This is a covert reference by Pynchon to Operation Paper Clip, an American programme recruiting top Nazi scientists to be smuggled to the United States to aid in the burgeoning technological race against the Soviet Union.
President Truman gave the order in August 1945, though the Joint Intelligence Objectives Agency (JIOA) had been actively recruiting since May of that year. Truman expressly forbade the recruitment of any scientists who had been more involved in Nazi activity than an ordinary citizen. However, the JIOA created false backgrounds and papers for their targets, as well as purging existing records of their affiliations.
The name 'Paperclip' came from the clips used to attach scientists' new identities to their JIOA personnel files.
Wernher von Braun, quoted at the start of Gravity's Rainbow, was one of the most high-level targets of Operation Paperclip. Though he designed the V-2 rockets that dominate the novel, he became a US citizen in 1955, helped the US reach the Moon in 1969. He received the National Medal of Science in 1975.