The Power and Propulsion Element (PPE), previously known as the Asteroid Redirect Vehicle propulsion system, is a planned

solar electric A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

propulsion module being developed by

Maxar Technologies Maxar Technologies Inc. is a space technology company headquartered in Westminster, Colorado, United States, specializing in manufacturing communication, Earth observation, radar, and on-orbit servicing satellites, satellite products, and relat ...

for

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

. It is one of the major components of the Gateway. The PPE will allow access to the entire lunar surface and a wide range of lunar orbits and double as a

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 ...

for visiting craft. The PPE originally started development at the

Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States. Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...

as a part of the now cancelled

Asteroid Redirect Mission The Asteroid Redirect Mission (ARM), also known as the Asteroid Retrieval and Utilization (ARU) mission and the Asteroid Initiative, was a space mission proposed by NASA in 2013; the mission was later cancelled. The Asteroid Retrieval Robotic ...

, but is now led and managed by the NASA John H. Glenn Research Center, in

Cleveland Cleveland ( ), officially the City of Cleveland, is a city in the U.S. state of Ohio and the county seat of Cuyahoga County. Located in the northeastern part of the state, it is situated along the southern shore of Lake Erie, across the U.S. ...

Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...

. When ARM was cancelled, the solar electric propulsion was repurposed as the PPE for the Gateway. The PPE is designed to be able to transfer the reusable Gateway to lunar orbit. It will also serve as the communications center of the Gateway. The PPE is intended to have a mass of 8–9 tons and the capability to generate 50 kW of solar electric power using Roll Out Solar Arrays for its Hall-effect thrusters, which can be supplemented by chemical propulsion. It is currently planned to launch 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 ...

in November 2024 along with the HALO module. The PPE will be compatible with the

International Docking System Standard The International Docking System Standard (IDSS) is an international standard for spacecraft docking adapters. It was created by the International Space Station Multilateral Coordination Board, on behalf of the International Space Station partne ...

. This means that any IDSS Spacecraft could theoretically dock to the PPE, such as Orion, the

International Space Station The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ...

Dragon 2 Dragon 2 is a class of partially reusable spacecraft developed and manufactured by American aerospace manufacturer SpaceX, primarily for flights to the International Space Station (ISS). SpaceX has also launched private missions such as Ins ...

Dream Chaser Dream Chaser is an American reusable lifting-body spaceplane being developed by Sierra Nevada Corporation (SNC) Space Systems. Originally intended as a crewed vehicle, the Dream Chaser Space System is set to be produced after the cargo varian ...

, and

Boeing Starliner The Boeing CST-100 Starliner
is a class of two partially reusable spacecraft designed to transp ...

. The other modules of the Lunar Gateway will most likely also be IDSS compatible.

Development

Asteroid Redirect Vehicle bus

The Asteroid Redirect Vehicle was a robotic, high performance solar electric spacecraft for the

(ARM). The mission was to send the spacecraft to a near-Earth

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

and capture a multi-ton boulder from the surface with a grappling device. It would then transport the asteroid into orbit around the moon where crewed missions to study it could be conducted more easily. The mission was cancelled in early 2017 and the spacecraft's propulsion segment became the Power and Propulsion Element (PPE) for the Deep Space Gateway, now known as the Gateway.

Reusable Space Tug missions

During the Asteroid Redirect Mission,

missions were purposed to separate Mars logistics that can spend a longer time in space than the crew into a separate mission, which could have reduced the costs by as much as 60% (if using advanced

solar electric propulsion Solar electric propulsion (SEP) refers to the combination of solar cells and electric thrusters to propel a spacecraft through outer space. This technology has been exploited in a variety of spacecraft by the European Space Agency (ESA), th ...

(ion engines) ). They would also reduce the overall mission risk by enabling check-out of critical systems at Mars before the crew departs Earth. This way if something goes wrong in those logistics, the crew is not in danger and the hardware can simply be fixed or relaunched. Not only would the solar electric propulsion (SEP) technologies and designs be applied to future missions, but the ARM spacecraft would be left in a stable orbit for reuse. The project had baselined any of multiple refueling capabilities. The asteroid-specific payload was at one end of the

spacecraft 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- ...

, either for possible removal and replacement via future servicing, or as a separable, reusable spacecraft, leaving a qualified space tug in cislunar space. This made adaption for Gateway easy, as the propulsion system was already designed to be multi-mission reusable. When the ARM was cancelled however, development on the bus and any reusable tug ideas died, temporarily.

Power and Propulsion Element

In 2017, a year after the

Artemis program The Artemis program is a robotic and human Moon exploration program led by the United States' National Aeronautics and Space Administration (NASA) along with three partner agencies: European Space Agency (ESA), Japan Aerospace Exploration ...

came into existence, the ARM space tug/propulsion bus was dusted off and repurposed as the main propulsion system for the Gateway space station, and officially became known as the Power and Propulsion Element or PPE. The PPE will be a smaller version of the Asteroid Redirect bus. The Gateway was eventually broken off from Artemis as a separate program to ensure the speedy moon landing by 2024 without having to wait for the Gateway to be completed.

Commercial company studies

On 1 November 2017, NASA commissioned 5 studies lasting four months into affordable ways to develop the Power and Propulsion Element (PPE), hopefully leveraging private companies' plans. These studies had a combined budget of US$2.4 million. The companies performing the PPE studies were

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and product ...

Lockheed Martin The Lockheed Martin Corporation is an American aerospace, arms, defense, information security, and technology corporation with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It ...

Orbital ATK Northrop Grumman Innovation Systems (NGIS) was a sector (business segment) of Northrop Grumman from 2018 through 2019. It was formed from Orbital ATK Inc. a company which resulted from the merger of Orbital Sciences Corporation and parts of Alli ...

Sierra Nevada The Sierra Nevada () is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily ...

and

Space Systems/Loral SSL, formerly Space Systems/Loral, LLC (SS/L), of Palo Alto, California, is a wholly owned manufacturing subsidiary of Maxar Technologies. SSL designs and builds satellites and space systems for a wide variety of government and commercial cust ...

. These awards are in addition to the ongoing set of NextSTEP-2 awards made in 2016 to study development and make ground prototypes of habitat modules that could be used on the Gateway as well as other commercial applications, so the Gateway is likely to incorporate components developed under NextSTEP as well.

Contract awarded

In May 2019,

was contracted by NASA to manufacture this module, which will also supply the station with electrical power and is based on Maxar's

SSL 1300 The SSL 1300, previously the LS-1300 and the FS-1300, is a satellite bus produced by Maxar Technologies. Total broadcast power ranges from 5 to 25 kW, and the platform can accommodate from 12 to 150 transponders. The SSL 1300 is a modular platf ...

series

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 ...

. The PPE will use

Busek Busek Co. Inc. is an American spacecraft propulsion company that provides thrusters, electronics, and complete systems for spacecraft. History Busek was founded in 1985 by Vlad Hruby and incorporated in Natick, Massachusetts. It started as a l ...

6kW Hall-effect thrusters and NASA

Advanced Electric Propulsion System Advanced Electric Propulsion System (AEPS) is a solar electric propulsion system for spacecraft that is being designed, developed and tested by NASA and Aerojet Rocketdyne for large-scale science missions and cargo transportation.Blue Origin Blue Origin, LLC is an American private spaceflight, privately funded aerospace manufacturer and sub-orbital spaceflight services company headquartered in Kent, Washington. Founded in 2000 by Jeff Bezos, the founder and executive chairman of Am ...

and

Draper Laboratory Draper Laboratory is an American non-profit research and development organization, headquartered in Cambridge, Massachusetts; its official name is The Charles Stark Draper Laboratory, Inc (sometimes abbreviated as CSDL). The laboratory specialize ...

on the project, with Blue Origin assisting in human-rating and safety aspect while Draper will work with trajectory and navigation development. NASA is supplying the PPE with a

S-band The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the conventional ...

communications system to provide a radio link with nearby vehicles and a passive docking adapter to receive the Gateway's future utilization module. Maxar stated they are experienced dealing with high power components from making satellites. They did mention that their satellites are around 20 to 30 kilowatts, while the PPE will be about 60 kilowatts, but they say much of the technology they have already developed will still be applicable. After a one-year demonstration period, NASA would then "exercise a contract option to take over control of the spacecraft".NASA updates Lunar Gateway plans
, Philip Sloss, ''NASASpaceFlight.com'', 11 September 2018 Its expected service time is about 15 years.

References

{{Future spaceflights 2024 in spaceflight Artemis program Crewed spacecraft Joint ventures Missions to the Moon NASA programs NASA space stations Spacecraft using halo orbits Proposed space stations