What are vacuum bombs and is Russia using them in Ukraine?

By David Hambling

According to the UK Ministry of Defence, Russia has confirmed that it has used the TOS-1A weapon system, which uses thermobaric rockets.

The use of highly destructive thermobaric weapons seems to be escalating the Russian invasion of Ukraine. The Ukrainian ambassador to the US told reporters on February 28th that Russia is using weapons and a number of images posted online have shown missiles.

The use of these weapons in populated areas would be a violation of international humanitarian law according to an adviser to a Netherlands-based peace organisation.

High explosives break apart on detonation, releasing energy. In contrast, thermobaric explosives typically involve powdered metal that burns in air, creating an intense fireball with a shockwave at its leading edge.

After the initial explosion, a low-pressure zone sucks back towards the explosion site, which is why thermobarics are sometimes called vacuum bombs. The push-pull effect can be very damaging to structures, but the main reason thermobaric explosions are so destructive is the pressure wave.

This is more dangerous than the brief pulse produced by high explosives, which can cause injuries in the lungs, and can cause a massive embolism, which can be fatal.

Read more: Would Vladimir Putin really use nuclear weapons in Ukraine?

A long thermobaric blast can go around corners, making it effective against trenches and tunnels, which would provide shelter from a normal blast.

Images posted by Ukrainian civilians seem to show that Russia has deployed a tracked vehicle with 24 rockets and thermobaric warheads. A single TOS-1 will cover an area of 200 by 300 metres.

Garlasco says that Russia has a record of using thermobarics against cities and towns in Syria, causing widespread civilian harm. Dozens of civilians were killed in the Russian attacks in Eastern Ghouta.

According to Garlasco, international humanitarian law means that weapons must be used against military targets and that they must be used proportionally so that the harm is in line with the military gain.

Garlasco says it is hard to understand how the vehicle can be used in a city.

Western armies have used smaller, individual thermobaric weapons in Iraq and elsewhere, but these were used against specific military targets such as caves and buildings in urban combat.

The TOS-1 is an indirect fire rocket that has the potential to cause widespread death and destruction in towns and cities. Garlasco says that such weapons should not be used in areas with high concentrations of civilians.