Hydra 70 Rocket

Hydra 70 Rocket

Army Rocket and Missile Systems


The Hydra 70 family of WAFAR (Wrap-Around Fin Aerial Rocket), based around the Mk 66 universal motor was developed from previous 2.75" Mk 40 motor based FFARs (Folding Fin Aerial Rocket). The Mk 40 was originally used during the Korean and Vietnam wars, beginning a rich history of providing close air support to ground forces from about 20 different firing platforms, both fixed-wing and armed helicopters, by all US armed forces. Today, the AH-64D Apache Longbow carries the Hydra rocket launcher standard on its weapon pylons. To provide some stability the four rocket nozzles were scarfed at an angle to impart a slight spin to the rocket during flight.

Mk 66 Rocket Motor Variants

Designation Description
Mk 66 Mod 0 70 mm (2.75”) WAFAR universal motor; common motor for the GD Hydra 70 series of rockets; original prototype; for US Army
Mk 66 Mod 1 Mk 66 variant; production variant; for US Army
Mk 66 Mod 2 Mk 66 Mod 1 variant; HERO (Hazards of Electromagnetic Radiation to Ordnance) safe; for US Navy and US Air Force
Mk 66 Mod 3 Mk 66 Mod 1 variant; HERO safe; Mk 66 Mod 2 for US Army
Mk 66 Mod 4 Mk 66 Mod 2/3 variant; for all services
Mk 66 Mod 5 Mk 66 Mod 4 variant; differences unknown
Mk 66 Mod 6 Mk 66 Mod 4/5 variant; designed to reduce the tendency of secondary launch gasses to combust in the parent aircraft’s engine (Primarily with regards to the AH-64 series of helicopters)


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 (FFAR) 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.


In the U.S. Army, Hydra 70 rockets are fired from the AH-64A Apache and AH-64D Apache Longbow helicopters using M261 19-tube rocket launchers, and the OH-58D Kiowa Warrior and the AH-1F "modernized" Cobra using seven-tube M260 rocket launchers. 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.

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. The M158 and M200 were used with the Mk 40 rocket motor. The MK40 rocket motor was replaced by the newer Mk 66 rocket motor. The M158 and M200 rocket launchers are not compatible with the Mk 66 rocket motor. The Hydra 70 rocket system is also used by the US Marine Corps, the US Navy, and the US Air Force.

Eurocopter Tiger

The Hydra is used on the Eurocopter Tiger.

Common US Mk 66 Compatible Launchers

Designation Description
M260 7-Tube LWL (LightWeight Launcher)
M261 19-Tube LWL (LightWeight Launcher)
LAU-130/A 7-Tube rocket launcher
LAU-131/A 19-Tube rocket launcher
LAU-68D/A 7-Tube LAU-68C/A variant; compatible w/ Mk 66 rocket motor; external thermal protection coating; launcher supports single and ripple firing
LAU-61C/A 19-Tube LAU-61B/A variant; compatible w/ Mk 66 rocket motor; external thermal protection coating; launcher supports single and ripple firing


Hydra 70 warheads fall into three categories:

  • Unitary warheads with impact-detonating fuses or remote-set multi-option fuzes.
  • Cargo warheads with airburst-range, with setable fuzes using the "wall-in-space" concept or fixed standoff fuses.
  • Training warheads.

Fuzing Options

# Designation Description
1 M423 Point Detonating
2 M427 Point Detonating
3 XM436 Airburst, Motor-Burnout Delay
4 XM438/M438 Point Detonating
5 M440 Point Detonating
6 Mk 352 Mod 0/1/2 Point Detonating
7 M429 Proximity Airburst
8 M433 Multi-Option Time Delay
9 M439 Multi-Option Time Delay, Pilot-Selectable
10 M442 Airburst, Motor-Burnout Delay
11 M446 Airburst, Motor-Burnout Delay
12 Model 113A Airburst, Motor-Burnout Delay

Common Warheads

Designation Description Fuzing Options
M151 High Explosive (HE) 1,2,5,7,8
M156 White Phosphorus (WP) 1,2,6,7
M229 High Explosive (HE); elogated M151 1,2,6,7
XM245 Submunition warhead w/ 32 XM100 CS canisters; Possibly a modernized XM80/XM99 3
M247 High-Explosive Anti-Tank (HEAT)/High-Explosive Dual Purpose (HEDP) 4 (Integral to Warhead)
M255 APERS warhead w/ 2500 28 grain (1.8 g) flechettes 9
M255E1/A1 APERS warhead w/ 1180 60 grain (3.8 g) flechettes 9
M257 Parachute Illumination 10 (Integral to Warhead)
M259 White Phosphorus (WP) 9
M261 Multi-Purpose Sub-Munition, w/ 9 M73 SMs 9
M264 White Phosphorus (WP); Red Color 9
M278 Infra-Red (IR) Parachute Illumination 10 (Integral to Warhead)
Mk 67 Mod 0 White Phosphorus (WP) 1,2,6,7
Mk 67 Mod 1 White Phosphorus (WP); Red Color 1,2,6,7
WDU-4/A APERS warhead w/ unknown number of flechettes of unknown weight 12 (Integral to Warhead)
WDU-4A/A APERS warhead w/ 2200 30 grain (1.3 g) flechettes 12 (Integral to Warhead)

NOTE: Some of the warheads described were designed for the older Mk 40 rocket motor, but most likely could work with the Mk 66 motor if upgraded or modernized models were not available.

Advanced Precision Kill Weapon System

The Advanced Precision Kill Weapon System (APKWS) is a program currently in development (2004) to provide a laser guided missile which is compatible with the existing Hydra 70 systems in service. Where possible the system will utilise existing Hydra 70 components such as launchers, rocket motor and warheads. The weapon will bridge the gap between the Hydra 70 and AGM-114 Hellfire systems and provide a cost-effective method of engaging lightly-armoured point targets.


All text is available under the terms of the GNU Free Documentation License

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