Delta A

The Delta A, or Thor-Delta A was an American expendable launch system used to launch two Explorer spacecraft in October 1962. A derivative of the Thor-Delta, it was a member of the Delta family of rockets.
The first stage was a Thor missile in the DM-21 configuration, and the second stage was the Delta A, an uprated version of the original Delta. An Altair solid rocket motor was used as a third stage. Both launches occurred from Cape Canaveral Air Force Station Launch Complex 17B, and were successful. The first launched Explorer 14, and the second Explorer 15.
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