Hydra 70

Hydra 70
Four dummy Hydra 70 rockets and an inert AGM-114 Hellfire
Type	Rocket
Place of origin	United States
Service history
In service	1948-present
Used by	See Users
Specifications
Mass	13.6 lb (6.2 kg) (Mk 66 Mod 4 rocket motor only)
Length	41.7 in (1,060 mm)
Diameter	2.75 in (70 mm)
Muzzle velocity	2,300 feet per second (700 m/s)
Effective firing range	8,700 yards (8,000 m)
Maximum firing range	11,500 yards (10,500 m)
Maximum speed	2,425 ft/s (739 m/s)
Guidance system	unguided
Launch platform	AH-64 Apache, AH-1Z Viper, AH-1 Cobra, OH-58 Kiowa, Eurocopter Tiger, A-10 Thunderbolt II, UH-60 Black Hawk, P-3 Orion, MH-6 Little Bird, F-16 Fighting Falcon, AV-8B Harrier II

The Hydra 70 rocket is a weapon derived from the 70 mm (2.8 in) 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.

Overview

The Hydra 70 family of WAFAR (Wrap-Around Fin Aerial Rocket), based on the Mk 66 universal motor, was developed from the previous 2.75 inch Mk 40 motor-based folding fin aerial rocket. The propellant grain is longer and of a different formulation than that of the MK40/MK4, however, the stabilizing rod and igniter are essentially the same design. The MK66 motors have a substantially higher thrust, 1,335 pounds-force (5,940 N) (Mod 2/3) 1,415 pounds-force (6,290 N) (Mod 4), and a longer range than the older motors. To provide additional stability the four rocket nozzles are scarfed at an angle to impart a slight spin to the rocket during flight. The Mk 40 was used during the Korean and Vietnam wars, being used to provide close air support to ground forces from about 20 different firing platforms, both fixed-wing and armed helicopters. Today, the OH-58D(R) Kiowa Warrior and AH-64D Apache Longbow, as well as the Marine Corp's AH-1 Cobra, carry the Hydra rocket launcher standard on its weapon pylons.

Mk 66 rocket motor variants

Designation	Description
Mk 66 Mod 0	70 mm (2.75 in) 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; incorporates a Salt rod to reduce exhaust gases; for all services
Mk 66 Mod 5	Mk 66 Mod 4 variant; Incorporates propellant venting during fast cook off
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 the AH-64 helicopter

Service

Hydra 70 rockets on an AH-1 Cobra helicopter

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.

USA

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 using seven-tube M260 rocket launchers. In the U.S. Marine Corps, either the M260 or M261 launchers are employed on the AH-1 Cobra and future 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 H-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

Hydra 70s in an M261 launcher on a Dutch AH-64 Apache. The tips of some of the rockets are white (and the rockets are shorter in length) because they have a different type of fuze/warhead.

Designation	Description
M260	7-Tube LWL (LightWeight Launcher)
M261	19-Tube LWL (LightWeight Launcher)
LAU-130/A	19-Tube rocket launcher
LAU-131/A	7-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

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 setable fuzes using the "wall-in-space" concept or fixed standoff fuzes.
• Training warheads.

Fuzing options

#	Designation	Description	Arming Range, Acceleration or Time
1	M423	Nose Mount, Point Detonating for slow speed platforms (helicopters)	47 to 102 yards (43 to 93 m)
2	M427	Nose Mount, Point Detonating for high speed platforms	197 to 466 yards (180 to 426 m)
3	XM436	Air burst, Motor-Burnout Delay
4	XM438/M438	Nose Mount, Point Detonating
5	M440	Point Detonating
6	Mk 352 Mod 0/1/2	Point Detonating
7	M429	Proximity Air burst
8	M433	Nose Mount, Resistance Capacitance (RC)	SuperQuick (PD) 11 to 49 yards (10 to 45 m) Delay in 5.5 yards (5.0 m) increments including 3.3 yards (3.0 m) Bunker penetrating option
9	M439	Base Mount, Resistance Capacitance (RC), Payload Discharging Pilot-Selectable	Discharges SMs between 547 and 7,874 yards (500 and 7,200 m) (766 to 7,546 yards [700 to 6,900 m] on AH-1s) 27Gs
10	M442	Air burst, Motor-Burnout Delay	Discharges Flare at 3,281 yards (3,000 m), 17-22G required for arming
11	M446	Base Mount, Air burst, Motor-Burnout Delay
12	Model 113A	Base Mount, Air burst, Motor-Burnout Delay

Common warheads

Designation	Description	Weight	Payload	Fuze Type	Fuzing options
M151	High explosive (HEPD) '10 pounder'	8.7 pounds (3.9 kg) (w/o Fuze)	2.3 pounds (1.0 kg) Comp B-4 HE	M423	1,2,5,7,8
M156	White phosphorus (WP)	9.65 pounds (4.38 kg)	2.2 pounds (1.00 kg) WP	M423 M429	1,2,6,7
M229	High explosive (HEPD); elongated M151 '17 pounder'	17.0 pounds (7.7 kg) (Fuzed)	4.8 pounds (2.2 kg) Comp B-4 HE	M423	1,2,6,7
XM245	Submunition warhead possibly a modernized XM80/XM99		32 XM100 CS canisters		3
M247	High-explosive anti-tank (HEAT)/high-explosive dual purpose (HEDP)	8.8 pounds (4.0 kg)	2.0 pounds (0.91 kg) Comp B HE	M438 PD	4 (integral to warhead)
M255	APERS (anti-personnel) warhead		2500 28 grains (1.8 g) flechettes		9
M255E1/A1	Flechette warhead	14.0 pounds (6.4 kg)	1179 60 grains (3.9 g) flechettes	M439	9
M257	Parachute illumination	11.0 pounds (5.0 kg)	One M257 Candle (Flare) 1 million candela	M442	10 (integral to warhead)
M259	White phosphorus (WP)				9
M261	Multi-purpose submunition (MPSM)	13.5 pounds (6.1 kg)	9 M73 (Grenade) Submunitions	M439 with M84 electric detonator	9
M264	Red phosphorus (RP) Smoke	8.6 pounds (3.9 kg)	72 RP Pellets	M439	9
M267	MPSM Practice	13.5 pounds (6.1 kg)	Three Marking SMs, 6 Metal Weights	M439 with M84 electric Detonator	9
M274	Practice (Smoke)	9.3 pounds (4.2 kg)	2 ounces (57 g) of potassium perchlorate and aluminum powder	M423	1
M278	Infra-red (IR) parachute illumination	11.0 pounds (5.0 kg)	One M278 IR Flare	M442	10 (integral to warhead)
Mk 67 Mod 0	White phosphorus (WP)				1,2,6,7
Mk 67 Mod 1	Red phosphorus (RP)				1,2,6,7
WTU-1/B	Practice	9.3 pounds (4.2 kg)	Inert	None	None
WDU-4/A	APERS warhead	9.3 pounds (4.2 kg)	96 flechettes of unknown weight		12 (integral to warhead)
WDU-4A/A	APERS warhead	9.3 pounds (4.2 kg)	2205 20 grains (1.3 g) flechettes		12 (integral to warhead)

NOTE: Though 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. However, this would not be necessary, as vast quantities of upgraded models exist today.^{[citation needed]}

Mk 66 rocket motor technical data

Weight: 13.6 pounds (6.2 kg)

Length: 41.7 inches (1,060 mm)

Burn time: 1.05 - 1.10 sec

Average thrust (77 F): 1,335 lb (Mod 2/3) 1,415 lb (Mod 4)

Motor burnout range: 1,300 feet (400 m)

Motor burnout velocity: 2,425 ft/s (739 m/s)

Launch spin rate: 10 rps, 35 rps after exiting launcher

Velocity at launcher exit: 148 ft/s (45 m/s)

Acceleration: 60-70 g (initial) 95-100 g (final)

Effective Range: 547 to 8,749 yards (500 to 8,000 m) depending on warhead and launch platform

Maximum Range: 11,483 yards (10,500 m) under optimum conditions

Precision guided Hydra 70

The Advanced Precision Kill Weapon System (APKWS) II is a program to provide a laser guidance to the existing Hydra 70 systems in service. It was cancelled by the US Army in February 2007, but was restarted by the US Navy in 2008. Similar programs are the US Navy Low-Cost Guided Imaging Rocket, Lockheed Martin Direct Attack Guided Rocket and the ATK/Elbit Guided Advanced Tactical Rocket – Laser. APKWS has been fired successfully from the AH-64 Apache by BAE Systems in trials at Yuma Proving Grounds in early September, 2013; US Navy trials of the APKWS with the A-10 Thunderbolt II, the AV-8B Harrier and the F-16 Fighting Falcon led to US Central Command's approval of a modified version of APKWS to be fired from fast-moving jet aircraft.

Users

• Australia
• Colombia
• Japan
• Kuwait
• Netherlands
• Philippines, The launchers are mounted on AS-211 "Warrior" trainers with secondary combat capability and 520MG Defender helicopters.
• Singapore
• Thailand
• United Arab Emirates
• United Kingdom
• United States
• {{Flag|South Korea}
• {{flag|Egypt{

See also

• U.S. Army Aviation and Missile Command
• SNEB rocket (68mm)
• CRV-7
• Zuni 5 in (127 mm)

External links

• "Hydra 70". GlobalSecurity. http://www.globalsecurity.org/military/systems/munitions/hydra-70.htm. Retrieved 2005-09-01. 
• "Hydra-70 Rockets: From Cutbacks to the Future of Warfare". Defense Industry Daily. 2006-4. http://www.defenseindustrydaily.com/2006/04/hydra70-rockets-from-cutbacks-to-the-future-of-warfare/index.php. .
• "Air-Launched 2.75-Inch Rockets". Designation Systems. http://www.designation-systems.net/dusrm/app4/275in-rockets.html. .
• "Warheads energetics". General Dynamics. http://www.gdatp.com/Products/Weapon_Systems/Warheads_energetics/Hydra-70.asp. .
• "2012 Army Weapon Systems Handbook". http://www.fas.org/man/dod-101/sys/land/wsh2012/index.html. 
• Hydra-70 Rocket System