Power and Propulsion Element

{{Short description|Power and propulsion module for the Gateway space station}}

{{Infobox spaceflight

| name = Power and Propulsion Element

| names_list = PPE
Asteroid Redirect Vehicle

| image = Gateway - PPE and HALO 004.png

| image_caption = Artist's impression of the PPE, attached to HALO, firing its engines in lunar orbit.

| image_size = 300px

| mission_type = Power and propulsion module

| operator = Northrop Grumman / NASA

| COSPAR_ID =

| SATCAT =

| website =

| mission_duration = 15 years (planned)

| spacecraft = PPE

| manufacturer = Maxar Technologies

| launch_mass = {{cvt|5000|kg}}

| dimensions =

| diameter =

| volume =

| power = 60 kW

| launch_date = 2027 (planned){{cite web |url=https://www.gao.gov/products/gao-24-106878 |title=Artemis Programs: NASA Should Document and Communicate Plans to Address Gateway's Mass Risk |work=GAO |date=31 July 2024 |access-date=31 July 2024}}

| launch_rocket = Falcon Heavy

| launch_site = Kennedy Space Center, LC-39A

| launch_contractor = SpaceX

|programme = Lunar Gateway

|previous_mission = CAPSTONE

|next_mission = HALO

}}

The Power and Propulsion Element (PPE), previously known as the Asteroid Redirect Vehicle propulsion system, is a planned solar electric ion propulsion module being developed by Maxar Technologies for NASA. It is one of the major components of the Lunar Gateway. The PPE will allow access to the entire lunar surface and a wide range of lunar orbits and double as a space tug for visiting craft.{{cite press release|url=https://www.nasa.gov/press-release/nasa-awards-artemis-contract-for-lunar-gateway-power-propulsion|title=NASA Awards Artemis Contract for lunar Gateway Power, Propulsion|publisher=NASA|date=23 May 2019|access-date=11 December 2019|archive-date=20 September 2019|archive-url=https://web.archive.org/web/20190920171731/https://www.nasa.gov/press-release/nasa-awards-artemis-contract-for-lunar-gateway-power-propulsion/|url-status=live}} {{PD-notice}}{{cite web |title=Deep Space Gateway and Transport: Concepts for Mars, Moon Exploration Unveiled|date=4 April 2017 |url=http://www.sci-news.com/space/deep-space-gateway-transport-mars-moon-exploration-04756.html|url-status=live|archive-url=https://web.archive.org/web/20190530113409/http://www.sci-news.com/space/deep-space-gateway-transport-mars-moon-exploration-04756.html|archive-date=30 May 2019|access-date=2019-05-30|publisher=Science News}}

The PPE originally started development at the Jet Propulsion Laboratory as a part of the now cancelled Asteroid Redirect Mission, but is now led and managed by the NASA John H. Glenn Research Center, in Cleveland, Ohio. When ARM was cancelled, the solar electric propulsion was repurposed as the PPE for the Gateway.{{cite web|date=2017-06-14|title=NASA closing out Asteroid Redirect Mission|url=https://spacenews.com/nasa-closing-out-asteroid-redirect-mission/|access-date=30 May 2019|publisher=SpaceNews}}{{cite web|title=Asteroid Redirect Robotic Mission|url=https://www.jpl.nasa.gov/missions/asteroid-redirect-robotic-mission-arrm/|url-status=live|archive-url=https://web.archive.org/web/20190530113407/https://www.jpl.nasa.gov/missions/asteroid-redirect-robotic-mission-arrm/|website=jpl.nasa.gov|publisher=NASA|archive-date=30 May 2019|access-date=30 May 2019}} {{PD-notice}} 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.{{cite web|last=Clark|first=Stephen|title=NASA chooses Maxar to build keystone module for lunar Gateway station |url=https://spaceflightnow.com/2019/05/24/nasa-chooses-maxar-to-build-keystone-module-for-lunar-gateway-station/|url-status=live|archive-url=https://web.archive.org/web/20190605140715/https://spaceflightnow.com/2019/05/24/nasa-chooses-maxar-to-build-keystone-module-for-lunar-gateway-station/|archive-date=5 June 2019|access-date=2019-05-30 |publisher=Spaceflight Now}} The PPE is intended to have a launch mass of {{cvt|5000|kg}} with propellant accounting for half that mass {{cite web|last=Boyle|first=Alan| url=https://www.geekwire.com/2019/nasa-says-maxar-will-build-first-big-piece-gateway-space-outpost-lunar-orbit/|title=NASA says Maxar will build the first big piece for Gateway station in lunar orbit|publisher=GeekWire|date=23 May 2019|access-date=28 August 2023}} and the capability to generate 50 kW {{cite web|last=Foust|first=Jeff|date=3 November 2017 |title=NASA issues study contracts for Deep Space Gateway element|url=https://spacenews.com/nasa-issues-study-contracts-for-deep-space-gateway-element/|publisher=SpaceNews|access-date=11 December 2019}} of solar electric power using Roll Out Solar Arrays for its Hall-effect thrusters, which can be supplemented by chemical propulsion.{{cite web|last1=Chris Gebhardt|title=NASA finally sets goals, missions for SLS – eyes multi-step plan to Mars|date=6 April 2017|url=https://www.nasaspaceflight.com/2017/04/nasa-goals-missions-sls-eyes-multi-step-mars|url-status=live|archive-url=https://web.archive.org/web/20170821221210/https://www.nasaspaceflight.com/2017/04/nasa-goals-missions-sls-eyes-multi-step-mars/|archive-date=21 August 2017|access-date=April 9, 2017|publisher=NASASpaceFlight.com}} It is currently planned to launch on a Falcon Heavy no earlier than 2027 along with the HALO module.{{Cite web |last=Dunbar |first=Brian |date=2023-12-18 |title=Gateway |url=https://www.nasa.gov/mission/gateway |access-date=2023-12-25 |website=NASA}}

Development

= Asteroid Redirect Vehicle bus =

The Asteroid Redirect Vehicle was a robotic, high performance solar electric spacecraft for the Asteroid Redirect Mission (ARM). The mission was to send the spacecraft to a near-Earth asteroid 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.{{cite web|title=JPL Seeks Robotic Spacecraft Development for Asteroid Redirect Mission|url=http://www.nasa.gov/feature/jpl/jpl-seeks-robotic-spacecraft-development-for-asteroid-redirect-mission|last=Greicius|first=Tony|date=2016-09-20|url-status=live|archive-url=https://web.archive.org/web/20190617075954/https://www.nasa.gov/feature/jpl/jpl-seeks-robotic-spacecraft-development-for-asteroid-redirect-mission/|archive-date=17 June 2019|access-date=30 May 2019|publisher=NASA}} {{PD-notice}} 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, space tug 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 (ion engines) {{cite news|last=Tate|first=Karl|date=2013-04-10|title=How to Catch an Asteroid: NASA Mission Explained (Infographic)|publisher=Space.com|url=http://www.space.com/20610-nasa-asteroid-capture-mission-infographic.html|access-date=2015-03-26}}). 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.{{cite journal|last1=Cassady|first1=J.|last2=Maliga|first2=K.|last3=Overton|first3=S.|last4=Martin|first4=T.|last5=Sanders|first5=S.|last6=Joyner|first6=C.|last7=Kokam|first7=T. |last8=Tantardini|first8=M.|year=2015|title=Next Steps in the Evolvable Path to Mars|journal=Proceedings of the IAC}}{{cite work|last=Craig|first=D.|title=Evolvable Mars Campaign |date=10 June 2015}}{{cite work|last=Troutman|first=P.|title=The Evolvable Mars Campaign: the Moons of Mars as a Destination|date=July 30, 2014}}{{cite news |last1=Howell|first1=E.|date=May 8, 2015|title=Human Mars Plan: Phobos by 2033, Martian Surface by 2039?|publisher=Space.com|url=http://www.space.com/29349-manned-mars-missions-phobos-moon.html|access-date=October 9, 2016}}{{cite journal|last1=McElratht|first1=T.|last2=Elliott|first2=J.|date=Jan 2014|title=There and Back again: Using planet-based SEP tugs to repeatably aid interplanetary payloads |journal=Advances in the Astronautical Sciences|issue=152|pages=2279–2298}}{{cite book|last1=Price|first1=Humphrey W.|title=AIAA SPACE 2014 Conference and Exposition|last2=Woolley|first2=Ryan |last3=Strange|first3=Nathan J.|last4=Baker|first4=John D.|year=2014|isbn=978-1-62410-257-8|chapter=Human Missions to Mars Orbit, Phobos, and Mars Surface Using 100-kWe-Class Solar Electric Propulsion |doi=10.2514/6.2014-4436}}

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, 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.{{cite work|last=Manzanek|first=D.|title=The Asteroid Redirect Mission|date=May 20, 2016|publisher=USNO Scientific Colloquium}}{{cite work |last1=Gates|first1=M.|title=Asteroid Redirect Mission (ARM)|last2=Manzanek|first2=D.|date=June 28, 2016|publisher=15th Meeting of the NASA Small Bodies Assessment Group}}{{cite journal |author1=Manzanek, D.|author2=Reeves, D.|author3=Hopkins, J.|author4=Wade, D.|author5=Tantardini M.|author6=Shen, H.|date=April 13, 2015|title=Enhanced Gravity Tractor Technique for Planetary Defense |journal=IAA-PDC}}{{cite work|title=NASA RFI: Spacecraft Bus Concepts to Support the ARM and In-Space Robotic Servicing- Section "Separable Spacecraft Architecture ARRM Concept"}}{{cite web|url=http://big11news.com/2020/03/11/nasa-bbc-news/|title=Will April 2020 be the last month on this Earth? NASA told the whole truth|publisher=Big 11 News|access-date=March 20, 2020|archive-date=20 March 2020|archive-url=https://web.archive.org/web/20200320050412/http://big11news.com/2020/03/11/nasa-bbc-news/|url-status=dead}} When the ARM was cancelled however, development on the bus and any reusable tug ideas died, temporarily.

= Power and Propulsion Element =

File:NASA and ESA's Lunar Gateway.png

In 2017, a year after the Artemis program came into existence, the ARM space tug/propulsion bus was repurposed as the main propulsion system for the Gateway space station. It officially became known as the Power and Propulsion Element or PPE. The PPE will be a smaller version of the Asteroid Redirect bus.{{cite web|last=Foust|first=Jeff|date=30 March 2018|title=NASA considers acquiring more than one gateway propulsion module|url=https://spacenews.com/nasa-considers-acquiring-more-than-one-gateway-propulsion-module/|publisher=SpaceNews|access-date=11 December 2019}} In 2018, the Gateway was split off from Artemis as a separate program to allow a 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, Lockheed Martin, Orbital ATK, Sierra Nevada and Space Systems/Loral.{{cite web|last1=Jimi Russell|title=NASA Selects Studies for Gateway Power and Propulsion Element|url=https://www.nasa.gov/press-release/nasa-selects-studies-for-gateway-power-and-propulsion-element|url-status=live|archive-url=https://web.archive.org/web/20180112203046/https://www.nasa.gov/press-release/nasa-selects-studies-for-gateway-power-and-propulsion-element/ |website=nasa.gov|date=November 2017|publisher=NASA|archive-date=12 January 2018|access-date=2 November 2017}} {{PD-notice}} 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,{{cite web|last1=Robyn Gatens|first1=Jason Crusan|title=Cislunar Habitation and Environmental Control and Life Support System |url=https://www.nasa.gov/sites/default/files/atoms/files/20170329-nacheoc-crusan-gatens-hab-eclss-v5b.pdf|url-status=live|archive-url=https://web.archive.org/web/20170331210530/https://www.nasa.gov/sites/default/files/atoms/files/20170329-nacheoc-crusan-gatens-hab-eclss-v5b.pdf|website=nasa.gov|publisher=NASA|archive-date=31 March 2017 |access-date=March 31, 2017}} {{PD-notice}} so the Gateway is likely to incorporate components developed under NextSTEP as well.{{cite web |last1=Erin Mahoney|title=NextSTEP Partners Develop Ground Prototypes to Expand our Knowledge of Deep Space Habitats|url=https://www.nasa.gov/feature/nextstep-partnerships-develop-ground-prototypes|url-status=live|archive-url=https://web.archive.org/web/20170410051227/https://www.nasa.gov/feature/nextstep-partnerships-develop-ground-prototypes/|archive-date=10 April 2017|access-date=6 November 2017 |website=nasa.gov|date=9 August 2016|publisher=NASA}} {{PD-notice}}

= Contract awarded =

In May 2019, Maxar Technologies 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 series satellite bus.{{cite press release|url=https://www.nasa.gov/press-release/nasa-awards-artemis-contract-for-lunar-gateway-power-propulsion|title=NASA Awards Artemis Contract for Lunar Gateway Power, Propulsion |publisher=NASA|date=23 May 2019|access-date=11 December 2019|archive-date=20 September 2019|archive-url=https://web.archive.org/web/20190920171731/https://www.nasa.gov/press-release/nasa-awards-artemis-contract-for-lunar-gateway-power-propulsion/|url-status=live}} {{PD-notice}} The PPE will use Busek 6 kW Hall-effect thrusters and NASA Advanced Electric Propulsion System (AEPS) Hall-effect thrusters.{{cite news|last=Foust|first=Jeff|date=May 23, 2019|title=NASA selects Maxar to build first Gateway element|publisher=SpaceNews|url=https://spacenews.com/nasa-selects-maxar-to-build-first-gateway-element|access-date=May 23, 2019}}[https://www.researchgate.net/profile/R_Cassady/publication/328997773_Status_of_Advanced_Electric_Propulsion_Systems_for_Exploration_Missions/links/5beee33692851c6b27c37074/Status-of-Advanced-Electric-Propulsion-Systems-for-Exploration-Missions.pdf Status of Advanced Electric Propulsion Systems for Exploration Missions] {{Webarchive |url=https://web.archive.org/web/20190613101313/https://www.researchgate.net/profile/R_Cassady/publication/328997773_Status_of_Advanced_Electric_Propulsion_Systems_for_Exploration_Missions/links/5beee33692851c6b27c37074/Status-of-Advanced-Electric-Propulsion-Systems-for-Exploration-Missions.pdf|date=13 June 2019}} R. Joseph Cassady, Sam Wiley, Jerry Jackson; Aerojet Rocketdyne, October 2018{{cite press release|title=Maxar and Busek Thruster System for NASA Lunar Gateway Passes Critical Milestone|url=https://www.prnewswire.com/news-releases/maxar-and-busek-thruster-system-for-nasa-lunar-gateway-passes-critical-milestone-301250199.html|access-date=2021-04-28|website=www.prnewswire.com|language=en}} Maxar was awarded a firm-fixed price contract of US$375 million to build the PPE. Maxar's SSL business unit, previously known as Space Systems/Loral, will lead the project. Maxar stated they will receive help from Blue Origin and Draper Laboratory 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 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".[https://www.nasaspaceflight.com/2018/09/nasa-lunar-gateway-plans/ NASA updates Lunar Gateway plans] {{Webarchive|url=https://web.archive.org/web/20190806063256/https://www.nasaspaceflight.com/2018/09/nasa-lunar-gateway-plans/|date=6 August 2019}}, Philip Sloss, NASASpaceFlight.com, 11 September 2018 Its expected service time is about 15 years.{{cite web|title=Gateway Update: NASA ADVISORY COUNCIL Human Exploration and Operations Committee|url=https://www.nasa.gov/sites/default/files/atoms/files/20181207-crusan-gateway-reduced-v4tagged.pdf|first=Jason|last=Crusan|date=7 December 2018|access-date=12 November 2022}}{{PD-notice}}

= To be launched with HALO =

As originally planned, PPE would be compatible with the International Docking System Standard (IDSS).{{Cite web|last=Robinson|first=Julie A.|date=11 October 2018|title=Update on Gateway with Science and Technology (Utilization) Discussion|url=https://sites.nationalacademies.org/cs/groups/depssite/documents/webpage/deps_189332.pdf|access-date=|website=}} This meant that any IDSS capable spacecraft could theoretically dock to the PPE, such as Orion, the International Space Station, Dragon 2, Dream Chaser, and Boeing Starliner.

In 2020, NASA announced that the PPE would be integrated before launch with HALO, the renamed Utilization Module.[https://www.nasaspaceflight.com/2020/08/northrop-halo-plans-gateway/ Northrop Grumman outlines HALO plans for Gateway’s central module Aug 2020] In February 2021 NASA contracted with SpaceX for launch of the integrated elements by a Falcon Heavy launch vehicle.{{cite web |url=https://www.nasa.gov/news-release/nasa-awards-contract-to-launch-initial-elements-for-lunar-outpost/ |title=NASA Awards Contract to Launch Initial Elements for Lunar Outpost |date=9 Feb 2021 |publisher=NASA}}

In mid 2024, the HALO module reached significant completion and entered into the stress test phase in Thales Alenia's facilities. Upon successful completion of the stress tests, it is planned to be shipped to the US Northrop Grumman facilities to undergo final launch preparation and integration with the Power and Propulsion Element.{{Cite web |date=2024-06-10 |title=Gateway's HALO Making Moves - NASA |url=https://www.nasa.gov/image-article/gateway-halo-making-moves/ |access-date=2024-06-18 |language=en-US}}