After working as an aeronautical engineer for Boeing and other companies, Froehlich began working for the Minnesota-based General Mills aeronautical research labs in the early 1950s. Better known as a food company, General Mills also made precision military equipment.

Froehlich helped design high-altitude balloons, specializing in designing small spheres able to endure hostile environments. In the 1950s, he helped develop unmanned balloons to take air samples in the upper stratosphere at altitudes of up to 100,000 feet in an effort to determine the effects of Russian nuclear testing. He helped build a mechanical arm for the U.S. Navy-owned bathyscaphe Trieste in 1960 that descended more than 35,000 feet underwater with explorer Jacques Piccard at the helm. On Navy contracts, he designed breathing systems and helium gas valves for balloons.

Froehlich’s talent and earlier experience were crucial factors in his selection as the project leader in the early 1960s for the design of a new US Navy deep-diving research submersible, later named the Alvin.

Froehlich’s earlier design of a workable prototype for a self-propelled, two-man deep-sea vessel called the Seapup was a key factor in winning the contract for General Mills against competitors Lockheed and North American Aviation.

The Navy was impressed by the work Froehlich had done and awarded the contract to General Mills, even though it was located a thousand miles from the ocean. Years later Mr. Froehlich told Minnesota Public Radio winning the bid to design and build the Alvin was an astonishing feat, because the Navy initially "was skeptical about a Wheaties company designing a submarine."

The Alvin project was the first program for a submersible in which the Bureau of Ships was not directly involved in the design. 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.

Froehlich applied the principles of aeronautics and balloons to help design the Alvin. Using steel, fiberglass, aluminum and a new buoyant material, called syntactic foam, he and his team assembled a vessel that was able to withstand pressures to 6,000 feet below sea level. Part of the unique design was to combine syntactic foam with hollow aluminum spheres to build the vessel. His knowledge of creating small spheres able to endure hostile environments was crucial to this work. 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 the Alvin project.

The Alvin was intended for undersea exploration and recovery, built on the concept of a small vehicle that could move freely without being connected to the mother ship and equipped with a mechanical arm.

The Alvin could hold three people (two scientific observers and a pilot). It measured 22 feet long and was eight feet at its widest. 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."

Confident in his design Froehlich participated in one of the first test dives - "to the great depth of 27 feet," he later said.

Despite Froehlich's role, the Navy named the craft Alvin, a contraction of Allyn Vine, a leading oceanographer at Woods Hole who had been an influential proponent of federal funding for manned undersea exploration.

The Alvin was launched in 1964 and was soon observing secrets of the deep and using its mechanical arm to sample the ocean floor. 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, it was used to recover a hydrogen bomb that had dropped in the Mediterranean after a collision between a B-52 bomber of the United States Air Force Strategic Air Command and a KC-135 tanker during mid-air refueling. After a search that continued for 80 days, the missing atomic bomb was located five miles offshore at a depth of 2,550 feet (780 meters) on an uncharted, precipitous 70 degree slope.

The Alvin was used to map the Mid-Atlantic Ridge, the underwater mountain chain in the center of the Atlantic Ocean where earthquakes are frequent along an expanding sea floor. In later decades, using the Alvin scientist Dr. Robert D. Ballard found giant tube worms and other previously undiscovered aquatic life near intensely hot sea vents at depths of 9,000 feet off the Galapagos Islands. In 1986, Ballard used it to locate and explore the remains of the Titanic in nearly 13,000 feet of water off Newfoundland.

Over time the Alvin structure was modified, its hull was lengthened, and its maximum diving depth increased to 14,760 feet (almost three miles). With a stronger titanium shell replacing the original stainless steel, the Alvin can make deeper dives and can now reach nearly 63 percent of the global ocean floor. It has proven to be the epitome of reliability. It is still operational, after more than 4,664 dives over 47 years. There is a two-year waiting list of scientists wanting to make deep ocean dives.

After leaving General Mills, Froehlich joined the 3M Company, where he worked on oil burners used to power navigation buoys. He also designed medical equipment and helped devise a surgical stapler and a tool to extract staples from the skin. He retired in 1989.

Mr. Froehlich died May 19, 2007, at age 84. He and his wife, Avanelle Froehlich, nee Olson, lived in St. Anthony, a Minneapolis suburb.

NOTE 1: This short biography has been compiled from information in the nomination form submitted to the Minnesota Inventors Hall of Fame and from information available on the Internet and a variety of other sources.

NOTE 2: Though it is the world’s oldest research submersible, Alvin remains state-of-the-art due to numerous reconstructions made over the years. The sub is completely disassembled every three to five years so engineers can inspect every last bolt, filter, pump, valve, circuit, tube, wire, light, and battery - all of which have been replaced at least once in the sub’s lifetime. Woods Hole Oceanographic Institute