The Altair was a solid-fuel rocket with a fiberglass casing, initially developed for use as the third stage of Vanguard rockets in 1959. It was manufactured by Allegany Ballistics Laboratory (ABL) as the X-248. It was also sometimes called the Burner 1.

Altair

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-Burner". Altairs were used as the third stage of early Delta rockets. The fourth stage of the Scout-X rocket used the "Altair-1A" stage, powered by a X-248A engine.

Altair 2

The Altair 2 (X-258) Thiokol (Star 25, TE-M-184-3) solid rocket engine first flew in 1963 and was the kick stage motor for Delta D, Scout A, Scout X-4, and Atlas-D OV1 as part of the Orbiting Vehicle satellites. It was retired in 1973.

Altair 3

The Altair 3 (FW-4S) solid rocket engine first flew in 1968 and was used on the Atlas-E/F OV1 as part of the OV1 upper stage. It was also used as the second stage of the ASM-135 ASAT anti-satellite missile. It as proposed as the fourth stage for Advanced Scout. The FW-4S motor is similar to Thiokol Star 20 (TE-M-640), and both are designated by NASA as Altair IIIA.