ESPA: The EELV Secondary Payload Adapter

Heavy Lift. Excess Capacity. Small Satellites.

The Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter, or ESPA, is an adapter ring developed by Moog CSA Engineering.  The ring mounts up to six 400-pound secondary satellites to "share a ride to space" with a primary payload up to 15,000 pounds.  The ESPA, which weighs 275 pounds, attaches between the primary payload and the Evolved Expendable Launch Vehicle (EELV) upper stage on Atlas V or Delta IV. 

The ESPA was developed under a Small Business Innovation Research (SBIR) contract to the Air Force Research Laboratory Space Vehicles Directorate (AFRL/VS) with support from the DoD Space Test Program at Kirtland Air Force Base.  Unused launch capacity, a growing interest in missions utilizing small satellites, and a desire for affordable launch opportunities led to the development.


Current ESPA Programs

  • STP-1, ESPA’s maiden voyage, launched on March 8,2007 from Cape Canaveral Air Force Station.  Using ESPA, six satellites were launched on an Atlas V launch vehicle.
  • NASA’s Lunar Crater Observation and Sensing Satellite (LCROSS) and the Lunar Reconnaissance Orbiter (LRO) were launched using a single ESPA ring.  ESPA was the spacecraft hub for the LCROSS Shepherding Satellite.  It also served as a mounting platform for science instruments and spacecraft components.
  • NASA Ames Small Spacecraft Division sponsored development of ESPA variants for Lunar and Science Missions under an SBIR contract.
  • DSX will use a four-port ESPA as the hub of a free-flyer spacecraft in Medium Earth Orbit.  The SoftRide Isolation System will be used to provide whole spacecraft vibration isolation for the DSX Avionics and Payload Modules on two of the ports.


ESPA Brochure

Download PDF

SoftRide ShockRing

SoftRide ShockRing is designed to attach satellites to ESPA and mitigate transmission of shock to sensitive payloads.  Vibration isolation systems are also available.

Moog CSA

For additional information on ESPA:

Moog CSA Engineering
2565 Leghorn St
Mountain View, CA 94043