Stridsvagn 103

Infobox Weapon
name=Stridsvagn 103


caption=
origin=SWE
type=Main battle tank
is_vehicle=yes
crew= 3 (Commander, gunner/driver, rear driver)
length= 9.00 m (incl. gun)
width= 103 B: 3.60 m 103 C: 3.80 m
height= 2.14 m
weight= 103 B: 39.7 tonnes 103 C: 42.5 tonnes
armour= Unknown
primary_armament= 105 mm L/62 rifled Gun
secondary_armament= two fixed 7.62 mm MG one Anti-aircraft 7.62 mm MG
engine= 103 A:
Rolls-Royce K 60 diesel
- 240 hp (179 kW)
"and"
Boeing GT502 gas turbine
- 300 hp (223 kW)
103 B:
Rolls-Royce K 60 diesel
- 240 hp (179 kW)
"and"
Caterpillar 553 gas turbine
- 490 hp (365 kW)
103 C:
Detroit diesel 6V53T
- 290 hp (216 kW)
"and"
Caterpillar 553 gas turbine
- 490 hp (365 kW)
suspension= Gas-hydraulic (hydropneumatic) suspension
speed= 60 km/h
pw_ratio= 18.3 hp/tonne (B and C)
vehicle_range= 390 km

The Stridsvagn 103 (Strv 103), or S-Tank, was a Swedish tank (although some consider it to be a tank destroyer). It was known for its unconventional turret-less design, with a fixed gun elevated by adjusting the hull suspension and traversed by engaging the tracks. The S-tank was developed in the 1950s and was the first main battle tank replacement to use a turbine engine, later copied by the M1 Abrams. The result was a very low-profile design with an emphasis on defense and heightened crew protection level. S-tanks formed a major portion of Swedish armored forces during the 1960s, 70s, 80s and part of the 90s, but have since been removed from service in favour of the 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 155mm 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 its most likely opponent, the T-72, is only 2.2 meters in height with its turret vs. the 2.14 meters of the Strv 103. Occasionally tanks deploy themselves into ‘hull down’ firing positions, either purpose dug or using the crest of a hill, in order to reduce the exposure of the vehicle to enemy fire. In this firing position the level of exposure is determined by the distance between the bottom of the gun barrel to the top of the turret or vehicle, and the angle to which the vehicle is able to depress the gun barrel. Because the Strv 103 orients the entire tank to depress and elevate the barrel, in a hull down position it has a very low apparent height and subsequent visual profile to the enemy. It can also lower the hull 13 centimeters. Such static use of a tank is at odds with the very concept of a tank, "i.e.", a mobile, protected gun platform able to bring heavy firepower to bear upon the enemy while attacking. Hence the S Tank is really a defensive vehicle.

This is not the first time such a system had been used: it was common among World War II-era tank destroyers and assault guns, but in a tank, the ability to quickly change aim a turret provided always proved to be great asset. However, some tank destroyers, such as 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. 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); it may be said turreted tanks rarely fire on the move.

Other features of the tank were also quite radical. The gun, a Bofors 105mm L/62 (and able to use the same ammunition as the British 105mm L7) would be equipped with an autoloader, allowing the crew to be reduced to two (though a third man was added for psychological reasons).Fact|date=February 2007 Most designs of the era used a crew of four, while 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 the same speed as forwards, keeping its frontal armour pointed at the enemy.

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 300 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 production prototypes, which were completed in 1961. By this point, the army was so happy with the design, an initial pre-production order of 10 was placed in 1960. With minor changes, the S-tank was adopted as the Strv 103 ("103" from the fact that it was the third tank with a 10 cm gun) and full production started in 1967 and ended in 1971 with 290 delivered. The changes included a new gyrostabilised commander's cupola armed with a 7.62 mm FN MAG, and upgraded frontal armour. A "screen", similar to those of the "Panzer" IV "Ausf." J of World War Two, was available to help defeat HEAT rounds; however, it was kept secret for many years and was only to be fitted in the event of war.

The Strv 103 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 in water. One tank in each platoon was fitted with a blade under the front hull that allowed it to dig itself into the ground for added protection.

The Stridsvagn 103 never saw combat and so its design remains unproven. It is the case that every other deployed main battle tank has a turret. In 1967, Norway carried out a two week comparative observation test with the Leopard 1 and found with closed hatches, the 103 spotted more targets and fired faster than the Leopard. In April to September 1968, two 103s were tested at the British armour school in Bovington and reported, "The turretless concept of the "S"-tank holds considerable advantage over turreted tanks". In BAOR 1973, the 103 was tested against the Chieftain. Availability never fell under 90% and the final report stated, "It has not been possible to prove any disadvantage in the "S" inability to fire on the move." In 1975, two 103s were tested at the American armour center at Fort Knox. The trial demonstrated the 103 fired more accurately than the M60A1E3, but on an average 0.5 seconds slower. [http://www.militaryphotos.net/forums/archive/index.php/t-27474.html]

trv 103B

As the weight of the Strv 103 had increased compared to the pre-production tanks the 103 turned out to be underpowered. Hence a more powerful version of the same gas turbine, manufactured by Caterpillar, was introduced after the first 80 produced tanks. The early version was soon upgraded to B-standard.

trv 103C

An upgrade program was started in 1986 to fit all vehicles with dramatically improved fire control systems. Also, each S-tank was fitted with a dozer blade, rather than just one per platoon. 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 and/or appliqué armour in the early 1990s, but in the end the S-Tank was instead phased out of Swedish service in favour of the Leopard 2, which started arriving in 1997. The last year in which the S-tank were used to train tank crews was 1997.

trv 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 fire-control computer, thermal viewers for both the gunner and the commander, making the crew able to fight during night-time and in bad weather conditions, and the installation of passive light enhancers for driving. Some minor changes to the suspension system and engine 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 under remote control. The only Strv 103D ever built is today is on display at the [http://www.pansarmuseet.se/ Axvall armor museum] , together with some 103C models. They are all still in running status.

ee also

*List of tanks
*Swedish Armed Forces

External links

* [http://www.foreningen-stridsvagns.se/ Society S-tank - Föreningen stridsvagn S] - Official site sv icon