Rideshare on EELV using ESPA - Challenges and Opportunities

Abstract

The Secretary of the Air Force (SECAF) issued a 2008 policy memorandum, directing the use of excess Evolved Expendable Launch Vehicle (EELV) payload weight capacity by maximizing the use of the EELV Secondary Payload Adapter (ESPA) system. This spawned the development of a standardized ESPA class auxiliary payload (APL) capability for EELV launches on both Atlas V and Delta IV launch vehicle variants. It also led to an Air Force commitment to support one EELV ESPA launch per year. The ESPA structure, which consists of a 62-inch diameter, 24-inch high adapter with accommodation for up to six APLs equally spaced around its outer shell, was developed as an approach to facilitate rideshare opportunities for small APLs on the Atlas V and Delta IV launch vehicles. However, over the course of several years’ work by the various rideshare stakeholders to develop an ESPA Standard Service (ESS) capability on EELV, a number of challenges have been encountered. These include identifying viable candidate ESS missions, coordination of primary payload and APL development and launch schedules, heightened emphasis on compliance with orbital debris mitigation requirements, and several technical and programmatic challenges. The concept of using excess lift capability on EELV launches holds significant appeal, especially considering the high cost of space launch and the increasing number of small experimental and operational payloads being developed by the DoD and other government, research and commercial entities, all of which require access to space. The goal is to make ESPA a viable, cost-effective option for fully realizing the potential for improved access to space on future EELV missions.