The Alcor was originally developed for the Air Force as a third Stage for their Athena sounding rocket, and in some applications was known as the Zebra. One of its main attractions was a very high mass fraction as a result of using the Aerowrap process of chamber fabrication. This process was used in early Minuteman developmental chambers, but never went into production because of problems with the joints between the cylindrical section and the ends. Only a few Alcor 1 units were produced when Aerojet shifted from polyurethane to polybutadiene propellant in the Minuteman, and a similar change was made in this motor family, which was designated the Alcor 1A. Other changes were made in the nozzle, chamber insulation, and expansion ratio. This resulted in a change from 30KS-8000 to 23KS-11,000 and a gain in mass fraction from 0.886 to 0.906. Both of these motors were used on stages of Astrobee vehicles (Astrobee 500 and 1500).
The Alcor 1A was qualified by a six motor demonstration test program, and six more were subjected to static test firings. A total of 57 units was delivered, with 24 having been flight tested and demonstrating 100% reliability. A second major product improvement (the Alcor 1B) occurred late in 1965 with the introduction of an all welded titanium chamber. All other features and performance were the same, but the mass fraction improved from 0.906 to 0.916, with a spin capability of 300 RPM, which is one of the highest performance levels in the industry. The nozzle used a graphite throat insert and silica phenolic tape entrance and exit sections with a glass roving structure.