Early in submarine history, submarines were more of working laboratories than anything else. The men manning these boats were constantly working at the bleeding edge of science, and deadly consequences occurred with no enemy other than the basic forces of nature and chemistry.
Case in Point: the USS E-2
Originally named “Sturgeon” while under construction, the re-named “E-2” was commissioned on 14 February 1912, just eight weeks before the great technical nautical wonder, the Titanic, would set sail on her maiden and final voyage.
She served for a number of years, patrolling around the New England coast, then Guantanamo Bay and the Gulf of Mexico.
Like most submarines, E-2 was an engine/battery submarine. While on the surface she would run on her diesel engines (E-2 was one of the first to run on diesel, rather than the more unstable/explosive gasoline engines) and these engines would charge her batteries. Unlike the engines, the batteries, producing no fumes and needing no oxygen, would run the submarine’s systems while underwater. When the batteries ran out, the sub had to surface.
The trouble with these wet-cell batteries, however appeared frequently and caused some limitations in maneuvering. Submarines could only dive and surface at less than a fifteen-degree angle or the batteries would have trouble. Any salt water at all hitting the batteries would cause deadly chlorine gas to form, asphyxiating the crew or even causing an explosion.
In fact, the first sub fatality in the American Navy, the F-4, in 1915, was partially caused by a corroded battery case, leading to a loss of control, and implosion during a dive.
These issues lead American Inventor, Thomas Edison, (yup, same Edison as in light bulbs and Nikolai Tesla’s rival ) as Chairman of the Naval Advisory Board, to invent a new battery that would be more stable, less prone to the angles of a submarine’s dives and ascents, and eliminate the chlorine gas. After five years of work, he believed he had a stable working model, which was photographed and proclaimed from this Washington Herald newspaper from October 1915 feature section:
Based on a nickel-potash solution, the battery could not produce chlorine gas, nor should it be unstable if doused with seawater for any reason. Lighter, stronger, it could potentially allow submarines to maneuver at up to a sixty-degree pitch, allowing for faster, tighter, maneuvering. Even more importantly, it could be charged within one hour, allowing submarines to remain hidden longer in enemy waters. With WWI already in full swing, and the US likely heading to war, the possibility for greater flexibility and safety combined was enticing, even if the Edison battery was nearly three times as expensive as the current lead-acid batteries.
By this time, the E-2, the selected test submarine, already had two 400-cell Edison batteries installed, and was undergoing dock-side tests, charging and discharging her batteries under carefully controlled conditions. 
E-2 already had one battery “incident” in her history. Thirteen months earlier, in September 1914, the E-2 was fifty feet underwater when, unbeknownst to the crew, the lead acid of the battery chewed through the battery tanks and into the seawater ballast tanks. Ensign Edward Gillam, E-2’s Commanding Officer, detected the feared chlorine gas leaking from the battery compartment, and drove the sub to the surface, using her pumps, rather than blowing the ballast tanks (the chlorine gas could have released inside in a cloud if he had, killing his crew). The crew managed to vent the gas but the brief exposure still injured and incapacitated nearly every one of the nineteen hands aboard, forcing the submarine to be towed back to port. (Later tests would show the acid had deeply pitted the entire battery tank, making this leak an inevitability. This discovery forced all D and E class subs to port to replace and double-line their battery tanks.)
Gillam’s lungs were badly scarred, and would need a year to recover. E-2 couldn’t remain sidelined that long, so a new CO, Lt. (j.g.) Charles “Savvy” Cooke, was chosen to replace him.
The Tests and Controversy
On December 7, 1915, the E-2 made her maiden voyage with the new batteries. The initial test was successful: the batteries “produced better speed on less fuel.” The experiments also proved that the Edison battery generated “nearly double the ordinary amount of hydrogen during the process of charging, but on discharge or while lying idle, gives off much less…observers aboard…reported that while in operation not enough gas was produced to be dangerous.”
But Cooke wasn’t comfortable with the amount of hydrogen gas the batteries produced. Dangerous as chlorine gas was, you could smell it and react, hopefully in time. Hydrogen gas is odorless, and could build up with no one knowing. Cooke requested the Navy’s Bureau of Steam Engineering install hydrogen gas measuring devices in the E-2 as a safety feature. And was denied. He suggested installing individual voltage meters for all 800 battery cells to see which ones produced hydrogen gas under certain conditions. And was turned down. By both the Navy and the Edison Company. (Miller Hutchinson, chief engineer at Edison’s lab, said they would increase the chances of a short circuit).
More tests would be needed, but the early results were encouraging enough that the Edison Battery would be installed on one of the newest boats, the L-8, under construction in Portsmouth. E-2, along with three other submarines, entered Brooklyn Navy Yard on December 30, 1915. As a standard safety precaution, all four submarines were stripped of their torpedoes and drained of all fuel, and they were each about fifty feet away from her closest neighbor.
On Saturday morning, January 15, several civilian and Naval personnel went inside the E-2, down to the battery compartment. New canvas pipes and fans had recently been installed to see if the new ventilation would cool the batteries uniformly, and so, that day, the men were measuring the voltage output and temperature of the batteries over a complete discharge, followed by a seven hour charge. For this first part at least, no one was expecting any hydrogen gas build up, though the fans and vent pipes were kept running as safety protocols demanded. At least five men, two Navy sailors and three civilian contractors, were inside the after battery compartment, and another ten worked throughout the vessel on multiple projects.
At 1:16 pm, there was a devastating explosion deep within the E-2. One man, standing the deck hatch, was blown twenty feet into the air, before landing on the drydock floor, thankfully with only minor injuries. The ladder he had been standing on was also blown sky-high, finally landing 150 feet away.
E-2 roared, the sound of the explosion rumbling and bouncing around the confined space. Within the battery compartment, four men, Roy Seaber of Cincinnatti, James Peck, civilian from Brooklyn, John Shultz, civilian from Brooklyn, and Joseph Logan, Civilian from Brooklyn, lay dead, and the man in charge of the discharging procedure, Chief Electrician’s Mate LL Mills, was badly injured. Another nine men lay too injured to move, forced to breathe the searing gas fumes now surging through the submarine.
From the outside, the E-2 looked was perfectly fine. The hull designed to withstand the ocean’s pressures from the outside had contained the explosion within, though her internal space was “badly shattered.” Rescuers coming from the dry dock then discovered a new twist: the watertight hull trapped the gasses inside the sub, forcing would-be rescuers, led by E-2’s Cooke, to don diving helmets while other men tried to pump pressurized air into the E-2, forcing the gas out.
Ambulances and medical personnel were on hand when the first of the injured men were hauled out to the open air. Many were badly burned. When the bodies of the men near the battery compartment were finally retrieved, they spoke of the severity of the explosion: all were badly burned, one was missing an appendage, and another was crushed.
Within hours, reporters were clamoring for the reason why. The navy offered one initial suggestion: that the hydrogen gas that the batteries built up when charged, had somehow been ignited by a spark. However “It is too early to state definitely the cause of the explosion,” Said acting Secretary of the Navy, (and future president) Franklin D. Roosevelt.
The batteries, as it turned out, had been discharging, and shouldn’t have been throwing off enough hydrogen to spark anything, much less a massive explosion. Soon, experts came up with other theories to investigate.
An explosion could have been caused by the diesel-oil engines. However, there had been no diesel onboard to run the engines, and besides, the engines were still intact. That couldn’t be the point of origin.
Perhaps a nearby air flask had exploded. An explosion of an air flask, however, should have blasted metal shards throughout the battery compartment, which hadn’t happened. So that theory was abandoned. 
Another option, intentional sabotage, was ruled out by January 17.
So what did happen?
That questions would be tackled by the required Naval Inquiry. The coroner of Brooklyn also announced a civilian inquiry on behalf of the three dead civilians.
Despite not being on board the E-2 at the time of the explosion, and leading the rescue effort, as CO, Cooke’s career was potentially on the line. Had he, at any time, though lack of training, lack of requested maintenance, lack of reporting, lack of security, lack of anything, put the E-2, and her crew, and the civilians, at risk? As CO, he was answerable for each and every incident that damaged his boat or crew, though not necessarily responsible. Responsibility could only be assigned by investigation.
Cooke needed a defense counsel, and chose a fellow submarine officer: Chester Nimitz, future WWII Commander of the Pacific Fleet.
Now Hutchinson, who lead the installation and testing of the Edison Batteries on behalf of the Edison Labs, and Cooke, who’s boat and crew were damaged and killed, were at war, each believing the other’s people or devices had to be the cause of the explosion. During the inquiry and the many press releases surrounding it, many conflicting statements were made:
- Hutchinson, inspecting the E-2 the day after the explosion, stated that the batteries were intact and undamaged, proving that the explosion, even if it happened in the same vicinity, had to have come from somewhere else.
- Naval Lt. C.S. McDowell, stated that he too had inspected the remains of the E-2, and said the after compartment of the Edison batteries “were completely ‘blown up’ [and] the forward batteries also damaged.”
- Cooke revealed his requests for safety devices, each of which had been turned down. 
- Hutchinson announced that the Edison battery was safe, and as proof, it was currently in use in three “non-German” European submarines, currently waging war in Europe. One of those unnamed subs had sunk seventeen ships thus far. This surprised many people, as it was assumed the US Navy would have exclusive rights to the Edison Battery if it passed its tests.
While the investigation continued, a fifth man succumbed to his injuries. But some of the others, crucially, Chief Electrician’s Make Lewis Miles, were slowly improving.
As soon as the survivors were stable, they started to give testimony. Five men were able to speak, though from reports, they had to speak through a head-full of bandages, only their eyes and mouths visible.
They were adamant about several points, however
1.) No one was smoking
2.) There was a blinding flash, then they were all insensible
3.) There was no smoking or sparking wires on the E-2 on January 15
The two critical testimonies came from Raymond Otto, a second class electrician’s mate from E-2’s crew, and Chief Electrician Lewis Mills, who had been in the battery compartment when the explosion happened. Otto, who had been partially blasted through E-2’s hatch, and burned his legs, was able to testify around January 19, but Miles, forever confined to a bed, and whose voice permanently restrained to a whisper, couldn’t testify until early February.
Both men, however, recalled the same unusual thing: four of the Edison Battery cells had depleted their charge, and were bubbling moments before the explosion. The bubbling was hydrogen gas, being produced as the cells, depleted of their charge, had begun to recharge ahead of the others. If they had produced enough hydrogen gas to stay ahead of the new ventilation system, a random spark (though from what, no one ever saw) could have, may have, caused the explosion.
By the end of January, the civilian coroner’s jury found that the cause of the civilians’ death was an “explosion of gases.” However, they also “were unable to determine the cause of the gases”  Despite testimony from naval and civilian experts, the civilian jury was not able to find any new conclusions regarding what gasses or sparks may or may not have sparked the explosion.
In the end, on the 19th of February 1916, the Naval Court of Inquiry wrapped up, though the results were strangely, not made public after conferences with officers of the Navy and Secretary of the Navy, Josephus Daniels. The official conclusion did, however, absolve Charles “Savvy” Cooke from any blame.
The press reported that the “court reached substantially the same decision as the board of investigation appointed by the navy commandant immediately after the accident” most likely buildup of hydrogen gas and a stray spark, though the “spark’s” origin was never discovered.
It remained a mystery what happened the afternoon of January 15.
The Navy decided to pull the Edison batteries from the under-construction L-8 in Portsmouth, but turn the E-2 into a floating laboratory, testing the Edison battery further.
They also pulled Cooke from his boat, reassigning him as an engineering officer on the Receiving Ship USS Salem in Boston. It was a step down in career, though the worst, for Cooke, was the sleepless nights wondering if he could have saved his crew, somehow. Four years later, he was in command of a submarine again. This was the brand new USS S-5, and Cooke would be her first CO. Six months after S-5’s commissioning, Cooke and his crew would be in the news again, for an incident that nearly killed them all. Quick thinking and luck, however, would save them. Just watch.
(The whole video is worth watching, but the video is cued to the S-5 story which is only about 2 minutes long.)
Cooke would command ships and submarines throughout the 30’s. On December 7, 1941, he was CO of the battleship Pennsylvania, in drydock when the Japanese attacked. Pennsylvania would survive, though damaged. The Cassin and Downes, sitting in front of Pennsylvania, would not be so lucky.
As an Admiral through WWII, Cooke oversaw much of the Pacific and Atlantic wars, including witnessing landings at Normandy. He retired in 1948 . He died on Christmas Eve, 1970, and was buried in Arlington National Cemetery. 
(His son Charles Cooke Jr. would follow his father into the military, and later, consider it “…a badge of honor to have earned a death threat from [President] Richard Nixon…”.  )
The E-2 would recover, and spend the next two years near the Navy Yards, testing the Edison and Ironside batteries thoroughly. Some naval records state that as the Edison batteries themselves survived the 15 January explosion, though this may be referring to the forward bank of batteries. The batteries were tested cell by cell to try and find the problem, or the origin of the explosion. None was ever found. Probably due to the inability to find the cause of the E-2 explosion, and thus, being unable to guarantee a repeat disaster, the Edison batteries were ultimately rejected and never installed in another American submarine.
USS E-2 was recommissioned in 1918, and served in WWI running anti-U-boat patrols off Cape Hatteras. None the worse for WWI, and having completed longer patrols than ever before, E-2 was decommissioned on 20 October 1921, and sold for scrap on 19 April 1922.
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