EELV secondary payload adapter (ESPA): providing increased access to space

In the early 2001, there exist few options for small satellites and space experiments needing access to space. Therefore, many small satellites wait years for access to space. At the same time, many expendable launch vehicles are flown every year with unused payload margin. The EELV Secondary Payload Adapter (ESPA) is designed to take advantage of this unused payload margin to deploy up to six 181 kg (400 lb) secondary payloads. ESPA consists of an aluminum cylinder with six standardized secondary payload (SPL) mounting locations. The fore and aft flanges on the ESPA ring duplicate the 157.5 cm (62.01 in) EELV Standard Interface Plane, making ESPA transparent to the primary payload. By taking advantage of existing unused payload margin, ESPA will increase access to space for small satellites and space experiments