 Late in 1960, Lockheed introduced the uprated Agena B stage which was restartable and had longer propellant tanks for more burn time.It first flew on the Thor and did not make its maiden voyage on an Atlas for months, when Midas 3 launched on July 12, 1961.Atlas-Agenas were then used for DoD and NASA programs, but proved a reliability nightmare as one failure after another happened.