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[7.0] Unguided Rockets

v3.0.0 / chapter 7 of 10 / 01 apr 12 / greg goebel / public domain

* During World War II, most of the major combatants developed and used unguided rockets for ground attack, and such munitions remain useful and important to the present day. This chapter provides a survey of unguided rockets.

HVARs, fat bombs, & RAM HVARS


[7.1] UNGUIDED ROCKETS IN WORLD WAR II
[7.2] 70 MILLIMETER ROCKET
[7.3] ZUNI / INTERNATIONAL UNGUIDED ROCKETS
[7.4] FOOTNOTE: RAYTHEON GRIFFIN / THALES LMM / IAI LAHAT

[7.1] UNGUIDED ROCKETS IN WORLD WAR II

* The origins of airborne rockets for ground attack are obscure, but their first major use was in World War II. Most of the major combatants developed unguided rockets for use with attack aircraft, and these weapons had devastating effect on armor and other targets. The simplicity and effectiveness of unguided rockets have kept them in use to the current day.

The Soviets were one of the first combatants to develop airborne rockets, introducing the "RS-82" rocket even before the Nazi invasion in the summer of 1941. The RS-82 had a diameter of 8.2 centimeters (3.23 inches) and was highly effective. Later it the war, the RS-82 was followed by a similar but bigger rocket, the "RS-132" (with, naturally, a diameter of 13.2 centimeters, or 5.2 inches). Both types of rockets were built with either a blast-fragmentation warhead for attacking soft targets or a hollow-charge warhead for attacking armor.

Soviet RS-82 unguided rockets

The earliest unguided rocket system used operationally by the United States in World War II was the "M-8" 11.4 centimeter (4.5 inch) triple-tube "Bazooka" launcher. This weapon consisted of what looked like three pipes bundled together, each containing a stubby rocket about 40 centimeters (16 inches) long, with the bundle attached to an aircraft's stores pylons in place of a bomb.

The M-8 had fins that unfolded in the airstream after launch. It was very inaccurate, but had a reasonable punch. The M-8 was used with US Army Air Force aircraft such as the Republic P-47 Thunderbolt, North American P-51 Mustang, and Lockheed P-38 Lightning.

The British developed their own unguided airborne "rocket projectile (RP)". This was a simple weapon with fixed cruciform tailfins and a tubular body 7.62 centimeters (3 inches) in diameter. The RP was originally developed for barrage anti-aircraft fire in the desperate days of 1940:41, but after the threat of invasion receded, the large stocks available were adapted for use by attack aircraft. The RP could be fitted with an 11 kilogram (25 pound) solid armor-piercing head, or a bulbous 12.5 centimeter (5 inch) high explosive warhead. The high-explosive version was also known as the "60 pounder" (27 kilogram) RP for the warhead weight. These rockets were used to arm the Hawker Hurricane, Hawker Typhoon, Bristol Beaufighter, de Havilland Mosquito, and other aircraft.

The relatively cluttered launch rails used by the RP usually reduced the speed of the carrier aircraft by a good fraction, but the rockets were effective enough to make the reduction in performance worthwhile. The Typhoon so was devastating in attacks on German armor with the 60-pounder that it became known as "Rockoon".

The RP was also supplied to some US aircraft such as the Grumman TBM Avenger, but combat experience demonstrated to the Americans needed something with more punch than the M-8 or the British RP. The US Navy accordingly sponsored the development of an improved aerial rocket at the California Institute of Technology (Caltech), resulting in the 12.7 centimeter (5 inch) "High Velocity Air Rocket (HVAR)", which was introduced in mid-1944. The HVAR was also occasionally known as "Holy Moses" because of its impressive destructive effect -- "Holy Moses!" being a popular exclamation at the time.

HVARs being loaded on F4U Corsair

The HVAR was 1.83 meters (6 feet) long and weighed 63.5 kilograms (140 pounds). It had fixed fins and was carried on streamlined stub pylons under the wings of aircraft such as the Thunderbolt, Mustang, Grumman F6F Hellcat, and Vought F4U Corsair. It had a steel-cased warhead and could penetrate 3.8 centimeters (1.5 inches) of armor and 1.2 meters (4 feet) of reinforced concrete. It was also used in the Korean War with good effect. Some photographs from that time show HVARs fitted with large conical armor-piercing "RAM" warheads. These were apparently improvised when UN forces found out just how hard a target a Soviet-built T-34 tank really was.

After developing the HVAR, the Caltech research group then developed a bigger unguided rocket named "Tiny Tim". The Tiny Tim resembled a scaled-up HVAR, had a diameter of 30 centimeters (a foot), a length of 3.12 meters (10 feet 3 inches), and a weight of 582 kilograms (1,284 pounds) including a 270 kilogram (590 pound) warhead. It was carried on standard bomb racks, igniting after it had fallen free of the aircraft. The Tiny Tim was intended for "bunker busting" and similar tasks. It was deployed on US Navy Hellcat fighters late in the war in the Pacific, and also used with A-1 Skyraiders and other aircraft during the Korean war.

Republic F-84 with HVARs & Tiny Tims

* The Germans were impressed by rocket-firing Allied fighter-bombers and decided to develop their own unguided air-to-ground rockets, with very little result. The first attempt was to use the "Panzerschreck" infantry anti-tank rocket, a scaled-up derivative of the American "Bazooka" rocket, from underwing launch tubes. Trials showed the Panzerschreck didn't have enough range, and so it was followed by the "Panzerblitz I", which took the hollow-charge warhead from the Panzerschreck and fitted it with an improved rocket motor. It was launched from underwing wooden "crate"-style racks.

The Panzerblitz I still wasn't satisfactory, and so the next step was to adapt the "R4M" rocket. The R4M was a fairly potent weapon that was used in some numbers at the end of the war for air-to-air combat. It had a diameter of 5.5 centimeters (2.17 inches), was kept on course with pop-open fins, and was fired from underwing racks. The R4M was modified for ground attack by fitting it with a hollow-charge warhead, creating the "Panzerblitz II".

Finally, there was an experimental fit of the 28-centimeter (11 inch) Werfer-Granate 28/32 barrage rocket for ground attack. The German air-to-surface rockets saw little or no service.

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[7.2] 70 MILLIMETER ROCKET

* The R4M was used as the basis for unguided rockets built by many nations after the war. Instead of mounting individual rockets individually on a stores pylon, unguided rockets were fitted to aircraft in "pods" that could be streamlined and could carry a large quantity of folding-fin rockets. In some cases, pods were built as the forward sections of external tanks.

Since such unguided rockets are very simple and easy to manufacture, they are widely available in many different versions. In 1948, the US introduced a 70 millimeter (2.75 inch) "Folding Fin Air Rocket (FFAR)", also once known as "Mighty Mouse", derived from the German R4M that was fired in clusters by 1950s interceptors such as the Northrop F-89 Scorpion, North American F-86D Sabre, and Lockheed F-94C Starfire to knock out Soviet bomber formations attacking the North American continent.

The FFAR saw little or no action in air-to-air combat, which was fortunate because most pilots who fired them in tests found them much too inaccurate. It was used for ground attack in the Vietnam War with good effect. It was standard armament for attack helicopters like the Bell AH-1 Hueycobra, and was often carried by fixed-wing close-support aircraft such as the A-1 Skyraider, fitted with different versions of cylindrical pods accommodating 7 or 19 rockets. The FFAR was often fitted with a smoke warhead for target marking by forward air controller aircraft.

* The old FFAR survives, and indeed remains in widespread use, in a slightly improved form as the standard "70 millimeter" rocket. 70 millimeter rockets are essentially simple munitions and made by a variety of vendors. Improvements have been added over the decades, such as the ability to "spin up" within the launch pod to ensure greater accuracy, more powerful motors, and most noticeably the replacement of the old folding fins with wraparound fins.

70 millimeter rocket launcher

The most common 70 millimeter rocket is the "Hydra 70" series. US Army gunship helicopters use the 7-tube M260 launcher and the 19-tube M261 launcher. US Navy aircraft use the 7-tube LAU-68D/A and 19-tube LAU-61C/A launchers. The launchers are reusable and have an ablative cooking to slow down "cook off" of the munitions in a fire.

The current Hydra-70 Mark 66 rocket motor is 106 centimeters (3 feet 6 inches) long and weighs 6.16 kilograms (13.6 pounds), when not fitted with a warhead. It burns for about 400 meters (1,300 feet) before burnout, giving the rocket a range of over 10 kilometers (6.2 miles) when launched at altitude. The range of the earlier Mark 40 rocket motor was only 8 kilometers (5 miles).

Hydra-70 rocket family

The Mark 66 has four nozzles that are slightly canted to set the rocket spinning at a rate of about 10 revolutions per second, improving the weapon's stability and accuracy. The Mark 66 has a wraparound, spring loaded tailfin assembly. Warheads are screwed into the front of the motor and include:

* The unguided rocket is a cheap, effective, and still popular weapon. Although not highly accurate, particularly because such a rocket tends to "jink" after launch until the fins deploy and the rocket stabilizes, it is generally fired in salvos and can saturate a dispersed target with shattering effect.

However, it is not well-suited to long range attack because of its inaccuracy. In an era of increasingly low-cost guidance systems, there's been a push to provide guidance schemes for such weapons. The Army and General Dynamics worked on a guided Hydra-70 system, designated the "Advanced Precision Kill Weapon System (APKWS)", nicknamed "Hellfire JR" after the Hellfire laser-guided antitank missile. The idea was to update the Hydra-70 with a laser seeker. The program suffered from "requirements creep" and was canceled after suffering from bad test results.

The Army scaled back their requirements and ran a second competition for the APKWS, with BAE Systems winning the contract. Initial all-up tests were in 2007. The APKWS amounts to a module, the "WGBU-59/B", that is screwed between the warhead and rocket motor of a standards Hydra-70 rocket, with the module providing guidance using four pop-out fins directed by a "distributed aperture semi-active laser seeker (DASALS)". The baseline rocket configuration uses the standard M151 HE warhead.

A sensor, or "eyeball", for the DASALS is mounted on each of the four pop-out wings, instead of the nose -- a nose-mounted sensor wouldn't be practical since APKWS uses ordinary Hydra-70 warheads. There are little control surfaces on the ends of each of the four pop-out wings. Before launch, the wings are sealed inside the seeker module, only popping out after a half-second following launch; this helps prevent damage to the seeker from the launch of another rocket in the launch pod. The seeker, which has a 40-degree field of view, then acquires the target, remaining on lock by balancing the inputs from the four eyeballs. BAE Systems says the APKWS costs about 15% as much as a Hellfire, though the low cost is partly due to the large existing stockpile of Hydra-70 rockets, all of which are easily converted to a guided configuration with the APKWS.

APKWS & WGBU-59/B

The US military is very enthusiastic about APKWS, the effort becoming a multiservice program, with the US Navy taking charge to get the weapon into service -- likely because the Army was so heavily committed in Iraq at the time. The weapon entered low-rate production in 2011 and was fielded in 2012, with initial deployment on US Marine Cobra helicopters in Afghanistan. It has proved very reliable and highly effective.

Although the APKWS is not effective against heavy armor and hardened targets, its low cost and small blast radius would be a particularly handy weapon for the sort of dirty little wars currently in fashion. It can be carried by any platform that can carry the Hydra-70 with little crew training; laser designation can be provided by ground forces or other platforms if the carrier platform doesn't have the capability. Its light weight also makes it an excellent weapon for small unmanned aerial vehicles (UAVs).

* APKWS isn't the only effort to build a guided 70 millimeter rocket. Lockheed Martin lost out on the competition for APKWS II, but went ahead on development of their "Direct Attack Guided Rocket (DAGR)" weapon anyway. DAGR has been successfully test-fired. Unlike APKWS, DAGR features a nose-mounted seeker, derived from the Hellfire anti-armor missile; it is unclear if the nose-mounted configuration limits compatibility with standard 70 millimeter rocket warheads. Lockheed Martin has developed a four-pack launcher that can replace a single Hellfire on a standard Hellfire launch rack, and has also conducted trials for ground launch.

DAGR ground launch

Raytheon and Emirates Advanced Investments (EAI) of the United Arab Emirates (UAE) are working on a laser-guided 70 millimeter rocket under the "Talon Laser Guided Rocket" program. Initial all-up firings of Talon were in 2009. Initial production is expected in 2010, with the weapon to then go into service with the UAE Land Forces for launch off their Boeing AH-64D Longbow helicopter gunships. It is also being evaluated by the Army for an "APKWS 2" program.

Rocket-maker ATK of the US and Elbit of Israel are collaborating on development of a 70 millimeter laser-guided missile under the designation of "Guided Advanced Tactical Rocket -- Laser (GATR-L)". Similarly, South Korea and the US are developing the "Low-Cost Guided Imaging Rocket (LOGIR)", which will use an imaging infrared seeker instead of laser guidance. It is seen as a cheaper solution, not requiring elaborate gear such as a laser target designator system, with "fire and forget" capability. It is not likely to be highly effective against moving targets, however.

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[7.3] ZUNI / INTERNATIONAL UNGUIDED ROCKETS

* The US Navy and Marine Corps -- though not the Army or Air Force -- also use a larger 12.7 centimeter (5 inch) rocket, known as the "Zuni", in ground attacks during the Vietnam War, carried in a four-round pod. The Zuni was developed in the early 1950s to replace the HVAR. Early Zunis used the "Mark 16" motor, while later production used the "Mark 71" motor. The Zuni remains in service, and like the Hydra-70 rocket, can be fitted with high-explosive, anti-armor, flare, smoke, chaff, and practice warheads.

Zuni packs & Bullpup ASM on F-8E Crusader

The Zuni is usually carried in an LAU-10 four-round launcher. Although there is a version of the LAU-10 that has an ablative coating, out of safety concerns the Navy withdrew the Zuni from carrier operations in the late 1980s, though it was retained for ground-based operations. More recently the Navy relaxed the carrier ban to allow the Zunis to be carried by sea-borne special operations helicopters. The Navy still has a big stockpile of Zunis and there is interest in a precision guided variant. Matra BAE Dynamics Alenia (MBDA) test-fired a Zuni with a laser seeker in 2009; BAE Systems also says that it would be straightforward to modify the APKWS seeker to the Zuni. So far there's no commitment to a "smart" Zuni, though it would be a fairly potent weapon, able to take out light armored vehicles.

* In 1966, the US Navy awarded a contract to Martin Marietta to develop an unguided rocket with a top speed of Mach 3 as a replacement for the 70 millimeter and Zuni rockets. The weapon was designated the "XAGR-14A Hypervelocity Aircraft Rocket / Tactical (HART)". As it was intended for anti-aircraft defense suppression, using anti-personnel warheads, it was known more informally as the "Zero Antiaircraft Potential (ZAP)" missile. ZAP weighed about 77 kilograms (170 pounds) and was 2.68 meters (8 feet 10 inches) long. Launch tests were performed in 1969, but for whatever reasons ZAP was canceled shortly afterwards.

* The most popular European unguided rockets are the old 68 millimeter (2.68 inch) SNEB, and the improved Thomson-Brandt Armaments (TBA) 68 millimeter and 100 millimeter rockets. Warhead options for the current TBA rockets include blast-fragmentation, hollow-charge anti-armor, illumination, smoke, chaff, penetrating demolition, and an interesting series of anti-armor warheads containing a number of large penetrating darts. Thales has been testing 68 millimeter rockets with laser and with GPS guidance under the "Systeme de Roquette A Corrections de Trajectoire (SOROCOT)" program, though they are not close to fielding yet.

Bofors of Sweden has also produced a range of unguided rockets, with diameters of 60 millimeters (2.4 inches and used generally for training), 75 millimeters (2.95 inches), 135 millimeters (5.3 inches), and 180 millimeters (7.1 inches). It is unclear if all these rockets are still in production.

The Soviets have been particularly enthusiastic about unguided rockets, and have produced them in a wide range of sizes. The smallest is the 57 millimeter "S-5" folding-fin rocket. It was introduced in the 1950s, has been manufactured in massive numbers, and is still in production. It is fired from eight-tube, 16-tube, or 32-tube launchers.

The 57 millimeter rocket, incidentally, has often been used as a "man-portable" weapon by insurgents in nations that obtained stocks of Soviet hardware such as Iraq, Libya, and Syria. Insurgents homebrew their own launch systems for the rockets, using pipes and other available materials; Iraqi insurgents even made one four-round launcher that an insurgent fighter perched on his head, with pistol grips to fire the rockets and a plexiglass face shield.

The 80 millimeter "S-8" and 122 millimeter "S-13" rockets were developed in the late 1970s. The S-8 is fired from a 20-round launcher, while the S-13, which is designed for runway cratering and attacking "hardened" targets, is fired from a five-round launcher. The Soviets even built a huge 240 millimeter (9.5 inch) unguided rocket, reminiscent of the US Tiny Tim. Sources also mention 160 millimeter and 212 millimeter unguided rockets, but it seems they were not built in large quantities.

A Russian company, Moscow-based "Automation & Mechanical Technology (Ametech)", is now offering laser-guided versions of the S-5, S-8, and S-13 rockets, designated the "S-5Cor", "S-8Cor", and "S-13Cor" respectively. Each features a warhead that separates from the rocket body after burnout and guides itself to the designating target using fins. This scheme was adopted because there was no simple way to retrofit the rocket itself to controlled guidance.

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[7.4] FOOTNOTE: RAYTHEON GRIFFIN / THALES LMM / IAI LAHAT

* For something of a lack of a better place to comment, along with providing guidance systems for the 70 millimeter rocket, arms manufacturers have been developing even smaller ground attack rockets from scratch -- as with the small smart munitions discussed earlier, with carriage by small UAVs in mind.

Raytheon has developed the "Griffin" guided missile -- confused in some sources with the unpowered Small Tactical Munition discussed earlier, possibly because the two programs are closely associated and leverage off the same technologies. The Griffin features GPS-INS midcourse guidance and a laser terminal seeker and is generally tube-launched; it is capable of being carried by aircraft and rotorcraft, though it can also be used by ground forces. It has a length of 1.07 meters (42 inches) and a weight of 14.9 kilograms (33 pounds), including a 5.9 kilogram (13 pound) warhead. The Griffin can be easily programmed using a graphical interface to specify targeting and setting the warhead to airburst, contact detonation, or delayed-action.

There are two variants, the "Griffin A" being an "aft eject" weapon, while the Griffin B is more conventionally forward-launched. The Griffin has a range of about 20 kilometers (12.5 miles) from a launch at altitude, with about a quarter of that range in a ground launch. Along with UAV carriage, the Griffin provides "ground pounders" with their own smart "air support", a battery of Griffins being easily carried by a light vehicle. The designation "AGM-175" has been used in connection with the Griffin, but Raytheon documentation makes no reference to it.

Thales LMM

* Another such weapon is the "Lightweight Multirole Missile (LMM)" made by the Belfast division of the European Thales defense conglomerate. The Belfast division was previously Shorts of the UK, which had built the Blowpipe, Starstreak, and Starburst series of infantry-launched anti-aircraft missiles. The LMM is a clear successor to that family, being compatible with Starstreak / Starburst launch systems.

The LMM uses laser beam riding guidance -- the shooter shines a laser at a target and the missile stays on the beam -- though Thales is working on an alternate semi-active laser seeker. The missile weighs 13 kilograms (28 pounds), has a two-phase (boost / sustain) solid rocket motor, and has four tailfins plus four moving forward control fins to provide high agility. The 3 kilogram (6.6 pound) warhead has a proximity fuze and is built around a hollow charge in a fragmentation case. It won't take out a tank, but it is effective against a wide range of lighter land, sea, and air targets. Maximum range is 8 kilometers (5 miles). Production began in 2011.

LAHAT four-round launcher

* Israel Aerospace Industries (IAI) has developed a lightweight laser seeking missile, the "Laser Homing Attack Missile (LAHAT)", with a length of 12.5 kilograms (27.6 pounds) and a length of 97.5 centimeters (38.4 inches). Maximum range is given as about 6 kilometers (3.7 miles). It features a tandem anti-armor warhead.

The LAHAT was actually designed for launch out of a 105 millimeter or 120 millimeter tank gun, being introduced in the late 1990s, but IAI then designed a four-round canister pack for use with helicopters or antitank vehicles. The weapon would seem amenable to carriage in single-tube or twin-tube launchers on small UAV, though it is unclear if IAI has performed experiments along such lines.

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