Ships That Go Bump In The Night - HMS Titanic, USS San Francisco, and Others

(Left, Original Captions): Apra Harbor, Guam (Jan. 27, 2005) The Los Angeles-class fast-attack submarine USS San Francisco (SSN 711) in dry dock to assess damage sustained after running aground approximately 350 miles south of Guam Jan. 8, 2005. The Navy former dry dock known as “Big Blue” is capable of docking ships that weigh up to 40,000 Long Tons. The Navy certified Big Blue for the one-time docking of San Francisco. San Francisco is the second fast-attack submarine to be attached to the forward-deployed Submarine Squadron Fifteen, home ported on board Naval Base Guam. U.S. Navy photo by Photographer's Mate 2nd Class Mark Allen Leonesio (RELEASED)

(Also): On January 7, 2005, the USS San Francisco, while on its way to making a routine port visit to Brisbane, Australia, ran aground and hit the ocean floor, approximately 350 nautical miles (560 kilometers) south of Guam, in the middle of the East Marianas Basin. The incident reportedly caused one critical injury and a number of minor ones to 23 of the submarine's crew ranging from broken bones, lacerations, bruises to a back injury. The critically wounded sailor later died of his injuries. Initial reports indicated that the submarine's hull was intact and that the submarine's nuclear reactor plant had not been damaged. The submarine resurfaced following the accident and proceeded to return to its homeport of Guam.


Provoked by blog musings regarding The Titanic, James McElroy (Michael's father) composed a very interesting essay about ships at sea colliding into objects:

Your bringing up the recent Nuclear Sub incident near Guam relative to the Titanic Disaster got me thinking of other accident studies, so I did a little research on the relative magnitudes, and the investigations thereof. Anyway here are some thoughts on what I found. I'm afraid we live in a very non-linear world, and are in constant ignorance of what is going on about us.

The Titanic is much upon our minds these days, and it has been an obsession with many people for 94 years. Just think, in only six years we will "celebrate" the Centennial of the sinking of the Titanic. You should start right now to secure performance rights for the show on Apr 14, 2012.

Your comparison of the Titanic vs. Iceberg to the USS San Francisco vs. Seamount (the USS Scorpion was another incident, top secret, hush hush espionage, and all that [Marc: Sorry! I got the name wrong!}) caused me to ponder the physics of the collisions. First of all, here is a photo of the result of the latest (7 Jan 2005) maritime disaster, from a USN oriented message board. There is a lot of talk back and forth from a miscellaneous collection of readers about the accident. Interesting reading.

I acquired a couple of books from my local library, the classic reference "A Night to Remember" by Walter Lord, and "The Night Lives On" by the same author. The first was published in 1955 and made into a movie by a British Studio in 1958, both are still readily available from Amazon.com. The second was published in 1989, shortly after the discovery of the hulk of the Titanic in 1985. It did not fare so well and is out of print. It focused mainly on the various Hearings conducted after the sinking, the later lives of principle passenger and crew survivors, and some information about the discovery of the wreck. It was very interesting and useful, but the Internet makes these kinds of books a hard sell today.

The results of the various inquiries are interesting. It is almost a given that the Bureaucrats came out blameless, the Maritime Industry was verified to be doing its best to build and operate increasingly large vessels safely and the crews (while some lower level members were faulted) was faced with an impossible situation. Humph! Some interesting things did come out however and changes were made (without admitting any blame, of course). For one thing, on the very next voyage of the Titanic's sister ship, the Olympic, the passengers refused to board the ship until enough lifeboats were aboard to carry all the passengers. As a result it was a very uncomfortable trip, with the boat deck very cluttered with, of all things, boats! There was tsk, tsking by the Board of Trade that this made the ships top heavy and less safe.

It became known at the hearings that the Titanic actually carried MORE lifeboats than were required by regulation. The number was a standard calculation based on tonnage, from the era of much smaller vessels. The justification was that larger ships took so long to sink (if they ever would) that they would be surrounded by rescue vessels and the boats would only be used to ferry passengers from the damaged vessel to the rescuers.

Was the Captain running the Titanic too fast, from pressure by an overbearing ship owner, or internal pressure to retire with the title of fastest ship on the crossing? At the hearings it became apparent that standard procedure of all captains was to go full out even at night, to shorten the turn around. Hopefully in fog they eased off a bit, though that wasn't discussed. Damage to ships from ice was infrequent, though the time between incidents was decreasing. All the ships in the North Atlantic trade could make many crossings before an unlucky one would earn a few weeks downtime for repairs.

In 1879 the Guidon Lines "Arizona" was the largest and fastest ship on the crossing (at the time). One midnight, in roughly the same area as the Titanic incident, while steaming at full speed it collided head on with an Iceberg. The first 30 ft of the bow was crushed, but the forward bulkhead was not seriously damaged. At slow speed it limped into St. John's Newfoundland, eventually repaired and put back into service. This event was used to justify the standard operating procedure of full speed in open ocean. Modern ships were just too big and strong to worry about a little ice.

It is instructive here to do a little comparison of various vessels involved in accidents. The "Arizona" was 5,750 Tons and capable of 17 knots. The USS San Francisco was (public data) 7,000 Tons and capable of 32 knots officially. Various people commenting on the message board stated that the Navy later admitted to 45+ knots for that class of submarine. The Titanic was 46,000 Tons, and capable of 24 knots. In case of a collision between a moving ship and an Iceberg (or seamount) the parameter of interest is it's kinetic energy which must be dissipated by crushing structure to bring the moving ship to a full halt.

Using the standard equation KE=M*V*V, where M is the mass in 1000 Ton units, and V is speed in knots we get:

Arizona KE = 5.75 * 17 * 17 = 1,662 (arbitrary units)
San Francisco KE = 7.0 * 42 * 42 = 12,348 (who knows how fast?)
Titanic KE = 46.0 * 24 * 24 = 26,496

Based on the photographic evidence of the USS San Francisco a collision with slightly less than half of the Titanic's Kinetic Energy is survivable. One must admit however that the structure of a Nuclear Submarine is a hell of a lot stronger than a 1912 Ocean Liner. This question actually came up in the Titanic Hearings in regard to the famous 37 seconds between warning until the bow began to move sideways. It was suggested that if the Titanic had hit head on, it would not have sunk. Maybe. A number was thrown out that the first 100 ft of the hull would have been crushed which would have taken out the first three, maybe four compartments, but left the engine room intact. Never saw any justification for the calculated number however. The Arizona lost 30 ft of structure with an impact of 1/16th of the Titanic's kinetic energy. No one could bring themselves to fault the helmsman's attempt to avoid the collision, however.

What happened in that 37 seconds? In the movie and theater versions there was the implication that the helmsman "froze" for several seconds and did not begin execution till later, but evidence given was that the execution was immediate. The order was "Hard to Port" and "Full Reverse". It would take a few seconds to swing the rudder to full and even more time to halt all that rotating mass and reverse the propellers. You don't change direction of a 882 foot steel beam moving in it's direction of least resistance easily. The iceberg must have been off center initially, and the turn made in the proper direction. It almost missed. The sad thing is that it turned just enough to maximize the damage. A little more and there would have been not a scratch, a little less and the crumple zone would have been determined. The fact is no one knew how the ship would respond to those commands.

Another thing that came out at the hearings was that the sea trials of this new leviathan were minimal at best. Of course it was the second of three sister ships. The Olympic had been in service for over a year. An emergency stop had been tested once, from 18 knots. It took 3 minutes 15 seconds and 3,000 feet from 18 knots. Turning tests were done, also at reduced and constant speed. At no time did testing occur at full speed, and certainly not at full load. The passengers on the maiden voyage were paying full price to participate in a Beta Test! The question was not raised during the hearings, but I can't feel but that the commands given, "Full Port Rudder" and "Full Engine Reverse" were contradictory. The rudder was straining to get the ship turned with a force proportional to the square of the water velocity over the rudder surface, while the reversing screws were modifying the water flow at the stern of the ship in a major way.

That the large propellers on the Titanic and it's sister the Olympic could do weird things to the water flow was undoubtable but apparently not appreciated. Both ships were involved in incidents which indicated that the effects of propeller wash was not understood. On it's first arrival in New York, the Olympic, for some obscure reason, reversed engines on one side at significant power and a tug working the ship to the dock was sucked under the stern, doing considerable damage to the tug and to the Olympic's propeller. On another occasion the Olympic and a Royal Navy Cruiser were proceeding side by side in a narrow channel, about 200 yards apart, when the Olympic increased power to move ahead and the Cruiser's bow swung into the stern quarter of the Olympic, doing considerable damage to both ships. At the inquest Naval Engineers presented evidence from model tank towing tests showing that the increased prop wash from the Olympic could cause the two vessels to impact. The Board of Trade harrumphed that boys playing with toy boats could not convince them the Navy helmsman was not at fault. As the Titanic left South Hampton on its maiden voyage with it's first load of passengers, another ocean liner was pulled from it's moorings as the Titanic passed, and a similar collision was avoided only by the heroic efforts of a passing tug, and reversing the Titanic's engine to swing the stern sideways.

Probably the correct action on sighting the iceberg would have been to leave the engines alone at full forward, and swing the rudder hard over. That would maximize the lateral force on the hull to execute a turn. Reversing the engines would reduce flow over the rudder surface. That was certainly the technique used by the Carpathia on it's mercy run toward the Titanic's reported position. The captain stated that he added as many lookouts as he could and swerved around any large ice reported. Of course his full speed was only 14 knots. After sunup, he said he looked back over his course into the area and noted many, many more icebergs than had been reported, and attributed his safe arrival to Divine Guidance. Too bad the Titanic didn't have some of that on board as well. It seems that no one on board really knew how the Titanic would respond to emergency maneuvers at full speed and load. If the Olympic had ever been tested under those conditions it was never mentioned at the hearings.

To put a more modern perspective on the numbers mentioned above it is instructive to look at the case of:

(1) a fully-loaded Boeing 747 impacting a mountain at cruise speed
437.5 Tons take off weight, 484 knots cruise speed
KE = 0.4375 * 484 * 484 = 102,487
Almost 4 times the impact energy of the Titanic!
No wonder there is so little left to pick up.

(2) a Ford Excursion, hitting a concrete bridge pier at 80 mph
3 tons gross weight at 69.4 knots
KE = 0.003 * 69.4 * 69.4 = 14.4
About 1/1000 the KE of the USS San Francisco
Ponder the survivability of that!

Once more it will be instructive to reread the book "You Must be Joking Mr. Feynman!", especially the chapter on his participation in the investigation of the Challenger disaster. The investigative board was getting bogged down in endless discussions of hypothetical minutiae when Feynman whipped out his little tabletop experiment demonstrating that the O-rings lost their seal at 0 degrees C, and when hot gases blew by they were gone. It became impossible to deny that the designers and management had screwed up in a big way.