Why did the Titanic sink? What really went wrong

Why did the Titanic sink? On the night of 14 April 1912, steaming at about 22 knots through waters it had been warned held ice, the liner struck an iceberg that opened its hull along the starboard bow. Water entered six forward compartments, two more than its design could survive, and it sank 2 hours and 40 minutes later. It carried lifeboats for only about half the people aboard, and about 1,500 died.

In short

• No single mistake sank the Titanic: speed, missed warnings, a glancing blow below the waterline and a design limit lined up.
• The ship could float with four forward compartments flooded. The iceberg opened six, so sinking was certain within minutes of the collision.
• The lifeboats had 1,178 seats for 2,201 people, and many left half full, which is why the death toll was so high.

What happened on the night of 14 April 1912?

The Titanic, the largest ship in the world, left Southampton on its first voyage on 10 April 1912, bound for New York. On 14 April it received several wireless warnings of ice ahead from other ships. The last of them, from the Mesaba at 9:40 p.m., described "much heavy pack ice and great number large icebergs" directly across its route, according to the British inquiry's report. It never reached the bridge; the wireless operator was busy sending passengers' messages via Cape Race.

The night was clear, cold and unusually calm, with no moon and no swell. That mattered: with no waves breaking at its base, an iceberg was much harder to see in the dark. At 11:40 p.m. the lookouts spotted one dead ahead and rang the warning. The officer on watch ordered the ship turned and the engines stopped, and the bow swung, but too late. The iceberg scraped along the starboard side below the waterline. Many passengers barely felt it.

Why couldn't the ship stay afloat?

The Titanic's hull was divided by 15 watertight bulkheads into 16 compartments, and it was built to stay afloat with any two of them flooded, or with the first four. The iceberg damaged six: the forepeak, three cargo holds and two boiler rooms, over a length of about 300 feet, the inquiry found.

The damage was not a long gash. Sonar surveys of the wreck found six narrow openings totaling only about one square meter, and metallurgists at the National Institute of Standards and Technology argued that the plates parted at their seams, where brittle wrought-iron rivets, with too much slag in them, snapped or popped out in the icy water.

The bulkheads were not capped at the top, so as the bow sank, water spilled over each one into the next, like water filling an ice-cube tray. The ship's designer, Thomas Andrews, who was aboard, told the captain within the hour that it would sink. The bow went under, the stern rose, the ship broke apart near the surface, and it disappeared at 2:20 a.m. on 15 April.

Why did so many people die?

Because there were not enough lifeboats, and those there were weren't filled. The ship carried 20 boats with room for 1,178 people. That was more than the outdated British rules required, which were based on a ship's tonnage, not the number aboard, and were written when ships were a quarter the size.

The arithmetic tells the story. The British inquiry counted 2,201 people aboard. With 1,178 seats, at most 54% could have been saved by boat even if every seat was used. In fact only 711 survived, so about 467 seats went empty. Early boats left far below capacity: the crew had never held a full lifeboat drill, some officers feared the davits would not hold a full boat, and many passengers at first refused to leave a ship that seemed safe.

The inquiry's own figures show who lived:

Group	Saved	Aboard	Share saved
First-class passengers	203	325	62%
Second-class passengers	118	285	41%
Third-class passengers	178	706	25%
Crew	212	885	24%
All women aboard	316	425	74%
All adult men aboard	338	1,667	20%

"Women and children first" was mostly obeyed, and class made a large difference: third-class passengers were berthed farthest from the boat deck, and few were guided up in time.

The Carpathia, 58 miles away, heard the distress call and steamed to the scene, arriving at about 4 a.m. to pick up the survivors. Another ship, the Californian, was much closer, stopped in the ice for the night, with its only wireless operator asleep. Its officers saw rockets and did not act. The British inquiry concluded that if it had come, "she might have saved many if not all of the lives that were lost."

The chain of causes, and what would have broken it

Link in the chain	What would have broken it
High speed in an area reported to hold ice, a common practice then	Slowing down for the night
Ice warnings not plotted or not delivered to the bridge	A full-time radio watch and procedure for warnings
A dark, calm night; lookouts without binoculars	Daylight, a swell, or seeing the iceberg seconds sooner
A glancing blow along the side that opened six compartments	Fewer compartments opened; some argue a head-on hit would have flooded fewer
Bulkheads not capped high enough	Higher or sealed bulkheads
Lifeboats for about half aboard, launched partly empty	Boats for everyone, and drilled crews
The Californian did not respond	A wireless watch around the clock

This is how most disasters happen, from shipwrecks to Chernobyl: a chain of decisions, each one ordinary, that together leave no margin.

Was the Titanic called unsinkable?

Partly. Before the voyage, a trade journal, The Shipbuilder, described its design as "practically unsinkable", and that belief seems to explain why passengers were slow to board the boats. The flat label "unsinkable" grew mainly in the retelling after the sinking, where it made the story more tragic. The myth worth dropping is that one thing, the iceberg, the rivets or the captain, sank the ship.

What changed after the Titanic?

Inquiries in the United States and Britain in 1912 both blamed speed in known ice and the shortage of boats. The first International Convention for the Safety of Life at Sea, SOLAS, was adopted in 1914 "in response to the Titanic disaster", the International Maritime Organization notes. It required lifeboat space for everyone aboard, lifeboat drills, and a 24-hour radio watch on passenger ships. The outbreak of World War 1 that year delayed it, but its rules were adopted in national law, and a later version still governs merchant ships.

The US Navy patrolled the North Atlantic ice for the rest of 1912, the Revenue Cutter Service took over in 1913, and its successor, the US Coast Guard, has run the International Ice Patrol ever since, tracking icebergs near the shipping lanes. The wreck itself was found in 1985, about 3,800 meters down, in two main pieces. Reading these records, from the inquiries' testimony to the wreck, is a case study in how historians weigh competing accounts.

Check yourself

• Without looking back: why was a ship designed to survive four flooded compartments doomed once six were opened?
• Using the inquiry's numbers, how many people could the lifeboats have carried, and how many were actually saved?
• Name three links in the chain of causes, and what would have broken each one.

Sources

• Report on the loss of the s.s. Titanic — British Wreck Commissioner's Inquiry, 1912, Titanic Inquiry Project
• Ice messages received, British Wreck Commissioner's Inquiry report — British Wreck Commissioner's Inquiry, 1912, Titanic Inquiry Project
• Numbers saved, British Wreck Commissioner's Inquiry report — British Wreck Commissioner's Inquiry, 1912, Titanic Inquiry Project
• Science showed how a tiny iron flaw doomed the Titanic — National Institute of Standards and Technology, 2017
• International Convention for the Safety of Life at Sea (SOLAS), 1974 — International Maritime Organization
• International Ice Patrol history — U.S. Coast Guard Navigation Center