The Long Tank Thor, a stretched version of the Thor missile, was used as the first stage of the Delta 0100 series. Castor-2solid rocket boosters were attached to increase thrust at lift-off, three on the 0300 variant, and nine on the 0900. The second stage was a Delta F.
Five 0100 series rockets were launched, three using the 0300 configuration, and two in the 0900 configuration. All launches occurred from Space Launch Complex 2W at Vandenberg AFB. There was one failure, the launch of ITOS E on July 16, 1973. A hydraulic pump malfunction led to loss of pressure to the second stage attitude control thrusters, causing the launch vehicle to tumble out of control and break up in the atmosphere.