Stridsvagn 103

Stridsvagn 103
Specifications
Mass	103 B: 39.7 tonnes 103 C: 42.5 tonnes
Length	9.00 m (incl. gun)
Width	103 B: 3.60 m 103 C: 3.80 m
Height	2.14 m
Crew	3 (Commander, gunner/driver, rear driver)

The Stridsvagn 103 (Strv 103), or S-Tank, was a Swedish main battle tank. It was known for its unconventional turretless design which required the entire tank to move in order to aim its main gun. The result was a very low-profile design with an emphasis on defence and heightened crew protection level. S-tanks formed a major portion of Swedish armored forces during the 1960s and 70s, but have since been removed from service in favour of the almost universal Leopard 2.

History

In the mid-1950s the Swedish army put out a contract tender for a new tank design to replace their Centurions. Although the Centurion was arguably the best tank in the world at the time, its performance lead over contemporary Soviet designs like the T-55 was only marginal, and any future designs would best it. A consortium of Landsverk, Volvo and Bofors responded with a new heavy tank design, known under the codename KRV, fitted with a 155 mm smoothbore gun, but this would be an expensive option.

Sven Berge of the Swedish Arms Administration proposed an alternative in 1956, given the codename S. Noting that the chance of being hit in combat was strongly related to height, he proposed that any new design should be as low as possible. The only practical way to do this was to eliminate the turret, which would also make the tank much lighter and simpler. Note however that the M1 Abrams, with its turret, is only 2.43 meters in height vs. the 2.14 meters of the S-103.

This is not the first time such a system had been used, it was common on World War II-era tank destroyers and assault guns for instance, but in the tank role the inability to quickly change aim that a turret provided always proved to be a serious problem. However, some assault guns like the Jagdpanther were both relatively cheap to make and very effective in defensive positions. Berge's design tried to solve the aiming problem through the use of a fully automated transmission and suspension system, which would turn and tilt the tank under gunner control. The gun itself would be fixed to the hull. However this made it impossible to use a stabilized gun, as a result the tank could not move and fire at the same time (at least not with any accuracy).

Other features of the tank were also quite radical. The gun, a Bofors L/62 (and able to use the same ammunition as the British L7 105 mm) would be equipped with an autoloader, allowing the crew to be reduced to two (though a third man was added for psychological reasons). Most designs of the era used a crew of four, the S-tank would eliminate the loader and gunner. One of the three left was the rear driver, who was facing the rear of the tank equipped with a complete setup for driving. This allowed the tank to be driven "backwards" at high speed, keeping its frontal armor pointed at the enemy. While this might seem odd, it is worth noting that the Swedish army has not proposed mounting an offensive war for the last 100 years. The purpose of the Swedish army has been to safeguard Sweden's nutrality, hence the very defensive nature of the S-103 was not a detriment, in fact it was desirable.

The Commander and gunner/driver both had the same set of sights and controls to fire the gun and drive the tank. Additionally the tank was powered by two engines, a 240 hp Rolls Royce K60 diesel for cruising and turning the tank for aim, and a 490 hp Boeing 502 turbine for "dashing" at high speed.

The concept was interesting enough that Bofors was asked to build a prototype of the suspension/drive train, which they completed successfully. In 1958 a follow-on contract called for two full prototypes, which were completed in 1961. By this point the army was so happy with the design that they had already placed an order for an initial pre-production run of 10 in 1960. With minor changes the S-tank was adopted as the Strv 103 and full production started in 1968 and ended in 1971 with 330 delivered. The changes included a new gyrostabilised commander's cupola armed with a 7.62 mm MH m/58, and upgraded frontal armour. A "fence" (seen in the image above) was also added to help defeat HEAT rounds, but was kept secret for many years and was only to be fitted in the event of war.

The Stridsvagn never saw combat and so its design remains unproven. It is the case that every other deployed Main Battle Tank has a turret.

Strv 103B

The turretless nature of the Strv 103 also made it fairly easy to make watertight. This was taken advantage of for the Strv 103B, which was fully amphibious. A floatation screen could be erected around the upper hull in about 20 minutes, and the tracks would drive the tank at about 6 km/h on water. Other changes for the B model included the addition of a blade under the front hull that allowed the tank to dig itself into the ground for added protection. A full suite of image intensifiers were also added for night combat and driving.

Strv 103C

An upgrade program was started in 1986 to fit all vehicles with dramatically improved fire control systems. A further upgrade in 1987/88 replaced the Rolls-Royce engine with a newer 290 hp (216 kW) Detroit Diesel with additional fuel tanks, and added a new laser rangefinder. There was some consideration of adding both reactive armor and/or additional armorplates in the early 1990s, but in the end the S-Tank was instead phased out of Swedish service in favour of the Leopard II, which started arriving in 1997. The last year in which the S-tank were used to train tank crews was 1997.

Strv 103D

In the mid-1990s, along with testing programs running for a new main battle tank for the Swedish armed forces, some upgrades took place for the 103C version. The designation was Strv 103D and only one prototype was ever made. The major changes were the installation of firecontrolcomputer, thermal viewers for both the gunner and the commander, making the crew able to fight during nighttime and in bad weather condition, and the installation of passive light enhancers for driving. Some minor changes to the suspension system and enginepack were also made. This prototype was used during the trials for the new main battle tank system for the Swedish armed forces alongside all the other tanks tested. For a few years this prototype was even tested with remote controlling. The only strv 103D ever built is today is on display at the Axvall armor museum, together with some 103C models. They are all still in running status.

See also

• List of tanks
• Swedish Armed Forces