 At the Redstone Arsenal and the adjoining Marshall Space Flight Center, near Huntsville Alabama the contingent of ex-German rocket scientists which had been brought into the United States under Operation Paperclip, including Dr Mueller, continued to refine their original instruments in conjunction with American engineers and scientists.At the suggestion of Dr Mueller, the technically difficult task of replacing the original ball bearings with gaseous bearings was achieved.Initially compressed nitrogen was used but later fluorocarbons which had the advantage of being recyclable on board the missile or aircraft during extended waiting periods was used.