Deep Space Gateway gets closer to approval

During 2017, the concept of the cis-lunar station made major strides toward becoming a reality. Even though most of the action was taking place behind the scene, the project was slowly entering public consciousness, prompting NASA to give it a new name: the Deep Space Gateway. In October, US Vice President Mike Pence seemingly came very close to endorsing the project in a major space policy announcement. This section provides exclusive details on the status of the project in 2017.

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The architecture of the cis-lunar station as it was envisioned at the beginning of 2017.

Key specifications of the Deep Space Gateway and its components at a glance as of October 2017:

Crew (when inhabitated)
4 people
Total pressurized volume
125 cubic meters
Total mass (with Orion spacecraft)
75 tons
Solar panel power supply capability
65-70 kilowatt at the start of the mission
Electric thruster capability
26.6 kilowatts for operations
Number of engines and their power
Four 13.3-kilowatt, one 15-20 kilowatt
Xenon fuel load
Around 1,200 kilograms
Hydrazine fuel load
400 kilograms
Xenon propellant load
From 400 to 1,000 kilograms
Hydrazine fuel load
From 1,000 to 400 kilograms
Key current feature
Science airlock
Key current function
Communications with the lunar surface
Total pressurized volume
76 cubic meters
Number of docking ports
Two radial and two axial ports
Life-support system
Open loop
Crew support capability
30 days in lunar orbit
Two isolated chambers allowing emergency ingress
Spacesuit support
Russian and US suits are available for backup
Docking ports
One zenith (sky-facing) and one axial (station facing) port
Crew chamber
Nadir (station-facing) compartment
Launch mode
Either co-manifested with the SLS rocket or launched on a smaller rocket
Cargo capacity inside pressurized module
4,200 kilograms (when launched on SLS) or 2,500 kilograms
Unpressurized cargo capacity
1,175 kilograms
End of mission mode
Robotic lunar lander
Ascent stage
Reusable stage
Descent stage
Main mission
Lunar sample return
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January: Tsukuba meeting

In 2017, the first major milestone of the cis-lunar station development took place in the middle of February in the Japanese city of Tsukuba. Members of the ISS Exploration Capabilities Study Team, IECST, reviewed designs of life-support systems, common standards, module designs, mission duration assessment, various concepts for human and robotic missions to the Moon and commercial operations in the low-Earth orbit.

The teams also worked to prepare further negotiations, which were then still expected to culminate with the summit of the Heads of Agencies in 2017. To prepare for that meeting they planned the so-called Mission Design Checkpoint Review, MDC, then scheduled for July.

The partners also worked on the latest flight manifest known as Scenario 4, Rev 3A, for the assembly and operation of the cis-lunar outpost during the 2020s.

Orbit dilemma resolved?

Perhaps, most importantly, during the Tsukuba meeting, the ISS partners agreed that the so-called Near-Rectilinear Halo Orbit, NRHO, would be the best destination for the cis-lunar base, as a compromise between different missions desired by the agencies participating in the project. The issue was a sticking point, because the partners interested in exploration of the lunar surface preferred an orbit as close as 100 kilometers above the Moon, while NASA wanted much farther locations, more suitable for missions into deep space, including Mars.

For more background on this phase of the project:


Shuttling the cis-lunar station periodically between a low lunar orbit and more distant cis-lunar regions was not seriously considered because the thermal control systems of the modules would require a significant boost to counteract solar radiation reflected from the surface of the Moon when the low orbit. (Interestingly, in November 2016, Sergei Krikalev, the Executive Director for Human Space flight at Roskosmos even suggested the creation of two outposts to satisfy both requirements.) Obviously, it was not a realistic proposition from the financial standpoint.

In an effort to find a compromise between lunar and martian exploration, NASA suggested that its SLS rocket would be able to deliver the lunar lander to the NRHO orbit, from which it could make two-way journeys to the lunar surface. As of 2017, the Europeans, Canadians and Japanese agreed to consider both robotic and manned lunar landers, which would be based at the cis-lunar station in the NRHO, sources said. Later during 2017, Roskosmos also came close to adopt that position.

March: MCB proposes new scenario, new name

At the end of March, NASA's Associate Administrator for Human Exploration and Operations William Gerstenmaier outlined a new version of the prospective deep-space exploration program for the agency's advisory council. The highlight of that plan was the faster development of a spacecraft capable of carrying astronauts to the vicinity of Mars than had been anticipated in the previous scenarios. The newest strategy advanced the launch of the spacecraft now identified as the Deep Space Transport or DST, to 2027. Launched unmanned on a dedicated SLS rocket, during Exploration Mission 6, this large vehicle would mark the start of the second phase in the assembly of the cis-lunar station. The station itself was now dubbed Deep Space Gateway replacing the original designation -- the International Manned Platform -- and the term "spaceport," which had been floated as potential name just a few months earlier.

The Deep Space Transport, DST, was now penciled for launch two or three years ahead of the estimates previously discussed by NASA with its ISS partners.

According to the newest plan, the DST would arrive first at the Deep Space Gateway in the lunar orbit before embarking on a "shakedown cruise" through the cis-lunar space. That test flight would last between 300 and 400 days in 2028 or 2029. After refurbishment and resupply, the same spacecraft could then embark on a Mars flyby mission as early as 2033. Possibly, this new more ambitious timeline was encouraged by positive pronouncements about Mars exploration from the new administration in the White House in early 2017.

Changes to the Orion flight manifest


The circa March 2017 flight manifest for the first phase of the cis-lunar station assembly proposed by the Multilateral Coordination Board, MCB, of the ISS project. The resulting outpost could make unmanned transfers between various cis-lunar orbits and support lunar landings.

Unlike the plan considered by ISS partners in Tsukuba in February, the MCB strategy reserved the second SLS rocket for the launch of an unmanned probe to Jupiter's moon Europa. Then, the 3rd SLS rocket would send the Orion spacecraft with its first crew and the first piece of the Deep Space Gateway, DSG, to the cis-lunar space as early as 2022. That would be one launch earlier than Exploration Mission 3, which had been previously expected to begin the assembly of the Deep Space Gateway.

However, the new timeline reduced the available mass of the first module from 10 to 8 tons, because of a safer, but less fuel-efficient, trajectory selected for the first Orion mission carrying the crew. It might be possible to eventually regain one ton thanks to the use of the xenon propellants on the Power and Propulsion Element, PPE, carried during this mission.

The new MCB plan also contained a few other notable differences. For example, it proposed two flights in 2024, delivering unpressurized logistics and a refueling tanker, even though, previously, the partners had not planned any unpressurized cargo missions. The previously planned pressurized cargo would be delivered separately from the Orion/SLS missions, using other unmanned rockets.

The MCB decision to fly a logistics module with the Orion during Exploration Mission 4 (EM-4), essentially left the second habitation module of the Deep Space Gateway without a ride to the lunar orbit. The elimination of the second habitation module was particularly upsetting to the Japanese team, which saw it as a focus for its contribution into the program.

The MCB scenario still supported a 41-day expedition which would spend a month onboard the cis-lunar station. However MCB hoped to accomplish that flight during the EM-4 mission in 2025, while the previous schedule had called for the EM-5 mission during the same year.

The MCB schedule also adopted the use of refueling during the operation of the Deep Space Gateway.

Finally, the MCB bumped the launch of the airlock module from 2025 to 2026 and shifted it to an SLS flight from the Russian Angara-5 rocket, effectively ruling out the Russian components of the station at that stage. The same change also allowed an increase in the mass of the airlock module from six tons to 10 tons and bump up the amount of cargo hitchhiking on that flight from 1,800 to 2,500 kilograms. The development of the module was still open for cooperation with international partners or commercial developers, according to NASA.

May meeting tries to reconcile MCB schedule

The two international groups studying the Deep Space Gateway -- IECST and ISWG -- met again in Montreal, Canada, on May 15 and May 16. This time, representatives from the Russian firm RKK Energia did not participate, because the company's contract with Roskosmos on the cis-lunar station had not been renewed at the time.

The remaining teams worked on the upcoming Mission Design Checkpoint Review, MDC, which was now postponed from July to October.

In addition to the usual coordination work and reviews of ongoing developments, the partners tried to reconcile their own assembly schedule, agreed at the previous meeting in Tsukuba, Japan, at the beginning of the year, with the flight manifest issued by MCB in March.

The participants of the Montreal meeting criticized the MCB plan as "mismatching" in total volume, logistics and mission duration to the schedule carefully drafted by the partners.

At the time, the assembly scenario for the Deep Space Gateway looked as following:

Noordwijk meeting

To resolve the problem of the "lost" second habitation module, engineers began considering enlarging the remaining habitation structure. Various geometries were considered, including conical shapes. That issue was settled at the third joint meeting of the IECST and ISWG groups in 2017, which was held from August 1 to August 3, in Noordwijk, the Netherlands. The partners agreed to stretch the one remaining habitation module.

The official goal of the Noordwijk meeting was to review progress in development of the conceptual design for the so-called reference configuration of the Deep Space Gateway during Phase 1 of its assembly. The partners also worked on the planning of objectives and reviewed the status of materials for the upcoming Checkpoint Review that was still planned at the time for October 2017.

The partners also agreed to remove a scientific airlock from the Power and Propulsion Element, PPE. The scientific airlock would be used to take experiments and other payloads from the interior of the station to the vacuum of space. The airlock was moved to a newly introduced module then known as ESPRIT or CATE. ESPRIT/CATE would also bring some extra propellant for the PPE module.

The Noordwijk meeting confirmed that the ESPRIT module would be able to dock with the PPE via the IDSS docking mechanism, which would also enable refueling.

In the meantime, in Noordwijk, NASA promised to solicit proposals from its industry for studies, lasting just between three and four months into concepts of the PPE module, which would potentially lead to the readiness of the spacecraft for launch at the time of Exploration Mission-2. These short contracts would be issued within the Next Space Technologies for Exploration Partnerships No. 2 (NextSTEP-2) issued by NASA.

Electric engine issues

Engineers also discussed the primary and storage positions for the European electric thruster, eHEAT, interfaces for the robotic arm, spacewalk communications antennas and cameras.

In Noordwijk, ESA presented to NASA, for evaluation, the latest version of the eHEAT thruster concept and its alternative locations on the PPE module mostly aimed at saving mass and development time. The Canadian Space Agency had to get involved to evaluate how to use its robotic arm to carry eHEAT around the station.

NASA also began looking into the possibility of the fitting power processing units associated with the European eHEAT thruster aboard the PPE module.

At the same time, the IECST team concluded that the Solar Electric Propulsion system would not be able to provide enough burn time for the planned maneuvers and transfers for the so-called "technology demonstration goals," apparently associated with the tests of the Deep Space Transport, DST, which would arrive to the cis-lunar space in the second phase of construction. Both hydrazine and xenon supplies would have to be increased.

Moreover, a NASA analysis apparently showed that the station would not be able to perform orbit transfers or even orbital maintenance maneuvers when it docked with the Orion spacecraft, because of Orion's restrictions on the so-called tail-to-Sun pointing. (This probably meant that the aft section of the Orion spacecraft, containing crucial propulsion system, could not be pointed directly at the Sun for prolonged periods of time.) In other words, no maneuvering of the station would be possible with the crew onboard. In Noordwijk, IECST assigned specialists to study the problem.

The Russians are back!

Unlike the previous few events which saw little representation from Moscow, a full-fledged Russian delegation showed up in Noordwijk, including representatives from Roskosmos, RKK Energia and the TsNIIMash research institute. At the time, the Russian representatives were not be able to present any new proposals, but the Russian-built airlock module remained on the table as an option, even though, its design was not reviewed in Noordwijk. Instead, NASA's renderings were showing a notional US-based design.

In the meantime, back in Moscow, Roskosmos held a meeting in the middle of August, which apparently paved the way to a political decision in Russia to join the Deep Space Gateway project. Roskosmos and NASA publicly announced that agreement at the International Astronautical Congress, which was held in Adelaide, Australia, in September 2017. At the same event, Roskosmos also presented partners with a concept of an add-on module for the Deep Space Gateway specifically designed to support lunar landings.

For more background on the Russian decision to join the Deep Space Gateway effort click below:


ESPRIT concept emerges in August 2017

In Noordwijk, ESA and NASA also unveiled the latest configuration of the ESPRIT module and its associated airlock concept. In turn, the Japanese Space Agency, JAXA, responded with early ideas for the HTV-X service module, which could carry the ESPRIT module to its destination after its launch on the Ariane-6 rocket. The Program Manager Meeting, PMM, in Noordwijk, recommended that this work be continued. The initial Concept Description Document, CDD, was scheduled to be completed by Sept. 8, 2017.

Across the board

Several developments in 2017 had a potential to affect the overall design of the Deep Space Gateway. In Noordwijk, the Europeans presented their industry's proposals to lighten the structural design of the cis-lunar station while still keeping the future spacecraft safe. This had become possible thanks to the extensive experience gained during the development and operation of the International Space Station. The partners agreed to study these options.

The IECST team also worked on the challenges of preserving the so-called "open architecture" of the gateway, which would allow the near-lunar facility to expand if opportunity arose with the emergence of new private or state actors, such as SpaceX or China. At the time, engineers saw some potential problems with the ability of the power supply and attitude control systems to handle unplanned "plug-in" vehicles into the proposed design of the station. As a result, some additional reviews of the "open architecture" concept were required.

Docking ports

Engineers were working on determining standards for pumping fluids (such as water and propellant) through the IDSS docking ports of the station's modules.

Solar sail

At the Noordwijk in August, the Canadian Space Agency, CSA, proposed the concept of a solar sail which could be deployed by the agency's robotic arm. The sail would be used to control the attitude of the cis-lunar station, thus potentially saving some hydrazine propellant spent on "gravity gradient and solar pressure disturbances." For more on this proposal, click below:


Industry activities


The Deep-Space Gateway as envisioned by Boeing in 2017. (This configuration did not match the overall architecture or the design of individual components which had been evaluated by the ISS partners at the time.)

In parallel with the agency-level work, industrial contractors involved in the ISS project continued their studies of the cis-lunar outpost. On June 19, the official TASS news agency quoted head of RKK Energia Vladimir Solntsev as saying that his company had been finishing preparation of an agreement on cooperation with the Boeing company, which would cover the development of deep-space exploration systems, including the cis-lunar station.

Inching toward the political approval?

On October 5, just a day after the 60th anniversary of Sputnik, Vice President Mike Pence chaired the first meeting of the reconstituted National Space Council. The White House revived the National Space Council in July with an official goal of advising and helping implementing space policy with exploration as a national priority.

In the opening statement, Pence declared that Americans would return to the Moon to use it as a training ground for an expedition to Mars. (Ironically, Pence delivered his speech in front of the retired Space Shuttle, whose tremendous cost has been widely blamed for keeping NASA in the Earth's orbit for three decades.)

Although Pence's speech lacked details, it came as close as it gets to a political endorsement of the Deep Space Gateway. Still, the project faced many political and, more importantly, financial hurdles, before it could leave the drawing board. So far, the US Congress had kept the funding of the SLS rocket and the Orion spacecraft largely on track, thus giving the Deep Space Gateway a very solid foundation.

Unless the White House would decide to re-orient the SLS/Orion toward other goals in space, such as direct expeditions to the surface of the Moon, the Deep Space Gateway stood a fairly good chance of becoming the destination for the human space flight effort during the 2020s.

Checkpoint Review

The so-called Checkpoint Review of the Deep Space Gateway project was held in Houston from Oct. 12 to Oct. 14, 2017.

At the time of the checkpoint review, NASA initiated the first Integrated Analysis Cycle, IAC-1, of the Gateway, aimed to advance the project so it could support the acquisition of the Power and Propulsion Element, PPE, and prepare Formulation Syncronization Review, FSR, in 2018.

The event saw participation of higher level officials from the five agencies than in previous meetings. The famous cosmonaut Sergei Krikalev led the Russian delegation, which also included a representative from the international cooperation office at RKK Energia. However, the Russian team did not include engineers involved in the development of prospective space systems. Even after Moscow's recent strategic decision to join NASA-led Deep Space Gateway, an internal debate on the use of the cis-lunar station continued at the engineering level in Russia. The leadership of the development team at RKK Energia fiercely opposed the idea of relying on the Deep Space Gateway for the lunar landing and, instead, advocated lunar landing scenarios staged from the low circular orbit around the Moon.

US refocuses human space flight on Moon landing

On December 11, The White House signed its first space policy directive, SPD-1, making it the official goal of US human space flight to return astronauts to the Moon to lay the foundations for a trip to Mars. The document contained no timeline, technical details or cost estimates, but the general spirit of the announcement seemingly matched the course set within the Deep-Space Gateway program.

In particular, the new policy called for NASA to “lead an innovative and sustainable program of exploration with commercial and international partners to enable human expansion across the Solar System and to bring back to Earth new knowledge and opportunities.”

According to NASA, the new policy originated from a unanimous recommendation by the new National Space Council, chaired by Vice President Mike Pence, after its first meeting on October 5. In addition to the direction to plan for human return to the Moon, the policy also formally ended NASA’s all-but-cancelled effort to send astronauts to an asteroid.


The flight manifest for Orion, SLS and DSG projects as envisioned by MCB in March 2017:

Launch date
2018 November
26-40 days
Unmanned test flight to lunar Distant Retrograde Orbit, DRO
Europa Clipper
Unmanned launch of the SLS rocket toward Jupiter
8-21 days
Orion with crew of 4 to conduct a multi-TLI, free return 14-21-day flight, delivering Power and Propulsion Bus, PPB to NRHO
16-26 (5*) days
Orion with crew of 4, heading to NRHO and carrying Hab Module
Unpressurized logistics and refueling vehicle to support the EM-3 mission
Logistics vehicle with 2,500 kilograms of pressurized cargo to support EM-4 mission
26-41 (30*) days
Orion, crew of 4, and a 10-ton logistics module with 5,400 kilograms of cargo
26-41 (30*) days
Orion, crew of 4, Airlock Module and 2,500 kilograms of cargo in NRHO
Deep-Space Transport
SLS/Block-1B cargo
191-221 (180-210*)
Orion, crew of 4, SLS logistics module with 5,400 kilograms of cargo; DST checkout in NRHO
2,500 kilograms of cargo to support EM-7 mission
Logistics and refueling for the DST spacecraft, with 41 tons to TLI
SLS/Block-1B cargo
300-400 days
Orion; crew of 4 and a logistics module; Docking to DSG, shakedown cruise in cis-lunar space
SLS/Block 2
cargo to support EM-9 mission
after 2030
Logistics and refueling for the DST spacecraft, with 45 tons to TLI
SLS/Block 2
after 2030
Orion; crew of 4 and a logistics module with 13 tons of cargo; Mars transit and return to NRHO
SLS/Block 2
after 2030
Cis-lunar support flight

*Mission duration at destination is shown in brackets.


Chronology of the Deep Space Gateway project in 2017:

February 6-15: The ISS Exploration Capabilities Study Team, IECST, and the International Spacecraft Working Group, ISWG, meet in Tsukuba, Japan.

March 28: NASA's Associate Administrator for Human Exploration and Operations William H. Gerstenmaier delivers "Progress in Defining the Deep Space Gateway and Transport Plan" to the NASA Advisory Council.

May 15-16: The ISS Exploration Capabilities Study Team, IECST, and the International Spacecraft Working Group, ISWG, meet in Montreal, Canada.

June 27: NASA's Human Exploration and Operations Mission Directorate, HEOMD, directs the maturation of the Gateway concept. Engineering teams begin "formulation" activities in the project.

August 1-3: The ISS Exploration Capabilities Study Team, IECST, and the International Spacecraft Working Group, ISWG, meet in Noordwijk, Netherlands.

September: Heads of Agencies meet during the International Astronautical Congress, IAC, in Adelaide, Australia. Russia publicly announces its decision to cooperate with NASA and other ISS partners on the project.

October 12-14: The ISS partners conduct a Checkpoint Review of the Deep Space Gateway project in Houston, TX.

December 11: The White House signed a space policy directive aimed to return American astronauts to the Moon and to "lay foundations" for a trip to Mars.


Next chapter: Development of the near-lunar station in 2018 (INSIDER CONTENT):


Read much more about the history of the Russian space program in a richly illustrated, large-format glossy edition:



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Page author: Anatoly Zak; Last update: June 11, 2019

Page editor: Alain Chabot; Last edit: December 12, 2017

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A circa 2017 depiction of the Deep-Space Gateway during the first phase of assembly, as it was envisioned by the Multi-national Coordination Board, MCB, in the ISS project. Click to enlarge. Credit: NASA


NASA illustration circa 2017 depicts the arrival of the Deep-Space Transport at the Deep-Space Gateway during the second phase in the assembly of the cis-lunar outpost as it was envisioned by the Mulit-national Coordination Board, MCB, in the ISS project. Click to enlarge. Credit: NASA


The Deep Space Transport arrives at Mars as envisioned by NASA in 2017. Click to enlarge. Credit: NASA


The Deep Space Transport Vehicle arrives at Mars as envisioned by Boeing in 2017. Click to enlarge. Credit: NASA


A circa 2017 notional depiction of the lunar lander approaching the Deep Space Gateway. Credit: NASA


A visualization of NRHO orbits shown to scale with the Moon and Earth. Click to enlarge. Credit: NASA


In his speech in October, Vice President Mike Pence promised to return American astronauts to the Moon. Click to enlarge. Credit: NASA


A "reference" configuration of the cis-lunar station accepted for the first Integrated Analysis Cycle, IAC-1, in October 2017. Notable is a single habitation/lab module.