|Carrier rocket||Space Launch System|
The Lunar Orbital Platform-Gateway (LOP-G) is a international project led by NASA proposed to create a lunar-orbit space station. It is intended to serve as a solar-powered communications hub, science laboratory, short-term habitation module, and holding area for rovers and other robots.
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.
The Gateway is meant to be developed, serviced, and utilized in collaboration with commercial and international partners. It will also serve as the staging point for crewed and robotic lunar exploration and a staging point for NASA's proposed Deep Space Transport craft to perform a 300-400 day shakedown mission prior to NASA's first crewed Mars mission. Deep Space Transport is a concept of a reusable vehicle that uses electric and chemical propulsion and would be specifically designed for crewed missions to destinations such as Mars.
The development is led by the International Space Station partners: ESA, NASA, Roscosmos, JAXA and CSA for construction in the 2020s. The International Space Exploration Coordination Group (ISECG), which comprises 14 space agencies participating with NASA, have concluded that LOP-G will be critical in expanding human presence to the Moon, Mars and deeper into the Solar System. Formerly known as the Deep Space Gateway, the station was renamed in NASA's proposal for the 2019 United States federal budget. The omnibus spending bill passed by Congress in March 2018 provided NASA with $504 million for preliminary studies during the 2019 fiscal year. The final funding amount enacted by Congress was slightly lower at $450 million.
Originally, NASA had intended to build the Gateway as part of the now cancelled Asteroid Redirect Mission. An informal joint statement on cooperation between NASA and Russia's Roscosmos was announced on 27 September 2017. Traveling to and from cislunar space (lunar orbit) will help gain the knowledge and experience necessary to venture beyond the Moon and into deep space. The LOP-G would be placed in a highly elliptical near-rectilinear halo orbit (NRHO) around the Moon which will bring the station within 1,500 km (930 mi) of the lunar surface at closest approach and as far away as 70,000 km (43,000 mi) on a six-day orbit. This orbit would allow lunar expeditions from the Gateway to reach a polar low lunar orbit using 730 m/s of delta-v in half a day. Orbital station-keeping would require less than 10 m/s of delta-v per year.
The Gateway could conceivably also support in-situ resource utilization (ISRU) development and testing from lunar and asteroid resources, and would offer the opportunity for gradual buildup of capabilities for more complex missions over time. Various components of the Gateway would be launched on commercial launch vehicles and on the Space Launch System as Orion co-manifested payloads on the flights EM-3 through EM-8. According to Roscosmos, they may also use Proton-M and Angara-A5M heavy launchers to fly payloads or crew.
The Power and Propulsion Element (PPE) for the LOP-G would have a mass of 8-9 t and be capable of generating 50 kW of solar electric power for its ion thrusters system for maneuverability, which can be supported by chemical propulsion. Patrick Troutman serves as the lead for strategic assessments for the Deep Space Transport and the Lunar Orbital Platform-Gateway.
On 7 November 2017, NASA asked the global science community to submit concepts for scientific studies that could take advantage of the Gateway's location in cislunar space. The Deep Space Gateway Concept Science Workshop was held in Denver, Colorado from February 27 to March 1, 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.
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. In February 2018 it was announced that those NextSTEP studies and other ISS partner studies would help to guide the capabilities required of the Gateway's habitation modules.
NASA has also 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 January 17, 2019 addressing one of these four themes. NASA will select 20 teams to continue developing proposed concepts. Fourteen of the teams will be invited to present their projects in person in June 2019 at the RASC-AL Forum in Cocoa Beach, Florida and will receive a $6,000 stipend to participate in the Forum.
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 are Boeing, Lockheed Martin, Orbital ATK, Sierra Nevada and Space Systems/Loral. 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 Orbital Platform-Gateway as well as other commercial applications, so the LOP-G is likely to incorporate components developed under NextSTEP as well.
NASA plans to award contracts to one or more of the commercial bidders in early 2019 to build, launch, and demonstrate an electric propulsion spacecraft that meets requirements for a Gateway PPE. After a one-year demonstration period, NASA would then "exercise a contract option to take over control of the spacecraft."
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. The engine is being developed by Glenn Research Center, the Jet Propulsion Laboratory, and Aerojet Rocketdyne. Four identical AEPS engines would consume the 50 kW generated.
The early concept for the lunar Gateway is still evolving, and may include the following component modules:
- The Power and Propulsion Element (PPE) will be used to generate electricity for the space station and its solar electric propulsion. It is targeting launch on a commercial vehicle in 2022.
- The European System Providing Refuelling, Infrastructure and Telecommunications (ESPRIT) module will provide additional xenon and hydrazine capacity, additional communications equipment, and an airlock for science packages. It would have a mass of approximately 4 tons, and a length of 3.91 m.
- The U.S. Utilization Module is a small pressurized space that would enable a crew ingress on the very first mission to the Gateway assembly sequence. It will initially store additional food and will be launched along with ESPRIT on EM-3.
- The International Partner Habitat and the U.S. Habitat are the two habitation modules. These will be launched on EM-4 and EM-5 and together will provide a minimum of 125 m3 of habitable volume to the station.
- The Gateway Logistics Modules will be used to refuel, resupply and provide logistics on board the space station. The first logistics module sent to LOP-G will also arrive with a robotic arm, which will be built by the Canadian Space Agency.
- The Gateway Airlock Module will be used for performing extravehicular activities outside the space station and will be the berth for the Deep Space Transport.
The work on crewed landers would be supported under a new budget line called "Advanced Cislunar and Surface Capabilities" included in the fiscal year 2019 budget proposal, which seeks $116.5 million for the program. Congress has yet to pass a final fiscal year 2019 appropriations bill for NASA. Some lander architectures have already been suggested and are listed below.
- HERACLES (Human-Enhanced Robotic Architecture and Capability for Lunar Exploration and Science) is a proposed ESA-JAXA-CSA robotic lander and sample-return mission utilising the Gateway station. It involves dispatching an 11-ton lunar lander from Earth aboard an Ariane 64:slides 7, 9 and 10 which would land on the Moon before an ascent module heads to the Gateway station. The ascent modules are reusable and would be paired at Gateway with a fresh lander module dispatched from Earth. The rovers would land on the first and fourth lander missions collecting samples and loading them on the ascent module then traversing the hundreds of kilometres between landing sites on the lunar surface to rendezvous and load the next lander. The ascent module would return each time to the Gateway where it would be captured by the Canadian robotic arm and samples transferred to an Orion craft for transport to Earth with returning astronauts while the 2nd and 3rd landings would each have 500 kg payload available for alternate uses. The aim of the project is the development by ESA of a reusable lunar ascent engine, four of which could be clustered to power a wholly reusable crewed or robotic lander in the future, alongside the development of Gateway telecommunication command and control technology. ESA envisages that HERACLES would be subject to ministerial approval in 2019, and could allow a sample-return on the fourth or fifth Orion flight in the 2026-2030 timeframe, generating an early scientific return for the station and robotic surveying of the conditions that will be encountered at future crewed landing sites several years in advance.
- The Lockheed Martin Lunar Lander concept, presented in October 2018, proposes a reusable crewed lunar lander with a mass of 22 tons and capable of carrying up to 1 ton of payload, and a crew of four, for a duration of two weeks before returning to the Gateway for servicing and refueling. A drawback is that not even the future Block 1B version of Space Launch System can place more than 45 tons onto a trajectory to the Moon, so additional launches would be required to transport fuel depots for the lander.
- Advanced Exploration Lander is a lander concept by a NASA team that is studying a three-stage vehicle that would allow departure from the Gateway and take the crew to a low lunar orbit and then separate, after which the descent module would handle the rest of the journey to the lunar surface. A crew of up to four would spend up to two weeks on the surface before boarding the ascent module, which would take them back to the Gateway. The three stages are: the transfer module (a space tug), the descent module and the ascent module. Each module would have a mass of approximately 12 to 15 metric tons that would be delivered separately by commercial launchers and integrated there. The astronauts would board the lander at the Gateway and its transfer module would take the lander from the Gateway's near-rectilinear halo orbit that goes between about 1,000 and 70,000 kilometers above the Moon, to a circular low orbit about 100 kilometers high. The ascent and descent stages would then go down together to the lunar surface, and at the end of the mission the ascent stage would fire its engines to go back directly the Gateway while leaving the descent stage behind. Both the ascent and transfer modules could be designed to be reused. If selected and funded, it could be tested as a stand-alone robotic mission in 2024 and begin crewed landings in 2028 departing from the Gateway.
|Year||Vehicle assembly objective||Mission name||Launch vehicle||Human/robotic elements|
|Q4 2022||Start of the Lunar Orbital Platform-Gateway assembly by launching the Power and Propulsion Element (PPE)||TBD||Commercial launch vehicle||Uncrewed|
|2024||ESPRIT and the U.S. Utilization Module launch and are mated to PPE in a L2 Southern Near Rectilinear Halo Orbit (NRHO)||EM-3||Space Launch System, Block 1B||Crewed|
|No Earlier Than 2024||Delivery of International Partner Habitat||EM-4||Space Launch System, Block 1B||Crewed|
|No Earlier Than 2025||Delivery of U.S. Habitat||EM-5||Space Launch System, Block 1B||Crewed|
|No Earlier Than 2024||Delivery of the first logistics module and the robotic arm||EM-6||Space Launch System, Block 1B||Crewed|
|2026||Orion capsule (crew 4) delivers the Airlock Module to the Gateway||EM-7||Space Launch System, Block 1B||Crewed|
|2027||Deep Space Transport (DST) to the Lunar Gateway||EM-8||Space Launch System, Block 1B||Uncrewed|
|2027||DST checkout mission||EM-9||Space Launch System, Block 1B||Crewed|
|2028||DST Cargo logistics and refuelling||EM-10||Space Launch System, Block 1B||Uncrewed|
|2029||DST one-year cruise test (shakedown cruise) in cislunar space||EM-11||Space Launch System, Block 2||Crewed|
|2030||Cargo DST logistics and refuelling mission||EM-12||Space Launch System, Block 2||Uncrewed|
|2033||DST cruise for injection into Mars orbit||EM-13||Space Launch System, Block 2||Crewed|
The lunar Gateway has received numerous criticisms from several space professionals for lacking a proper scientific goal, while NASA officials promote the Gateway as a "reusable command module" that could direct activities on the lunar surface.
Michael Griffin, the former NASA administrator, said that in his opinion, the Gateway can 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 best serve as a fuel depot. He said that "putting a Gateway before boots on the Moon is, from a space-systems engineer's standpoint, a stupid architecture".
Former NASA Astronaut Terry 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 safety dictum of separating the crew from the cargo which was put in place following the Space Shuttle Columbia accident in 2003.
Mars Society founder Robert Zubrin, who has been one of the staunchest advocates for a human mission to Mars, called the lunar Gateway "NASA's worst plan yet" in an article on the National Review. Zubrin went on to say "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" and that "there is nothing at all in lunar orbit: nothing to use, nothing to explore, nothing to do". 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."
Retired aerospace engineer Gerald Black stated that the "LOP-G is useless for supporting human return to the lunar surface and a lunar base." He added that it is not even planned to be used as a rocket fuel depot and that stopping at LOP-G on the way to or from the Moon would serve no useful purpose and it would actually waste rocket fuel.
Pei Zhaoyu, deputy director of the Lunar Exploration and Space Program Center of the China National Space Administration, concludes that, from a cost-benefit standpoint, the gateway would have "lost cost-effectiveness." Pei said the Chinese plan is to focus on a research station on the surface.
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 as to "why would you want 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.
Former NASA Astronauts Eileen Collins, who was a Space Shuttle pilot and commander, and Harrison Schmidt, who was Lunar Module pilot aboard Apollo 17, although did not mention the Gateway directly, criticized NASA's plans for not being ambitious enough. Collins stated that "2028 for humans on the moon seems like it's so far off" and that "we can do it sooner" while Schmidt stated that "the pace of the proposed program didn't match what took place under Apollo."
Mark Whittington, who is a contributor to the Hill Newspaper and an author of several space exploration studies stated in an article that "NASA’s unnecessary $504 million lunar orbit project doesn’t help us get back to the Moon". Whittington also pointed out "that a lunar orbiting space station was not necessary for men to go to the moon and back 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."
Ethan Siegel, a Ph.D. astrophysicist and senior contributor to Forbes, wrote in an article that "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, allowing you to control landers and rovers there with less of a time delay than you experience on Earth. By approximately one second." and that the Lunar Gateway is "a great way to spend a great deal of money, advancing science and humanity in no appreciable way."
- Commercial Resupply Services
- Deep Space Transport
- Deep Space Habitat
- Exploration Gateway Platform
- International Space Station
- Lunar Orbital Station, a proposed Russian space station
- Next Space Technologies for Exploration Partnerships
- Orbital Piloted Assembly and Experiment Complex
- Project Prometheus
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