The basic concept behind Excalibur was conceived in the 1970s by George Chapline Jr. and further developed by Peter L. Hagelstein, both part of Edward Teller's "O-Group" in LLNL. After a successful test in 1980, in 1981 Teller and Lowell Wood began talks with US president Ronald Reagan about the concept. These talks, combined with strong support from lobbyists at the Heritage Foundation, helped Reagan ultimately to announce the Strategic Defense Initiative (SDI) in 1983. Further underground nuclear tests through the early 1980s suggested progress was being made, and this influenced the 1986 Reykjavík Summit, where Reagan refused to give up the possibility of proof-testing SDI technology with nuclear testing in space.