The Moog ESPA is manufactured from a 7000-series aluminum ring forging. The original ESPA replicates the EELV standard interface, i.e., 62.01” (1575 mm) in diameter, with 120 evenly spaced fasteners, and allows a primary payload up to 17,000 pounds to be mounted on top of an ESPA without requiring any modifications. Variants of the original configuration have been developed for other launch vehicles. Satellites are mounted externally to the ESPA ring with a variety of port options, and features can be added for internal mounting or mission specific structure modifications.
ESPA mounts to the standard NSSL (formerly EELV) interface bolt pattern (Atlas V, Falcon 9, Delta IV, OmegA, Vulcan, New Glenn) and is a drop-in component in the launch stack. Small payloads mount to ESPA ports featuring either a 15-inch diameter bolt circle with 24 fasteners or a 4-point mount with pads at each corner of a 15-inch square; both of these interfaces have become small satellite standards. ESPA is qualified to carry 567 lbs (257 kg), and a Heavy interface (with 5/16” diameter fastener hardware) has been introduced with a capacity of 991 lbs (450 kg). All small satellite mass capabilities require the center of gravity (CG) to be within 20 inches (50.8 cm) of the ESPA port surface. Alternative configurations can be accommodated.
While the ESPA ring is regularly customized to fit the unique needs of the customer, there are three basic configurations: the standard ESPA, ESPA Heavy (with 5/16” instead of 1/4” fasteners), and ESPA Grande.