In 1954, the United States Air Force was looking for solutions to problems with vacuum tubes in electronics which were prone to overheating and were unreliable. Dr. Siegfried Hansen was working with vacuum tubes at Litton Industries and realized that working in a vacuum would facilitate his research. The U.S. Air Force built a vacuum chamber at Litton Industries to further Dr. Hansen's research and Hansen began to develop a special suit to wear in the chamber that would be flexible enough to work in but that could be fully pressurized. The suit that Hansen developed, completed in 1957, eventually became known as the Litton Mark I suit. In 1963, NASA contracted with Litton Industries to develop and build a protective "hard" suit that could be pressurized for extravehicular activity and Litton introduced the RX-1 suit in 1964. Over the next several years, Litton Industries developed a series of these suits, all given the RX designation.