Lunar Gateway

Artist's concept of the Lunar Gateway orbiting the Moon. The Orion spacecraft is about to dock on the right.
Station statistics
Crew	4 (planned)
Carrier rocket	Commercial launch vehicles Proton-M Angara [1][2]
Launch pad	Kennedy Space Center
Mission status	Modules in development: PPE, HALO, ESPRIT and iHab.
Pressurised volume	Planned: ≥125 m3 (4,400 cu ft)[3]
Pericynthion altitude	3,000 km (1,900 mi)[4]
Apocynthion altitude	70,000 km (43,000 mi)[4]
Orbital inclination	Polar
Orbital period	≈7 days [4]

The Lunar Gateway is an in-development 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.^[5] It is expected to play a major role in NASA's Artemis program.

While the project is led by NASA, the Gateway is meant to be developed, serviced, and utilized in collaboration with commercial and international partners. 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.^[6][7][8]

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.^[9]

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.^[7][10][11] 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.^[12] 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.^[13][14] When the budgeting process was complete, US$332 million ^[15] had been committed by Congress to preliminary studies.^[16][17]

Current planning

Although the configuration is not final, this infographic shows the current lineup of parts comprising the Gateway. Modules shown in blue are U.S. contributions; modules shown in purple are proposed international components; modules in yellow are both U.S. and international, or yet to be determined. Credits: NASA

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

NASA and Lockheed Martin employees group photo with one of the LOP-G space station 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 station composed of only two modules: the Power and Propulsion Element (PPE) and the Habitation and Logistics Outpost (HALO).^[18][19]

The Lunar 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.^[4][20][21] 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.^[22]

The Gateway could conceivably also support in-situ resource utilization (ISRU) development and testing from lunar and asteroid sources,^[23] and would offer the opportunity for gradual buildup of capabilities for more complex missions over time.^[24] Various components of the Gateway were originally planned to be assembled using the SLS as co-manifested flights with the Orion spacecraft,^[25] but will now be launched on commercial launch vehicles.^[26] According to Roscosmos, they may also use Proton-M and Angara-A5M heavy launchers to fly payloads or crew.^[11]

All modules will be connected using the International Docking System Standard.^[27]

Contracted 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.^[28] When ARM was cancelled, the solar electric propulsion was repurposed for the Gateway.^[29][30] The PPE will allow access to the entire lunar surface and act as a space tug for visiting craft.^[31] It will also serve as the command and communications center of the Gateway.^[32][33] The PPE is intended to have a mass of 8-9 t and the capability to generate 50 kW^[34] of solar electric power for its ion thrusters, which can be supplemented by chemical propulsion.^[35] It is currently planned to launch on a commercial launch vehicle in 2022.^[36][37] 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.^[38][39] 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.^[40]

• The Habitation and Logistics Outpost (HALO),^[41][42] also called the Minimal Habitation Module (MHM) and formerly known as the Utilization Module,^[43] will be built by Northrop Grumman Innovation Systems (NGIS).^[18][44] A commercial launch vehicle would launch the HALO before the end of year 2023. The HALO is based on a Cygnus Cargo resupply module^[18] 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,^[45] yet, it will feature a functional pressurized volume providing sufficient command, control & 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.^[44]

• 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.^[3] It will have a mass of approximately 4 t (8,800 lb), and a length of 3.91 m (12.8 ft).^[46] The studies and design are being performed mostly by Airbus^[47] and OHB.^[48] The module construction was approved in November 2019.^[49][50]

• The International Habitation Module (iHAB) will be an additional habitation module built by ESA in collaboration with Japan.^[49] Together with the HALO module, they will provide a combined 125 m³ (4,400 cu ft) of habitable volume to the station.^[3]

Proposed modules

The concept for the Lunar Gateway is still evolving, and is intended to include the following modules:^[51]

• The Gateway Logistics Modules will be used to refuel, resupply and provide logistics on board the 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.^[52][53]

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

Proposed timeline

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 Lunar Gateway.^[54]

History

Deep Space Habitat concept.

Studies

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.^[59] 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.^[60]

On 27 September 2017, an informal joint statement on cooperation between NASA and Russia's Roscosmos was announced.^[11] The solar electric Power and Propulsion Element (PPE) of the Gateway was originally a part of the now-canceled Asteroid Redirect Mission.^[61][34]

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.^[9] 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.^[62]

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 the following areas:

• Gateway Uncrewed Utilization & Operations
• Gateway-Based Human Lunar Surface Access
• Gateway Logistics as a Science Platform
• 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 $6,000 stipend to participate in the Forum.^[5] "Lunar Exploration and Access to Polar Regions" from the University of Puerto Rico at Mayagüez was the winning concept.^[63]

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.^[64][34] 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 Lunar Gateway as well as other commercial applications,^[8] so the Gateway is likely to incorporate components developed under NextSTEP as well.^[34][65]

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.^[66] Four identical AEPS engines would consume the 50 kW generated.^[66]

In 2019, the contract to manufacture the PPE was awarded to a division of Maxar Technologies (formerly SSL).^[31] After a one-year demonstration period, NASA would then "exercise a contract option to take over control of the spacecraft."^[67] Its expected service time is about 15 years.^[68]

Criticism

NASA officials promote the Gateway as a "reusable command module" that could direct activities on the lunar surface.^[69] However, the lunar Gateway has received criticisms from several space professionals:

Former NASA Astronaut Terry W. Virts, who was a pilot of STS-130 aboard Space Shuttle Endeavour and Commander of the International Space Station on Expedition 43, wrote in an Op-ed on Ars Technica that the Lunar Gateway would "shackle human exploration, not enable it". Terry stated that there is no concrete human spaceflight goal with the Gateway and that he cannot envision a new technology that would be developed or validated by building another modular space station. 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.^[70]

Mars Society founder Robert Zubrin, who has consistently advocated a human mission to Mars, called the Lunar Gateway "NASA's worst plan yet" in an article in the National Review. Zubrin went on to state that, in his opinion, the proposed Gateway would not be useful to go to the Moon, Mars, near-Earth asteroids, or any other possible destination. He also stated that the ISS could accomplish many of the goals for the Gateway, and that "there is nothing at all in lunar orbit". Zubrin also stated that "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." He also stated that a station in lunar orbit without shielding would: "expose human subjects to irradiation – a form of medical research for which a number of Nazi doctors were hanged at Nuremberg.^[71]

Retired aerospace engineer Gerald Black stated that the Lunar 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 Lunar Gateway on the way to or from the Moon would serve no useful purpose and cost propellant.^[72]

In July 2018, 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 Lunar Gateway would have "lost cost-effectiveness."^[73] Pei said the Chinese plan is to focus on a research station on the surface.^[74]

Michael D. Griffin, a former NASA administrator, said that in his opinion, the Lunar Gateway can be useful only after there are facilities on the Moon producing propellant that could be transported to the Lunar Gateway. Griffin thinks that after that is achieved, the Lunar Gateway would then best serve as a fuel depot.^[69]

Former 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.^[75]

Former NASA astronaut Eileen Collins, who was a Space Shuttle pilot and commander, and Harrison Schmitt, who was Lunar Module pilot aboard Apollo 17, criticized NASA's plans for not being ambitious enough. Although they did not mention the Lunar Gateway directly, Collins stated that "2028 for humans on the moon seems like it's so far off" and that "we can do it sooner", while Schmitt stated that "the pace of the proposed program didn't match what took place under Apollo."^[75]

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."^[76]

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 Lunar Gateway is "a great way to spend a great deal of money, advancing science and humanity in no appreciable way."^[77]

Former NASA Associate Administrator Doug Cooke wrote in an article on The Hill stating that the Gateway should be deferred in favor of further developing the Space Launch System's Exploration Upper Stage. Cooke also wrote that the SLS Block 1B can be used to launch a lunar lander in a single launch thus reducing the amount of critical mission operations.^[78]

George Abbey, a former director of NASA's Johnson Space Center stated that "The "lunar Gateway" is, in essence, building a space station to orbit a natural space station, namely the moon." and that "If we are going to return the moon, we should go directly there, not build a space station to orbit it."^[79]

Supportive reasoning

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."^[80]

"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," Bridenstine arguing for the international cooperation in applying the Gateway and concludes with "That's American leadership."

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
• International Space Station – Space station in low Earth orbit
• Lunar Orbital Station
• 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

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