The Kursk Submarine Disaster: The Hidden Science Behind One of the Sea's Deadliest Tragedies

The Kursk wasn't sunk by an enemy, a collision, or a storm. It was undone by chemistry — a chain of ordinary reactions that began with an unstable torpedo fuel, was reconstructed by seismographs thousands of kilometres away, and ended, hours later, with the very device meant to keep 23 trapped men alive.

On the morning of 12 August 2000, the Barents Sea shook twice. Aboard the battlecruiser Pyotr Velikiy, flagship of Russia's Northern Fleet and the centrepiece of the country's largest naval exercise in more than a decade, sailors felt the shocks and assumed they were part of the wargame. They were not. A few kilometres away and a hundred metres down, one of the most powerful submarines ever built was already dying.

The Kursk — a nuclear-powered Oscar II–class cruise-missile submarine, longer than a football pitch and designed to sink aircraft carriers — went to the bottom with all 118 men aboard. In the years since, the disaster has been wrapped in Cold War echoes and political scandal. But the actual mechanism of what happened is stranger and, in a way, sadder than any of that. From the first blast to the last breath, the Kursk was destroyed not by a weapon or the sea, but by chemistry — three times over. To understand the disaster, you have to follow the reactions.

A fuel that wants to come apart

The story begins with a substance most people have never heard of: high-test peroxide, or HTP.

HTP is simply hydrogen peroxide — the same molecule sold in dilute form as an antiseptic — concentrated to enormous strength. At that concentration it makes a superb torpedo propellant: it carries its own oxygen, burns fiercely with fuel, and leaves almost no telltale wake behind a running torpedo. Several navies were tempted by it in the mid-twentieth century for exactly those reasons.

The problem is that concentrated hydrogen peroxide does not want to stay hydrogen peroxide. It sits in a chemically restless state, primed to break down into water and oxygen, releasing heat as it goes. Normally it does this slowly. But introduce almost any catalyst — a fleck of rust, a trace of copper, a dirty metal surface — and the breakdown becomes fast, hot, and self-feeding. The heat speeds the reaction, which makes more heat, and the liquid flashes to a violently expanding cloud of superheated steam and pure oxygen.

Navies learned this the hard way. In 1955 the British submarine HMS Sidon was destroyed in harbour when an HTP-powered torpedo ruptured and detonated, killing thirteen men. The Royal Navy drew the obvious conclusion and abandoned HTP torpedoes altogether. The Soviet, and later Russian, navy kept using them. On the Kursk, four and a half decades after Sidon, the same chemistry was waiting in a practice torpedo.

The first ninety seconds

That morning the crew was preparing to fire dummy torpedoes at the fleet. As a large Type 65-76 "Kit" practice torpedo was being handled, a defective weld in its casing let its high-test peroxide leak out — into the confined space of the weapon and its tube, onto exactly the kind of metal surfaces that trigger runaway decomposition.

What followed took seconds. The leaking peroxide catalytically tore itself apart, spraying the torpedo's interior with superheated water and oxygen under mounting pressure until the casing burst and the kerosene fuel tank ruptured and ignited. This first explosion was, by the standards of what came next, small — on the order of a hundred to two hundred kilograms of TNT — but its effects inside the hull were savage, with temperatures estimated at around 2,700 °C. It ripped through the torpedo room in the bow, wrecked the control room, and almost certainly killed or incapacitated the men at the submarine's controls in an instant.

The Kursk was now a crippled boat with a fire raging in a compartment full of live weapons. And it had about two minutes left.

135 seconds: the number that told the story

Here the science turns forensic, and genuinely remarkable.

The first, smaller explosion was still large enough to send a faint tremor through the seabed and the water. Seismic and acoustic sensors far away registered it. Then, precisely 135 seconds later — two minutes and fifteen seconds — they registered a second event, vastly larger. In the heat of the bow fire, somewhere between five and seven torpedo warheads had cooked off at once. The blast was equivalent to several tonnes of TNT, and it was picked up by seismograph stations across northern Europe and by arrays as far away as Alaska and Canada.

Think about what that means. Scientists sitting at instruments thousands of kilometres from the Barents Sea recorded the Kursk's destruction as two clean pulses on a rolling drum — and the exact gap between them, 135 seconds, was preserved in the rock. That seismic signature became one of the most important pieces of evidence in the entire investigation. Its shape — two sharp, distinct explosions rather than the messy signal a collision or a general fire would produce — is a large part of how investigators reconstructed the sequence and ruled out the rival theory, popular early on, that the Kursk had struck a NATO submarine. The sea itself had kept the record.

Why it sank — and why it didn't become a nuclear catastrophe

The second explosion destroyed much of the forward half of the submarine. The sea poured in through the shattered bow, and the Kursk settled onto the seabed at a depth of around 108 metres, tilted some twenty degrees. As many as ninety-five of the crew are thought to have died in the two blasts and the immediate flooding.

But amid the catastrophe, one part of the boat's engineering did exactly what it was designed to do. A heavily reinforced bulkhead separated the weapons and forward compartments from the reactor spaces, and behind it the two nuclear reactors shut themselves down automatically — control rods dropping in to halt the chain reaction the moment the emergency hit. Despite a violent explosion, a sinking, and a year on the seabed before recovery, the Kursk's reactors never leaked; investigators later described them as having behaved essentially perfectly. The disaster killed 118 people, but it was not, and never became, a nuclear accident. In the middle of a story about chemistry going wrong, that is one system of physics going right.

The men in the ninth compartment

Toward the stern, beyond the reach of the blasts, some of the crew were still alive.

Twenty-three men from the rear compartments survived the explosions and gathered in the ninth compartment, at the very back of the boat, because it held an escape hatch. In charge was Captain-Lieutenant Dmitri Kolesnikov, the twenty-seven-year-old head of the turbine department and one of the last surviving officers aboard. In the dark — the reactors had shut down, and emergency power would not last long — with the water rising and the air slowly thickening with carbon dioxide, he did something extraordinarily disciplined. He wrote.

One of his notes listed the twenty-three men who had made it to the compartment. Another, timed at 15:15 — more than four hours after the explosion — was written by feel in the dark, acknowledging that their chances were slim and sending word to those above, and to his wife. Other evidence recovered from the compartment indicates that some of the men were still alive at least six hours after the ship went down. Whatever else is disputed about the Kursk, this much is not: for hours, in the cold and the dark at the bottom of the sea, men were alive and waiting.

The chemistry that was supposed to save them

To stay alive in a sealed compartment, the survivors needed to do two things: get rid of the carbon dioxide they were exhaling, and replace the oxygen they were using up. Submarines carry an elegant chemical solution to exactly this problem — the same basic technology used on spacecraft. Cartridges of potassium superoxide react with the carbon dioxide and moisture in exhaled breath and, in doing so, release fresh oxygen. In effect, the chemical drinks in the gas that is suffocating you and gives back the gas that keeps you alive. The men in the ninth compartment were using these cartridges to buy time.

But potassium superoxide is, like the peroxide that started the disaster, fiercely reactive — and it does not tolerate contact with oil and water. The ninth compartment was flooding slowly, and a film of oil lay on the rising water. At some point a cartridge came into contact with that oily seawater. The reaction was immediate and violent: a flash fire that swept the compartment and consumed the very oxygen the men were fighting to preserve. The evidence suggests a few of them briefly survived the flames by dropping beneath the water — fire marks show it stood at about waist height — but the fire had burned the breathable air out of the space. The last survivors died of asphyxiation.

It is a devastating symmetry. The same broad kind of chemistry — a violent, oxygen-driven reaction touched off by contamination — that destroyed the front of the boat also killed the last men in the back of it. Chemistry sank the Kursk, and chemistry took the crew that the explosions had spared.

The rescue that came too late

The final layer of the tragedy is the one that had nothing to do with chemistry at all.

British and Norwegian forces offered help almost immediately. Russia declined, and days passed. The Russian Navy's own rescue vehicles — ageing diving bells and submersibles — repeatedly failed to lock onto the Kursk's escape hatch in the cold and the current. Only after five days did the Russian leadership accept foreign assistance; President Vladimir Putin authorised it while still at a seaside resort, a decision that drew fierce public criticism at home and abroad. When Norwegian divers finally opened the hatch to the ninth compartment on 21 August, seven days after the sinking, they found it flooded, and no one alive.

By the best forensic reckoning, the men had already been dead for days by the time the argument over who would rescue them was resolved. The delay did not, in the end, cost lives that a faster response would have saved. But it turned a mechanical disaster into a national scandal, and it is a large part of why the name Kursk still carries such weight. The chemistry was merciless and fast; the human response was slow — and the contrast is the thing people remember.

What the Kursk really was

The Kursk is often filed away as a relic of great-power rivalry, a Cold War submarine lost in murky circumstances. The truth is quieter and, once you see it, harder to forget. Every step of the disaster was an ordinary chemical reaction, unremarkable on its own: concentrated peroxide breaking down into water and oxygen; warheads burning in a fire; a life-support cartridge making oxygen from carbon dioxide. Line those reactions up in a steel tube under the sea, in the wrong order, and they destroy one of the most formidable machines ever built and kill everyone inside it.

The wreck was raised the following year, the crew recovered and buried, and torpedoes running on high-test peroxide have almost entirely vanished from the world's navies — the last, belated verdict on a fuel that could never quite be trusted. The sea did not sink the Kursk. Its own chemistry did. Remembering the 118 men aboard means, in part, understanding the exact chain of reactions that took them — because behind almost every disaster at sea, there is a hidden science, and this one was written in it from beginning to end.

Sources and further reading

• "Kursk submarine disaster," Wikipedia — timeline, the 65-76 "Kit" torpedo, the HTP/faulty-weld finding, the second explosion (~3–7 tonnes TNT), and the recovery.

• Official Russian investigation (concluded July 2002) as reported by CBS News and others — attributing the first explosion to a torpedo malfunction and high-test peroxide, and ruling out a NATO collision.

• Royal Society of Chemistry education materials on the Kursk and high-test peroxide — on the catalytic decomposition of HTP and the parallel to the 1955 HMS Sidon disaster.

• Reporting and analysis on the seismic record of the disaster (NORSAR and other stations) — establishing the 135-second interval between the two explosions.

• Accounts of the recovery by Smit Salvage / Mammoet and the official findings on the ninth compartment — the 23 survivors, Captain-Lieutenant Dmitri Kolesnikov's notes, and the potassium superoxide cartridge that triggered the fatal flash fire.

• Robert Moore, A Time to Die: The Untold Story of the Kursk Tragedy — a detailed narrative reconstruction of the disaster and the rescue attempt.