Project Winterhaven.
documentedgovernment_studyPrivate Aerospace Contractors
Brown's 1952 proposal to ONR for a Mach-3 electrogravitic 'combat saucer'; a documented proposal, not a built craft.
Project Winterhaven was a 1952 proposal Townsend Brown submitted to the Office of Naval Research outlining a multi-year plan to develop a Mach-3 anti-gravity combat saucer based on the Biefeld-Brown effect. The 1956 Electrogravitics Systems report cites it. The proposal is documented; whether the military formally adopted it is unclear and no operational craft resulted.