The EELV Secondary Payload Adapter (ESPA) is an

adapter An adapter or adaptor is a device that converts attributes of one electrical device or system to those of an otherwise incompatible device or system. Some modify power or signal attributes, while others merely adapt the physical form of one con ...

for launching

secondary payload Secondary payload, also known as rideshare payload, is a smaller-sized payload transported to orbit on a launch vehicle that is mostly paid for—and with the date and time of launch and the orbital trajectory determined—by the entity that cont ...

s on orbital

launch vehicle A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...

s. Originally developed for US launch vehicles in the 2000s to launch secondary payloads on space missions of the

United States Department of Defense The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national secu ...

that used the

Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture be ...

and

Delta IV Delta IV is a group of five expendable launch systems in the Delta (rocket family), Delta rocket family introduced in the early 2000s. Originally designed by Boeing's Defense, Space and Security division for the National Security Space Launch, ...

, the adapter design has become a ''de facto'' standard and is now also used for spaceflight missions on non-governmental

private Private or privates may refer to: Music * " In Private", by Dusty Springfield from the 1990 album ''Reputation'' * Private (band), a Denmark-based band * "Private" (Ryōko Hirosue song), from the 1999 album ''Private'', written and also recorde ...

spacecraft missions as well. For example, multiple ESPA rings were used on a non-DoD launch of the

SpaceX Space Exploration Technologies Corp. (SpaceX) is an American spacecraft manufacturer, launcher, and a satellite communications corporation headquartered in Hawthorne, California. It was founded in 2002 by Elon Musk with the stated goal of ...

Falcon 9 Falcon 9 is a partially reusable medium lift launch vehicle that can carry cargo and crew into Earth orbit, produced by American aerospace company SpaceX. The rocket has two stages. The first (booster) stage carries the second stage and payl ...

that carried the

Orbcomm ''ORBCOMM'' is an American company that offers industrial Internet of things (IoT) and machine to machine (M2M) communications hardware, software and services designed to track, monitor, and control fixed and mobile assets in markets including t ...

OG-2 constellation of communication satellites. The use of ESPA ring technology reduces launch costs for the primary mission and enables secondary and even tertiary missions with minimal impact to the original mission.

History

Development was funded by the Air Force Research Laboratory Space Vehicles Directorate (AFRL/RV) for the United States Department of Defense (DoD) Space Test Program (STP) under a Small Business Innovative Research (SBIR) grant in the late 1990s. Moog CSA Engineering teamed with AFRL to design, build and qualify the ring in the early 2000s. Additional studies have been done on ESPA applications for lunar and science missions under an SBIR from NASA Ames Research Center. , the ring is produced by Moog CSA Engineering. A number of missions have used the ESPA ring. The ESPA ring's maiden mission was on STP-1 in 2007. , the ESPA ring had been used on all 3 EELV-class rockets (

and

). Multiple ESPA rings may be used on a single launch, stacked to increase the satellite carrying capacity. Two ESPA Grande rings were used on Orbcomm OG-2 flight 1 in 2014 and three stacked Grande rings for the 11-satellite

Orbcomm OG-2 flight 2 Falcon 9 flight 20 (also known as Orbcomm OG2 M2) was a Falcon 9 space launch that occurred on 22 December 2015 at 01:29:00 UTC (21 December, 8:29:00 pm local time). It was the first time that the first stage of an orbital rocket made a succe ...

deployment in 2015.

Technical characteristics

The initial ESPA ring was designed to support a primary

payload Payload is the object or the entity which is being carried by an aircraft or launch vehicle. Sometimes payload also refers to the carrying capacity of an aircraft or launch vehicle, usually measured in terms of weight. Depending on the nature of ...

and up to six secondary payloads. Each secondary spacecraft is mounted radially on a diameter port and is allocated × × 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. ESPA Grande ports are in diameter, and can support payloads. Moog's version of the ESPA Grande supports up to payloads.

Derivatives

Derivatives of the ESPA ring include

satellite dispenser A satellite dispenser is a space tug usually released from the upper stage (sometimes called kick stage) of a rocket and designed to fly small secondary payloads to their desired location before deploying them. Project West Ford launched 480,000,0 ...

space tug ''Space Tug'' is a young adult science fiction novel by author Murray Leinster. It was published in 1953 by Shasta Publishers in an edition of 5,000 copies. It is the second novel in the author's Joe Kenmore series. Groff Conklin gave it a mixe ...

s and

satellite bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are opposed to specially produced satellites. Bus-d ...

es.

SHERPA

Commercial derivatives of the ESPA Grande ring include the Spaceflight Secondary Payload System (SSPS) and SHERPA developed and manufactured by

Andrews Space Andrews Space was founded in 1999 by Jason Andrews and Marian Joh to be a catalyst in the commercialization, exploration and development of space. Originally named Andrews Space & Technology, the company shortened its name in 2003 to Andrews Space. ...

under contract to Spaceflight Services. SSPS includes five -diameter ports, each capable of carrying payloads weighing up . "The SSPS operates very similar to a standalone spacecraft with a flight computer, electrical power system,

orbit determination Orbit determination is the estimation of orbits of objects such as moons, planets, and spacecraft. One major application is to allow tracking newly observed asteroids and verify that they have not been previously discovered. The basic methods wer ...

capability, and payload

power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may a ...

switching." SHERPA is a powered variant of SSPS capable of large orbit change.

LCROSS

When NASA upgraded its

Lunar Reconnaissance Orbiter The Lunar Reconnaissance Orbiter (LRO) is a NASA robotic spacecraft currently orbiting the Moon in an eccentric polar mapping orbit. Data collected by LRO have been described as essential for planning NASA's future human and robotic missions t ...

(LRO) mission's launch vehicle to an Atlas V, it freed around 2,200 lbs. of additional mass for what would later become the Lunar Crater Observation and Sensing Satellite (LCROSS). NASA held a competition to see how best to use the space and a number of proposals came from the Ames Research Center. The winning proposal included Moog CSA Engineering's ESPA ring serving as the base mechanical

to launch the

LCROSS The Lunar Crater Observation and Sensing Satellite (LCROSS) 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. Launched immedi ...

spacecraft as a secondary payload under the LRO. LCROSS ultimately impacted the lunar surface and confirmed the presence of water ice. The LCROSS Lunar-impact water detection mission in 2009 took advantage of the structural capabilities of ESPA ring to attach all six of its science experiments, command and

control Control may refer to: Basic meanings Economics and business * Control (management), an element of management * Control, an element of management accounting * Comptroller (or controller), a senior financial officer in an organization * Controllin ...

systems, communications equipment, batteries, solar panels, and even a small monopropellant propulsion system to implement pre-impact payload separation and

ESPAStar

The ESPAStar is a comparable design concept by

Orbital Sciences Corporation Orbital Sciences Corporation (commonly referred to as Orbital) was an American company specializing in the design, manufacture, and launch of small- and medium- class space and launch vehicle systems for commercial, military and other governmen ...

. Its maiden flight was on the AFSPC-11 mission as the EAGLE secondary payload.

Long Duration Propulsive ESPA (LDPE)

The LDPE (Long Duration Propulsive ESPA) is based on a

Northrop Grumman Northrop Grumman Corporation is an American multinational aerospace and defense technology company. With 90,000 employees and an annual revenue in excess of $30 billion, it is one of the world's largest weapons manufacturers and military techn ...

payload adapter used to help attach the upper stage to the main satellite in addition to hosting a few slots for other smallsats. However, the entire system is powered by the ESPAStar satellite bus, which is in charge of power consumption and distribution as well as propulsion making it a fully operational space tug capable of deploying different payloads at different orbits. ESPAStar has the capability to host 6 smallsat payloads totaling 1,920 kg (4,230 lb). The system is also able to provide 400 meters per second of delta-V via a Hydrazine propulsion module. The first LDPE was launched on 7 December 2021 on an

rocket as part of the STP-3 mission. It carried the Ascent cubesat from the

Air Force Research Laboratory The Air Force Research Laboratory (AFRL) is a scientific research organization operated by the United States Air Force Materiel Command dedicated to leading the discovery, development, and integration of aerospace warfighting technologies, pl ...

that was used to test commercial off-the-shelf technologies in geosynchronous orbit, including cold gas thrusters, electric propulsion, and a global position receiver. A second LDPE was launched on 1 November 2022 on a

Falcon Heavy Falcon Heavy is a partially reusable heavy-lift launch vehicle that is produced by SpaceX, an American aerospace manufacturer. The rocket consists of two strap-on boosters made from Falcon 9 first stages, a center core also made from a Falc ...

rocket as part of the USSF-44 mission, and it carried three separable payloads and three hosted payloads. The separable payloads included Alpine, a cubesat from Millennium Space Systemto demonstrate GEO small satellite designs and leverage commercial GEO communications; LINUSS, a Lockheed Martin project consisting of two 12U cubesats to test GEO satellite servicing; and Tetra-1, an SSC small satellite designed as a pathfinder for innovative methods of space vehicle design and on-orbit Tactics Techniques and Procedures development. The hosted payloads included: Mustang, a small sized communications experiment; Xenon, a commercial off-the-shelf component maturation for flight at GEO; and Energetic Charged Particle-Lite, an SSC space weather sensor. A third LDPE was launched on 15 January 2023 on a

as part of the USSF-67 mission, and it carried five hosted payloads. Among those, two belonged to the

Space Systems Command Space Systems Command (SSC) is the United States Space Force's space development, acquisition, launch, and logistics field command. It is headquartered at Los Angeles Air Force Base, California and manages the United States' space launch ra ...

: Catcher, a prototype sensor to provide local space domain awareness insights, and WASSAT, a sensor consisting of four cameras to search for and track other spacecrafts and space debris. The other three payloads have been provided by the Space Rapid Capabilities Office and included two prototypes for space situational awareness missions and one to test encrypted space-to-ground communications.

References

External links

Triple ESPA ring for SpaceX Orbcomm OG-2 launch
October 2015. {{Space Spaceflight technology