K. Eric Drexler was very strongly influenced by ideas on Limits to Growth in the early 1970s. His response in his first year at Massachusetts Institute of Technology was to seek out someone who was working on extraterrestrial resources. He found Dr. Gerard K. O'Neill of Princeton University, a physicist famous for a strong focus on particle accelerators and his landmark work on the concepts of space colonization. Drexler was involved in NASA summer studies in 1975 and 1976. Besides working summers for O'Neill building mass driver prototypes, he delivered papers at the first three Space Manufacturing conferences at Princeton. The 1977 and 1979 papers were co-authored with Keith Henson, and patents were issued on both subjects, vapor phase fabrication and space radiators.