The Delta M or Thor-Delta M was an American expendable launch system used for thirteen orbital launches between 1968 and 1971. It was a member of the Delta family of rockets.
The Delta M had a three stage configuration. The first stage was the Long Tank Thor, a stretched version of the Thor missile, previously flown on the Delta L. Three Castor-2 solid rocket boosters were attached to the first stage to increase thrust at lift-off. A Delta E was used as the second stage, and the third stage was a Star-37D solid rocket motor. On the final flight, six boosters were flown instead of three, in a configuration known as the Delta M6, or "Super Six".
All thirteen launches were made from Launch Complex 17A at the Cape Canaveral Air Force Station. The maiden flight was on 18 September 1968, and carried the Intelsat 301 satellite. It failed to reach orbit after it went out of control and was destroyed by range safety. The fifth flight also failed, leaving Intelsat 305 in an unusable orbit, due to a third stage malfunction. Of the thirteen launches, twelve carried geosynchronous communications satellites. The thirteenth, which was the final flight and the only one in the M6 configuration, placed Explorer 43 into a highly elliptical orbit.
- Wade, Mark. "Delta". Encyclopedia Astronautica. Retrieved 2009-02-11.
- Krebs, Gunter. "Thor family". Gunter's Space Page. Retrieved 2009-02-11.