Nebraska Engineering Fall, 2006
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Retirement at Sea

Retirement at Sea

After a land-locked career in mechanical engineering, Don Johnson is taking his expertise to the high seas.

A retired professor of mechanical engineering, Johnson is working on a Central American project, studying a Civil War-era submarine off the coast of Panama. The sub—called the Sub Marine Explorer—is the sixth sunken craft Johnson has helped study. Other missions have led Johnson to study corrosion of the USS Arizona, the CSS Hunley, a B-29 in Lake Mead, a ferry in New York Harbor and a Japanese mini-sub.

“Everything I did at UNL was a lead-in to this work,” Johnson said from his Arizona home. “I worked with Dr. Russ Nelson to develop the metallurgy program at UNL. And, that’s how this whole thing kind of got started.”

Don Johnson with the Sub Marine Explorer. Courtesy photos.
Don Johnson with the Sub Marine Explorer. Courtesy photos.

Johnson taught at UNL for 27 years, from 1963 to 1990. He spent his first year in retirement in Taiwan before returning to Lincoln. In 1997 he moved to Arizona to officially settle into retirement.

A year later—during a leisurely trip to Hawaii—Johnson started charting a water-laden retirement path.

“I was at Pearl Harbor and went to see the Arizona memorial,” Johnson said. “I made a connection with the park service staff out there and asked if a metallurgical engineer had done any work on the USS Arizona.

“They told me they would like to talk about it.”

The National Park Service put Johnson in touch with the Submerged Resources Center in Santa Fe, N.M. Founded to study effects related to the creation of Lake Powell in the 1970s, the SRC is responsible for all underwater sites in the National Parks system.

Johnson started studying the Arizona in 1998. UNL professor Bill Weins (who died in 2001) and John Makinson (one of Weins’ former students) assisted Johnson initially.

“What we do is a metallurgical analysis of the material in the submerged craft,” Johnson said. “We study corrosion and the products that occur as a result of corrosion. Basically, we want to know what kind of condition the ship or submarine is in so we can predict how long it will last underwater or if it can be recovered and put into a museum.”

Johnson continues to be committed to using UNL facilities for the ongoing research. Corrosion analysis of materials from the submarine are being conducted in UNL laboratories. Campus researchers who assist Johnson are James Carr, professor of chemistry; Brent Wilson, assistant professor of mechanical engineering; and Jody Redepenning, associate professor of chemistry. Wilson said eight students also have helped with the research effort.

“The primary thing we look at is where iron comes in contact with concretion,” Wilson said. “We go back to original assembly drawings and documents and are able to get a basic idea on how much iron has actually corroded away.”

It still amazes me that I'm doing this kind of work in retirement.The project has built a better understanding of concretion—biological material and sediment that builds on sunken craft—and its corrosive effect on iron (buoyed by the ongoing study of the USS Arizona). The study is leading toward new, less invasive research methods.

“We are looking at different methods for assessment because a lot of these vessels are artifacts that we really don’t want to cut into,” Wilson said. “But, as we learn more about concretion, we are able to make advancements toward new techniques that are less destructive.”

The UNL team has yet to study samples from the Sub Marine Explorer. Johnson said an initial assessment has been completed and project leaders are petitioning for additional funding from federal sources.

“We’ve completed a structural analysis; we’ve looked inside and done profiling of the sea floor around the sub to establish the stability of the site,” Johnson said. “It’s going to be a very interesting project because most of the metal is gone from one side of the sub, while the other side is about the same thickness as when it was built.”

Johnson’s sea-based research has earned him the regional and national George B. Hartzog award from the National Park Service. He received the honor May 12.

For Johnson, this new study area is an ideal way to spend retirement.

“It still amazes me that I’m doing this kind of work in retirement,” said Johnson, who joined the Navy shortly before World War II ended. “Doing work on these sites, particularly the USS Arizona, really means a lot to me. And, I’m pleased we’ve been able to maintain a connection with UNL.”

Saga of the Explorer

Abandoned off the coast of San Telmo Island, Panama on the Archipelago of the Pearls, the Sub Marine Explorer has a rich history that started in the Civil War shipyards of New York.

Built in 1865, the Explorer was originally to be used by the Union in the fight against the Confederate States. However, construction of the vessel was completed toward the end of the conflict, and Union officials opted not to purchase the sub.

Julius H. Kroehl, a German immigrant and engineer who worked with the forges and foundries of New York’s shipyards and ironworks, designed the Explorer. Instead of abandoning the sub, Kroehl and a group of investors purchased the sub, had it disassembled and shipped to Panama for use in pearl retrieval efforts.

“As the story goes, divers and Julius Kroehl lost their lives because no one knew about the bends at that time,” said Don Johnson, a UNL emeritus professor in mechanical engineering who is helping assess the condition of the Explorer. “So, it was abandoned and remains at that exact location to this day.”

The sub was abandoned in 1869 after a group of pearl divers died within days after a four-hour dive. Kroehl died after a dive in 1867.

Inhabitants of the island knew of the craft’s location because it has been exposed at low tide for 137 years.

The most common tale related to the sub, posted on a German Web site, identifies it as a Japanese craft built for war, perhaps to attack the Panama Canal during World War II.

James Delgado of the Vancouver Maritime Museum rediscovered the sub in 2001. Follow-up studies in 2001 and 2002 gathered dimensions and pictures of the sub, which were used to identify it as the Explorer. Archeologist Richard Wills—who worked on the recovery of the CSS Hunley, a Civil War-era sub built by the Confederates—positively identified the Explorer based on diagrams from 1866.

The Explorer is, as yet, the only Union-built submarine from the Civil War era to have survived.

Only five submarines built prior to 1870 are available for study today. The Explorer is one of two from the five surviving submarines that used a pressurized compartment to allow divers to enter and exit the craft at depth.