So, this post showing some excellent ‘splodey was pretty popular. And TOW missile video posts have long been a mainstay here. But it wasn’t until I started looking in the comments that I realized I have never actually done a post about the history of the TOW, how it works, and its variants. Craig kindly laid the groundwork with a post on missiles in the age before TOW, so lets carry on from there.
The TOW and the older SS10 and SS11 missiles that Craig posted about all shared a couple of characteristics. They were all armed with a HEAT warhead to defeat tanks, and they were all wire guided.
The older missiles used a guidance technique known as Command-to-Line-of-Sight (CLOS). Simply put, The gunner launched the missile, and a flare on the back of the missile showed the gunner where it was. He then steered the missile along his line of sight to the target. As long as he saw the flare heading at the target, all was well. Typically, the missile was controlled by a small joystick, and the guidance corrections the gunner made were sent along a pair of very, very thin copper wires trailed from the missile. While this was pretty nifty at the time, it was awfully low tech, and required very intense training for the gunner to achieve any proficiency. The gunner had to keep track of both the target and the missile, and “fly” the missile to the target. Hard enough on a stationary target, but against a moving target like a tank, it was very difficult indeed.
Building on that basic concept, the Army capitalized on its technical know-how and the miniaturization of electronics in the ’60s to introduce a much improved technique: Semi-automatic Command-to-Line-of-Sight (SACLOS).
The big difference between CLOS and SACLOS is the way the missile is commanded. In SACLOS, and optical sensor in the gunner’s sight tracks the missile’s flare (or “beacon”) and measures its deviation from the line of sight, as determined by the crosshairs in the sight. When the missile guidance set senses a deviation, it would send the correction, rather than the gunner having to make a correction. In effect, all the gunner had to do was keep the crosshairs on the target for the time of launch until impact. This was much, much easier than trying to manually fly the missile to the target.
The original TOW missile was the BGM-71A. It was a revolutionary improvement over previous missiles. The missile was stored and launched from a sealed fiberglass tube, that protected it from the elements and rough handling. It was optically tracked from either a ground launch platform or a stabilized sight on a helicopter, and it was guided via copper wires, hence the acronym TOW. The orignally TOW had a 6″ diameter missile body, with a 5″ diameter HEAT warhead, and a range of 3000 meters.
Pretty soon, it was clear that the missile had sufficient energy to fly further than 3000 meters, and by simply adding more wire, the range was increased to 3750 meters. The next version, I-TOW (Improved TOW) added a standoff probe to the warhead to make sure it detonated the optimum distance from the target.
Increases in Soviet armor lead to an improved missile, and more importantly, an improved guidance set. This TOW 2 featured a larger 6″ diameter warhead, a slightly modified probe, and critically, added a thermal sight system to the launcher, meaning for the first time, the TOW could be used at night. The TOW 2 incorporated a xenon beacon at the rear of the missile to allow this thermal sight to track it at night or in low visibility.
With the advent of reactive armor, the TOW2A was designed with tandem warheads. The first warhead would detonate the reactive armor, while the second would punch through the now exposed site.
TOW 2B was a different approach. As mentioned in the linked video, it uses two downward firing EFPs to punch through the thinner top armor of tanks. The TOW2B overflies its target, never actually striking it. The gunner merely keeps the crosshairs on the target, the guidance set handles the “offset” aim for him. By giving later versions of the TOW2B an aerodynamically improved nose, and increased wire capacity, the TOW2B Aero has increased range to 4500 meters. This is the current production anti-armor model of the TOW for the US Army, though enormous numbers of earlier TOW2 models are sill in the inventory and issued.
With the current fights in Afghanistan and Iraq facing little in the way of armored threats, the limitations of the HEAT warhead became an issue. While a HEAT warhead is better than none, it has little real anti-personnel capability. This has lead to the development of the BGM-71H, which is similar to the TOW 2A, except the HEAT warheads have been replaced by a blast/fragmentation warhead better suited to killing troops and destroying bunkers.
In addition, a wireless variant of the TOW2B is in production.
Recently, the ITAS (Improved Target Acquisition System) has begun replacing older TOW2 sights in ground mounts. This has a much improved thermal sight, not only improving accuracy, but also serving as a very handy surveillance tool for infantry units.
The TOW has proven to be a remarkably adaptable weapon system, with a wide range of improvements incorporated over the years. Improvements to both the missile, and the guidance sets have kept it a very viable system on the modern battlefield. But there are some limitations to further growth. Primarily, the fixed diameter and length of the missile imposed by the launch tube size means that there is only so much space to grow. Also, given that limitation, the missile remains fairly slow, meaning the time from launch to impact is quite lengthy, over 3o seconds to maximum range. This can give the enemy time to either shoot back or attempt to flee.
Even with these limitations, the TOW is a very effective system, and there are no current plans to replace it as the heavy anti-armor missile system.