Chaff (countermeasure)

Chaff, originally called Window[1] by the British and Düppel by the Second World War era German Luftwaffe (from the Berlin suburb where it was first developed), is a radar countermeasure in which aircraft or other targets spread a cloud of small, thin pieces of aluminium, metallized glass fibre or plastic, which either appears as a cluster of primary targets on radar screens or swamps the screen with multiple returns.

Modern armed forces use chaff (in naval applications, for instance, using short-range SRBOC rockets) to distract radar-guided missiles from their targets. Most military aircraft and warships have chaff dispensing systems for self-defense. An intercontinental ballistic missile may release in its midcourse phase several independent warheads as well as penetration aids such as decoy balloons and chaff.

Usnchaff
Modern US Navy RR-144 (top) and RR-129 (bottom) chaff countermeasures and containers. Note how the strips of the RR-129 chaff (bottom) are of different widths, while those of the RR-144 (top) are all the same width. The RR-144 is designed to prevent interference with civil ATC radar systems.

Second World War

Window - Lancaster Dropping Window
A Lancaster dropping chaff (the crescent-shaped white cloud on the left of the picture) over Essen during a thousand-bomber raid.

The idea of using chaff developed independently in the United Kingdom, Germany, the United States and Japan. In 1937, British researcher Gerald Touch, while working with Robert Watson-Watt on radar, suggested that lengths of wire suspended from balloons or parachutes might overwhelm a radar system with false echoes[2] and R. V. Jones had suggested that pieces of metal foil falling through the air might do the same.[3] In early 1942, a Telecommunications Research Establishment (TRE) researcher named Joan Curran investigated the idea and came up with a scheme for dumping packets of aluminium strips from aircraft to generate a cloud of false echoes.[4] An early idea was to use sheets the size of a notebook page; these would be printed so they would also serve as propaganda leaflets.[5] It was found that the most effective version was strips of black paper backed with aluminium foil, exactly 27 cm × 2 cm (10.63 in × 0.79 in) and packed into bundles each weighing 1 pound (0.45 kg). The head of the TRE, A. P. Rowe, code-named the device "Window". In Germany, similar research had led to the development of Düppel. The German code name came from the estate where the first German tests with chaff took place, circa 1942.[6] Once the British had passed the idea to the US via the Tizard Mission, Fred Whipple developed a system (according to Harvard Gazette Archives) for dispensing strips for the USAAF, but it is not known if this was ever used.

The systems used the same concept of small aluminium strips (or wires) cut to a half of the target radar's wavelength. When hit by the radar, such lengths of metal resonate and re-radiate the signal.[5] Opposing defences would find it almost impossible to distinguish the aircraft from the echoes caused by the chaff. Other radar-confusing techniques included Mandrel, Piperack and Jostle.[7] Ignorance about the extent of knowledge of the principle in the opposing air force led planners to judge that it was too dangerous to use, since the opponent could duplicate it. The British government's leading scientific adviser, Professor Lindemann, pointed out that if the Royal Air Force (RAF) used it against the Germans, the Luftwaffe would quickly copy it and could launch a new Blitz. This caused concern in RAF Fighter Command and Anti-Aircraft Command, who managed to suppress the use of Window until July 1943.[8] It was felt that the new generation of centimetric radars available to Fighter Command would cope with Luftwaffe retaliation.

RAF "Window" radar countermeasures
Two forms of RAF "Window" radar countermeasure: chopped aluminium wire and paper backed with aluminium foil.

Examination of the Würzburg radar equipment brought back to the UK during Operation Biting (February 1942) and subsequent reconnaissance revealed to the British that all German radars were operating in no more than three frequency ranges, making them prone to jamming. "Bomber" Harris, Commander-in-Chief (C-in-C) of RAF Bomber Command, finally got approval to use Window as part of Operation Gomorrah, the fire raids against Hamburg. The first aircrew trained to use Window were in 76 Squadron. Twenty-four crews were briefed on how to drop the bundles of aluminised-paper strips (treated-paper was used to minimise the weight and to maximise the time that the strips would remain in the air, prolonging the effect), one every minute through the flare chute, using a stopwatch to time them. The results proved spectacular. The radar-guided master searchlights wandered aimlessly across the sky. The anti-aircraft guns fired randomly or not at all and the night fighters, their radar displays swamped with false echoes, utterly failed to find the bomber stream. Over a week of attacks, Allied attacks devastated a vast area of Hamburg, resulting in more than 40,000 civilian deaths, with the loss of only 12 out of the 791 bombers on the first night. Squadrons quickly had special chutes fitted to their bombers to make chaff deployment even easier. Seeing this as a development that made it safer to go on operations, many crews got in as many trips as they could before the Germans found a counter-countermeasure.

Giant Wurzburg Display - Window Effect
The effect of chaff on the display of a Würzburg Riese radar. The effect of jamming appears in the left "jagged" half of the circular ring, contrasting with the normal "smooth" (unjammed) display on the right half of the circle, with a real target at the 3 o'clock position – on the jammed left side the real target "blip" would have been indistinguishable from the jamming.

Although the metal strips puzzled the German civilians at first, German scientists knew exactly what they were - Düppel - but had refrained from using it for the same reasons as Lindemann had pointed out to the British. For over a year the curious situation arose where both sides of the conflict knew how to use chaff to jam the other side's radar but had refrained from doing for fear of their opponent replying in kind. Window rendered the ground-controlled Himmelbett (canopy bed) fighters of the Kammhuber Line unable to track their targets in the night sky and the early UHF-band versions of the airborne intercept Lichtenstein radar (following the capture of a Ju 88R-1 night fighter by the British in May 1943) useless, blinding radar-guided guns and spotlights dependent on the ground-based radar. Oberst Hajo Herrmann developed Wilde Sau (Wild Boar) to cope with the lack of accurate ground guidance and led to the formation of three new fighter wings to use the tactic, numbered JG 300, JG 301 and JG 302. Ground operators would radio-direct single-seat fighters and night fighters to areas where the concentrations of chaff were greatest (which would indicate the source of the chaff) for the fighter pilots to see targets, often against the illumination from fires and searchlights below. A few of the single-seat fighters had the FuG 350 Naxos device to detect H2S (which was the first airborne, ground scanning radar system) emissions from the bombers.

Six weeks after the Hamburg raid, the Luftwaffe used Düppel in 80 cm × 1.9 cm (31.50 in × 0.75 in) lengths during a raid on the night of 7/8 October 1943.[9] In raids in 1943 and the 'mini-blitz' of Operation Steinbock between February and May 1944, Düppel allowed German bombers again to attempt operations over London. Although theoretically effective, the small number of bombers, notably in relation to the large RAF night-fighter force, doomed the effort from the start. The British fighters were able to go aloft in large numbers and often found the German bombers in spite of Düppel. The Germans obtained better results during the air raid on Bari in Italy, on 2 December 1943, when Allied radars were deceived by the use of Düppel.[10]

Letter from Secretary of the Navy, James Forrestal, to Merwyn Bly
Letter from Secretary of the Navy, James Forrestal to Merwyn Bly

Chaff in the United States was co-invented by astronomer Fred Whipple and Navy engineer Merwyn Bly. Whipple proposed the idea to the Air Force he was working with at the time.[11] Early tests failed as the foil strips stuck together and fell as clumps to little or no effect. Bly solved this by designing a cartridge that forced the strips to rub against it as they were expelled, gaining an electrostatic charge. Since the strips all had a similar charge they repelled each other, enabling the full countermeasure effect. After the war, Bly received the Navy Distinguished Civilian Service Award for his work.

In the Pacific Theater, Navy Lieutenant Commander Sudo Hajime invented a Japanese version called Giman-shi, or "deceiving paper." It was first used with some success in mid 1943, during night battles over the Solomon Islands.[12] Competing demands for the scarce aluminum necessary for its manufacture limited its use.[13] On February 21, 1945, during the Battle of Iwo Jima, Giman-shi was successfully used prior to a Kamikaze attack on the USS Saratoga.[14]

Falklands War

British warships in the Falklands War (1982) made heavy use of chaff.

During this war, British Sea Harrier aircraft lacked their conventional chaff-dispensing mechanism.[15] Therefore, Royal Navy engineers designed an impromptu delivery system of welding rods, split pins and string, which allowed six packets of chaff to be stored in the airbrake well and be deployed in flight. It was often referred to as the "Heath Robinson chaff modification", due to its complexity.[16]

See also

Notes

  1. ^ Churchill, Winston Spencer (1951). The Second World War: Closing the Ring. Houghton Mifflin Company, Boston. p. 643.
  2. ^ Jones. p. 39
  3. ^ Jones. p. 290
  4. ^ Goebel. section 8.3 The British Begin Countermeasures
  5. ^ a b Jones, p. 291
  6. ^ Jones, p. 299
  7. ^ Mandrel was an airborne jammer targeted at the German Freya radars. Jones. p.295
  8. ^ Jones, pp. 291–299
  9. ^ The Blitz-Then and Now (Volume 3) page 309.
  10. ^ Saunders, D. M., Capt. USN (1967). The Bari Incident. no isbn. Annapolis, MD: United States Naval Institute. United States Naval Institute Proceedings.
  11. ^ Gewertz, Ken (18 October 2001). "Fred Whipple: Stargazer". Harvard Gazette: The Big Picture. President and Fellows of Harvard College. Retrieved 4 February 2014.
  12. ^ Kennedy, David M. (2007). The Library of Congress World War II Companion. Simon and Schuster. p. 395. ISBN 9781416553069. Retrieved 19 June 2018.
  13. ^ Tillman, Barrett (2006). Clash of the carriers : the true story of the Marianas Turkey Shoot of World War II. Penguin. ISBN 9781440623998. Retrieved 19 June 2018.
  14. ^ Stem, Robert (2010). Fire From the Sky: Surviving the Kamikaze Threat. Pen and Sword. p. 164. ISBN 9781473814219.
  15. ^ Sharkey Ward (2000). Sea Harrier Over the Falklands (Cassell Military Paperbacks). Sterling*+ Publishing Company. p. 245. ISBN 0-304-35542-9.
  16. ^ Morgan, David L. (2006). Hostile Skies: My Falklands Air War. London: Orion Publishing. pp. 59, 73 and photo section. ISBN 0-297-84645-0.

References

External links

AN/ALE-47

The AN/ALE-47 Airborne Countermeasures Dispenser System is used to protect military aircraft from incoming radar and infrared homing missiles. It works by dispensing flares or chaff. It is used on a variety of U.S. Air Force, Navy, and Army aircraft, as well as in other militaries.

Chaff (disambiguation)

Chaff is dry inedible plant material.

Chaff may also refer to:

Chaff (countermeasure), a radar countermeasure for aircraft or other targets

Chaff algorithm, an algorithm for solving instances of the boolean satisfiability problem

Chaffing and winnowing, a method in cryptography to protect a message without encryption

Chaff (newspaper), a former students' newspaper of Massey University Students' Association

Confetti

Confetti are small pieces or streamers of paper, mylar, or metallic material which are usually thrown at celebrations, especially parades and weddings. The origins are from the Latin confectum, with confetti the plural of Italian confetto, small sweet. Modern paper confetti trace back to symbolic rituals of tossing grains and sweets during special occasions, traditional for numerous cultures throughout history as an ancient custom dating back to pagan times, but adapted from sweets and grains to paper through the centuries.

Confetti are made in a variety of colors, and commercially available confetti come in many different shapes. A distinction is made between confetti and glitter; glitter is smaller than confetti (pieces usually no larger than 1mm) and is universally shiny. Most table confetti are also shiny. While they are called metallic confetti they are actually metallized PVC. The most popular shape is the star. Seasonally, Snowflake Confetti are the most requested shape. Most party supply stores carry paper and metallic confetti. Confetti are commonly used at social gatherings such as parties, weddings, and Bar Mitzvahs, but are often considered taboo at funerals, due to the somber atmosphere. The simplest confetti are simply shredded paper (see ticker-tape parade), and can be made with scissors or a paper shredder. Other confetti often consist of chads punched out of scrap paper. A hole punch can be used to make small round chads. For more elaborate chads, a ticket punch can be used. Most pieces of paper flats will flutter as tumblewings giving flight times because of gliding aerodynamics.

In recent years the use of confetti as a cosmetic addition to trophy presentations at sporting events has become increasingly common. In this case, larger strips of paper (typically measuring 20 mm × 60 mm) in the colors appropriate to the team or celebration are used. For smaller volumes of confetti, ABS or PVC "barrels" are filled and the confetti is projected via a "cannon" (a small pressure vessel) using compressed air or carbon dioxide. For larger venues or volumes of confetti, a venturi air mover powered by carbon dioxide is used to propel significantly larger volumes of confetti greater distances.

De Havilland Mosquito operational history

The de Havilland Mosquito was a British light bomber that served in many roles during and after the Second World War. Mosquito-equipped squadrons performed medium bomber, reconnaissance, tactical strike, anti-submarine warfare and shipping attack and night fighter duties, both defensive and offensive. Mosquitos were widely used by the RAF Pathfinder Force, which marked targets for night-time strategic bombing. Despite an initially high loss rate due to low-level daylight attack operations, the Mosquito ended the war with the lowest losses of any of the aircraft types in RAF Bomber Command service.

Kamov Ka-50

The Kamov Ka-50 "Black Shark" (Russian: Чёрная акула, translit. Chornaya Akula, 'kitefin shark', NATO reporting name: Hokum A) is a single-seat Russian attack helicopter with the distinctive coaxial rotor system of the Kamov design bureau. It was designed in the 1980s and adopted for service in the Russian army in 1995. It is manufactured by the Progress company in Arsenyev. It is used as a heavily armed scout helicopter. It is the world's first operational helicopter with a rescue ejection system.During the late 1990s, Kamov and Israel Aerospace Industries developed a tandem-seat cockpit version, the Kamov Ka-50-2 "Erdogan" (Russian: Эрдоган, Turkish: Erdoğan), to compete in Turkey's attack helicopter competition. Kamov also designed another two-seat variant, the Kamov Ka-52 "Alligator" (Russian: Аллигатор, NATO reporting name: Hokum B).

Laus (radar)

Laus (English: louse) was the name for a series of German ECCM equipment during World War II. They were additions to German radar equipment in order to counteract the Allied use of 'Window' (German: Düppel), a chaff radar countermeasure.

SS Atlantic Conveyor

Atlantic Conveyor was a British merchant navy ship, registered in Liverpool, that was requisitioned during the Falklands War.

She was hit on 25 May 1982 by two Argentine air-launched AM39 Exocet missiles, killing 12 sailors. Atlantic Conveyor sank whilst under tow on 28 May 1982.

The wrecksite is designated under the Protection of Military Remains Act 1986.

Sikorsky HH-60 Pave Hawk

The Sikorsky MH-60G/HH-60G Pave Hawk is a twin-turboshaft engine helicopter in service with the United States Air Force. It is a derivative of the UH-60 Black Hawk and incorporates the US Air Force PAVE electronic systems program. The HH-60/MH-60 is a member of the Sikorsky S-70 family.

The MH-60G Pave Hawk's primary mission is insertion and recovery of special operations personnel, while the HH-60G Pave Hawk's core mission is recovery of personnel under hostile conditions, including combat search and rescue. Both versions conduct day or night operations into hostile environments. Because of its versatility, the HH-60G may also perform peacetime operations such as civil search and rescue, emergency aeromedical evacuation (MEDEVAC), disaster relief, international aid and counter-drug activities.

Tinsel

Tinsel is a type of decorative material that mimics the effect of ice, consisting of thin strips of sparkling material attached to a thread. When in long narrow strips not attached to thread, it is called "lametta", and emulates icicles. It was originally a metallic garland for Christmas decoration. The modern production of tinsel typically involves plastic, and is used particularly to decorate Christmas trees. It may be hung from ceilings or wrapped around statues, lampposts, and so on. Modern tinsel was invented in Nuremberg, Germany, in 1610, and was originally made of shredded silver.

According to the Concise Oxford Dictionary, the word is from the Old French word estincele, meaning “sparkle”.

RAF strategic bombing during the Second World War
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