cutaway view - Altair is labeled as "third-stage rocket motor".The X-248 was one of two third-stage designs used during
Project Vanguard. Early launches used a stage developed by the
Grand Central Rocket Company, but the last used the X-248 which enabled the Vanguard to launch more massive payload. The X-248 was used as the second stage of some early
Thor flights. These vehicles were designated "
Thor-LV2D Burner-1". Altairs were used as the third stage of early
Delta rockets. rocket.The fourth stage of the
Scout-X rocket used the "Altair-1A" stage, powered by a X-248A engine. This initial variant could produce of thrust, and had a diameter of . ==Altair 2==