Robert Scott Lazar claims to have worked on reverse engineering extraterrestrial technology at a site called S-4, near the Area 51 test facility, and that the UFOs use gravity wave propulsion. This is powered by the, at the time, undiscovered element 115. He further claims to have read US government briefing documents that describe alien involvement in human affairs over the past 10,000 years. Lazar is responsible for bringing the secret test site Area 51 to the attention of the general public. In May 1989, Lazar appeared in a special interview with investigative reporter George Knapp on Las Vegas TV station KLAS, under the pseudonym "Dennis" and with his face hidden, to discuss his purported employment at "S-4", a subsidiary facility he claimed exists near United States Air Force facility Area 51. Supposedly adjacent to Papoose dry lake, which is located south of the main Area 51 facility at Groom Lake, he said the facility included concealed aircraft hangars built into the side of a mountain. In his interview with Knapp, Lazar said he was involved in reverse engineering several flying saucers. He appeared under his own name and unmasked in another interview with Knapp in November. Regarding the propulsion of the studied vehicles, Lazar claims that the atomic element 115, at that time not discovered, served as the fuel, and that this was used to generate gravity waves. Lazar also claims that he was given briefing documents describing the historical involvement by extraterrestrial beings from Zeta Reticuli with this planet for the past 10,000 years.