EELV Secondary Payload Adapter
Encyclopedia
The EELV Secondary Payload Adapter (ESPA) is an interstage
adapter ring utilized for launching secondary payloads on US DoD
space
missions that utilize the Evolved Expendable Launch Vehicles (EELV) Atlas V
and Delta IV. This reduces launch costs for the primary mission and enables secondary and even tertiary missions with minimal impact to the original mission. The adapter design has become a de facto standard and is now planned for use on some private
spacecraft missions as well.
, the ESPA ring is used on Atlas V
and Delta IV rockets, although SpaceX
has recently announced pricing for ESPA-compatible payloads on their Falcon 9
rocket.
Lunar-impact water detection mission in 2009 took advantage of the structural capabilities of the Evolved Expendable Launch Vehicle Secondary Payload Adapter (ESPA) ring to attach all six of its science experiments, command and control systems, communications equipment, batteries, solar panels, and even a small monopropellant propulsion system
to implement pre-impact payload separation and control
.
Multistage rocket
A multistage rocket is a rocket that usestwo or more stages, each of which contains its own engines and propellant. A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or...
adapter ring utilized for launching secondary payloads on US DoD
United States Department of Defense
The United States Department of Defense is the U.S...
space
Outer space
Outer space is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, and neutrinos....
missions that utilize the Evolved Expendable Launch Vehicles (EELV) Atlas V
Atlas V
Atlas V is an active expendable launch system in the Atlas rocket family. Atlas V was formerly operated by Lockheed Martin, and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance...
and Delta IV. This reduces launch costs for the primary mission and enables secondary and even tertiary missions with minimal impact to the original mission. The adapter design has become a de facto standard and is now planned for use on some private
Private spaceflight
Private spaceflight is flight above Earth altitude conducted by and paid for by an entity other than a government. In the early decades of the Space Age, the government space agencies of the Soviet Union and United States pioneered space technology augmented by collaboration with affiliated design...
spacecraft missions as well.
History
Development was funded by the Air Force Research Laboratory Space Vehicles Directorate (AFRL/VS) for the United States Department of Defense (DoD) Space Test Program (STP) under a Small Business Innovative Research (SBIR) grant in the late 1990's. Additional studies have been done on ESPA applications for lunar and science missions under an SBIR from NASA Ames Research CenterTechnical characteristics
ESPA was designed to support a 15000 pounds (6,803.9 kg) primary payload and up to six 400 pounds (181.4 kg) secondary payloads. The standard version of the ring measures 60 inches (152.4 cm) in diameter by 26 inches (66 cm) tall and has an empty mass of 250 pounds (113.4 kg). Each secondary spacecraft is mounted radially on a 15 inches (38.1 cm) diameter port and is allocated 24 inches (61 cm) x 24 inches (61 cm) x 48 inches (121.9 cm) volume. This has led to the colloquial designation of “ESPA-class” payloads. The design includes a standard electrical interface for the attached payloads; however mission-specific requirements may preclude each secondary payload from receiving more than a single, non-redundant payload separation signal., the ESPA ring is used on Atlas V
Atlas V
Atlas V is an active expendable launch system in the Atlas rocket family. Atlas V was formerly operated by Lockheed Martin, and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance...
and Delta IV rockets, although SpaceX
SpaceX
Space Exploration Technologies Corporation, or more popularly and informally known as SpaceX, is an American space transport company that operates out of Hawthorne, California...
has recently announced pricing for ESPA-compatible payloads on their Falcon 9
Falcon 9
Falcon 9 is a rocket-powered spaceflight launch system designed and manufactured by SpaceX. Both stages of its two-stage-to-orbit vehicle use liquid oxygen and rocket-grade kerosene propellants...
rocket.
Notable missions
A number of missions have utilized the ESPA ring. For example, the LCROSSLCROSS
The Lunar Crater Observation and Sensing Satellite was a robotic spacecraft operated by NASA. The mission was conceived as a low-cost means of determining the nature of hydrogen detected at the polar regions of the moon. The main LCROSS mission objective was to explore the presence of water ice...
Lunar-impact water detection mission in 2009 took advantage of the structural capabilities of the Evolved Expendable Launch Vehicle Secondary Payload Adapter (ESPA) ring to attach all six of its science experiments, command and control systems, communications equipment, batteries, solar panels, and even a small monopropellant propulsion system
Monopropellant rocket
A monopropellant rocket is a rocket that uses a single chemical as its propellant.-Chemical-reaction monopropellant rockets:...
to implement pre-impact payload separation and control
Reaction control system
A reaction control system is a subsystem of a spacecraft whose purpose is attitude control and steering by the use of thrusters. An RCS system is capable of providing small amounts of thrust in any desired direction or combination of directions. An RCS is also capable of providing torque to allow...
.