Comet (tank)

Background

Combat experience against the Germans in the Western Desert Campaign demonstrated to the British many shortcomings with their cruiser tanks. Hence a request was made in 1941 for a new heavy cruiser tank that could achieve battle superiority over German models. For reasons of economy and efficiency, it had to use as many components as possible from the current A15 Cruiser tank Mk VI Crusader tank.

The initial designs for the new Cromwell tank evolved into the A24 Cruiser Tank Mk VII Cavalier tank and the A27L Cruiser tank Mk VII Centaur tank, both powered by the Nuffield Liberty. Design progressed through the Cruiser tank Mk VII (A27M) Cromwell, a third parallel development to the Cavalier and Centaur, sharing many of the same characteristics.

Under the newer A27M specification, Cromwell integrated a number of new and advanced features. The new Meteor engine proved to be very reliable and gave the tank good mobility, but some problems appeared based on the vehicle's shared heritage and significant jump in engine power. The tank was prone to throwing its tracks if track tension was not maintained properly or if it turned at too high a speed or too sharply. There were also some problems with suspension breakage, partly due to the Cromwell's high speed. Cromwell ran through a number of design changes as a result.

The biggest complaint, however, was related to firepower. Cromwell had originally been designed to carry the 57 mm Ordnance QF 6-pounder, also retrofitted to the Crusader tanks. In combat, these were found to be useful against other tanks, but lacking any reasonable high explosive load they were ineffective against anti-tank guns or static emplacements. Prior to the Cromwell entering combat service, the Ordnance QF 75 mm was introduced which equipped the majority of Cromwells, essentially an adapted version of the 6-pounder firing shells from the US 75 mm gun from the Sherman. This offered somewhat lower anti-tank performance than the 6-pounder, but its much larger shell provided a truly effective high explosive load.

Several attempts had been made to further improve the firepower by fitting a more powerful gun. In parallel with development of the Cromwell and QF 75 mm gun, a new Vickers High Velocity 75mm tank gun had been in development. This proved too large for the Cromwell turret ring, and left a shortage in offensive anti-tank capability.^[2] A prior requirement for a 17-pounder armed tank led to development of the A30 Cruiser Mk VIII Challenger. Based on the Cromwell, the hull had to be lengthened and a much larger turret set on top to allow a second loader for the 17-pounder, a requirement of the older specification believed necessary for the larger 17-pounder ammunition. The very high turret of the Challenger was considered a liability and this led to experiments with the similar A30 Avenger version, a dedicated anti-tank version with an open-top turret.

Conversion of the Sherman tanks to the Sherman Firefly (a Sherman tank fitted with the 17 pounder gun) was significantly faster than Challenger production however, and driven by operational needs of the Normandy invasion production of Challenger was dropped. Fireflies (and the limited number of Challengers) provided additional firepower to Cromwell and Sherman armed troops. One Firefly would be issued to each troop of Cromwells (giving three Cromwells and one Sherman Firefly). Problems were encountered due to the different maintenance requirements and associated supply complication of two tank models, as well as the performance difference between Cromwell and Sherman and the Sherman's silhouette, even larger than the Challenger. The large size and obvious difference of both Challenger and Firefly made them a priority target for Axis forces.

Recognising that a common low profile vehicle was required to replace the mixed fleet of Cromwell, Challenger and Firefly tanks, a new specification of tank was created. This removed Challengers need for a second loader and mounted the newer Vickers High Velocity weapon intended for Cromwell.

Tank, Cruiser, Comet l (A34)

A Comet's crew loading 77 mm HV ammunition into their tank.

With the A34 (the General Staff specification), later named Comet, the tank designers opted to correct some of the Cromwell's flaws in armament, track design and suspension while building upon the Cromwell's main strengths, its low height, high speed and mobility. This replaced the need for Challenger and Firefly, and acted upon the experiences gained through design and early deployment of Cromwell.

Originally, it had been expected that Cromwell would use a new gun from Vickers: the "High Velocity 75mm". However, as designed, the gun would not fit into the turret size available.^[2] Development of the gun continued, and as work commenced on the Comet, the gun design evolved into the 77 mm HV.^[2] The gun now used the same calibre (76.2 mm) projectile as the 17-pounder, but the cartridge case was from the older QF 3 inch 20 cwt anti-aircraft gun loaded to higher pressures. The resulting round was completely different from 17-pounder ammunition. Overall the round was shorter, more compact and more easily stored and handled within the tank.

The 77 mm HV was effectively a shortened 17-pounder. This made it possible to mount the gun on a smaller turret ring. The gun was still capable against opponents, and firing APDS rounds, it was more accurate and consistent than APDS from the 17pdr and 6pdr, which were inaccurate over 700m and often ricocheted. The Challenger turret had been so large to allow space for two loaders.^{[lower-roman 2]}

Several other improvements were made over the Cromwell's original design, and many of its design revisions were incorporated, such as safety hatches for both driver and hull gunner. The hull was now fully welded as standard and armour was increased, ranging from 32 mm to 74 mm on the hull, while the turret was from 57 to 102 mm.

A new lower-profile welded turret was created using a cast gun mantlet for the 77 mm. The turret was electrically traversed (a design feature taken from the Churchill tank), with a generator powered by the main engine rather than the hydraulic system of the Cromwell. Ammunition for the 77 mm gun was stored in armoured bins.

Comet's suspension was strengthened, and track return rollers were added. As with later Cromwells, the Comet tank's top speed was limited from the Cromwell's 40+ mph to a slower, but respectable 32 mph (51 km/h). This change preserved the lifespan of suspension and engine components and reduced track wear.

Similar to later Churchills, Comet benefitted from lessons learned in the co-operation of tanks with infantry. It was fitted as standard with two radio sets: a Wireless Set No. 19, for communication with the regiment and the troop, and a No. 38 Wireless for communication with infantry units. Like many British tanks, it also had a telephone handset mounted on the rear so that accompanying infantry could talk to the crew.

Second World War

Comet tanks of the 2nd Fife and Forfar Yeomanry, 11th Armoured Division, crossing the Weser at Petershagen, Germany, 7 April 1945

The British 11th Armoured Division was the first formation to receive the new tanks, with deliveries commenced in December 1944. It would also be the only division to be completely refitted with the Comet by the end of the war. The Comet saw combat and 26 were destroyed but due to its late arrival in the war in north west Europe, it did not participate in big battles.^[5] The Comet was involved in the crossing of the Rhine and the later Berlin Victory Parade in July 1945. The Comet's maximum speed of 32 miles per hour (51 km/h) was greatly exploited on the German Autobahn (motorways).

Postwar era

During the following Korean War, the Comet served alongside the heavier Centurion tank, a successor introduced in the closing days of the Second World War on an experimental basis but too late to see combat. The Centurion was formally adopted in 1949 and was partly based on the Comet design. The Comet remained in British service until 1958, when the remaining tanks were sold to foreign governments; up until the 1980s, it was used by the armies of various nations such as South Africa, which maintained several as modified recovery vehicles. Two examples were still being held in reserve by the South African Army as late as 2000.^[6]

Forty-one Comet Mk I Model Bs were also used by Finnish Defence Forces armoured brigade until 1970. The tanks were stored until 2007, when four of them were auctioned. Four Comets were delivered to the Irish Army in 1959 and a further four in 1960. Severe budget cutbacks affected the service lives of the Comets, as not enough spares were purchased. The Comet appealed to the Irish Army as it was cheap to buy and run, had low ground pressure and good anti-tank capability. However, faulty fuzes meant the withdrawal of the HE ammunition, which limited the tank's role to an anti-tank vehicle. With stocks of 77 mm ammunition dwindling in 1969, the army began an experiment to prolong the life of the vehicle. It involved replacing the turret with an open mounting with the Bofors 90 mm Pv-1110 recoilless rifle. The project was cancelled due to lack of funds. The last 77 mm Comet shoot was in 1973 with the tanks being withdrawn soon afterwards. One is preserved in the Irish Curragh Camp and two more survive in other barracks.

Cuba was also an operator of the Comet tank, with some 15 purchased from the UK before the Cuban Revolution of 1959 (which saw the fall of US-backed dictator Fulgencio Batista's regime and the beginning of Cuba being under Fidel Castro's rule). Starting in 1958, the USA began to cut off weapons sales to Cuba following an American government's decision for prohibiting Cuba to use its US-supplied armaments against pro-communist/socialist rebels under Castro throughout the country. Thus, Batista was forced to seek his buying of arms from other nations, which included the UK, which also sold about 17 Hawker Sea Fury fighter aircraft together with the Comet tanks. After the collapse of Batista's government at the end of 1958, the new Cuban government under Castro sought for replacement and repair parts and ammunition for their Comets from the British government, which promptly turned them down in conjunction with the USA's armaments blockade over Cuba. Thus, the few Comets in Cuba were soon retired from service and either scrapped or abandoned, being replaced with larger quantities of T-34/85 and T-54/55 tanks received from the Soviet Union.

Burma (as it was then known; now Myanmar) was also another user of the Comet tank, with an estimated 25 bought from their former British colonial rulers in between the late 1950s and the early 1960s. These were operated until around the 1990s, up until which then they were most likely scrapped and replaced with newer tanks, such as the Chinese Type 69 main battle tank.

Tanks of comparable role, performance, and era

• German Panther - medium tank, entered service in 1943
• Soviet T-34-85 - medium tank, entered service in 1944
• United States M4 Sherman (M4A3E8) - medium tank, entered service in 1944
• United States M26 Pershing - heavy tank / medium tank, entered service in early 1945