Harold Froehlich, 84; designed Alvin deep-sea research vessel

WASHINGTON -- Harold "Bud" Froehlich, 84, the designer and chief engineer of the Alvin deep-sea research vessel, which has located sunken bombs, underwater life forms, and the Titanic, died May 19 at St. John's Hospital in Maplewood, Minn. He had multiple myeloma.

Mr. Froehlich, a Minneapolis native, was an aerospace and mechanical engineer at General Mills when he was named project manager of the Alvin in the early 1960s. Better known as a food company, Minnesota-based General Mills also made precision military equipment and high-altitude balloons.

The second was Mr. Froehlich's specialty, and his knowledge of creating small spheres able to endure hostile environments was crucial to his work on Alvin. He told a reporter that "the same basic engineering principle is used to control both, ballast."

Although submersibles existed before Alvin, they were limited because of their mechanics. One designed by Jacques Cousteau was viable only in shallow waters, and deep-diving bathyscaphs had restricted maneuverability because they weighed so much.

While at General Mills, Mr. Froehlich helped build a mechanical arm for the Navy-owned bathyscaph Trieste in 1960, which descended more than 35,000 feet underwater with explorer Jacques Piccard at the helm.

Alvin took advantage of a new buoyant material called syntactic foam to attain broader movement underwater. Mr. Froehlich and his collaborators combined syntactic foam with large, hollow aluminum spheres to build the vessel.

The result was a smaller vehicle better suited to the needs of the Navy's Office of Naval Research and its scientific collaborators at Woods Hole Oceanographic Institution, a nonprofit research organization in Massachusetts that had an oversight role on Alvin.

Mr. Froehlich participated in one the first test dives made in 1964 near Woods Hole, "to the great depth of 27 feet," he later said.

Refinements to Alvin followed, and by the next year, the vessel was able to take two passengers 6,000 feet underwater. In later years, with a stronger titanium shell replacing the original stainless steel, Alvin could reach depths of more than 14,000 feet.

Mr. Froehlich told Minnesota Public Radio years later that winning the bid was an astonishing feat, because the Navy initially "was skeptical about a Wheaties company designing a submarine."

The Alvin, named for Woods Hole scientist Allyn Vine, could hold three people, including the driver. It measured 22 feet and was 8 feet at its widest. According to "Water Baby," an Alvin history, Mr. Froehlich chose the width "because it was the legal width limit of any object that could be transported on a highway without special permits or an escort."

Mr. Froehlich moved on to other work in 1964, soon after the Alvin was completed, but his basic design survived the decades as the vessel undertook a series of important missions. In 1966, Alvin was used to find a hydrogen bomb that had dropped after a US military plane crashed off Spain.

In later decades, scientist Robert Ballard found giant tube worms and other previously undiscovered aquatic life near intensely hot sea vents 7,000 feet down off the Galapagos Islands. Ballard also guided a trek to the North Atlantic in 1986 to find the Titanic, which rested more than 12,000 feet underwater.

In 1989, Mr. Froehlich, Vine, and Navy official Charles Momsen received the Elmer A. Sperry Award for "the invention, development, and deployment of the deep diving submarine, Alvin." Also that year, Mr. Froehlich retired from Minnesota-based 3M, where he designed surgical equipment, including skin staplers.