BGM-71 TOW
The BGM-71 TOW is an American anti-tank missile. First produced in 1968, TOW is one of the most widely used anti-tank guided missiles. It can be found in a wide variety of manually carried and vehicle-mounted forms, as well as in widespread use on helicopters. Originally designed by Hughes Aircraft in the 1960s, the weapon is currently produced by RTX.
TOW was designed to address the shortcomings of previous missiles like the SS.10 and ENTAC. In particular, there was a desire to improve the guidance system to make it easier to use, and greatly increase effective range. Earlier designs generally used a small joystick to directly control the missile's flight while the operator attempted to get it to line up with the target, a concept now known as MACLOS. In practice, users tended to overcorrect and fly the missile back and forth across the target. TOW used a new system that simply required the operator to keep a gunsight aligned on the target, and the electronics would calculate the control inputs needed, a concept today known as SACLOS. It did this by looking for a bright infrared lamp on the back of the missile and comparing that to the line-of-sight of the gunsight. The sights could also be equipped with infrared cameras or image intensifiers for night-time use, and it had roughly double the range of the earlier designs.
TOW was rapidly deployed on a wide range of man portable and light vehicles like jeeps and a variety of dedicated light armoured vehicles like the M901. The need for the missile to be visible in the sights for the guidance system to work meant that it was initially not suitable for launch from helicopters, as these might be firing at targets to one side or the other while the missile would be held facing forward. This led to the introduction of a new sighting system that could calculate the angle between the sights and the tube and quickly steer it into the sights. This became one of the TOW's most widely used applications, and was the primary armament of many Cold War era attack helicopters among many western forces.
TOW was among the most widely used weapons of its class from the 1960s into to the 1980s when a number of new systems began to replace it in certain roles. For helicopter use, the laser guided AGM-114 Hellfire began to replace TOW in the 1980s, and more recently, smaller missiles like FGM-148 Javelin using top-attack profiles have largely replaced TOW in the man-portable roles. TOW remains widely used in vehicle mounts, but in US use the CCMS-H is planned to replace it in these roles.
History
Previous designs
Late in World War II, the German Army began experimenting with modified versions of the Ruhrstahl X-4 wire-guided missile. Originally developed for the Luftwaffe as an anti-bomber weapon, by changing the warhead to one using a high-explosive anti-tank design, the new X-7 version made an effective anti-armor weapon with a range of hundreds of meters. This would greatly improve the effectiveness of infantry anti-tank operations, which at that time were generally based on smaller weapons like the Panzerfaust and Panzerschreck, limited in the best case to ranges on the order of. X-7 was never fully developed before the war ended.In the immediate post-war era, the design was picked up by development teams in France and Australia. In France, Nord Aviation's Jean Bastien-Thiry developed an updated version of the X-7 using a solid fuel rocket as the very small and highly portable SS.10. Development started in 1948, with the first rounds fired in 1952. Evaluations by the US Army in 1953 concluded it was not ready for operation, but that its progress should be tracked. The Army then instructed the Redstone Arsenal to develop its own version of the basic concept, which emerged as the SSM-A-23 Dart, a larger design with roughly twice the range of the SS.10. While the development of the Dart continued, Nord delivered a workable version of the SS.10, as well as the extended-range SS.11. In the summer of 1958, the development of the Dart was canceled in favor of purchasing the two French designs.
During the same period, the British Army joined the Australian efforts to build a heavyweight long-range weapon, the Malkara, with a range of about. The tracking system, similar to the SS.11, proved difficult to use and a new project started under the codename Orange William to address this. This system used a computer to calculate the impact point, sending commands to the missile using an infrared link. But the link was found not to work in smoke or dust, making it largely useless on the battlefield, and the project was abandoned.
New concept
In January 1958, the Army's Office of Ordnance Research and Development formed the Ad Hoc Working Group at the Ballistic Research Laboratories to define a future replacement for the SS.10 and 11. The team included members from Picatinny Arsenal, Frankford Arsenal, Redstone Arsenal, Watervliet Arsenal, Detroit Arsenal and Harry Diamond Laboratories. The group almost immediately decided not to attempt to define a weapon concept, and instead spend the next two years studying the problem while researching the possibility of using alternative guidance systems and continually watching foreign developments where the US was lagging.Meanwhile, aware of the British Army's dissatisfaction with the Malkara, Vickers started a private design of a smaller weapon similar to SS.10 but with a greatly improved guidance system. The resulting Vickers Vigilant was far easier to use in the field and required much less training. The Army, meanwhile, had come up with their own design that combined a system like the Vigilant with a much larger missile to produce Swingfire. The goal was to allow the launcher to remain completely undercover while a gunner took a portable sight forward to aim at the targets from a concealed location.
It was at some point during these early stages that the British became aware of the US developments. Having approved Swingfire to some degree based on the possibility of foreign sales, the emergence of a possible US competitor was a concern. Meetings between Solly Zuckerman and John H. Rubel led to the July 1961 Rubel-Zuckerman agreement, wherein the UK would continue development of the long-range Swingfire while the US concentrated on shorter-range missiles, up to, with new guidance systems. The US agreed to not introduce a system that competed directly with Swingfire or Vigilant without prior consultation but was free to develop new unguided "assault weapons" to replace the LAW. Both the US and Canadian Army agreed to purchase Swingfire for the long-range role.
HAW
Despite the efforts to reach an agreement over anti-tank missiles, in the early summer of 1961, the Chief of Ordnance asked BRL to deliver a formal definition for what was then known as the "Heavy Assault Weapon for the Long Range period", or HAW for short. They asked for a weapon to be delivered sometime between 1965 and 1970. BRL assigned the work to the Armored Systems Evaluation Branch of the Weapon Systems Laboratory. David Hardison, the Branch Chief, reconvened the Ad Hoc panel to review a long list of twenty-seven design proposals, all of which were found lacking.Hardison then began preparing a list of the ideal characteristics of a HAW weapon. Of primary importance was the adoption of some form of semi-automatic guidance, as the manual guidance systems of earlier weapons like SS.11 were found to be difficult to use as the relative movements of the launcher and target increased; MCLOS worked well for stationary launchers and slow-moving targets but had proven much more difficult to use from moving vehicles, and especially helicopters.
Experience with the MGM-51 Shillelagh missile demonstrated that the simplest solution to successfully tracking the missile was to optically track a flare attached to the missile using an infrared seeker. This was essentially identical to a heat seeking missile, but tracking its own missile rather than a separate target. Flares, however, were not ideal illumination sources, especially in the case where multiple rounds might be fired and the optical system might track the wrong one. In place of the flare, the panel selected an infrared lamp whose output would be modulated with a shutter so each missile would have a unique signal.
Using this style of guidance demanded that the missile be brought into the line-of-sight of the tracking system as soon as possible; in Shillelagh this was almost immediate because the missile was launched from a gun barrel directly into the view of the tracker. Earlier manual weapons like SS.10 and ENTAC flew upwards after launch to clear the ground when being launched by infantry lying on the ground, and thus would not be immediately visible along the line-of-sight. To ensure the HAW could be tracked successfully, it would have to be launched from a tube, like Shillelagh, but one that was lightweight to ensure mobility.
Finally, Shillelagh sent guidance commands to the missile using an infrared link, but as the British had discovered, this proved relatively unreliable in the field and was subject to countermeasures like random flashing IR lamps. For the shorter ranges envisioned for HAW, wire guidance was perfectly suitable and both much less expensive and largely immune to countermeasures.
TOW emerges
The resulting design was tube-launched, optically tracked, and wire-guided. BRL programmer Harry Reed immediately christened it "TOW", a name that the system carried into production.One problem that was noted early on was that the tube launch would make it difficult for the missile to be launched from a helicopter unless it was pointed relatively directly toward the target. Earlier systems were manually guided and did not need to be "gathered" quickly, so these were easier to launch at high crossing angles. Seeing this might be a major problem in the short term, TOW simply dropped the helicopter-launch requirement.
When the BRL team returned the HAW/TOW study, the Pentagon gave them six months to come up with an actual requirement instead of a list of desirable features. Reed gathered submissions from the industry and quickly selected three contractors for further details, Hughes Aircraft, Martin Marietta, and McDonnell Douglas. All three companies concluded the concept was able to be produced.
On 12 January 1962, the BRL officially assigned the development of the TOW concept to the U.S. Army Missile Command, who in turn formed the Antitank/Aircraft Weapons Commodity Office on 19 November 1962. In December 1962, Hughes was instructed to continue development while a development contract was being drawn up. Budget approval for development was granted in January 1963 as the XM65 TOW, and the final development contract, the first 100 percent cost-plus-incentive-fee, was signed on 3 May 1963. This led to the TOW Project Office opening on 1 October 1964.
The British learned of the TOW program when it was sent to MICOM. In May, the US suggested they abandon Swingfire in favor of TOW, pointing out that the French were also introducing a long-range missile, and with three similar weapons in the marketplace, the British would find foreign sales difficult. However, the British Army was convinced that the launch vehicle would only survive if it was completely undercover, and TOW required the launcher to remain in sight of the target through the entire flight of the missile. They continued the development of Swingfire.
In 1969, the House Authorization Subcommittee considered ending the TOW program in favor of the Shillelagh. A series of presentations by both missile teams followed, and ultimately the decision was made to continue both programs in September 1970.