Stridsvagn 103
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| General Characteristics | |
| Length: | 7.04 m |
| Width: | 3.63 m |
| Height: | 2.43 m |
| Weight: | 39.7 t |
| Speed: | 50 km/h (road) 6 km/h (water) |
| Range: | 390 km |
| Primary armament: | 105 mm rifled Gun |
| Secondary armament: | two 7.62 mm MG one Anti-aircraft 7.62 mm MG |
| Power plant: | one 490 hp (365 kW) gas turbine and one 240 hp (179 kW) diesel engine |
| Crew: | 3 (Commander, gunner/driver, radio operator) |
The Stridsvagn 103, or S-Tank, is a Swedish tank. It is known for its unconventional turretless design that moves the entire tank in order to aim its main gun. The result is a very low-profile design with an emphasis on defence. S-tanks formed a major portion of Swedish armored forces during the 1960s and 70s, but has since been removed from service in favour of the almost universal Leopard II.
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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 as the KRV, but this would be an expensive option.
Sven Berge of the Swedish Army proposed an alternative in 1956. 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. 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. Berge's design provided this ability 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 move only a tiny amount, using servo motors for fine tuning the aim. This limited amount of motion made it impossible to make the gun fully stabilized, making it possible to fire only while sitting still.
Other features of the tank were equally "radical". The gun, the then-universal British L7 105mm, would be equipped with an autoloader, allowing the crew to be reduced to three. Most designs of the era used a crew of five, the S103 would eliminate the loader and gunner. One of the three left was the radio operator, who sat at 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. Additionally the tank was powered by two engines, a 240hp Rolls Royce diesel for cruising and turning the tank for aim, and a 490hp Boeing 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 sucessfully. 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 on 10 in 1960. Full production started in 1966 as the S103A with minor changes, and ended in 1971 with 300 delivered.
S103B
The turretless nature of the S103 also made it fairly easy to make watertight. This was taken advantage of for the S103B, 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 6km/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. 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.
S103C
An upgrade program was started in 1986 to fit all remaining vehicles with dramatically improved fire control systems. A further upgrade in 1987/88 replaced the Rolls Royce engine with a newer 290hp Detroit Diesel with additional fuel tanks, and added a new laser rangefinder. There was some consideration of adding reactive armor 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.