What really killed the crew of the H.L. Hunley

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Alyrium Denryle
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What really killed the crew of the H.L. Hunley

Post by Alyrium Denryle » 2017-08-24 05:09am

Now we know.

http://www.cbc.ca/news/technology/hunle ... -1.4259123
Scientists have solved a longstanding mystery about the first submarine ever to sink an enemy ship — what killed the sub's own crew.

On Feb. 17, 1864, during the American Civil War, the 12-metre long Confederate submarine H.L. Hunley made history when its torpedo took down the 1,100-tonne Union ship USS Housatonic outside Charleston Harbor, S.C.

The Hunley itself later sank, with its crew of eight aboard.

According to research led by Rachel Lance, who studied the incident during her Ph.D. in biomedical engineering at Duke University, the crew were killed by massive lung and brain injuries caused indirectly by their own torpedo. Lance, who graduated in 2016, published the findings Wednesday in the journal PLOS ONE.

The sunken submarine was found in 1995 and raised from the bottom in 2000. Mysteriously, the skeletons of all eight of the crew were all still at their stations, with no broken bones, and the sub was in very good condition, Lance reports.

"There were some holes in the hull that were the result of time under the sea. But there was no actual damage found to have happened from the blast itself," she said in an interview with Duke University.

The exit hatches were closed and the bilge pumps that would have been used if the sub started to take on water were not set to pump, suggesting that the crew never tried to save themselves as the sub sank.

Still, some scientists had proposed that the crew may have suffocated or drowned.

Recreating the blast

Lance solved the mystery by creating a 2-metre-long scale model made of mild steel, fitting it with sensors, and setting off a series of blasts intended to recreate the torpedo explosion.

Unlike a modern-day torpedo, the Hunley's weapon couldn't be fired into the water and away from the sub. Instead, it was a copper keg of gunpowder attached in front of the sub by a short pole called a spar that was rammed into the enemy ship by the advancing sub, with the crew inside.

"Their spar was only 16 feet long, so they were actually very close to the 135 pound charge, especially since the spar was at a downward angle," Lance said.

When the charge exploded, the blast would have caused the submarine's hull to transmit a powerful, secondary shock wave into the submarine, crushing their lungs and brain and killing them instantly. Lance calculated that each crew member had only a 15 per cent chance of survival from the blast.

In fact, there was no indication that any of them survived.

In the end, the crew of the USS Housatonic fared better. Five of its members died in the torpedo blast, but the damaged ship came to rest in relatively shallow water, allowing the survivors to climb rigging, deploy lifeboats and escape.

The research funded by Duke University, the U.S. Department of Defence, the U.S. Army and the Hagley Library's Center for the History of Business, Technology and Society.
And here is the full paper.

http://journals.plos.org/plosone/articl ... 244#sec016
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Re: What really killed the crew of the H.L. Hunley

Post by Simon_Jester » 2017-08-25 02:18am

That's interesting to know.

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Re: What really killed the crew of the H.L. Hunley

Post by SpottedKitty » 2017-08-25 10:24am

Simon_Jester wrote:
2017-08-25 02:18am
Let it be noted: when your attack mode is a bomb-onna-stick, use a loooong stick.
To be fair in this case, no-one back then really understood how dangerous concussive shock is when transmitted underwater, and how much worse it is than in air. And the sub's shape didn't help; a long thin cigar only a few feet across. The shock waves would have been focussed into the middle of the cylinder, right where the crew's squishy bits were. Remember, the crew were also the engine, sitting down in the confined space and hand-cranking a big propeller at the back. Later sub designs used a double hull letting them survive explosions that weren't too close, but this early attempt didn't have that safety factor.
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Re: What really killed the crew of the H.L. Hunley

Post by Marko Dash » 2017-09-09 06:37am

i might be misremembering this, but wasn't the original design supposed to have had a detachable spar that would then be triggered by a cord setting off a percussion cap as the sub backed up?
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Re: What really killed the crew of the H.L. Hunley

Post by LaCroix » 2017-09-09 04:40pm

According to some sources, the torpedo is thought to have been on an "explode on impact" setting, maybe due to perceived problems with ramming the spar into the enemy vessel ( a lot of spar torpedoes failed doing so). If so, it exploded about 6.7 m ahead of the sub.

A WW2 depth charge had about 250lbs of explosives and had a lethal radius of about 12 m against a welded high-quality steel, double hulled German submarine that is 6 m wide and capable to dive a couple hundred meters.

Their bomb had half the power, but their boat was only 12m long, and 1.2 m in diameter, had a riveted civil war era single hull, and probably only able to dive a couple of meters.

I'm pretty much amazed that it wasn't squished flat. Most likely only because she faced the explosion, which minimized the exposure. Not enough for the crew, though.
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Re: What really killed the crew of the H.L. Hunley

Post by Sea Skimmer » 2017-09-12 10:39am

The Confederates were probably well aware that the bomb would or might kill them, the sub had already killed three crews so its not like it wasn't already a blatant suicide mission. The US Civil War was full of them. People built way more suicidal spar torpedo craft after the war too.

The key factor is they already knew a smaller ordnance wouldn't work, CSS David had attacked New Ironsides off Charleston in late 1863 with a 60lb blackpowder charge which had failed to inflict serious damage on the Union vessel. It also still caused non trivial damage to the Confederate sneak craft. The same thing happened in a later attack by the David as well. I think it no coincidence that the next sneak craft design decided to use a doubled up bomb weight.

LaCroix wrote:
2017-09-09 04:40pm

A WW2 depth charge had about 250lbs of explosives and had a lethal radius of about 12 m against a welded high-quality steel, double hulled German submarine that is 6 m wide and capable to dive a couple hundred meters.

Their bomb had half the power, but their boat was only 12m long, and 1.2 m in diameter, had a riveted civil war era single hull, and probably only able to dive a couple of meters.
You can't compare a low explosive like blackpowder to high explosives like that. Also German U-boats don't have double hulls. They have a single hull and the outer casing is free flooding, meaning it will transmit shock efficently, and basically just a way to streamline the ballast tanks. Other then the Russians nuke subs IIRC only Dutch subs ever had double hulls on a systematic basis.

Really more important is the fact that the U-boat weighs at least 500 tons, mass is the best way to mitigate shock effects. That's why shock hardness worries so much about small interior fittings ect.. they feel the shock last but because they have low mass and aren't fully rigidly attached to the hull they shake much more.
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