Heavy flamethrower multiple rocket launcher system Solntsepyok

TOS (Russian: тяжелая огнеметная система) is a family of Russian heavy flamethrower systems of 220-mm caliber. They fire incendiary or thermobaric ammunition.

The idea of developing a powerful MLRS for the use of incendiary and thermobaric missiles originated in the USSR in the late 1970s. Work on this project was entrusted to the Design Bureau of Transport Engineering (Omsk). The new system had a factory name, Object 634 or TOS-1. The complex consisted of 30 guides on the chassis of a T-72 tank and a TZM charging machine based on KrAZ-255B. The use of a tank base allowed the complex to be used directly in combat. So, it was a forced step, and the combat range of the system was too short - only 3.5 kilometers..

The system was intended to disable lightly armored and automotive vehicles, set fire to and destroy structures and buildings, destroy enemy manpower (located in open areas and in fortifications) with shrapnel and shock waves, and cause fires.

Even as of 2022, after its repeated use in several wars, the system has not been officially adopted by artillery units, but is listed in the staffs of auxiliary units: radiation, chemical, and biological defense troops. The system was unofficially called “Pinocchio” in the troops because of its distinctive appearance.

Between December 1988 and February 1989, two TOS-1 vehicles took part in combat operations in the Charikar Valley and South Salangan (during Operation Typhoon). The tactics of using MLRS consisted of a sudden fire attack on the enemy, rapid withdrawal of combat vehicles and guards from under possible fire, and retreat to the permanent deployment points of Soviet troops. In fact, the chosen firing position was attacked only once, and the time spent by the combat vehicle in the firing position was reduced to a minimum.

• On June 4, 2016, a heavy flamethrower system TOS-1A “Solntsepek” was destroyed in Syria near Aleppo.
• In the fall of 2020, during the second Karabakh war, the Azerbaijani armed forces destroyed the Armenian TOS-1A with the help of the Bayraktar TB2 UAV.
• On March 1, 2022, the Armed Forces of Ukraine captured a heavy flamethrower system TOS-1A “Solntsepyok” and its spare parts.
• On March 3, 2022, a transport-loading vehicle from the TOS-1A “Solntsepyok” complex was seized by local residents in the Chernihiv region.
• On March 19, 2022, a vehicle from the TOS-1A “Solntsepyok” complex was destroyed.
• On March 26, 2022, the Armed Forces of Ukraine captured a TOS-1A Solntsepyok vehicle in Husarivka (Balakliya district).
• On March 29, 2022, the Ukrainian military destroyed a heavy flamethrower system TOS-1A “Solntsepyok” from the Stugna-P ATGM.
• On April 1, 2022, the Ukrainian Armed Forces captured a second heavy flamethrower system TOS-1A “Solntsepyok”.
• On April 2, 2022, the Armed Forces of Ukraine captured another heavy flamethrower system TOS-1A “Solntsepyok”.
• On April 15, 2022, the Armed Forces of Ukraine captured another TOS-1A “Solntsepyok” flamethrower system with a full ammunition package.
• On May 20, 2022, the Armed Forces of Ukraine destroyed another TOS-1A Solntsepyok MLRS with the help of the Stugna-P ATGM.
• At least one TOS-1A “Solntsepyok” MLRS was destroyed during the Kharkiv counteroffensive of the Armed Forces of Ukraine in September 2022.

The effect of a volumetric explosion of dust and gas or aerosol clouds was discovered by mankind in ancient times. Mill explosions were not a rare occurrence. It was enough to reach a critical concentration of flour dust in the mill room, and the lighting was by candlelight, as the mill was literally blown to pieces by a powerful explosion.

Miners are well aware of how fine coal dust explodes in the air of mine workings. Similarly, ultrafine sawdust sprayed in the air of furniture factory workshops, powdered sugar in sugar factories, aerosol clouds of ordinary oil, fine dust in pharmaceutical factories, and many other fine combustible materials sprayed in the air explode.

Aeronautical thermobaric munition in a section

The principle of operation of a volumetric explosive munition is based on the detonation of a cloud of flammable aerosol. Due to the large size of the cloud (orders of magnitude larger than the size of charges with condensed explosives), the shock wave retains its devastating effect at a considerable distance from the center of the cloud.

The explosion occurs in two stages:

1. a small charge of a conventional explosive is detonated by a detonator, usually a non-contact detonator (its purpose is to evenly distribute the combustible over the cloud volume);
2. with a short delay (90-500 milliseconds), a second charge (spark charge) (or several charges) is detonated, which causes the aerosol to detonate. The main destruction is caused by a supersonic air shock wave (aerosol cloud detonation speed of 1500-3000 m/s) and high temperature (depending on the caloric content of the fuel). High-calorie propellants are used as the main charge in thermobaric munitions:
   • ethylene oxide
   • acetylene peroxide
   • diborane (or borohydrides)
   • dimethyl hydrazine
   • propane
   • propyl nitrate, zopropyl nitrate
   • liquid heptane
   • gasoline

Various formulations are also used, such as the American MAPP:

• 18 % propane
• 7.4 % propylene
• 10 % of normal butane
• 26.1 % propadiene
• 37 % methyl acetylene
• <1 % ethane, cyclopropane and unsaturated butanes

Fuel for TBMs must meet several criteria:

• High specific heating value of the aerosol
• Large volume of gaseous explosion products (explosiveness)
• Minimum viscosity for fast spraying

Thermobaric munitions have two factors of destructionя:

1. the shock wave;
2. high temperature in the area of explosion (up to 1000 °C), which can cause ignition of surrounding combustible materials.

The effect of a TBM explosion on a person is terrible: the shock wave causes contusion, ruptured eardrums, nosebleeds, lung barotrauma of varying degrees, often with hemorrhages in the lungs, and bone fractures. The clinical picture is complicated by extensive burns of varying degrees and thermal shock. There have been cases of lungs completely burning out from the inside.

Modern TBMs are typically a thin-walled cylinder, 2-3 times longer than its diameter, filled with high-calorie propellant and designed to be sprayed at an optimum height above the surface (7-10m). The initiating detonator, which usually weighs 1-2% of the propellant weight, is located along the symmetry axis of the munition. Its explosion destroys the casing and atomizes the propellant in the air to form an explosive air-fuel aerosol mixture. Ideally, the aerosol cloud should be detonated as soon as it reaches the size that ensures optimal combustion. The actual volumetric detonation does not occur after the detonation of the initiating detonator (without oxygen, the propellant does not burn), but after the detonation of secondary spark detonators (located in the tail of the munition), with a delay of 125 to 500 milliseconds. The longer the delay, the greater the likelihood of the cloud wearing off or losing its critical concentration; the shorter the delay, the higher the risk of incomplete combustion of the mixture due to lack of oxygen. Therefore, designers are experimenting, often preferring a minimum 125-millisecond delay. To detonate an aerosol cloud, both traditional delayed detonators and a chemical method are used (bromine or chlorine trifluoride is self-igniting upon contact with fuel).

The specific heat of combustion of high-calorie propellants (44-52 MJ/kg) is much higher than the heat of combustion of explosive mixtures with an oxidizer (2-25 MJ/kg). In order for the combustion energy to be at least partially transferred to the shock wave, it is necessary that it be completed within a time of ~2R/c (R is the radius of the cloud, c is the speed of sound in the air), otherwise most of the combustion energy of aerosol propellant is dissipated as heat.

Differences between thermobaric and conventional munitions:

• TNTs are 5-8 times stronger than TNT in terms of shock wave strength and have a huge ability to destroy enemy manpower. However, they are not a universal means of destruction and the extent of their use depends on what type of munition or weapon is appropriate and most effective in each case.
• TNTs do not have fragmentation or cumulative effects on the target.
• The ability of TBMs to crush and destroy objects by exploding a cloud of fuel-air aerosol mixture is quite small. All destruction in this case is only secondary, i.e., occurs during the release process due to collision with other objects, the ground, etc.
• For a volumetric explosion, a sufficiently large free volume of space is required and the presence of oxygen is mandatory.
• In conditions of strong winds and continuous rain, the aerosol cloud either does not form at all or is strongly dispersed.

Differences between thermobaric and nuclear munitions:

• A TBM explosion does not cause ionizing radiation and radiation contamination of the area;
• TBMs are much simpler and cheaper to produce and store than nuclear munitions.

The Soviet army began using TBMs against Afghan guerrillas in the winter of 1983, particularly in the Pandhera Gorge, where ODABs dropped by Tu-95MS strategic bombers destroyed several villages. At the same time, the RPO-A flamethrower with a thermobaric grenade became widely used by special forces.