He founded Marman Products, an aerospace manufacturing firm, which purchased the patent for a new type of hose clamp, now called the Marman Clamp, which found its way onto all sorts high pressure hoses in aerospace, and were particularly useful for turbochargers, an area where the US excelled in WWII.

Additionally, they found their way into space applications, “When John Glenn rode into orbit aboard Friendship 7 in 1962, a six-foot-diameter Marman-type clamp released the capsule from the Atlas rocket, with explosive bolts blasting open the clamp,” and is still widely used today.