ESPA Overview

Heavy lift. Excess capacity. And now a way to use it.

The ESPA ring, or the Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter was developed to utilize excess launch capacity by mounting additional payloads below the primary spacecraft.  This reduces launch costs for the primary mission and enables secondary and even tertiary missions with minimal impact to the original mission.

ESPA allows up to six secondary satellites, up to 400 pounds each, to "share a ride to space" on Delta IV or Atlas V launch vehicles while carrying a large primary satellite.  ESPA can accommodate up to a 15,000-pound primary satellite using the standard EELV interface plane bolt pattern, which is a drop-in component in the launch stack.  The standard secondary interface is a 15-inch-diameter bolt circle with 24 fasteners.

The ESPA structure underwent extensive engineering analysis and a qualification test program to demonstrate its capability to withstand the harsh launch vibration environment.  Moog CSA can provide the mechanical design, stress analysis and structural test engineering to tailor ESPA for each customer's needs.

ESPA was developed by CSA Engineering, under an SBIR contract to the Air Force Research Laboratory Space Vehicles Directorate (AFRL/VS) for the DoD Space Test Program (SMC/Det 12).  STP developed technology requirements and operational inputs.  AFRL/VS led the research and development effort and integrated the technology development team.

On-Going ESPA Development

  • Small Launch ESPA - 38.8-inch ring, 8- or 15-inch ports for Minotaur 4, Falcon 1e, Taurus, or Delta 2.
  • ESPA Grande - The "stretch" version of the ESPA Ring, accommodates four 300-kg secondary spacecraft on 24-inch ports.
  • Separating ESPA - Integrated Separation System reduces adapter mass and height. Ruag (Saab Space) and Lightband separation systems.
  • Multiple Secondary Satellite Payload Integration - Mission planning, document management, flight avionics, coupled loads analysis, separation systems, integration validation and test.
  • Propulsive ESPA - Utilizing Moog CSA / ISP propulsion components.

Noteworthy ESPA Programs

  • STP-1, the maiden voyage of ESPA, launched in April 2007 from Cape Canaveral Air Force Station.
  • LCROSS (The Lunar CRater Observation and Sensing Satellite) impacted the moon on October 9, 2009.  The ESPA Ring was used as the primary structure for LCROSS.
  • DSX will use ESPA as the hub of a free-flyer spacecraft.
  • ESPA Orbital Maneuvering System (OMS). Development support provided by the Air Force Research Lab and Dod Space Test Program.
  • ESPA variants for lunar and science missions.  Sponsored development provided by NASA Ames Small Spacecraft Division.
  • EAGLE (the ESPA Augmented Geostationary Laboratory Experiment)
    An ESPA ring will be used as part of this free-flying design with its own integrated propulsion system.

Small Satellite Rideshare Wiki

Learn more about ESPA on the new Small Satellite Rideshare Wiki.

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