Hydra 70

The Hydra 70 rocket is an American made diameter fin-stabilized unguided rocket used primarily in the air-to-ground role. It can be equipped with a variety of warheads, and in more recent versions, guidance systems for point attacks. The Hydra is widely used by US and allied forces, competing with the Canadian CRV7, with which it is physically interchangeable.

Overview The Hydra 70 is derived from the diameter Mk 4/Mk 40 Folding-Fin Aerial Rocket developed by the United States Navy for use as a free-flight aerial rocket in the late 1940s. The Mk 40 was used during the Korean and Vietnam wars to provide close air support to ground forces from about 20 different firing platforms, both fixed-wing and armed helicopters.

The main change made to produce the Hydra was the Mk. 66 motor which uses a new propellant that offers considerably more thrust, (Mod 2/3) (Mod 4). The fins of the Mk 40 flipped forward from the rear when the rocket left the launching tube, but in the Hydra they are curved to match the outside diameter of the rocket fuselage and flip sideways to open, which is referred to as WAFAR (Wrap-Around Fin Aerial Rocket) instead of FFAR (folding-fin aerial rocket). To improve stability during the time the fins are still opening, the four motor nozzles have a slight cant angle to impart a spin while the rocket is still in the launch tube.

Today, the OH-58D(R) Kiowa Warrior, the Black Hawk, and AH-64E Apache Longbow, as well as the Marine Corps' versatile UH-1 Huey and AH-1 Cobra, carry the Hydra rocket launcher standard on its weapon pylons..

Mk 66 rocket motor variants Designation DescriptionMk 66 Mod 070 mm (2.75 in) WAFAR universal motor; common motor for the GD Hydra 70 series of rockets; original prototype; for US Army. Introduced in 1972..Mk 66 Mod 1Mk 66 variant; production variant; for US ArmyMk 66 Mod 2Mk 66 Mod 1 variant; HERO (Hazards of Electromagnetic Radiation to Ordnance) safe; for US Navy and US Air Force. Began production in 1986.Mk 66 Mod 3Mk 66 Mod 1 variant; HERO safe; Mk 66 Mod 2 for US ArmyMk 66 Mod 4Mk 66 Mod 2/3 variant; incorporates a Salt rod to reduce exhaust gases; for all services. Began production in 1999.Mk 66 Mod 5Mk 66 Mod 4 variant; Incorporates propellant venting during fast cook offMk 66 Mod 6Mk 66 Mod 4/5 variant; designed to reduce the tendency of secondary launch gases to combust in the parent aircraft’s engine, primarily with the AH-64 helicopter

Service

The family of Hydra 70 (70 mm) 2.75 inch rockets perform a variety of functions. The war reserve unitary and cargo warheads are used for anti-materiel, anti-personnel, and suppression missions. The Hydra 70 family of folding-fin aerial rockets also includes smoke screening, illumination, and training warheads. Hydra 70 rockets are known mainly by either their warhead type or by the rocket motor designation, Mk 66 in US military service.

United States In the U.S. Army, Hydra 70 rockets are fired from the AH-64 Apache and AH-64D Apache Longbow helicopter variants using M261 19-tube rocket launchers, and the OH-58D Kiowa Warrior using seven-tube M260 rocket launchers. In the U.S. Marine Corps, either the M260 or M261 launchers are employed on the AH-1W SuperCobra and AH-1Z Viper, depending upon the mission. The M260 and M261 are used with the Mk 66 series of rocket motor, which replaced the Mk 40 series. The Mk 66 has a reduced system weight and provides a remote fuze setting interface. Hydra 70s have also been fired from UH-60 and AH-6 series aircraft in US Army service.

The AH-1G Cobra and the UH-1B "Huey" used a variety of launchers including the M158 seven-tube and M200 19-tube rocket launchers designed for the Mk 40 rocket motor; however, these models have been replaced by upgraded variants in the U.S. Marine Corps because they were not compatible with the Mk 66 rocket motor. The Hydra 70 rocket system is also used by the U.S. Navy and the U.S. Air Force.

Common U.S. Mk 66 compatible launchers

Designation DescriptionM2607-Tube LWL (LightWeight Launcher, 35 lb, 15.9 kg)M26119-Tube LWL (LightWeight Launcher, 80 lb, 36.3 kg)LAU-130/A19-Tube rocket launcherLAU-131/A7-Tube rocket launcherLAU-68D/A7-Tube LAU-68C/A variant; compatible w/ Mk 66 rocket motor; external thermal protection coating; launcher supports single and ripple firingLAU-69D/A19-Tube LAU-61B/A variant; compatible w/ Mk 66 rocket motor; external thermal protection coating; launcher supports single and ripple firing

Accidents In 2019, a 72-year-old Taiwanese man was killed after a discarded Hydra rocket which he had cut into with an electric saw exploded. He had believed it to be a length of pipe. The rocket had been caught in the net of a fishing vessel and then discarded by the crew ashore as scrap metal.

Warheads Hydra 70 warheads fall into three categories: Unitary warheads with impact-detonating fuzes or remote-set multi-option fuzes. Cargo warheads with air burst-range, with settable fuzes using the "wall-in-space" concept or fixed standoff fuzes. Training warheads.

Fuzing options # Designation Description Arming Range, Acceleration or Time1M423Nose Mount, Point Detonating for slow speed platforms (helicopters)2M427Nose Mount, Point Detonating for high speed platforms3XM436Air burst, Motor-Burnout Delay4XM438/M438Nose Mount, Point Detonating5M440Point Detonating6Mk 352 Mod 0/1/2Point Detonating7M429Proximity Air burst8M433Nose Mount, Resistance Capacitance (RC)SuperQuick (PD) Delay in increments including Bunker penetrating option9M439Base Mount, Resistance Capacitance (RC), Payload Discharging Pilot-SelectableDischarges submunitions between ( on AH-1s) 27Gs10M442Air burst, Motor-Burnout DelayDischarges Flare at , 17-22 g required for arming11M446Base Mount, Air burst, Motor-Burnout Delay12Model 113ABase Mount, Air burst, Motor-Burnout Delay

Common warheads The most common warhead for the Hydra 70 rocket is the M151 "10-Pounder," which has a blast radius of 10 meters and lethal fragmentation radius of around 50 meters.New laser-guided rocket capability tested - AF.mil, 3 October 2016 The M247 HEDP warheads have similar penetration to the standard M72 LAW warhead (~300 mm of rolled homogenous armor).CAT-UXO: "70mm M247 Hydra Rocket." Retrieved October 8, 2024.

Designation Description Weight Payload Fuze Type Fuzing optionsM151High explosive (HEDP) '10 pounder' (w/o Fuze) Comp B-4 HEM4231,2,5,7,8M156White phosphorus munitions (WP) WPM423 M4291,2,6,7M229High explosive (HEDP); elongated M151 '17 pounder' (Fuzed) Comp B-4 HEM4231,2,6,7M247High-explosive anti-tank (HEAT)/high-explosive dual purpose (HEDP) Comp B HEM438 PD4 (integral to warhead)M255APERS (anti-personnel) warhead2500 flechettes9M255E1/A1Flechette warhead1179 flechettesM4399M257Parachute illuminationOne M257 Candle (Flare) 1 million candelaM44210 (integral to warhead)M259White phosphorus (WP)9M261Multi-purpose submunition (MPSM)9 M73 (Grenade) SubmunitionsM439 with M84 electric detonator9M264Red phosphorus (RP) Smoke72 RP PelletsM4399M267MPSM PracticeThree Marking SMs, 6 Metal WeightsM439 with M84 electric detonator9M274Practice (Smoke) of potassium perchlorate and aluminum powderM4231M278Infra-red (IR) parachute illuminationOne M278 IR FlareM44210 (integral to warhead)M282Multipurpose penetrator warhead PBXN-110delayedMk 67 Mod 0White phosphorus (WP)1,2,6,7Mk 67 Mod 1Red phosphorus (RP)1,2,6,7WTU-1/BPracticeInertNoneNoneWDU-4/AAPERS warhead96 flechettes of unknown weight12 (integral to warhead)WDU-4A/AAPERS warhead2205 flechettesM405A212 (integral to warhead)

Mk 66 rocket motor technical data Weight: Length: Burn time: 1.07 sec Average thrust (): (Mod 2/3) (Mod 4) Motor burnout range: Motor burnout velocity: Launch spin rate: 10 rps, 35 rps after exiting launcher Velocity at launcher exit: Acceleration: 60–70 g (initial) 95–100 g (final) Effective Range: depending on warhead and launch platform Maximum Range: under optimum conditions

Precision guided Hydra 70 There are several design efforts to turn the Hydra 70 rocket into a precision guided munition (PGM) to produce a weapon with greater accuracy but at less cost than other guided missiles. These include: The BAE Systems Advanced Precision Kill Weapon System (APKWS) II U.S. Navy Low-Cost Guided Imaging Rocket (LOGIR) Lockheed Martin Direct Attack Guided Rocket (DAGR) The ATK/Elbit Guided Advanced Tactical Rocket – Laser (GATR-L) Raytheon TALON Forges de Zeebrugge SAL-Laser Guided Rocket (FZ275 LGR)- IHS Jane, 13 January 2016

The APKWS was the first to be fielded in March 2012,U.S. Marines Field APKWS Guided Rocket in Afghanistan - Ainonline.com, 27 April 2012 and the TALON entered full rate production for the United Arab Emirates Armed Forces in September 2014.Raytheon begins full rate production on TALON Laser Guided Rockets for the UAE - Raytheon new release, 15 September 2014

The Turkish ROKETSAN Cirit is a similar missile compatible with 70 mm rocket launchers, but it was developed from scratch and does not use Hydra 70 components.

Operators

− APKWS

− Used on Bell OH-58D Kiowa helicopters

− APKWS

− APKWS − APKWS − APKWS

− APKWS − APKWS

− APKWS − Used on Mi-24 gunships

Hydra 70

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