the United States as part of the technology package delivered by the Tizard Mission when the United States entered the war. Pye's group was apparently unable to get their rugged pentodes to function reliably under high pressures until 6 August 1941, which
656-612: A parallel arrangement of sensing fuzes for target destruction and a time fuze for self-destruction if no target is detected. Detonate Too Many Requests If you report this error to the Wikimedia System Administrators, please include the details below. Request from 172.68.168.133 via cp1102 cp1102, Varnish XID 571452867 Upstream caches: cp1102 int Error: 429, Too Many Requests at Thu, 28 Nov 2024 07:47:42 GMT Proximity fuze A proximity fuze (also VT fuze or "variable time fuze")
738-486: A parallel time fuze to detonate and destroy the mine after a pre-determined period to minimize casualties after the anticipated duration of hostilities. Detonation of modern naval mines may require simultaneous detection of a series arrangement of acoustic , magnetic , and/or pressure sensors to complicate mine-sweeping efforts. The multiple safety/arming features in the M734 fuze used for mortars are representative of
820-461: A plane perpendicular to the missile's main axis onto a photocell. When the cell current changed a certain amount in a certain time interval, the detonation was triggered. Some modern air-to-air missiles (e.g., the ASRAAM and AA-12 Adder ) use lasers to trigger detonation. They project narrow beams of laser light perpendicular to the flight of the missile. As the missile cruises towards its target
902-407: A range of set burst heights [e.g. 2, 4 or 10 m (7, 13 or 33 ft)] above ground that are selected by gun crews. The shell bursts at the appropriate height above ground. The idea of a proximity fuse had long been considered militarily useful. Several ideas had been considered, including optical systems that shone a light, sometimes infrared , and triggered when the reflection reached
SECTION 10
#1732780062201984-447: A series time fuze to ensure that they do not initiate (explode) prematurely within a danger distance of the munition launch platform. In general, the munition has to travel a certain distance, wait for a period of time (via a clockwork , electronic or chemical delay mechanism), or have some form of arming pin or plug removed. Only when these processes have occurred will the arming process of the series time fuze be complete. Mines often have
1066-587: A wide range of possible ideas for designing a fuze, including a photoelectric fuze and a radio fuze, with United States during the Tizard Mission in late 1940. To work in shells, a fuze needed to be miniaturized, survive the high acceleration of cannon launch, and be reliable. The National Defense Research Committee assigned the task to the physicist Merle Tuve at the Department of Terrestrial Magnetism. Also eventually pulled in were researchers from
1148-412: Is a fuze that detonates an explosive device automatically when it approaches within a certain distance of its target. Proximity fuzes are designed for elusive military targets such as aircraft and missiles, as well as ships at sea and ground forces. This sophisticated trigger mechanism may increase lethality by 5 to 10 times compared to the common contact fuze or timed fuze. Before the invention of
1230-453: Is about 0.7 meters), the transmitter is in or out of resonance. This causes a small cycling of the radiated power and consequently the oscillator supply current of about 200–800 Hz, the Doppler frequency. This signal is sent through a band-pass filter , amplified, and triggers the detonation when it exceeds a given amplitude. Optical sensing was developed in 1935, and patented in
1312-431: Is set to one of safe , nose , or tail at the crew's choice. Base fuzes are also used by artillery and tanks for shells of the 'squash head' type. Some types of armour piercing shells have also used base fuzes, as have nuclear artillery shells. The most sophisticated fuze mechanisms of all are those fitted to nuclear weapons , and their safety/arming devices are correspondingly complex. In addition to PAL protection,
1394-515: Is the main sensing principle for artillery shells. The device described in World War II patent works as follows: The shell contains a micro- transmitter which uses the shell body as an antenna and emits a continuous wave of roughly 180–220 MHz. As the shell approaches a reflecting object, an interference pattern is created. This pattern changes with shrinking distance: every half wavelength in distance (a half wavelength at this frequency
1476-647: The British Army 's Anti-Aircraft Command , that was engaged in defending Britain against the V-1 flying bomb. As most of the British heavy anti-aircraft guns were deployed in a long, thin coastal strip (leaving inland free for fighter interceptors), dud shells fell into the sea, safely out of reach of capture. Over the course of the German V-1 campaign, the proportion of flying bombs that were destroyed flying through
1558-799: The Doppler effect of reflected radio waves. The use of the Doppler effect developed by this group was later incorporated in all radio proximity fuzes for bomb, rocket, and mortar applications. Later, the Ordnance Development Division of the National Bureau of Standards (which became the Harry Diamond Laboratories – and later merged into the Army Research Laboratory – in honor of its former chief in subsequent years) developed
1640-620: The National Bureau of Standards (this research unit of NBS later became part of the Army Research Laboratory ). Work was split in 1942, with Tuve's group working on proximity fuzes for shells, while the National Bureau of Standards researchers focused on the technically easier task of bombs and rockets. Work on the radio shell fuze was completed by Tuve's group, known as Section T, at The Johns Hopkins University Applied Physics Lab (APL). Over 100 American companies were mobilized to build some 20 million shell fuzes. The proximity fuze
1722-551: The United Kingdom in 1936, by a Swedish inventor, probably Edward W. Brandt, using a petoscope . It was first tested as a part of a detonation device for bombs that were to be dropped over bomber aircraft, part of the UK's Air Ministry's "bombs on bombers" concept. It was considered (and later patented by Brandt) for use with anti-aircraft missiles fired from the ground. It used then a toroidal lens, that concentrated all light from
SECTION 20
#17327800622011804-445: The gunpowder propellant charge escaping past the shell on firing to ignite the wood fuze and hence initiate the timer. In the mid-to-late 19th century adjustable metal time fuzes, the fore-runners of today's time fuzes, containing burning gunpowder as the delay mechanism became common, in conjunction with the introduction of rifled artillery. Rifled guns introduced a tight fit between shell and barrel and hence could no longer rely on
1886-435: The "fuse" and "fuze" spelling. The UK Ministry of Defence states ( emphasis in original): Historically, it was spelled with either 's' or 'z', and both spellings can still be found. In the United States and some military forces, fuze is used to denote a sophisticated ignition device incorporating mechanical and/or electronic components (for example a proximity fuze for an artillery shell , magnetic / acoustic fuze on
1968-502: The British cover name for solid-fueled rockets , and fired at targets supported by balloons. Rockets have relatively low acceleration and no spin creating centrifugal force , so the stresses on the delicate electronic fuze are relatively benign. It was understood that the limited application was not ideal; a proximity fuze would be useful on all types of artillery and especially anti-aircraft artillery, but those had very high accelerations. As early as September 1939, John Cockcroft began
2050-802: The Bureau of Ordnance's Research and Development Division, coined the term to be descriptive without hinting at the technology. The anti-aircraft artillery range at Kirtland Air Force Base in New Mexico was used as one of the test facilities for the proximity fuze, where almost 50,000 test firings were conducted from 1942 to 1945. Testing also occurred at Aberdeen Proving Ground in Maryland, where about 15,000 bombs were dropped. Other locations include Ft. Fisher in North Carolina and Blossom Point, Maryland. US Navy development and early production
2132-613: The German ZUS40 anti-removal bomb fuze. A fuze must be designed to function appropriately considering relative movement of the munition with respect to its target. The target may move past stationary munitions like land mines or naval mines; or the target may be approached by a rocket, torpedo, artillery shell, or air-dropped bomb. Timing of fuze function may be described as optimum if detonation occurs when target damage will be maximized, early if detonation occurs prior to optimum, late if detonation occurs past optimum, or dud if
2214-724: The July 1943 Battle of Gela during the invasion of Sicily. After General Dwight D. Eisenhower demanded he be allowed to use the fuzes, 200,000 shells with VT fuzes (code named "POZIT" ) were used in the Battle of the Bulge in December 1944. They made the Allied heavy artillery far more devastating, as all the shells now exploded just before hitting the ground. German divisions were caught out in open as they had felt safe from timed fire because it
2296-633: The Tizard Mission travelled to the US to introduce their researchers to a number of UK developments, and the topic of proximity fuses was raised. The details of the British experiments were passed to the United States Naval Research Laboratory and National Defense Research Committee (NDRC). Information was also shared with Canada in 1940 and the National Research Council of Canada delegated work on
2378-424: The accelerating artillery shell to remove a safety feature as the projectile accelerates from rest to its in-flight speed. Rotational arming requires that the artillery shell reach a certain rpm before centrifugal forces cause a safety feature to disengage or move an arming mechanism to its armed position. Artillery shells are fired through a rifled barrel , which forces them to spin during flight. In other cases
2460-493: The amplitude of this low frequency 'beat' signal corresponds to the amplitude of the signal reflected from the target. If the amplified beat frequency signal's amplitude was large enough, indicating a nearby object, then it triggered the fourth tube – a gas-filled thyratron . Upon being triggered, the thyratron conducted a large current that set off the electrical detonator. In order to be used with gun projectiles, which experience extremely high acceleration and centrifugal forces,
2542-458: The bomb, mine or projectile has a fuze that prevents accidental initiation e.g. stopping the rotation of a small propeller (unless a lanyard pulls out a pin) so that the striker-pin cannot hit the detonator even if the weapon is dropped on the ground. These types of fuze operate with aircraft weapons, where the weapon may have to be jettisoned over friendly territory to allow a damaged aircraft to continue to fly. The crew can choose to jettison
Fuze - Misplaced Pages Continue
2624-432: The centre during flight, then igniting or exploding whatever the projectile may have been filled with. By the 19th century devices more recognisable as modern artillery "fuzes" were being made of carefully selected wood and trimmed to burn for a predictable time after firing. These were still typically fired from smoothbore muzzle-loaders with a relatively large gap between the shell and barrel, and still relied on flame from
2706-491: The coastal gun belt rose from 17% to 74%, reaching 82% during one day. A minor problem encountered by the British was that the fuze was sensitive enough to detonate the shell if it passed too close to a seabird and a number of seabird "kills" were recorded. The Pentagon refused to allow the Allied field artillery use of the fuzes in 1944, although the United States Navy fired proximity-fuzed anti-aircraft shells in
2788-621: The concept of radar in the UK was made by W. A. S. Butement and P. E. Pollard, who constructed a small breadboard model of a pulsed radar in 1931. They suggested the system would be useful for coast artillery units to accurately measure the range to shipping even at night. The War Office was not interested in the concept, and told the two to work on other issues. In 1936, the Air Ministry took over Bawdsey Manor in Suffolk to further develop their prototype radar systems that emerged
2870-523: The correct order. As an additional safety precaution, most modern nuclear weapons utilize a timed two point detonation system such that ONLY a precisely firing of both detonators in sequence will result in the correct conditions to cause a fission reaction Note: some fuzes, e.g. those used in air-dropped bombs and landmines may contain anti-handling devices specifically designed to kill bomb disposal personnel. The technology to incorporate booby-trap mechanisms in fuzes has existed since at least 1940 e.g.
2952-654: The defense of London. While no one invention won the war, the proximity fuze must be listed among the very small group of developments, such as radar, upon which victory very largely depended. The fuze was later found to be able to detonate artillery shells in air bursts , greatly increasing their anti-personnel effects. In Germany, more than 30 (perhaps as many as 50) different proximity fuze designs were developed, or researched, for anti-aircraft use, but none saw service. These included acoustic fuzes triggered by engine sound, one developed by Rheinmetall-Borsig based on electrostatic fields, and radio fuzes. In mid-November 1939,
3034-407: The detonator from the main charge until the shell is fired. A fuze may contain only the electronic or mechanical elements necessary to signal or actuate the detonator , but some fuzes contain a small amount of primary explosive to initiate the detonation. Fuzes for large explosive charges may include an explosive booster . Some professional publications about explosives and munitions distinguish
3116-521: The device to detonate. Barometric fuzes cause a bomb to detonate at a certain pre-set altitude above sea level by means of a radar , barometric altimeter or an infrared rangefinder . A fuze assembly may include more than one fuze in series or parallel arrangements. The RPG-7 usually has an impact (PIBD) fuze in parallel with a 4.5 second time fuze, so detonation should occur on impact, but otherwise takes place after 4.5 seconds. Military weapons containing explosives have fuzing systems including
3198-478: The finished product were complete, a sample of the fuzes produced from each lot was shipped to the National Bureau of Standards, where they were subjected to a series of rigorous tests at the specially built Control Testing Laboratory. These tests included low- and high-temperature tests, humidity tests, and sudden jolt tests. By 1944, a large proportion of the American electronics industry concentrated on making
3280-445: The first automated production techniques for manufacturing radio proximity fuzes at low cost. While working for a defense contractor in the mid-1940s, Soviet spy Julius Rosenberg stole a working model of an American proximity fuze and delivered it to Soviet intelligence. It was not a fuze for anti-aircraft shells, the most valuable type. In the US, NDRC focused on radio fuzes for use with anti-aircraft artillery, where acceleration
3362-414: The flame from the propellant to initiate the timer. The new metal fuzes typically use the shock of firing ("setback") and/or the projectiles's rotation to "arm" the fuze and initiate the timer : hence introducing a safety factor previously absent. As late as World War I, some countries were still using hand-grenades with simple black match fuses much like those of modern fireworks: the infantryman lit
Fuze - Misplaced Pages Continue
3444-428: The form of an anti-handling device designed specifically to kill or severely injure anyone who tampers with the munition in some way e.g. lifting or tilting it. Regardless of the sensor used, the pre-set triggering distance is calculated such that the explosion will occur sufficiently close to the target that it is either destroyed or severely damaged. Remote detonators use wires or radio waves to remotely command
3526-562: The fuse before throwing the grenade and hoped the fuse burned for the several seconds intended. These were soon superseded in 1915 by the Mills bomb , the first modern hand grenade with a relatively safe and reliable time fuze initiated by pulling out a safety pin and releasing an arming handle on throwing. Modern time fuzes often use an electronic delay system. Impact, percussion or contact fuzes detonate when their forward motion rapidly decreases, typically on physically striking an object such as
3608-408: The fuze and the target was not constant but rather constantly changing due to the high speed of the fuze and any motion of the target. When the distance between the fuze and the target changed rapidly, then the phase relationship also changed rapidly. The signals were in-phase one instant and out-of-phase a few hundred microseconds later. The result was a heterodyne beat frequency which corresponded to
3690-460: The fuze design also needed to utilize many shock-hardening techniques. These included planar electrodes, and packing the components in wax and oil to equalize the stresses. To prevent premature detonation, the inbuilt battery that armed the shell had a several millisecond delay before its electrolytes were activated, giving the projectile time to clear the area of the gun. The designation VT means 'variable time'. Captain S. R. Shumaker, Director of
3772-522: The fuze for anti-aircraft shells was done in the United States, not in England. Tuve said that despite being pleased by the outcome of the Butement et al. vs. Varian patent suit, which affirmed that the fuze was a UK invention and thereby saved the U.S. Navy millions of dollars by waiving royalty fees, the fuze design delivered by the Tizard Mission was "not the one we made to work!". A key improvement
3854-512: The fuze to a team at the University of Toronto . Prior to and following receipt of circuitry designs from the British, various experiments were carried out by Richard B. Roberts, Henry H. Porter, and Robert B. Brode under the direction of NDRC Section T Chairman Merle Tuve. Tuve's group was known as Section T, which was located at APL throughout the war. As Tuve later put it in an interview: "We heard some rumors of circuits they were using in
3936-601: The fuzes. Procurement contracts increased from US$ 60 million in 1942, to $ 200 million in 1943, to $ 300 million in 1944 and were topped by $ 450 million in 1945. As volume increased, efficiency came into play and the cost per fuze fell from $ 732 in 1942 to $ 18 in 1945. This permitted the purchase of over 22 million fuzes for approximately one billion dollars ($ 14.6 billion in 2021 USD ). The main suppliers were Crosley , RCA , Eastman Kodak , McQuay-Norris and Sylvania . There were also over two thousand suppliers and subsuppliers, ranging from powder manufacturers to machine shops. It
4018-433: The fuzing used in nuclear weapons features multiple, highly sophisticated environmental sensors e.g. sensors requiring highly specific acceleration and deceleration profiles before the warhead can be fully armed. The intensity and duration of the acceleration/deceleration must match the environmental conditions which the bomb/missile warhead would actually experience when dropped or fired. Furthermore, these events must occur in
4100-456: The ground; it would not be very effective at scattering shrapnel. A timer fuze can be set to explode a few meters above the ground but the timing is vital and usually requires observers to provide information for adjusting the timing. Observers may not be practical in many situations, the ground may be uneven, and the practice is slow in any event. Proximity fuzes fitted to such weapons as artillery and mortar shells solve this problem by having
4182-515: The gunners to determine, was the same as that of the target and (2) a fuze would emit high-frequency radio waves that would interact with the target and produce, as a consequence of the high relative speed of target and projectile, a Doppler-frequency signal sensed in the oscillator. In May 1940, a formal proposal from Butement, Edward Shire, and Amherst Thomson was sent to the British Air Defence Establishment based on
SECTION 50
#17327800622014264-434: The idea of a proximity fuze in the early stages of World War II . Their system involved a small, short range, Doppler radar . British tests were then carried out with "unrotated projectiles" (the contemporary British term for unguided rockets). However, British scientists were uncertain whether a fuze could be developed for anti-aircraft shells, which had to withstand much higher accelerations than rockets. The British shared
4346-404: The laser energy simply beams out into space. As the missile passes its target some of the energy strikes the target and is reflected to the missile, where detectors sense it and detonate the warhead. Acoustic proximity fuzes are actuated by the acoustic emissions from a target (example an aircraft's engine or ship's propeller). Actuation can be either through an electronic circuit coupled to
4428-422: The late 1930s, Butement turned his attention to other concepts, and among these was the idea of a proximity fuze: ...Into this stepped W. A. S. Butement, designer of radar sets CD/CHL and GL , with a proposal on 30 October 1939 for two kinds of radio fuze: (1) a radar set would track the projectile, and the operator would transmit a signal to a radio receiver in the fuze when the range, the difficult quantity for
4510-442: The latest activation of the individual components. Series combinations are useful for safety arming devices, but increase the percentage of late and dud munitions. Parallel fuze combinations minimize duds by detonating at the earliest activation of individual components, but increase the possibility of premature early function of the munition. Sophisticated military munition fuzes typically contain an arming device in series with
4592-582: The munition fails to detonate. Any given batch of a specific design may be tested to determine the anticipated percentage of early , optimum . late , and dud expected from that fuze installation. Combination fuze design attempts to maximize optimum detonation while recognizing dangers of early fuze function (and potential dangers of late function for subsequent occupation of the target zone by friendly forces or for gravity return of anti-aircraft munitions used in defense of surface positions.) Series fuze combinations minimize early function by detonating at
4674-485: The next year as Chain Home . The Army was suddenly extremely interested in the topic of radar, and sent Butement and Pollard to Bawdsey to form what became known as the "Army Cell". Their first project was a revival of their original work on coast defense, but they were soon told to start a second project to develop a range-only radar to aid anti-aircraft guns . As these projects moved from development into prototype form in
4756-402: The oscillator's plate current, thereby enabling detection. However, the phase relationship between the oscillator's transmitted signal and the signal reflected from the target varied depended on the round trip distance between the fuze and the target. When the reflected signal was in phase, the oscillator amplitude would increase and the oscillator's plate current would also increase. But when
4838-467: The proximity fuze, detonation was induced by direct contact, a timer set at launch, or an altimeter. All of these earlier methods have disadvantages. The probability of a direct hit on a small moving target is low; a shell that just misses the target will not explode. A time- or height-triggered fuze requires good prediction by the gunner and accurate timing by the fuze. If either is wrong, then even accurately aimed shells may explode harmlessly before reaching
4920-424: The reflected signal was out of phase then the combined radio signal amplitude would decrease, which would decrease the plate current. So the changing phase relationship between the oscillator signal and the reflected signal complicated the measurement of the amplitude of that small reflected signal. This problem was resolved by taking advantage of the change in frequency of the reflected signal. The distance between
5002-466: The rockets over in England, then they gave us the circuits, but I had already articulated the thing into the rockets, the bombs and shell." As Tuve understood, the circuitry of the fuze was rudimentary. In his words, "The one outstanding characteristic in this situation is the fact that success of this type of fuze is not dependent on a basic technical idea – all of the ideas are simple and well known everywhere." The critical work of adapting
SECTION 60
#17327800622015084-485: The second of the two concepts. A breadboard circuit was constructed, and the concept was tested in the laboratory by moving a sheet of tin at various distances. Early field testing connected the circuit to a thyratron trigger operating a tower-mounted camera which photographed passing aircraft to determine distance of fuze function. Prototype fuzes were then constructed in June 1940, and installed in "unrotated projectiles",
5166-490: The shell nose ("point detonating") or shell base ("base detonating"). Proximity fuzes cause a missile warhead or other munition (e.g. air-dropped bomb or sea mine ) to detonate when it comes within a certain pre-set distance of the target, or vice versa. Proximity fuzes utilize sensors incorporating one or more combinations of the following: radar , active sonar , passive acoustic, infrared , magnetic , photoelectric , seismic or even television cameras. These may take
5248-414: The sophistication of modern electronic fuzes. Safety/arming mechanisms can be as simple as the spring-loaded safety levers on M67 or RGD-5 grenade fuzes, which will not initiate the explosive train so long as the pin is kept in the grenade, or the safety lever is held down on a pinless grenade. Alternatively, it can be as complex as the electronic timer-countdown on an influence sea mine, which gives
5330-573: The target or after passing it. At the start of the Blitz , it was estimated that it took 20,000 rounds to shoot down a single aircraft; other estimates put the figure as high as 100,000 or as low as 2,500. With a proximity fuze, the shell or missile need only pass close by the target at some time during its flight. The proximity fuze makes the problem simpler than the previous methods. Proximity fuzes are also useful for producing air bursts against ground targets. A contact fuze would explode when it hit
5412-455: The target. The detonation may be instantaneous or deliberately delayed to occur a preset fraction of a second after penetration of the target. An instantaneous "Superquick" fuze will detonate instantly on the slightest physical contact with the target. A fuze with a graze action will also detonate on change of direction caused by a slight glancing blow on a physical obstruction such as the ground. Impact fuzes in artillery usage may be mounted in
5494-414: The technology used, the device may self-destruct (or render itself safe without detonation) some seconds, minutes, hours, days, or even months after being deployed. Early artillery time fuzes were nothing more than a hole filled with gunpowder leading from the surface to the centre of the projectile. The flame from the burning of the gunpowder propellant ignited this "fuze" on firing, and burned through to
5576-785: The testing stopped when drones were destroyed early on the first day. The three drones were destroyed with just four projectiles. A particularly successful application was the 90 mm shell with VT fuze with the SCR-584 automatic tracking radar and the M9 Gun Director fire control computer . The combination of these three inventions was successful in shooting down many V-1 flying bombs aimed at London and Antwerp, otherwise difficult targets for anti-aircraft guns due to their small size and high speed. The Allied fuze used constructive and destructive interference to detect its target. The design had four or five electron tubes. One tube
5658-466: The use of acoustic proximity fuzes for anti-aircraft weapons but concluded that there were more promising technological approaches. The NDRC research highlighted the speed of sound as a major limitation in the design and use of acoustic fuzes, particularly in relation to missiles and high-speed aircraft. Hydroacoustic influence is widely used as a detonation mechanism for naval mines and torpedoes . A ship's propeller rotating in water produces
5740-515: The velocity difference. Viewed another way, the received signal frequency was Doppler-shifted from the oscillator frequency by the relative motion of the fuze and target. Consequently, a low frequency signal, corresponding to the frequency difference between the oscillator and the received signal, developed at the oscillator's plate terminal. Two of the four tubes in the VT fuze were used to detect, filter, and amplify this low frequency signal. Note here that
5822-414: The vessel laying it sufficient time to move out of the blast zone before the magnetic or acoustic sensors are fully activated. In modern artillery shells, most fuzes incorporate several safety features to prevent a fuze arming before it leaves the gun barrel. These safety features may include arming on "setback" or by centrifugal force, and often both operating together. Set-back arming uses the inertia of
5904-416: The weapons safe by dropping the devices with safety pins still attached, or drop them live by removing the safety pins as the weapons leave the aircraft. Aerial bombs and depth charges can be nose and tail fuzed using different detonator/initiator characteristics so that the crew can choose which effect fuze will suit target conditions that may not have been known before the flight. The arming switch
5986-563: Was a mechanical device utilizing a diaphragm tone filter sensitive to frequencies between 140 and 500 Hz connected to a resonating vibratory reed switch used to fire an electrical igniter. The Schmetterling , Enzian , Rheintochter and X4 guided missiles were all designed for use with the Kranich acoustic proximity fuze. During WW2 , the National Defense Research Committee (NDRC) investigated
6068-530: Was able to come up with a new fuze design and managed to demonstrate its feasibility through extensive testing at the Naval Proving Ground at Dahlgren, Virginia. On 6 May 1941, the NBS team built six fuzes which were placed in air-dropped bombs and successfully tested over water. Given their previous work on radio and radiosondes at NBS, Diamond and Hinman developed the proximity fuze which employed
6150-451: Was after the successful tests by the American group. Looking for a short-term solution to the valve problem, in 1940 the British ordered 20,000 miniature electron tubes intended for use in hearing aids from Western Electric Company and Radio Corporation of America . An American team under Admiral Harold G. Bowen, Sr. correctly deduced that they were meant for experiments with proximity fuzes for bombs and rockets. In September 1940,
6232-509: Was among the first mass-production applications of printed circuits . Vannevar Bush , head of the U.S. Office of Scientific Research and Development (OSRD) during the war, credited the proximity fuze with three significant effects. At first the fuzes were only used in situations where they could not be captured by the Germans. They were used in land-based artillery in the South Pacific in 1944. Also in 1944, fuzes were allocated to
6314-437: Was an oscillator connected to an antenna; it functioned as both a transmitter and an autodyne detector (receiver). When the target was far away, little of the oscillator's transmitted energy would be reflected to the fuze. When a target was nearby, it would reflect a significant portion of the oscillator's signal. The amplitude of the reflected signal corresponded to the closeness of the target. This reflected signal would affect
6396-487: Was introduced by Lloyd Berkner , who developed a system using separate transmitter and receiver circuits. In December 1940, Tuve invited Harry Diamond and Wilbur S. Hinman, Jr, of the United States National Bureau of Standards (NBS) to investigate Berkner's improved fuze and develop a proximity fuze for rockets and bombs to use against German Luftwaffe aircraft. In just two days, Diamond
6478-507: Was one of the most important technological innovations of World War II. It was so important that it was a secret guarded to a similar level as the atom bomb project or D-Day invasion. Admiral Lewis Strauss wrote that, One of the most original and effective military developments in World War II was the proximity, or 'VT', fuze. It found use in both the Army and the Navy, and was employed in
6560-646: Was outsourced to the Wurlitzer company, at their barrel organ factory in North Tonawanda, New York . First large scale production of tubes for the new fuzes was at a General Electric plant in Cleveland, Ohio formerly used for manufacture of Christmas-tree lamps. Fuze assembly was completed at General Electric plants in Schenectady, New York and Bridgeport, Connecticut . Once inspections of
6642-586: Was thought that the bad weather would prevent accurate observation. U.S. General George S. Patton credited the introduction of proximity fuzes with saving Liège and stated that their use required a revision of the tactics of land warfare. Bombs and rockets fitted with radio proximity fuzes were in limited service with both the USAAF and USN at the end of WWII. The main targets for these proximity fuze detonated bombs and rockets were anti-aircraft emplacements and airfields . Radio frequency sensing ( radar )
6724-418: Was up to 20,000 g , compared to about 100 g for rockets and much less for dropped bombs. In addition to extreme acceleration, artillery shells were spun by the rifling of the gun barrels to close to 30,000 rpm, creating immense centrifugal force. Working with Western Electric Company and Raytheon Company , miniature hearing-aid tubes were modified to withstand this extreme stress. The T-3 fuze had
#200799