The V-3 Super Cannon Could Hit London from France

The V-3 is a 130 meter long artillery piece designed to bombard London from the Pas-de-Calais region of France, further extending the reach of the long-range bombardment capabilities already demonstrated by the V-1 flying bomb and V-2 rocket.

The V-3 was notable for its use of the multi-charge principle, which aimed to achieve unprecedented ranges for artillery fire

However, the V-3 cannon’s operational impact was negligible, as it was troubled by technical challenges, logistical issues, and the Allied forces’ strategic response.

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Background

During the Second World War, Germany invested large amounts of resources into “V”, or “Vengeance” (Vergeltungswaffen) weapons. They aimed to retaliate against Allied targets as a form of psychological warfare and strategic bombing.

Germany hoped that these efforts would turn the tide of the war through technological innovation, aiming to demoralize the Allied population and force governments into negotiating peace.

The most well-known of these weapons were the V-1 flying bomb and the V-2 rocket, which were early, practical cruise and ballistic missiles.

But there is a lesser known Vengeance weapon, the V-3.

A V-2 rocket launching, on the north-east German coast in 1943. von-Braun was the projects leader.

The V-3 cannon was a supergun designed for long-range bombardment, intended to shell London from installations in the Pas-de-Calais region of France. The project was spearheaded by German engineer August Cönders, who proposed a design that would utilise the multi-charge principle.

The multi-charge principle is a method of increasing the velocity and range of a projectile beyond the capabilities of traditional single-explosion cannons. This is achieved through the use of additional propellant charges placed along the length of the cannon’s barrel.

These charges are detonated at precisely timed intervals, ideally when the projectile is just past them. Each detonation provides an additional boost of acceleration to the projectile, significantly increasing its muzzle velocity by the time it exits the barrel.

Cross-sectional drawing of a multi-charge gun. The angled protrusions along the barrel contain additional charges that boost the projectile as it passes by.

This allows for a greater range and speed of the projectile, theoretically enabling artillery to hit targets at distances previously unachievable with conventional artillery. However, the complexity of timing the explosions and the engineering challenges of constructing such a weapon limited its practical application and effectiveness.

The principle dates back to the mid 1800s, but as of 1940, it hadn’t yet been proven practical. Cönders hoped that he could tame the idea and use it to relentlessly bombard London from France with volleys of projectiles that couldn’t be intercepted.

After a rather short period of testing, the construction of a full scale weapon was greenlit in 1943. The project quickly became bogged down with engineering challenges though, namely getting the secondary charges to ignite at exactly the right time.

The V-3 prototype. Note the charges positioned on the sides of the barrel.

Another issue often faced in this type of gun was obturation; the seal between the projectile and the barrel. In multi-charge weapons, if the initial blast can bypass the projectile slightly, it’ll ignite the secondary charges too early and actually slow the projectile down.

This was solved on the V-3 by placing a piston between the projectile and the initial charge to seal it from the rest of the barrel. To achieve enough velocity, a large quantity of charges were needed, as was a very long barrel. The charges were positioned either side of the barrel in a staggered arrangement.

While the weapon was still very much in development, the construction of a firing site began in France known as the Fortress of Mimoyecques, near Calais,

Due to the enormous size and rather impractical nature of the barrel, the V-3 could not be aimed. It had to be constructed at a set angle and fixed in place.

Section of V-3 barrel.

The V-3 Design

The V-3 was a 150 mm gun, with a 130 meter long smoothbore barrel. At the heart of the V-3’s design were the secondary propellant charges placed in side chambers along the barrel’s length.

These charges were engineered to detonate at precisely the right moment when the projectile passed by, providing additional acceleration. The timing mechanism for these charges was critical; it had to be incredibly accurate to ensure that each charge provided the maximum boost to the projectile’s velocity without causing damage to the weapon or deviating the projectile off course.

The full-scale test weapon, located in modern-day Poland.

The barrel was constructed in sections, making the replacement of damaged portions simple. While the gun was planned to have a range of over 100 miles, set backs with the project meant the gun was never able to be tested at full capacity.

A version that was half as long was used, firing 1.8-meter long, fin stabilised sabot projectiles that each contained just under 10 kg of explosives. This shorter version managed to obtain velocities of almost 950 meters per second, and a range of at least 27 miles.

V-3 projectile.

Fortress of Mimoyecques

The V-3’s main site was meant to be near the village of Mimoyecques in Pas-de-Calais, France. This area was already occupied by V-1 and V-2 launch sites.

The construction of the Fortress of Mimoyecques began in 1943, under the strictest secrecy. The site was chosen for its strategic location, nestled within a limestone hill, which provided natural protection and camouflage.

The plan was to construct a massive underground bunker system that would house several V-3 cannons. The construction involved the excavation of a complex network of tunnels and chambers deep within the hill that would be serviced by an underground railway line.

Drawing depicting the planned V-3 weapon site at Mimoyecques.

The facility was designed to include five parallel shafts that would each contain five stacked barrels, for a total of 50 guns all pointed at London. The shafts, and therefore the guns, were angled at 50 degrees. The complex was to have living quarters for the crew, ammunition storage, and ventilation systems, making it a self-sufficient military installation.

The strategic significance of the Fortress of Mimoyecques and its potential to damage London did not go unnoticed by the Allied forces. In fact, they noticed work at the site almost as soon as it began.

However, they were not sure what the site’s purpose was, and believed it was a launch facility for V-2 rockets. As part of Operation Crossbow, a concerted effort to counter the German V-weapons threat, the Allies conducted aerial attacks against the site.

The moonscape of craters over the Fortress of Mimoyecques after Allied bombing, taken in August 1944. The gun opening is circled near the upper right corner.

These bombing raids, which began in late 1943, aimed at disrupting construction and neutralizing the threat. Half of the planned shafts were abandoned after damage, with the Germans instead opting to direct all their resources on the remaining shafts.

However, even this was mostly brought to an end when the RAF’s 617 Squadron, famously known as the “Dambusters,” deployed “Tallboy” deep-penetration bombs against the facility in July 1944.

The precision and power of the attack caused extensive damage to the tunnels and infrastructure, effectively halting the project and ensuring that the V-3 cannon would never become operational from this site.

The extensive network of tunnels at the site can still be visited today. Image by CC BY-SA 3.0.

Shortened Version

With the V-3s at the Fortress of Mimoyecques out of action, work switched to a smaller scale effort in German territory.

Two guns, half the length of the original V-3s, were constructed near Lampaden in western Germany. They were aimed at the city of Luxembourg, around 27 miles away. The first rounds were fired at the end of 1944, and until late February 1945, the site would fire a total of 183 rounds.

Concrete supports that once held the experimental V-3 on a hillside in Poland. Image by Adam Z CC BY-SA 3.0.

Approximately 140 rounds hit Luxembourg, resulting in the deaths of 10 people. Of course, any number is a tragedy, but this is a rather low exchange for the considerable effort that went into designing, building and preparing the guns.

The site was captured by the Allies shortly after firing stopped, marking the end of the V-3’s short, and disappointing service.