The Science of Sinking the Vandenberg
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On the surface, it sounds like a simple plan.
Each of 42 charges totaling 179 pounds of explosive material will create 3 million pounds of pressure per square inch, tearing 42 holes in the hull of the Gen. Hoyt S. Vandenberg below the water line.
That’s the science, but bringing the old ship down will require as much art as engineering savvy. Getting the ship and the 6 million pounds of iron and concrete ballast inside it to settle properly on the sandy floor — seven miles southeast of Key West and half a mile from the nearest reef — required years of model-making, planning and input from explosive experts, engineers and scientists, said project founder Joe Weatherby.
Permits from 18 different agencies define the location, surveyed during more than 130 dives, according to Sheri Lohr of Artificial Reefs of the Keys.
“There have been hundreds of dives by just about everyone we could round up,” Weatherby said. “Local dive operators, folks from the [Florida Keys National Marine] Sanctuary, Mel Fisher divers, Special Forces divers, we took comments from the public at one time — everyone. We made sure there are no Spanish galleons down there.”
The Florida Fish and Wildlife Conservation Commission also approved the site.
The goal is to have the ship stay upright as it sinks straight down, then settle on the ocean floor 140 feet below, said Mark Loizeaux, of Controlled Demolition Inc. of Maryland, which has brought down oil rigs, offshore towers and such buildings as the Seattle Kingdome, Titan missile launch facilities and Alfred P. Murrah Federal Building in Oklahoma City.
Essentially the Vandenberg under water should look the same as it does today moored at the Truman Waterfront.
Series of thuds
Reef Makers CEO Jeff Dey is helping Loizeaux and his team and naval architects determine where on each side of the hull to place the 21 cutting charges.
Each charge will contain four small charges positioned like a square picture frame, each of which will detonate in a tenth of second from the other, Loizeaux said. They will not all detonate at the same time in an effort to minimize the environmental impact, Dey said.
“From a technical aspect, we want the buoyancy to stay in the center of the vessel, above the center of gravity; that way the ship stays upright,” Loizeaux said.
The holes created by the explosives were positioned by marine architects, Dey said.
“We’re making the holes where we’re told to make them,” Loizeaux added.
The charges are essentially military charges that will explode at 27,000 feet per second, cutting a narrow line through the hull.
“The cutting charges are designed to leave a sharp line, like a knife,” Dey said. “A very clean cut.”
The team assembling those charges will use a non-electrical system to detonate the charges, similar to those used in military and civilian operations, which most commonly are started using a fuse.
“We’re not using an electric system because we’re on a steel vessel in water in Florida, with the possibility of thunderstorms,” Loizeaux said.
Those explosives and the blasting material used to ignite them will be “nowhere near each other until we’re at sea,” he said.
“It’s going to be anti-climatic,” Dey said. “There will be explosives, but this ain’t Hollywood. You’ll hear a series of thuds, a little vibration in the water and the vessel will start to move below the waterline.”
Like an elevator
Crews have been scuttling the Vandenberg over the last few weeks. How those holes are cut into the ship is just as important as where the explosives are placed, Dey said.
Scientists and engineers with the Stevens Institute of Technology in Hoboken, N.J., built scale models to determine how the ship should be scuttled.
“Same weight and everything was to scale,” Dey said. “They made the calculations and cut holes in the exterior of the model and did several sink tests using black powder.”
In those tests, the model Vandenberg sank as engineers had hoped, though slightly from stern to bow, and settled nicely on its hull in 2 feet of water, Dey said.
The real Vandenberg should sink in about two to five minutes.
“Optimally, we’d like to see it go down like an elevator, straight down,” Dey said.
Once the ship is sunk, a dive team comprising 20 members of the Monroe County Sheriff’s Office and Key West police and fire departments will examine the ship to make sure all the explosive charges detonated. If there are still live charges, a second team of divers will hit the water and remove them, said Bob Smith, former head of the Florida Keys Community College dive program who is overseeing the dive teams.
The divers, who will be taken to the Vandenberg and working from two Mel Fisher treasure salvaging vessels, will make sure the ship sank properly and the super structure has not shifted or parts fell off as it went down.
“If something has shifted we want to know,” Smith said.
The failed sinking of the Spiegel Grove off Key Largo in 2002 used an entirely different method that involved flooding the interior chambers with water. The 510-foot ship landed upside down after it sank two hours early, forcing workers and local dignitaries who were on the deck to scramble to disembark.
With her bow anchored by a heavy chain, workers began filling the stern chambers, but pumped in too much water, which filled one side more than the other, causing it to roll as it descended.
After contractors hoisted her on her side, Hurricane Dennis finished the job, its strong waves pushing her upright.
With the Vandenberg, the key from an explosive contingency standpoint is redundancy, Loizeaux said.
“If you need one, put two,” he said. “The number of openings will be far more than is required for the sinking. Adding explosives is not expensive; getting everything in place and there is the expensive part.”
Engineers also are concerned about air pockets forming in portions of the ship that could cause the Vandenberg to list as she sinks. Much of the scuttling above the waterline is designed to provide the displaced air an avenue to escape, Dey said.
For all the science behind the sinking, one of the biggest concerns is the one beyond anyone’s control. The sinking is scheduled sometime between May 26 and June 1.
“The largest contingency will be the weather,” Loizeaux said. “At the end of the day, we need Mother Nature to work with us.”