1500-ton Self-Propelled 80cm Gun
By Gary Zimmer
In a paperback titled Tanks of the Axis Powers published over 20 years ago there is a brief mention of some of Germany's armoured follies. It mentions a 1500 ton super heavy tank, cased in 250mm of armour, armed with an 80cm gun and two 15cm weapons, and powered by four U-boat diesels. Although there was no illustration I have always been curious as to what this 1500 tonner would look like.
However we do know something about the proposed main weapon, the 80cm. Although not the largest calibre gun ever made, or the longest ranged, the 80cm railway gun 'Dora' was the biggest. As far as we know it was used only sparingly, to shell Sevastopol in the Crimea, and later Warsaw. Too large to be transported whole, Dora required several trains to transport it. Before assembly could begin, and this took several weeks to acomplish, a second track had to be laid at the chosen firing site. Movable straddle cranes also had to be assembled, these were on their own additional rails. The two 20 axle halves of the chassis were shunted onto the double tracks side by side, and coupled together. Only then could the cranes start putting the really big bits on. Once assembled Dora must have been an awesome sight, all one thousand three hundred and fifty tons of it. The barrel alone weighed 100 tons, the breech was also another 100 tons. It could fling a 7 ton shell about 45 km. As a piece of static siege artillery there was no question of its effect, but even its creators, Krupp, admitted while it was a valuable research tool, as a practical weapon of war it was useless.
Alleged wartime sketch of the "Monster"
Which brings us to the 1500 tonner, aptly named 'Monster' by armaments minister Albert Speer. It may have been an attempt to make some use of Dora, or simply an extension of a policy to self-propell all heavy artillery, but someone got the idea of putting Dora on tracks.
The wartime sketch (provided courtesy Karl Horvat, an Australian researcher) is all we have, but it allows us to deduce a few things.
One reason why you can't simply scale up an existing tank design is ground pressure. If you know the mass and dimensions (i.e. area of track in contact with the ground) of a vehicle, it is quite easy to work out ground pressure. Put simply, weight will be roughly proportional to the volume or the cube of the dimensions, while the area of track in contact with the ground will be proportional to the square of dimensions. If we double the size of a tank, we get eight times the weight but only four times the track area, thus twice the ground pressure. (There's also twice the stress in suspensions, axles and everything else, it's why elephants have thicker legs than flamingos.)
A very light tracked vehicle, such as a Bren carrier, will have what appears to be ridiculously narrow tracks. As a vehicle gets heavier, the proportion of its width covered by track increases. A Centurion has about 40% of its width as track, while for the 188 ton Maus tank, the figure was about 66% or two thirds. In fact the most striking thing about Maus is this proportion of track width to overall width.
Assuming a pressure of 1.2 kg per sq cm for this 1500 tonner, that's about midway between that of a Centurion and a Maus, and seems a realistic place to start. Working backwards, we can use ground pressure and weight (1500 tons, or thereabouts) to find how much contact area it needs. Track width appears to be around 80% of the width, giving tracks of 2.4m width (each) for an overall width of 6m. The illustration appears to be about 6m wide, as is the gun on its rail mount. If we stick to an assumed six metre width, close to an upper limit if we ever consider movement by road, this behemoth thus requires 27m of track on the ground. There's only one problem with this, it won't turn.
The Landkreuzer P. 1500 Monster was a pre-prototype ultraheavy tank meant as a mobile platform for the Krupp 800mm Schwerer Gustav artillery piece, in fact, a mobile grand cannon.
If completed it would have easily surpassed the Panzer VIII Maus, and even the extremely large Landkreuzer P. 1000 Ratte in size.
It would have been 42 m (138 ft) long, would have weighed 2500 tonnes, with a 250 mm hull front armor, 4 MAN U-boat (submarine) diesel engines, [though it would only have enough power to reach up to speeds of 10-15 kph] and an operating crew of over 100 men.
The main armament would have been an 800 mm Dora/Schwerer Gustav K (E) railway gun 10 times bigger in diameter than modern tank cannons, and a secondary armament of two 150 mm SFH 18/1 L/30 howitzers and multiple 15 mm MG 151/15 machine guns.
The shorter a tracked vehicle is, that is track length on the ground, the less resistance there is to turning. Also, the wider it is, the outside track is able to generate a greater turning moment, and overcome the resistance of both tracks to being pushed sideways. A governing aspect of tracked vehicle design is the ratio of the distance between track centres, and track contact length. Typically, this is about 2:1 for most vehicles. The 1500 tonner has a length/width ratio of about 7.5 to 1, and this is horrific. The way out of this is chassis articulation. By using four track units, each 14m long, and allowing each pair to be turned independently, it might just work.
Having four track units ties in nicely with the four U-boat diesels. All the Porsche heavy tanks were electric drive, and it seems hard to imagine anything else for a machine this size. In a U-boat, the diesels drove dual purpose electric motor-generators, but on the 1500 tonner these would function as generators only. It seems logical that each diesel would have its own generator. These four generators would each run an electric motor in each of the four track units. Of course the diesels and generators could be anywhere in the vehicle, as no mechanical drive to the tracks would be required. The other pieces of information are harder to fit into the picture. Just where the two turrets, each with a 15cm gun, would fit I have no idea. If the layout of Dora is preserved, as the illustration seems to indicate, there appears to be no place for them. Also, having these turrets side by side, as Axis suggests, implies a much greater width than 6m if these turrets are not to foul. More puzzling still is the 25cm of frontal armour. The illustration shows that the loading decks, and of course the crew doing the loading, had no protection at all, nor would they need any being many miles from whatever they were shooting at. Having this extent of armour is only required if the machine is going to be used as a direct fire weapon, in other words as a tank and not a piece of self-propelled artillery.
It also appears that the shell hoists are retained, as on the rail gun. While having no on-board stowage of 80cm rounds is not an issue for SP artillery, it would be an absolute must for a 'tank'. Dora was supplied with 80cm rounds from the rail lines it sat upon, but this would not be any use to an SP operating away from any railhead.
I imagine that ammunition vehicles would be required to deliver one round at a time to the hoists, they could possibly be similar to the Panzer IV carriers used with the Karl Mörsers. Apart from these carriers there would probably be a whole retinue of vehicles accompanying this giant machine; fire control and signals vehicles, a flak unit, the cook's truck, and so on.
Landkreuzer P1000 Ratte
The 80cm 'Gustav' in Action
The largest gun ever built had an operational career of 13 days, during which a total of 48 shells were fired in anger. It took 25 trainloads of equipment, 2000 men and up to six weeks to assemble. It seem unlikely that such a weapon will ever be seen again.
The 80-cm K (E), for all its size and weight, to say nothing of its 'overkill' firepower, went into action on only one occasion. It was originally intended to smash through the extensive Maginot Line forts but when the campaign in the West took place in 1940 the 80-cm K (E) was still in the Krupp workshops at Essen and, in any event, the German army bypassed the Maginot Line altogether. Thus when the 80-cm equipment had completed its gun proofing trials at Hillersleben and its service acceptance trials at Rugenwalde there was nothing for the gun and its crew to do. To justify the labour and effort of getting the huge gun and its entourage into action, the potential target had to justify all the bother involved, and there were no really large fortification lines left in Europe for the gun to tackle. The two major fortification systems, the Sudetenland defences and the Maginot Line, were both in German hands and it seemed that the 80-cm K (E), or 'schwere Gustav' (heavy Gustav) as it became known, was redundant even before it had fired an aggressive shot
During early 1941 one potential target appeared on the planner's drawing boards and that was Gibraltar. It was planned to assault this isolated fortress at the mouth of the Mediterranean to deny the inland sea to the Allies but as Spain was neutral permission had to be obtained from General Franco to allow German troops to travel through Spain to make the attack. Operational planning for the assault (named Operation 'Felix') got to the stage at which German parachute and glider troops were actively training for the assault before a meeting between Hitler and Franco showed that the wily Spanish dictator was not going to allow himself or his country to become mixed up in a major European conflict, Thus another potential target for the 'schwere Gustav' came and went.
The invasion of the Soviet Union (Operation 'Barbarossa') took place during the second half of 1941 without any assistance from the 80-cm K (E), but by early 1942 the advances of the German army were so rapid and deep that they were on the approaches to the Crimea. Ahead of them lay the naval base of Sevastopol, which was potentially a useful supply port and base for the southern German armies. The need for such a supply base was not very pressing, but what attracted the German operational planners was that Sevastopol was a heavily-fortified port. Around the perimeter of the city was a long chain of fortifications. some of them dating back to the days before the Crimean War of 1854-6 but others more modern, and near the sea coasts there were numerous heavy coastal .batteries. The place looked ideal for an investment and siege in the old manner, to be followed up by a huge assault which would demonstrate to the world the power of the German army. Soon the relatively light forces that advanced into the Crimea were supplemented by more and more troops and the German planners started to scour Europe for heavy guns to form an old-fashioned siege train.
For centuries it had been the task of the siege train to bombard a besieged fortress into submission or else open a breach for attacking troops to storm. The Germans decided to repeat this performance on a massive scale. From all corners of Europe the German army assembled a massive gun park of all types of artillery from small-calibre field guns up to pre World War I large-calibre howitzers. Some were German in origin but others were old captured weapons, and to these were added the modern embellishments of artillery rockets and super-heavy artillery. Into this category came the 60-cm (23.6-in) mobile mortars known as the Karl-Gerät, and it was realized that at last the propaganda coup could be topped by the first operational use of 'schwere Gustav'.
Accordingly the 80-cm K (E) trundled to the Crimea on specially re-laid track. Well ahead of its progress a small army of labourers started to prepare the gun's chosen firing position at Bakhchisaray, a small village outside Sevastopol.
Well over 1,500 men under the control of a German army engineer unit dug through a small knoll to form a wide railway cutting on an arc of double track, and the sides of the cutting were raised to provide cover and protection for the gun. On the approaches railway troops laboured to re-lay track and strengthen possible trouble points against the passing of the 'schwere Gustav'. Work on the eventual firing site reached the point where the area behind the curve of firing tracks resembled a small marshalling yard over 1. 2 km (0. 75 miles) long. It resembled a marshalling yard, and that was exactly what it was. In the area the 25 separate loads that formed the gun and its carriage had to be assembled and pushed and pulled into the right position and order. Farther to the rear were the accommodation areas where the numerous men of the gun crew lived and prepared for their task
The manpower involved in assembling 'Schwere Gustav' was large, Each of the 80-cm K (E)s had a complete detachment of no less than 1,420 men under the command of a full colonel. He had his own headquarters and planning staff, and there was the main gun crew which numbered about 500, most of whom were involved with the complicated ammunition care and handling. Once in action these 500 would remain with the gun, but the rest of the gun's manpower was made up from various units including an intelligence section to determine what targets to engage. Quite a number of troops were involved in the two light anti-aircraft defence battalions that always accompanied the gun when it travelled and also supplied manpower for some assembly tasks. Once the gun was in position these AA battalions warded off unwanted aerial intruders. Two guard companies constantly patrolled the perimeter of the gun position (at one time these companies were Romanian), and at all times there was a small group of civilian technicians from Krupp who dealt with the technical aspects of their monster charge and advised the soldiers. Railway troops and the usual administrative personnel added to the manpower total.
Even using this small army of men it took between three and six weeks to assemble the gun, even using the two I 10-tonne cranes that had been designed specially for the task. just getting the right sub-assembly load into position at the right time was a masterpiece of railway marshalling and planning, but eventually it was all sorted out and by early June 1942, 'schwere Gustav' was ready, along with the rest of the siege train with all their cumbersome carriages and ammunition emplaced ready to hand.
Firing commenced on June 5, 1942. 'Schwere Gustav' was but one voice in a huge choir that heralded one of the largest and heaviest artillery bombardments of all time. By the time Sevastopol fell early in July 1942 it was calculated that no fewer than 562,944 artillery projectiles had fallen on the port, the bulk of them from heavy-calibre guns and howitzers, and this total does not include the noisy storms of artillery rockets and the extra weight of the infantry's own unit artillery. How the civilians of Sevastopol survived it all can now be explained quite easily. They simply went underground. The city knew the bombardment was coming, for not only had their own party and other authorities told them what to expect, but the Germans constantly assailed them with radio broadcasts and other propaganda as to the wrath that was to befall them. By the time the real bombardment started they had already dug deep shelters both underground and in the walls of quarries and hillsides, and there they lived and remained for weeks, A surprising number survived it all.
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Landkreuzer P1000 Ratte