Titanic's Guardian Angel
In our roundtable discussion filmed for the National Geographic documentary, Jim Cameron suggested that as water rose above the level of the Fireman's Passage, it was no longer physically restricted to the starboard side. Once water made it to Scotland Road, it had unhindered access down the length of the ship along the port side. This is all true, but again, what arrested the original momentum to starboard and switched it to port? Why would the water move to the port side and not simply pool to starboard?
My first thought was to look for precedence. Has a list (or heel) transition happened before; if so, what caused it? In 2012, M.V. Costa Concordia struck a rock on her port side and took on an initial 10-degree port angle of loll. The engineering spaces were quickly flooded, the water stopping the generators which in turn left the ship without either electrical power or propulsion. Wind and current, aided by a locked starboard rudder, turned the ship and pushed her toward shore in a direction 180 degrees from her last heading. During the reversal of course (approximately 18 minutes after the grounding), the ship's heel transitioned from port to starboard. Finally, the ship grounded a second and final time and came to rest on her starboard side. After the accident, a computer simulation run by the Institute of Ship Design and Safety at the Technische Universität Hamburg-Harburg attributed the shift in heel from port to starboard primarily (among other factors created by the collision) to a compromise of Watertight Door 24, which allowed progressive flooding of starboard-side spaces and access for water to move up decks along the starboard side when the ship began to roll. Without that leak (but with all other factors considered), the analysis concluded, the ship never would loll to starboard but instead capsize to port 2.5 hours after the grounding. With all the WTDs closed/uncompromised (and all other factors considered), the ship would stay on a relatively even keel until finally capsizing to port over 5 hours after the grounding. The ship was doomed to sink regardless, but if not for the failure of one door in a critical location, the ship never would have rolled to starboard.
The example of Costa Concordia indicated that a specific circumstance most likely was responsible for the hull rolling over on the side opposite the initial damage. I could find nothing similar in Titanic's sinking timeline that would explain the change in her stability that would set the stage for a shift in her condition of heel. But what if the instability was pre-existing? This is where Beesley's observation came into play. If Titanic was already slightly unstable with a tendency to port, then once enough water entered the hull to create a free-surface effect, the water could very well tend to port, despite the initial influx on the starboard side.
This was interesting only in the academic sense because it would not affect the ultimate outcome…the ship would inevitably sink. But for the lives of passengers aboard, the impact was immensely profound. In our unrestricted simulation, the ship lolled onto her starboard side approximately an hour after the collision. This seemed to coincide with Thomas Andrews's estimation of the time that Titanic had to remain afloat. How many lifeboats could have been safely launched during that time? The decks would have taken on a steadily increasing list to starboard…looking at the current lifeboat launching timeline, by the time the first boat could be readied, the starboard boats might have been hanging several feet away from the side of the ship and the port boats unable even to be released from their deck cradles. The flooding simulation wanted to tell us that no one should have survived the disaster; at least, not in any lifeboat launched in a controlled manner.
But when the starboard list was arrested and later allowed to slowly transition to a port list, our Titanic flooding model stayed on a relatively even keel for a couple of hours until the port list developed into a lolling condition on her port side. According to survivor testimony, this scenario seems to correspond with actual events. Given that extra time and a more stable condition, all 16 of the lifeboats under davits (and two collapsibles) were safely launched (although the last few were a bit dicey as stability was increasingly degrading). Andrews had estimated that the ship would take an hour – and hour-and-a-half at most – to sink; in actuality, Titanic lasted over two-and-a-half hours, remaining relatively stable during much of that time. In this case, the transition from a starboard to a port list bought time and stability needed for the lifeboats to be safely launched.
Why did the transition happen so slowly? Once the port list was established – especially with a pre-existing tendency to port – one would expect the ship to quickly roll onto her side. That didn't seem to be the case with the real ship. I was discussing this with Jim Cameron when he mentioned something that he had encountered during his 2012 dive to Challenger Deep. His vehicle, the roughly torpedo-shaped Deepsea Challenger, was designed to dive vertically and was extremely stable in that attitude. During launch and recovery operation, though, the sub needed to be positioned horizontally and this was done using lift bags. In early tests, a dummy sub was used to test stability of the design in the horizontal attitude and it proved to be highly unstable, rolling up to 45 degrees. This was solved by lengthening the straps on the lift bags so that one end was down about 30 degrees, increasing the roll stability by "borrowing" a bit of the sub's strong vertical righting moment. In much the same fashion, as Titanic's bow flooded it lowered the centre of gravity well below the centre of buoyancy, increasing the righting moment of the ship that in turn slowed the tendency to roll. The port list would continue to increase, but the flooded bow would act as a dampening agent, of sorts, slowing that roll and buying precious time for those left aboard. The steady, progressive flooding that Titanic experienced helped to retain stability.
Most historians see the bunker coal fire as an event that hastened the end of Titanic. They cite both Barrett's and Leading Fireman Charles Hendrickson's description of the fire damage to the bulkhead and with that perspective, interpret Barrett's description of the sudden flooding of Boiler Room #5 as a premature failure of the bulkhead. For these reasons, most people accept the notion that the bunker fire was just another calamitous event that helped to seal Titanic's fate. I don't agree. Prior to my assignment to ship's company aboard the USS Constellation, I had to undergo damage control training at the "Buttercup" trainer in Newport, RI. With a 37,000-gallon tank, realistic sinking scenarios can be simulated in order to practice damage control procedures. Based on my experience there, I knew that even a small breach in the bulkhead would result in a water flow that would rapidly fill a space, even when the flooding space is less than 5 feet under water (as it was in the trainer). Reading Barrett's description, I believe that he witnessed the failure of a coal bunker door or possibly even a portion of the bunker wall itself…if the watertight bulkhead itself had failed, I calculate that Barrett would have been immediately overwhelmed by the water, despite having the massive boilers acting as a shelter of sorts. I believe that what he witnessed instead was the water that had collected behind the bunker walls suddenly breaking free of their confinement. I also don't believe that the "lurch" described by Second Officer Charles Lightoller signified the failure of the bulkhead — as cited by some historians — simply because Barrett, the man who supposedly witnessed the collapse in the boiler room, had safely left the ship in Lifeboat #13 approximately a half-hour earlier. At the time Barrett was chased topside by a sudden rush of water, there was no reported change in the ship's condition that I can find in topside witness statements that would have signaled the sudden loss of an entire boiler room due to a bulkhead collapse.
What I have seen in our computer modelling, coupled with my own experience in a flooding situation, has caused me to focus not on the damage caused by the fire but rather on the effects of the de-bunkering that was conducted in order to combat the fire. The movement and consumption of coal from Bunkers 'Y' and 'W' made the hull slightly unstable, with a tendency to port. When the collision opened up the starboard side, the water influx initially caused the ship to loll to starboard. With increasing water volume inside the hull, though, a free surface effect component took hold and counteracted the starboard list. Precious time was bought for the lifeboats to be loaded and launched while the starboard list transitioned to a port list. The port angle of loll was resisted from increasing by the stabilizing effect of the submerging bow. The last lifeboat was launched just before the increasing angle of loll grew to be outside the ability of the davits to safely launch the lifeboats. The coal de-bunkering and submerging bow had bought only just enough time for the 16 lifeboats under davits and two of the four collapsibles to be launched. Without the transition in her angle of heel, the ship would have lolled to starboard too quickly for any of the lifeboats to be safely launched, possibly resulting in the loss of all life aboard. Given this perspective, I would conclude that for the hundreds of people who safely made their way off the ship in a lifeboat, the coal fire that had erupted days before would eventually prove to be a gift from their guardian angel.
All images courtesy of the author unless noted otherwise.