The General Dynamics Mauler was a self-propelled anti-aircraft missile system designed to a late 1950s US Army requirement for a system to combat low-flying high-performance tactical fighters and short-range ballistic missiles.
The system was a XM546 vehicle, based on the M113 chassis, carrying nine MIM-46 missiles in launch canisters, a tracking and illumination continuous wave radar, and the fire control system.
An ambitious design for its era, the Mauler ran into intractable problems during development, and was eventually canceled in November 1965. Cancellation of Mauler left the US Army with no modern anti-aircraft weapon, and they rushed development of the much simpler MIM-72 Chaparral and M163 Tracked Vulcan to fill this niche. These weapons were much less capable than Mauler, and were intended solely as a stop-gap solution until more capable vehicles were developed. In spite of this, no real replacement entered service until the late 1990s.
Both the US Navy and British Army were also expecting Mauler to fulfil their own short-range needs and its cancellation left them with the same problem. They developed RIM-7 Sea Sparrow and Rapier missile, respectively, to fill these needs.
Background
Duster and Vigilante After WWII, the US Army's first mobile anti-aircraft weapons were based on the Bofors 40 mm guns with first the M19 Multiple Gun Motor Carriage then the M42 Duster. First entering production in 1952, the Duster quickly became outdated as aircraft performance increased. Since manual acquisition, tracking and ranging left much to be desired RADUSTER envisioned adding radar ranging to the Duster. By 1955 it was realized that no simple modification to the M42 Duster would meet the need. Thus in 1956 the plan was to improve the T50 antiaircraft fire control system to the RADUSTER. One development RADUSTER and three user test weapons were created before termination.
Driven by the need to counter jet aircraft flying at up to and a slant range of , the new system of a 37 mm Gatling gun on top of a modified M113 Armored Personnel Carrier chassis was approved as the T249 Vigilante in late 1956. A T248 towed version was also developed. Compared to the M42, the high (3,000 rounds per minute) firing rate of the Vigilante gave it much better performance against high-speed aircraft.
As the Vigilante program continued, the Army decided that any gun-based system was hopeless as speeds increased and engagement times dropped. The Vigilante had a maximum effective range of about , and its shells took about 5 seconds to cross this distance. A jet aircraft flying at would cover over a kilometer during those 5 seconds. By the time a radar-assisted sighting system could develop a firing solution, the target would be out of range. The Army decided to cancel Vigilante and keep the Duster in service until a much more capable phase III all-missile system arrived to replace it.
Phase III Phase III was intended to produce an ultimate answer to air defense of front line Army troops. A small mobile missile system was envisioned to engage both aircraft and missiles up to 10,000 feet. It was very clear by May 1956 that this was beyond the state of the art. The Army decided to pursue the "best weapon system that could be developed to meet requirements of the forward area on a liberal time scale" to be available in the 1965 period.
FAAD Under the "Forward Area Air Defense" project, the Army began collecting theoretical data on the requirements for a missile-based system in 1959.
Guidance was a major area of concern. Most anti-aircraft missiles of the era used semi-active radar homing, with an "illumination radar" on the ground that reflected signals off the target that were picked up by a small receiver in the missile's nose. This system had the advantage that the radar signal continued to grow in strength as the missile approached the target, making it increasingly easy to track. More importantly, the reflected signal was a cone shape centered on the target, so guidance became increasingly accurate as the missile approached.
On the downside, the SARH concept also meant that any other reflections could confuse the missile's seeker. Since SARH relied on making the seeker in the missile as simple as possible in order to fit into the missile body, it was common for seekers of the era to be easily confused by reflections from trees, buildings or the ground. It was difficult for the missile to distinguish the target in a cluttered environment.
For FAAD, they decided to use a beam riding guidance system. This had been used in early missiles like the RIM-2 Terrier, but had been abandoned in favor of semi-active systems for all of the reasons above. In particular, in the case of beam-riding the signal is shaped like a cone centered on the broadcaster, which means it becomes increasingly inaccurate as the missile flies towards the target. Some sort of secondary terminal guidance system was almost always needed with beam-riding weapons.
In spite of these disadvantages, beam-riding offered FAAD the ability to guide the missiles in close proximity to the ground. Since the guidance signal is received at the rear of the missile body, the signal would remain clear as long as there were no obstructions between the missile and launcher. It was only the launch platform that had to have the ability to distinguish targets from ground clutter, not the missile. FAAD used a continuous wave radar, which uses the Doppler shift of the moving targets to locate them against any sort of background. For terminal guidance, FAAD used an advanced infrared homing system.
Given the quick engagement times, on the order of seconds, the Army decided that FAAD had to have semi-automatic actions. In combat, the operators would select targets on a long-range search radar and then simply say "go" to attack them. The system's fire control computer would slew the weapons and fire automatically as soon as they came in range.
After running Monte Carlo simulations on an IBM 650, they decided to use a blast-fragmentation warhead, deciding that the continuous-rod warhead would be less effective.Margolin, M, J, et al. "Warheads for Mauler Weapon System", US Army, Pictinny Arsenal, report PATM-137B46-(A57)-Vol-2, 1 November 1958
For mobility, the system would be based on the M113, the Army's latest APC and one of the more advanced vehicles in the inventory. The modifications needed to support a missile system were relatively simple, and the crew area inside the chassis offered room for the needed equipment. The resulting vehicle was known as the XM-546.
Development
Several companies responded to the FAAD contract tender, which General Dynamics (Convair Pomona Division) won in 1959.Andreas Parsch, "General Dynamics MIM-46 Mauler", Directory of U.S. Military Rockets and Missiles, 2002 In 1960 the project was given the official name "Mauler". The Mauler development program which was to begin in May 1959 did not get underway until March 1960.
The Army was not the only potential user of the Mauler system; both the British Army and US Navy planned on using Mauler for their own needs. The British Army's intended role was essentially identical to the US's, but the Navy was looking for a solution to the problem of air attack against their capital ships both by high-speed aircraft as well as early (non-skimming) anti-shipping missiles. Starting in 1960 they had developed a program for a "Basic Point Defense Missile System", and intended to use a modified version of the Mauler, the "RIM-46A Sea Mauler", to fill this role. Mauler's beam riding system made it preferable to other missile systems because it would have fewer problems with clutter from the sea. Additionally, its fast-acting semi-automatic fire control was highly desired for a weapon that was expected to counter targets with engagement times under a minute. Expecting its arrival, the Navy's latest destroyer escorts, the , were built with space reserved for the Sea Mauler launchers when they arrived.Norman Friedman, "U.S. Destroyers: An illustrated design history", Naval Institute Press, 2004, pg. 360
Development was complicated by the diversity of platforms the Mauler system was to be installed upon. A compatible identification friend or foe system (IFF) was a particular problem. Development of the missile airframe and engine progressed rapidly. Unguided examples, known as "Launch Test Vehicles", started firing tests in September 1961. These were quickly followed by the "Control Test Vehicle" guided examples in 1961, which flew simple paths to test the aerodynamic controls. Both test series demonstrated a variety of problems, including failures of the rocket casings, and excessive drag and wing flutter. A competing system with the British and potentially other NATO states was the PT.428 which eventually developed successfully into the Rapier missile.
The first "Guidance Test Vehicle", essentially the service prototypes, started firing in June 1963. These also demonstrated an array of problems, most worrying was the continued tendency to lose guidance instructions immediately after launch. Additionally, when mounted in the 3 by 3 box launcher, the missiles would break their containers and damage the missiles in adjacent containers. Eventually no less than 22 different container materials would be used in an attempt to find a suitable solution.Wade Jr, Jack R., Lyons, Charles E., "Finish and Coating Development for Mauler Weapon Pod", US Army Missile Command, report RL-TM-65-6, 1 Jul 1965
Problems Mauler development was restricted by funding resulting in an Army Ordnance Missile Command recommendation that either funds be acquired from other sources (such as the Navy, Marine Corps or NATO) or that development be stretched out by up to two years. By 1963 funding shortfalls resulted in dependence upon unorthodox methods to keep the program going. Production plans had to be adjusted in 1963 which presented a problem as the M42 Duster system had been retired. Achievement of an operational Mauler capability was out of the question.
The Performance Evaluation & Review Technique (PERT) originally devised for the Polaris system in 1958 was introduced into the Mauler effort in 1962–63. Cagle described the contractor's reaction to PERT as "somewhat less than enthusiastic". In spring 1964 another management revision was introduced and the Mauler Program Management Charter was established. A Feasibility Validation Program had been established in 1963 which was to determine if Mauler could be successfully developed in the time available and at reasonable cost. It was determined that Mauler could engage jets and piston aircraft though at a lesser than desirable range but helicopters were an elusive target.
It was apparent by early 1965 that the Mauler program would be unsuccessful. Inadequate funding, a lack of guidance from higher headquarters, changes in requirements, and unsolved technical problems led to a loss of confidence. The program was cancelled in July 1965 after six years of delays.
Cancellation By this point there were serious doubts that the system would be entering service any time soon. On 16 September 1963 the Army Materiel Command asked the Aviation and Missile Command to study adapting the Navy's AIM-9 Sidewinder missile as the basis of a short-range anti-aircraft system. Their analysis suggested that the conversion would be simple, but the missile's long lock-on time and optical guidance would make it ineffective in close combat.