Thursday 25 January 2024

Flame War

A search for methods to combat tanks began as soon as the tanks themselves reached the battlefield. The first anti-tank rifles and anti-tank cannons were already created during the First World War. They turned out to be quite bulky and could not be used by an individual to combat armoured vehicles. The Germans were the first to design improvised anti-tank grenades that could be used by one person. Bottles of incendiary fluid came later. They also turned up during the First World War, but then they were used for a very different purpose. These bottles were first used against armoured vehicles in Ethiopia and then in Spain. They were quite an effective weapon against first Italian CV 33 tankettes and then Republican T-26 tanks. The Japanese also used bottles filled with gasoline during the battles at Lake Hasan and Khalkhi-Gol. "Bottle artillery" proved its effectiveness once again.

Trials of Molotov cocktails against an A-34 tank, April 1940. The trials were not entirely successful.

Bottles with incendiary fluid reached widespread use in the Winter War. The Finns used anti-tank grenades and bottles primarily against the engine deck. This is when the nickname "Molotov cocktail" became popular. The T-26 suffered against these weapons, as a successful hit led to the engine stalling and could even cause a fire. Special covers were developed for T-26 tanks that protected the air intakes on the engine deck, but hey appeared after the Winter War.

Experimental T-34 (A-34) tanks were also tested against "bottle artillery" in April of 1940. The trials were not entirely successful. Burning liquid managed to enter the engine compartment and cause damage. The issue of improving protection was raised, but the rush died down by 1941. As usual, a new wave of activity was only ignited by the start of another war.

An illustration on using Molotov cocktails from the field manual, August 1941. A photo of the Nb.Fz. is inserted into the image.

Before the start of the Great Patriotic War, anti-tank artillery was expected to defeat any enemy armoured vehicles. The fact that this was a mistake became clear very quickly. Work on anti-tank rifles quickly began and the RPG-40 grenade developed at GSKB-30 under the direction of M.I. Puzerev was accepted into service on July 7th, 1941. On the same day, Stalin signed GKO decree #43ss "On anti-tank incendiary grenades (bottles)". According to the degree, development of bottles with incendiary fluid would begin at NII-6 on July 10th. 120,000 bottles were expected to be produced daily. In reality, these bottles were already being assembled and used from the first days of the war and the decree merely expanded this process to an industrial scale. The issue of protecting Soviet tanks from this weapon was also raised. This was a serious issue, since the Winter War was not yet forgotten. Several institutions were tasked with developing protection, including the NIBT Proving Grounds.

There were several proposals for different types of protection including special firefighting tanks and fire suppressing paint.

One of the institutions tasked with the development of this protection was the NKVD Central Scientific Research Institute of Firefighting (modern day NII of Firefighting). Having analyzed the task, the TsNIIPO NKVD gave several suggestions. Some of them were quite exotic, for instance the conversion of chemical tanks into firefighting tanks. Using 5L chemical fire extinguishers was simpler. 2-3 fire extinguishers filled with foam could be carried in one tank. Other types of fire extinguishers and fireproof paint were also proposed. Special trials would determine which variant was the most effective.

Result of a bottle filled with #1 fluid hitting the front of a BT-7 tank.

This issue was reviewed at a meeting attended by S.V. Kaftanov, a GKO science attaché. It was decided at the meeting to urgently test various firefighting methods. The due date was August 15th, 1941. The NIBT Proving Grounds was chosen as the location where methods developed by the TsNIIPO NKVD and Red Army Chemical Defense Academy would be tested. A BT-7 tank and the hull of a T-40 amphibious tank were chosen as targets. Tanks were attacked with bottles filled with #1 and KS fluid developed at NII-6. The BT-7 was hit with #1 fluid and the T-40 was hit with KS fluid. This separation was also meant to test different methods of putting out different types of flammable fluids. The design of the fire extinguishers was also different. The crew would begin to put out the fire 20 seconds after the bottle hit in ever case to let the fire spread. 

Putting out the fire with a tetrachloride fire extinguisher.

The BT-7 was tested first. To make the trials as realistic as possible, the engine was running. It took 45 seconds to put out the fire with a 2.5L tetrachloride fire extinguisher. 50% of the fire extinguisher's fluid was used up, shot both from the turret hatch and the pistol port. 

It took 40 seconds to put out the fire with the 4L Bogatyr fire extinguisher. The operator was located outside of the tank. In this case, the fire extinguisher was fully expended. Throwing half-liter bottles filled with tetrachloride at the fire also put it out after 40 seconds. The best result was given by special ampoules developed by the Chemical Defense Academy, which put out the fire in 30 seconds when thrown out of the turret hatch.

Throwing tetrachloride ampoules.

The ampoules worked best in the second stage of the trials when the bottle with #1 fluid was thrown on the engine deck. Two ampoules put out the fire in 15 seconds. The fire did not even have time to enter the engine compartment. Bundles of carbon dioxide fire extinguishers used inside the tank and other types of fire extinguishers used outside did not work as well. The carbon dioxide fire extinguisher extinguished the fire in 75 seconds, but the fire entered the engine compartment and the engine stalled. The tetrachloride fire extinguisher took more time, 80 seconds. The engine also stalled from the burning fluid entering its compartment.

Putting out the fire on the engine deck.

The KS fluid used against the T-40 tank hull was harder to extinguish. The Bogatyr fire extinguisher put out the fire in 70 seconds, but the fire ignited again afterwards. A copper sulfate mixture put out the fire in 135 seconds after 8 bottles with it were thrown. Thanks to the white phosphorous in the KS fluid, it reignited afterwards. An iron chloride compound took the same 135 seconds and 5 bottles to put out the fire. A calcium chloride compound took 115 seconds and 6 bottles. 4 bottles of Bentonite could put out the fire in 100 seconds, but only temporarily. Even after being hosed down with water three times, the white phosphorous continued to burn for a whole day. It seems that the NIBT Proving Grounds had a hunch about this when they allocated just a hull instead of a whole tank. The BT-7 would have simply burned out completely.

Putting out KS fluid proved very difficult.

As a result of the trials, tetrachloride was chosen as the most effective means of fighting #1 fluid. Thin-walled bottles would be used instead of special ampoules. The copper sulfate compound was found to be the most effective against KS fluid, but with some nuances. The commission admitted that there was no universal method. The GABTU proposed to develop a rack of fire extinguishers and put it into production, but this never happened. September was a difficult time when there were few resources to spare for these side projects, plus it turned out that German tanks suffered from Molotov cocktails more than Soviet ones anyway. Protection from Molotov cocktails ended up on the long list of projects that were lost in the chaotic first months of the war.

Original article by Yuri Pasholok.

1 comment:

  1. Carbon Tet? Not exactly a chemical I'd want to have in a breakable container near me (toxic, absorbed directly through the skin, carcinogen, the works). Plus oxidation (burning) can produce phosgene, one of the poisonous gases used in WWI.