Summary

A lunar orbital space station under development

Lunar Gateway

Concept art of the Gateway as it is intended to appear in 2024; the PPE and HALO modules are visible with a cargo spacecraft docked.
Station statistics
Crew	4 (planned)
Launch	2024 (planned) [1]
Carrier rocket	SpaceX Falcon Heavy, or ULA Vulcan Centaur, or Blue Origin New Glenn
Launch pad	Kennedy Space Center
Mission status	Modules in development: PPE HALO
Pressurised volume	Planned: ≥125 m3 (4,400 cu ft)[2]
Pericynthion altitude	3,000 kilometres (1,900 mi)[3]
Apocynthion altitude	70,000 kilometres (43,000 mi)[3]
Orbital inclination	Polar near-rectilinear halo orbit (NRHO)[3]
Orbital period	≈7 days[3]
Configuration
Although not the final configuration, this infographic shows the current lineup of parts comprising the Gateway.   US modules   International modules   US and/or international modules

The Lunar Gateway is a planned space station in lunar orbit intended to serve as a solar-powered communication hub, science laboratory, short-term habitation module, and holding area for rovers and other robots.^[4] It is expected to play a major role in NASA's Artemis program, after 2024. While the project is led by NASA, the Gateway is meant to be developed, serviced, and utilized in collaboration with commercial and international partners: Canada (CSA), Europe (ESA), and Japan (JAXA). It will serve as the staging point for both robotic and crewed exploration of the lunar south pole, and is the proposed staging point for NASA's Deep Space Transport concept for transport to Mars.^[5][6][7] Formerly known as the Deep Space Gateway (DSG), the station was renamed Lunar Orbital Platform-Gateway (LOP-G) in NASA's 2018 proposal for the 2019 United States federal budget.^[8][9] When the budgeting process was complete, US$332 million had been committed by Congress to preliminary studies.^[10][11][12]

The science disciplines to be studied on the Gateway are expected to include planetary science, astrophysics, Earth observations, heliophysics, fundamental space biology, and human health and performance.^[13] Gateway development includes all of the International Space Station partners: ESA, NASA, Roscosmos, JAXA, and CSA. Construction is planned to take place in the 2020s.^[6][14][15] The International Space Exploration Coordination Group (ISECG), which is composed of more than 14 space agencies including all major ones, has concluded that Gateway will be critical in expanding a human presence to the Moon, Mars, and deeper into the Solar System.^[16]

Name and logo

The Gateway is with its name and logo associated with the American frontier symbol of the St. Louis Gateway Arch.^[17]

The Gateway logo

History

Studies

2012 concept for the Deep Space Habitat, consisting a cryogenic propulsion stage, an ISS-derived habitat module, and a MPLM

An earlier NASA proposal for a cislunar station had been made public in 2012 and was dubbed the Deep Space Habitat. That proposal had led to funding in 2015 under the NextSTEP program to study the requirements of deep space habitats.^[18] In February 2018, it was announced that the NextSTEP studies and other ISS partner studies would help to guide the capabilities required of the Gateway's habitation modules.^[19] On 27 September 2017, an informal joint statement on cooperation between NASA and Russia's Roscosmos was announced.^[15] The solar electric Power and Propulsion Element (PPE) of the Gateway was originally a part of the now-canceled Asteroid Redirect Mission.^[20][21] On 7 November 2017, NASA asked the global science community to submit concepts for scientific studies that could take advantage of the Deep Space Gateway's location in cislunar space.^[13] The Deep Space Gateway Concept Science Workshop was held in Denver, Colorado from 27 February to 1 March 2018. This three-day conference was a workshop where 196 presentations were given for possible scientific studies that could be advanced through the use of the Gateway.^[22]

In 2018, NASA initiated a Revolutionary Aerospace Systems Concepts Academic Linkage (RASC-AL) competition for universities to develop concepts and capabilities for the Gateway. The competitors are asked to employ original engineering and analysis in one of four areas; "Gateway Uncrewed Utilization and Operations", "Gateway-Based Human Lunar Surface Access", "Gateway Logistics as a Science Platform", and "Design of a Gateway-Based Cislunar Tug". Teams of undergraduate and graduate students were asked to submit a response by 17 January 2019 addressing one of these four themes. NASA will select 20 teams to continue developing proposed concepts. Fourteen of the teams presented their projects in person in June 2019 at the RASC-AL Forum in Cocoa Beach, Florida, receiving a US$6,000 stipend to participate in the Forum.^[4] "Lunar Exploration and Access to Polar Regions" from the University of Puerto Rico at Mayagüez was the winning concept.^[23]

Power and propulsion

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 $2.4 million. The companies performing the PPE studies were Boeing, Lockheed Martin, Orbital ATK, Sierra Nevada and Space Systems/Loral.^[24][21] 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,^[7] so the Gateway is likely to incorporate components developed under NextSTEP as well.^[21][25] NASA officials stated that the most likely ion engine to be used on the PPE is the 14 kW Hall thruster called Advanced Electric Propulsion System (AEPS) which has an Isp of up to 2,600 s (25 km/s). The engine is being developed by Glenn Research Center, the Jet Propulsion Laboratory, and Aerojet Rocketdyne.^[26] Four identical AEPS engines would consume the 50 kW generated.^[26] In 2019, the contract to manufacture the PPE was awarded to a division of Maxar Technologies (formerly SSL).^[27] After a one-year demonstration period, NASA would then "exercise a contract option to take over control of the spacecraft".^[28] Its expected service time is about 15 years.^[29]

Orbit and operations

The Gateway is planned to be deployed in a highly elliptical seven-day near-rectilinear halo orbit (NRHO) around the Moon, which would bring the station within 3,000 kilometres (1,900 mi) of the lunar north pole at closest approach and as far away as 70,000 kilometres (43,000 mi) over the lunar south pole.^[3][30][31] Traveling to and from cislunar space (lunar orbit) is intended to develop the knowledge and experience necessary to venture beyond the Moon and into deep space. The proposed NRHO orbit would allow lunar expeditions from the Gateway to reach a low polar orbit with a delta-v of 730 m/s and a half a day of transit time. Orbital station-keeping would require less than 10 m/s of delta-v per year, and the orbital inclination could be shifted with a relatively small delta-v expenditure, allowing access to most of the lunar surface. Spacecraft launched from Earth would perform a powered flyby of the Moon (delta-v=~180 m/s) followed by a ~240 m/s delta-v NRHO orbit insertion burn to dock with the Gateway as it approaches the apoapsis point of its orbit. The total travel time would be 5 days; the return to Earth would be similar in terms of trip duration and delta-v requirement if the spacecraft spends 11 days at the Gateway. The crewed mission duration of 21 days and ~840 m/s delta-v are limited by the capabilities of the Orion life support and propulsion systems.^[32]

One of the advantages of a NRHO orbit is the minimal amount of communications blackout with the Earth.

Gateway will be the first mini-space station to be both human-rated, and autonomously operating most of the time in its early years, as well as being the first deep-space station, far from Low Earth orbit. This will be enabled by more sophisticated executive control software than on any prior space station, which will monitor and control all systems. The high-level architecture is provided by the Robotics and Intelligence for Human Spaceflight lab at NASA, and implemented at NASA facilities.^{[citation needed]} The Gateway could conceivably also support in-situ resource utilization (ISRU) development and testing from lunar and asteroid sources,^[33] and would offer the opportunity for gradual buildup of capabilities for more complex missions over time.^[34]

Structure

Four astronauts inside of the Gateway mock-up module at the Space Station Processing Facility.

NASA and Lockheed Martin employees group photo with one of the Gateway modules training mock-up inside the SSPF.

For supporting the first crewed mission to the station (Artemis 3) planned for 2024, the Gateway will be a minimalistic mini-space station composed of only two modules: the Power and Propulsion Element (PPE) and the Habitation and Logistics Outpost (HALO).^[35][36] Various components of the Gateway were originally planned to be assembled using the Space Launch System (SLS) as co-manifested flights with the Orion spacecraft,^[37] but will now be launched on commercial launch vehicles.^[38] According to Roscosmos, they may also use Proton-M and Angara-A5M heavy launchers to fly payloads or crew;^[15] however, this is no longer on the agenda.^[39] All modules will be connected using the International Docking System Standard.^[40] Both PPE and HALO will be assembled on Earth and launched together with a single launcher in November 2023 and they are expected to reach lunar orbit after nine to ten months.^[41] The Canadian Space Agency, the European Space Agency and the Japan Aerospace Exploration Agency plan to participate in the Gateway project, contributing a robotic arm, refueling and communications hardware, and habitation and research capacity. Those international elements will launch after the PPE and HALO are placed into lunar orbit.^[42]

Planned modules

• The Power and Propulsion Element (PPE) started development at the Jet Propulsion Laboratory during the now canceled Asteroid Redirect Mission. The original concept was a robotic, high performance solar electric spacecraft that would retrieve a multi-ton boulder from an asteroid and bring it to lunar orbit for study.^[43] When ARM was cancelled, the solar electric propulsion was repurposed for the Gateway.^[44][45] The PPE will allow access to the entire lunar surface and act as a space tug for visiting craft.^[27] It will also serve as the command and communications center of the Gateway.^[46][47] The PPE is intended to have a mass of 8-9 tons and the capability to generate 50 kW^[21] of solar electric power for its ion thrusters, which can be supplemented by chemical propulsion.^[48] It is currently planned to launch on a commercial launch vehicle in November 2023 with HALO module.^{[49][50][51][52]} 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 1300 series satellite bus. The PPE will use Advanced Electric Propulsion System (AEPS) Hall-effect thrusters.^[53][54] Maxar was awarded a firm-fixed price contract of $375 million to build the PPE. NASA is supplying the PPE with an 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.^[55]

• The Habitation and Logistics Outpost (HALO),^[56][57] also called the Minimal Habitation Module (MHM) and formerly known as the Utilization Module,^[58] will be built by Northrop Grumman Innovation Systems (NGIS).^[35][59] A commercial launch vehicle would launch the HALO in November 2023 with PPE module.^[49][50] The HALO is based on a Cygnus Cargo resupply module^[35] to the outside of which radial docking ports, body mounted radiators (BMRs), batteries and communications antennae will be added. The HALO will be a scaled-down habitation module,^[60] yet it will feature a functional pressurized volume providing sufficient command, control and data handling capabilities, energy storage and power distribution, thermal control, communications and tracking capabilities, two axial and up to two radial docking ports, stowage volume, environmental control and life support systems to augment the Orion spacecraft and support a crew of four for at least 30 days.^[59] On 5 June 2020, Northrop Grumman Innovation Systems was awarded a contract, by NASA, of $187 million to complete the preliminary design of HALO. NASA will sign a separate contract with Northrop for the fabrication of the HALO, and for integration with the PPE, being built by Maxar.^[61]

• The European System Providing Refueling, Infrastructure and Telecommunications (ESPRIT) service module will provide additional xenon and hydrazine capacity, additional communications equipment, and an airlock for science packages, in 2025.^[2] It will have a mass of approximately 4,000 kg (8,800 lb), and a length of 3.91 m (12.8 ft).^[62] The studies and design are being performed mostly by Airbus^[63] and OHB.^[64] The module construction was approved in November 2019.^[65][66]

Proposed modules

The concept for the Gateway is still evolving, and is intended to include the following modules:^[67]

• The International Habitation Module (iHAB) will be an additional habitation module built by ESA in collaboration with Japan.^[65] Together with the HALO module, they will provide a combined 125 m³ (4,400 cu ft) of habitable volume to the station, after 2024.^[2]

• The Gateway Logistics Modules will be used to refuel, resupply and provide logistics on board the mini-space station. The first logistics module sent to the Gateway will also arrive with a robotic arm, which will be built by the Canadian Space Agency.^[68][69]

• The Gateway Airlock Module will be used for performing extravehicular activities outside the mini-space station and would have the docking port for the proposed Deep Space Transport.

Construction

Crewed flights to the Gateway are expected to use Orion and SLS, while other missions are expected to be done by commercial launch providers. In March 2020, NASA announced SpaceX with its future spacecraft Dragon XL as a first commercial partner to deliver supplies to the Gateway.^[70] The 2 modules (PPE and HALO) will be launched together on a single launcher in November 2023.^[50]

Reactions

NASA officials promote the Gateway as a "reusable command module" that could direct activities on the lunar surface.^[75] However, the Gateway has received criticisms from several space professionals.

Michael D. Griffin, a former NASA administrator, said that the Gateway could be useful only after there are facilities on the Moon producing propellant that could be transported to the Gateway. Griffin thinks that after that is achieved, the Gateway would then serve as a fuel depot.^[75]

Former NASA Associate Administrator Doug Cooke wrote in an article on The Hill stating, "NASA can significantly increase speed, simplicity, cost and probability of mission success by deferring Gateway, leveraging SLS, and reducing critical mission operations". He also wrote, "NASA should launch the lander elements (ascent and descent/transfer) on a SLS Block 1B. If an independent transfer element is required, it can be launched on a commercial launcher".^[76] George Abbey, a former director of NASA's Johnson Space Center said, "The Gateway is, in essence, building a space station to orbit a natural space station, namely the Moon. [...] If we are going to return the Moon, we should go directly there, not build a space station to orbit it".^[77]

Former NASA astronaut Terry W. Virts, who was a pilot of STS-130 aboard Space Shuttle Endeavour and commander of the ISS on Expedition 43, wrote in an Op-ed on Ars Technica that the Gateway would "shackle human exploration, not enable it". He also said, "If we don't have the goal [of Gateway], we are putting the proverbial chicken before the egg by developing "Gemini" before we know what "Apollo" will look like. Regardless of a future destination, as someone who lived on the ISS for 200 days, I cannot envision a new technology that would be developed or validated by building another modular space station. Without a specific goal, we're unlikely to ever identify one". Terry further criticized NASA for abandoning its planned goal of separating crew from cargo, which was put in place following the Space Shuttle Columbia disaster in 2003.^[78] Apollo 11 astronaut Buzz Aldrin stated that he is "quite opposed to the Gateway" and that "using the Gateway as a staging area for robotic or human missions to the lunar surface is absurd". Aldrin also questioned the benefit of the idea to "send a crew to an intermediate point in space, pick up a lander there and go down". On the other hand, Aldrin expressed support for Robert Zubrin's Moon Direct concept which involves lunar landers traveling from Earth orbit to the lunar surface and back.^[79]

Pei Zhaoyu, deputy director of the Lunar Exploration and Space Program Center of the China National Space Administration, concluded that, from a cost-benefit standpoint, the Gateway would have "lost cost-effectiveness".^[80] Pei said the Chinese plan is to focus on a research station on the surface.^[81]

Mars advocacy and Mars Society founder Robert Zubrin called the Gateway "NASA's worst plan yet" in an article in the National Review. He said, "We do not need a lunar-orbiting station to go to the Moon. We do not need such a station to go to Mars. We do not need it to go to near-Earth asteroids. We do not need it to go anywhere. Nor can we accomplish anything in such a station that we cannot do in the Earth-orbiting International Space Station, except to expose human subjects to irradiation – a form of medical research for which a number of Nazi doctors were hanged at Nuremberg". Zubrin also stated, "If the goal is to build a Moon base, it should be built on the surface of the Moon. That is where the science is, that is where the shielding material is, and that is where the resources to make propellant and other useful things are to be found".^{[82][neutrality is disputed]}

Retired aerospace engineer Gerald Black stated that the Gateway is "useless for supporting human return to the lunar surface and a lunar base". He added that it was not planned to be used as a rocket fuel depot and that stopping at the Gateway on the way to or from the Moon would serve no useful purpose and cost propellant.^[83]

Mark Whittington, who is a contributor to The Hill newspaper and an author of several space exploration studies, stated in an article that the "lunar orbit project doesn't help us get back to the Moon". Whittington also pointed out that a lunar orbiting space station was not utilized during the Apollo program and that a "reusable lunar lander could be refueled from a depot on the lunar surface and left in a parking orbit between missions without the need for a big, complex space station."^[84]

Astrophysicist Ethan Siegel wrote an article in Forbes titled "NASA's Idea For A Space Station In Lunar Orbit Takes Humanity Nowhere". Siegel stated that "Orbiting the Moon represents barely incremental progress; the only scientific "advantages" to being in lunar orbit as opposed to low Earth orbit are twofold: 1. You're outside of the Van Allen belts. 2. You're closer to the lunar surface", reducing the time delay. His final opinion was that the Gateway is "a great way to spend a great deal of money, advancing science and humanity in no appreciable way".^[85]

On 10 December 2018, NASA Administrator Jim Bridenstine said at a presentation "There are people who say we need to get there, and we need to get there tomorrow", speaking of a crewed mission to the Moon, countering with "What we're doing here at NASA is following Space Policy Directive 1", speaking of the Gateway and following up with "I would argue that we got there in 1969. That race is over, and we won. The time now is to build a sustainable, reusable architecture. [...] The next time we go to the moon, we're going to have American boots on the moon with the American flag on their shoulders, and they're going to be standing side-by-side with our international partners who have never been to the moon before".^[86]

Dan Hartman, the program manager for Gateway, on 30 March 2020, told Ars Technica that the benefits of using Gateway are extending the mission duration, buying down risk, providing research capability and the capability to re-use ascent modules. "When you go single, I'll say direct mission to the Moon, you're limited on the supplies, either with the Lander or with Orion. With the Gateway, with just with one logistics module, we think we can extend to about twice the mission duration, so 30 days to 60 days. Obviously, the more crew time you have in lunar orbit helps us with research in the human aspects of living in deep space. The more duration we have, certainly that'll help us buy down significant risk with the extreme environments that we're going to be subjecting our crews to. Because we've got to go figure out how to operate in deep space. Obviously we'll demonstrate new hardware and offer that sustainable flexible path for our Lunar Lander system. With the Gateway, the thinking is we'll be able to reuse the ascent modules potentially multiple times. And again, if we can get mission duration beyond the 30 days, it's going to offer us some additional environmental capabilities. We think it's a tremendous risk buy down asset, not only to explore the Moon sustainably, but to prove out some things that we need to do to get to Mars".^{[87][neutrality is disputed]}

See also

• CAPSTONE (spacecraft) – A NASA satellite to test the Lunar Gateway orbit
• Commercial Resupply Services – Series of contracts awarded by NASA from 2008–2016 for delivery of cargo and supplies to the ISS
• Deep Space Transport – A crewed interplanetary spacecraft concept
• Deep Space Habitat
• Exploration Gateway Platform – Original station design concept of the Lunar Gateway
• International Space Station – Space station in low Earth orbit
• Lunar Orbital Station – Proposed Russian space station on Moon orbit
• Lunar outpost (NASA) – Concepts for an extended human presence on the Moon
• Next Space Technologies for Exploration Partnerships
• Orbital Piloted Assembly and Experiment Complex – Proposed Russian space station
• Project Prometheus – NASA nuclear electric propulsion project 2003-2006

References

External links

• Deep Space Gateway to Open Opportunities for Distant Destinations - NASA Moon to Mars
• First human outpost near the Moon – RussianSpaceWeb page about the Lunar Gateway
• History of the Gateway planning