The SS Richard Montgomery: the explosive WWII wreck beneath the Thames

The WWII ship, the SS Richard Montgomery, carries cargo which could blow up at any moment

If you walk along the banks of the River Thames in Sheerness, Kent, you can see three ship’s masts sticking out from the water. At first glance, they look harmless. They look like a rusting relic of a disaster from days past. But if you look closer, you’ll see signs warning of the danger beneath. The masts belong to the SS Richard Montgomery. The ship was a US Liberty ship used during World War Two. It arrived in the Thames Estuary in August 1944 with a hold stocked full of munitions. However, the severe weather caused it to drag its anchor and fill with water.

As the tide receded. the ship was left stranded on the sandbank. Its hull soon began to buckle and crack under the weight of the cargo. A salvage operation was quickly launched. But, in September 1944, this had to be abandoned when the ship finally broke in two and sank. Half of the cargo had successfully been removed, but the rest – an estimated 1,400 tons of munitions – is still lying on the riverbed today.

Potential detonation

If the SS Richard Montgomery detonates it could send a catastrophic tsunami up the Thames, destroying everything in its path. One of the biggest risks of detonation is the collapse of the remaining wreckage. For this reason, the UK’s Maritime and Coastguard Agency conducts an annual survey on the SS Richard Montgomery its condition. Recent findings show that the wreck is indeed slowly deteriorating. However, as removing the ship’s cargo is likely to be a complicated and dangerous mission, it is safer to leave it alone for now.

How the wreck is monitored

The SS Richard Montgomery is surveyed every year using two key techniques. Multi-beam sonar studies the submerged parts of the vessel and works by emitting sound waves in the direction of the ship. The sonar then measures how long it takes for them to bounce back.

Meanwhile, laser scanning is used to study the parts of the vessel that is above the water and works in much the same way but with lasers instead of sound waves. The data recorded using both methods can then be combined and turned into a detailed 3D image of the ship. A third instrument, an ultrasonic thickness gauge, is also used every ten years to assess the thickness of the ship’s hull by analysing how ultrasonic sound waves travel through it.

This article was originally published in How It Works issue 115, written by Jo Stass  

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