The Delta 3000 series paired the RS-27-powered extended long-tank first stage with Castor IV strap-on motors and either the TR-201 or improved AJ10-118K second stage. Configurations flew with no solid upper stage, TE-364 third stages, or the commercial PAM-D payload-assist stage. Thirty-eight vehicles flew from December 1975 through March 1989 across eight exact configuration labels.