A NASA render of an astronaut sifting lunar regolith. Credit: NASA

There were few major surprises when NASA rolled out a detailed architecture for human exploration of the moon and Mars at the 38th Space Symposium April 18. The 150-page document largely reinforced plans for the initial series of Artemis missions to the moon using the Space Launch System, Orion, Gateway, Human Landing System and other programs in development for years.

“The Architecture Concept Review details plans for early human exploration of the moon’s south pole,” NASA Deputy Administrator Pam Melroy said in a conference speech announcing the architecture. “It provides more definition for plans through Artemis 4 and sets the stage for the first crewed missions to Mars.”

However, the architecture represents a fundamental change in how NASA plans its exploration programs. The Architecture Concept Review document and supporting white papers are intended to tie long-term objectives for human exploration to current and future programs. That’s intended to provide coherence and — NASA hopes — durability against inevitable technical and political challenges that will allow Artemis to continue when past efforts have failed.


“It’s a pivot to a new kind of approach, a new methodology,” said Kurt “Spuds” Vogel, director of space architectures at NASA and one of the people leading the development of the new architecture. He described work on the architecture in a talk April 24 at a meeting of the Lunar Surface Innovation Consortium (LSIC), a group of companies and organizations working on technologies for lunar exploration.

NASA Deputy Administrator Pam Melroy at the 28th Space Symposium in April 2023.

Vogel came to NASA in mid-2021 from the Defense Advanced Research Projects Agency at the request of Melroy, a former DARPA deputy director. He recalled Melroy asking him to come to NASA to provide “another set of eyes” on the agency’s plans.

He saw an opportunity to get out of the cycles of past efforts to return humans to the moon and go on to Mars that started with great fanfare but fell apart within a few years. “This has been a 30-plus-year ride,” he said, going back to President George H.W. Bush’s announcement of the Space Exploration Initiative in 1989 and its resurrection 15 years later by his son’s 2004 Vision for Space Exploration speech and the “Apollo on steroids” Constellation program that followed. “We’ve been on this roller coaster, and one of the big dips in that roller coaster ride is when Constellation got canceled,” he said. “There’s a lot of PTSD that everyone experienced from that, both inside the agency and our partners.”

NASA then switched to a “capabilities-based” approach of developing programs, like the Space Launch System and Orion, without a broader architecture. Now it was time, Vogel and others at NASA believed, to develop a more comprehensive architecture into which those programs and others could fit. That would show policymakers and international partners that NASA had a rigorous plan.

It would also provide guidance within the agency. Without that architecture, “everyone tells their own story, where the thing they’re working on is the most important,” he said. “They’ve got their own vision of how it fits.”

That creates confusion inside and outside NASA. “We want to get out of this cycle,” he concluded.


Throughout the development of the architecture, NASA repeated two phrases. One is what Melroy called the overarching goal or “bumper sticker” of the effort: “Create a blueprint for sustained human presence and exploration throughout the solar system.”

The second is one that defined the overall process: “Architect from the right and execute from the left.” That meant starting from the goal and working backward to develop the plans and programs needed to achieve the goal, then carrying them out.

That process publicly started last May when NASA released a set of 50 objectives for achieving that goal in science, transportation, infrastructure and operations. NASA took public feedback on those objectives and held workshops with both industry and international partners, resulting in a revised, expanded list of 63 objectives Melroy announced at the International Astronautical Congress in Paris last September.

NASA then took each objective and broke it down into “characteristics and needs,” or the features or products needed to achieve those goals. Those are then further decomposed into functions needed to achieve those characteristics and needs, as well as use cases that describe how those functions are used. Those functions and use cases can then be grouped together to identify similar features and “sub-architectures” in areas like transportation and habitation.

“We broke down the objectives that are tied to human lunar return into characteristics, needs, use cases, functions and requirements,” Jim Free, NASA associate administrator for exploration systems development, said in an interview shortly before the release of the architecture document. “We’ve connected the big-picture agency strategy to these near-term missions.”

The intent, he said, was to link all the objectives to individual programs. “In our documentation, you’ll actually be able to see in the appendices the breakdowns from objectives to specific parts of the mission and elements of the architecture.”

From left: Jim Free, NASA associate administrator for exploration systems development, NASA Deputy Administrator Pam Melroy and Kurt “Spuds” Vogel, NASA director of space architectures, lead a Moon to Mars workshop last summer at the Royal Institution in London.

For example, one of the objects is to “develop cislunar systems that crew can routinely operate to and from lunar orbit and the lunar surface for extended durations.” NASA broke that down into five characteristics and needs for transporting crew and cargo from Earth to lunar orbit and from orbit to the surface. That, in turn, became six use cases, like “crew transport between cislunar space and lunar surface,” and 17 functions that ranged from stacking and integrating launch vehicles to recovering crew and cargo after splashdown.

The report focused on the first phase of the overall moon-to-Mars effort, “human lunar return, “ which included missions through Artemis 4. NASA found nearly 40 use cases and more than 50 functions relevant to the objectives tied to those missions, then examined which program or programs were fulfilling them.

Fortunately for NASA, those use cases and functions match up with the existing programs in development for the early Artemis missions. Only three, all related to crew training, were not allocated to any specific program, which NASA said in the report reflected the nature of how the human systems sub-architecture was defined, and not any actual gap in planning for those missions.


Along with the main architecture document, NASA released several white papers going into detail about specific aspects of the architecture. One, for example, discussed why NASA selected the near-rectilinear halo orbit for the Gateway and compared that orbit against alternative orbits.

“They’re very important to me personally,” Melroy, a former space shuttle commander, said of the white papers in an April 25 talk at the LSIC meeting. It reflected the experience from the years when Melroy, an Air Force combat veteran who’s also worked for the FAA and Lockheed Martin, was not at NASA. “I often took a look at the agency and said, ‘Why are we doing that?’” The papers, she said, helped explain the technical trades the agency made when choosing parts of the architecture.

The architecture document is intended to be a living document. Melroy said NASA will solicit feedback on it with workshops this summer. “The objectives will stay with us, but we know that the architecture is going to evolve,” she said, reflecting new technologies and new capabilities.

The goal is to hold the next architecture concept review in November, holding them annually to refine and extend the architecture. “It’s a very tight turnaround for us to get to November, but that’s what is going to align us with the budget,” she said.

NASA rendering of a lunar base camp.

The future reviews will look further out. This document focused on human lunar return, only the first of four phases of the overall exploration campaign. More advanced lunar exploration, called “foundational exploration” and “sustained lunar evolution,” will go through a similar process of converting objectives into functions and use cases, identifying programs that can achieve them or gaps that need to be filled with new capabilities. A fourth phase is devoted to initial human missions to Mars.

Even as that work gears up, NASA is rethinking some aspects of later Artemis missions. NASA originally talked about establishing a single “Artemis Base Camp” on the moon, building up infrastructure like rovers and habitats there.

Free, though, said at Space Symposium that NASA is instead thinking of creating a few smaller bases because of changing lighting conditions at the south pole, where missing a launch window for a particular site might delay a mission there by months. Multiple sites could also improve science. “We could maybe have two or three sites to go to that help our science diversity,” he said.

Those trades will come later. “NASA has positioned this strategy for longevity and success,” Melroy said in her Space Symposium speech. “This is a critical milestone for us in our moon-to-Mars strategy. We feel very aligned with our partners. We want to continue to stay that way.”

This article originally appeared in the May 2023 issue of SpaceNews magazine.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...