The Gemini-Titan 10 spacecraft attempts to rendezvous with the Agena Target Docking Vehicle on July 18, 1966. After docking, astronauts John Young and Michael Collins fired the 16,000 pound thrust engine of the Agena’s primary propulsion system to boost the combined spaceships into an orbit with “an apogee of 413 nautical miles to set a new altitude record for manned spaceflight.” (NASA)

Wonderful photoset.