Lunar Gateway

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 km (1,900 mi) of the lunar north pole at closest approach and as far away as 70,000 km (43,000 mi) over the lunar south pole.[3][32][33] 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 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 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.[34]

One of the advantages of an NRHO 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. The Gateway could conceivably also support in-situ resource utilization (ISRU) development and testing from lunar and asteroid sources,[35] and would offer the opportunity for gradual buildup of capabilities for more complex missions over time.[36]

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).[37][38] 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,[39] but will now be launched on commercial launch vehicles.[40] According to Roscosmos, they may also use Proton-M and Angara-A5M heavy launchers to fly payloads or crew;[13] however, this is no longer on the agenda.[41] All modules will be connected using the International Docking System Standard.[42] Both PPE and HALO will be assembled on Earth and launched together on a single launcher in January 2024,[43] and they are expected to reach lunar orbit after nine to ten months.[44] 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.[45]

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.[81] The two modules (PPE and HALO) will be launched together on a single launcher in January 2024.[43]

NASA officials promote the Gateway as a "reusable command module" that could direct activities on the lunar surface.[86] However, the Gateway has received both positive and negative reactions from 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.[86]

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".[87] 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".[88]

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.[89] 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.[90]

Pei Zhaoyu, deputy director of the Lunar Exploration and Space Program Center of the China National Space Administration (CNSA), concluded that, from a cost-benefit standpoint, the Gateway would have "low cost-effectiveness".[91] Pei said the Chinese plan is to focus on a national research station on the surface.[92] In July 2019, Pei announced that China was holding discussions with Russia and the ESA on international co-operation [93] and in August 2020 unveiled China's concept; the International Lunar Research Station (ILRS) [94] with co-operation from Russia and tentative agreement from ESA.

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".[95]

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.[96]

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".[97]

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".[98]

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".[99]

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".[100]

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

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