Deadly physics: The “Herald of Free Enterprise” ferry disaster of 1987.

Thirty-eight years ago last week, on March 6, 1987, a terrible and completely preventable tragedy occurred in the North Sea, just off the Belgian port of Zeebrugge. At about 6:00 that evening a car ferry called the Herald of Free Enterprise, owned and operated by Townsend Thoresen Company, left the dock at Zeebrugge with 459 passengers, their cars and a number of cargo trucks on board. She was headed for Dover, on the coast of England. Many of the passengers had been tempted by a recent advertisement in the British newspapers offering super-cheap trips to the continent and back. Unbeknownst to them, 193 of them had taken their last step on dry land. Minutes after leaving port the Herald of Free Enterprise took on water and capsized, and for an abysmally stupid and outrageous reason: a crew member neglected to close the huge doors at the front of the ship before it left the dock. Instead of doing his duty, this crew member went back to his cabin to sleep.

Gross human error was unquestionably the cause of the Herald of Free Enterprise disaster, but explaining just how the crewman’s fatal mistake ultimately caused 193 deaths takes a bit of physics to understand. Large-scale car ferries of this kind, “RO-RO” ships (roll-on, roll-off), are basically big floating garages. Passengers drove their cars aboard, got out, went to a passenger area for the duration of the voyage, then at their destination would drive their cars off. I once crossed the English Channel on such a ferry from Portsmouth to Calais, though I was on foot. The Herald of Free Enterprise, built in 1980, had two passenger car decks meant for simultaneous loading from two different angles. However, the port facilities at Zeebrugge weren’t built for this. The ferry operators used the lower deck only, but in order to couple with the ramp at Zeebrugge, the ship’s front ballast tanks were filled. In simpler terms, the ship’s bow was sitting lower in the water than it normally did.