Burner 1
The Burner 1 stage was based on the Allegany Ballistics Laboratory (ABL) X-248 Altair rocket stage used for the third stage of some Vanguard launch vehicles. For the Burner designation, Boeing equipped the stage with 3-axis control. The solid rocket engine later designated Thiokol FW-4 (TE 364-1). The first Thor Burner launch occurred on January 19, 1965 for the US military meteorological program DMSP B4A-01 satellite (first Block 4A).
Read more about this topic: Burner (rocket Stage)