Turtle research may aid military armor

WOODS HOLE — What started out as an experiment to protect sea turtles during underwater explosions may end up saving the lives of soldiers on land.

Scientists from the Woods Hole Oceanographic Institution and the U.S. Navy say the skulls and shells of sea turtles have an amazing and unexpected resistance to underwater shock waves. With added research, that resistance could have human applications in the form of improved body armor design, said Darlene Ketten, a WHOI biologist.
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"Basically, sea turtles are shielded from shock waves, so perhaps there is some pliability for human use," Ketten said.

The experiment first began more than five years ago in a test pond in Maryland, where the Navy gauged the safety of ship hulls by setting off explosions near test vessels. They tried to clear the area of marine mammals and sea turtles prior to detonation, but needed to determine how far the animals had to be from the blast to remain safe.

Using cadaver dolphins and sea turtles that died as a result of stranding, Ketten and her team set out to measure the impact that various underwater explosions had on the creatures in an effort to determine how far away they had to be from the blast.

All of the carcasses were given a CT scan before the blast, then Ketten attached pressure sensors to the dead animals.

The pressure wave readings were then compared to the original CT scan to determine the extent of the injuries, and all major organs were necropsied and examined for trauma as well, Ketten said.

Ketten said the peak received pressure was tested from 0 to 300 pounds per square inch (psi).

Dolphins remained relatively unharmed when subjected to pressure between 10 to 25 pounds per square inch, but were "devastated" by broken bones, bleeding and collapsed lungs at 300 psi.

Ketten said 20 psi is roughly the pressure a 200-pound person's heel exerts on the floor when walking normally, while a large dog's jaw can produce more than 400 psi of pressure when it bites.

And while sea turtles suffered some injuries like broken flippers and minor brain damage at 300 psi of pressure, Ketten said the trauma was "phenomenally low in comparison."

"I have to admit, I didn't know much about turtles going into this, but it turns out turtles are very much resistant to mechanical damage," Ketten said.

The skulls of the turtles include a broad shelf of bone that may reflect shock waves away from the brain. She likened it to the helmets worn by some World War I soldiers with a flange in back.

Ketten said sea turtles resemble and move like "underwater tanks," and she noted the extra protection around the skull might be nature's strategy to compensate for the fact that sea turtles can't contract their head into a shell like land turtles.

Kathy Zagzebski, executive director of the National Marine Life Center in Buzzards Bay, said she has no problem with deceased sea turtles being used to further WHOI's research, and likened it to people who donate their bodies to science.

In fact, Zagzebski has partnered with WHOI and alerts Ketten whenever sea turtles die as a result of stranding on the Cape.

"There's a lot you can learn from live animals in ways that don't hurt them, but if an animal does die, which is unfortunate, there's still a lot you can learn," Zagzebski said.

A few miles down the road from WHOI at the Falmouth police station, Police Chief Anthony Riello reflected on the possibility of sea turtle research translating into police protection.

"It's a critical area when you're talking about officer safety or safety in the military, so we definitely have to keep an open mind," Riello said. "Any advances they can make would certainly be welcome."

Ketten said she needs more turtles for additional tests. She hopes an engineer can take her research to the next level and use her findings to potentially save lives.

"It would be very cool to have our soldiers protected by 'turtledom,' " Ketten said.

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