Moon to Mars Part I: Forging the Path

This is a joint article between Nik Alexander and Emily B.

At its core, the Artemis Program represents a new way of thinking in space exploration. Previous programs across the world have been defined by fixed final objectives, whether it be to build a space station in Low Earth Orbit or put humans on the moon. NASA’s Moon to Mars objectives incorporate the Artemis Program as part of the roadmap to the Red Planet. This program in all of its four phases, represents a new paradigm, one in which the goals and objectives of the program evolve to support even broader ambitions. Artemis is not only a lunar program, but a technology maturation program for eventual human flights to Mars. Within this program, there are four distinct phases – each with their own unique facets. The first two, Human Lunar Return and Foundational Exploration, signal a shift from the previous paradigm of Apollo Era exploration to one of a sustainable age. The transition from Human Lunar Return to Foundational Exploration is defined by the addition of new assets to mission profiles in conjunction with Orion, SLS, Gateway and the Human Landing System – enabling greater reach and mobility for crews on the surface and in space.

Human Lunar Return

Artemis I represents the first step towards a new age of sustainable, long term exploration with an “all up” validation of the systems required for deep space travel. Launched atop an SLS Block 1 vehicle on November 16th, 2022, this flight, while encountering some issues with the Orion spacecraft’s heat shield, aptly demonstrated the functionality of the SLS-Orion system to operate at lunar distances and contend with the challenges of deep space. Artemis II will push this envelope further, integrating a crew of four into the Block 1 system to help checkout Orion and all of its vital human systems. This mission, in many ways, is similar to both Apollo 8 and 9, as combined all up test of the Orion-SLS stack with humans in the loop. During this mission, the crew will initially enter a 24 hour checkout orbit, designed to facilitate an easy return should any issues crop up with the Orion spacecraft. Following this, the Orion spacecraft will perform its final translunar injection burn, sending the spacecraft on a flyby trajectory around the Moon. The crew, consisting of Commander Reid Weisman, Pilot Victor Glover, and Mission Specialists Christina Koch and Jeremy Hansen, will spend roughly 10 days in space performing this validation testing, before splashing down in the Pacific Ocean, paving the way for the next phase of Human Lunar Return – the landings.

Under the current architecture plan, which is subject to amendments as needed, Artemis III will see another crew aboard Orion launch atop SLS Block 1 to the unique near-rectilinear halo orbit around the Moon. This orbit does not orbit the moon, but orbits the space around it – enabling a constant line of sight with Earth and easy abort modes from the surface. Upon arrival, the crew will rendezvous with their lander, SpaceX’s Starship Human Landing System. From their halo orbit, two preselected crew members will descend to the surface, where they will become the first humans on the Moon in over 50 years. Following a roughly week-long stay, the crew will ascend back to the halo orbit, where they will rendezvous with Orion and head home. This crew will return home as heroes, and set the stage for the final test campaign mission in Human Lunar Return.

For Artemis IV, all of the program’s various operational elements will be in play. This mission will see the upgraded and more powerful SLS Block 1B, using the new Exploration Upper Stage and Universal Stage Adapter – lifting up to 42 tons to the moon. The flight of Artemis IV will see the final integration of one of the most crucial elements of the Artemis architecture – Gateway. Gateway is a lunar space station that acts as a staging ground for human expeditions to the lunar surface, and demonstrates key technologies needed for Martian exploration through the use of precision navigation and deep space electric propulsion. In its initial configuration, Gateway will consist of two co-manifested modules: the Power and Propulsion Element (PPE) and the Habitation and Logistics Outpost (HALO). For Artemis IV, the crew will launch atop their upgraded SLS vehicle with a payload in tow, the European-Japanese i-Hab module. This module will be tugged to Gateway by Orion, where the crew will spend time integrating the two spacecraft before conducting a landing mission similar to Artemis III. With the safe return of the crew to Earth, the initial testing phase of Artemis under Human Lunar Return will draw to a close, ushering in a truly active period of lunar operations.

Human Lunar Return is centered on the establishment of various architecture elements and thorough proving of their functionality in an operational environment. Each flight builds on the others, and adds new complexity to the system that furthers fundamental exploration goals. Human Lunar Return also enables new forms of cooperation in cislunar space and on the lunar surface through collaboration with international partners, a valuable asset from the ISS program which Apollo did not have. Once all of these crucial tests are completed, missions will increase in complexity and subsequently in capability, ushering in a truly groundbreaking era of lunar science and human exploration of our nearest celestial neighbor. By learning as we fly, and learning together, NASA and their international partners can begin the next phase of Artemis – laying the groundwork for sustainable science on the lunar surface. 

Foundational Exploration

After the initial return missions, the Artemis partners will shift focus to expanding capabilities on and around the moon. Critical to these capabilities is expanding the reach of individual missions though consistent and large-scale mobility. This buildup of infrastructure and subsequent utilization of it for sustainable lunar and cislunar operations forms the Foundational Exploration phase. This build up begins with Artemis V, when Orion will bring ESA’s Lunar View module to Gateway. Lunar View, previously called the ESPRIT Refueling Module, will enable the PPE’s Xenon and Hydrazine tanks to be refueled in space, at first via a propellant load included at launch and later via potential additional loads brought by visiting vehicles. Lunar View will provide the propellants via special plumbing inside HALO that passes through the docking port and connects it to PPE. This refueling capability is crucial to enable Gateway to meet its 15-year design life.

Artemis V’s surface mission will also see a new element join the fray: the Lunar Terrain Vehicle (LTV). The LTV, as covered previously by Space Scout, is an unpressurized rover capable of carrying two astronauts far from their HLS lander while carrying extra cargo or payloads. The LTV can drive autonomously and reposition itself in between Artemis missions, conducting tasks for either NASA or commercial customers. Next is Artemis VI, which will introduce the Crew/Science Airlock to Gateway. Provided by the UAE’s Mohammed Bin Rashid Space Centre (MBRSC), the Airlock will enable maintenance EVAs, provide further external payload mounts, and enable deployment of small satellites and other objects into the NRHO environment. With this addition, Gateway will have achieved its “Expanded Capability” configuration and be ready to move into full scale operations and utilization.

The final currently manifested major infrastructure element is the Pressurized Rover, provided by the Japan Aerospace Exploration Agency (JAXA) and is planned to be available for use beginning with Artemis VII. The Pressurized Rover will enable sorties away from the lander that last days or weeks instead of hours, as even the LTV range is limited by the life support systems of its crew. As discussed previously by Space Scout , the rover will allow staging of EVAs very far from the lander and provide crucial experience for longer term lunar living and trips to Mars. It is notionally planned to be deployed by a Human-class Delivery Lander (HDL), a cargo-carrying derivative of one of the HLS systems. This is not the end. While not fully formulated or manifested yet, future elements may include an Italian-built Surface Habitat, a Canadian Utility Rover, a Fission Surface Power reactor, and one or more medium-size cargo landers.

Technology is an Exploration Enabler

If we are to explore the Moon instead of simply visiting it, we will need the ability to conduct in-depth operations over an extended period across a variety of sites. Sustainable exploration means making the best use of our resources by doing more on any given mission, which things like expansive mobility, longer duration stays, and Gateway help achieve. The Apollo program took everything that would be used by a given mission with it in one launch. This simplified mission and architecture design and allowed the program to move very fast, but the result was that missions had to land in relatively low-risk areas and the scale of exploration was limited by the Lunar Module’s stringent endurance and downmass limits. Hardware present near and on the Moon allows much more flexible and capable missions due to assets and infrastructure persisting between missions as well as the ability to conduct activities between missions.

In addition to the architecture elements directly used by astronauts discussed above, additional support systems and technologies are key to achieving the expanded exploration scope. The primary limiter on scientific return is the accessibility of sites of interest, which depends on mobility systems, landing proximity and traverse range. Being able to land closer to science targets means less time needs to be wasted going between them and the lander as well as being able to conduct more intensive investigations. Any given lander will have a “landing ellipse”, or an elliptical shape that contains around 99.8% of the potential final landing coordinates given the known uncertainties in the system. This ellipse must be reasonably free of hazards that could damage or destroy the lander, so a smaller landing ellipse unlocks more challenging and interesting landing sites.

Once landing accuracy is improved, a mission must still have to contend with communications range and navigation ability. To conduct EVA traverses even as far as Apollo 17’s rover trips, communications back to both Earth and teams at the habitat are critical. WiFi can only reach for 100-300 meters, and UHF radio, used on ISS EVAs, only around 1 km. EVA suit range is up to 2 km without mobility systems, and later Foundational Exploration missions with such systems could go tens or hundreds of kilometers from the lander or outpost.

Even at the edge of on-foot traverse  range, new communications systems will be needed. One promising idea is to leverage the 4G/LTE technology that has powered most terrestrial cellular networks since the early 2010s for use on the lunar surface. LTE can potentially reach tens of kilometers with data rates over an order of magnitude higher than the UHF system currently used on the ISS. Recognizing this, NASA has partnered with Nokia Bell Labs to demonstrate a 4G/LTE network on Intuitive Machines’ IM-2 mission. IM-2 is planned for the fourth quarter of 2024 as of writing and will test Nokia’s LTE base station on the Nova-C lander and a mobile transceiver on a small rover. If successful, the demonstration could pave the way for 4G/LTE networks to be the new standard for lunar surface communications.

Just as important as communication is navigation. Getting to small points of interest and landing precisely requires accurate knowledge of where you are in space or on the surface. There is no GPS equivalent in orbit around the moon, so missions are forced to use infrequent and limited ground station doppler ranging or weak and hard to acquire GPS signals. These methods are insufficient for any landing sequence and, while potentially usable for post-landing geolocation, do not offer high precision. A need for 100-meter or better position knowledge anywhere on the lunar surface has been identified, and the LunaNet initiative includes Position, Navigation, and Timing (PNT) services as one of its core pillars. LunaNet is a set of interoperability standards so that multiple commercial and international satellite networks at the moon can act as one coherent system to users on and around the Moon. NASA’s Lunar Communications Relay and Navigation Services (LCRNS) project aims to be one of the first LunaNet components to enter service, as does ESA’s Moonlight system. Moonlight’s Lunar Pathfinder is planned to launch in 2026 as a rideshare aboard Firefly’s Blue Ghost Mission 2, and LCRNS is planned to enter service in 2027.

The final major requirement for sustainable and wide-ranging exploration is logistics. Supplies are critical to any mission, but especially increasingly long-duration lunar missions. Not just consumables like air, food, and water, but also outfitting supplies, science and utilization payloads, maintenance items, and more. The primary drivers of the magnitude of logistics needed are mission duration, number of crew members, life support architecture, and EVA cadence. A larger crew will obviously need more life support consumables, and a longer mission will additionally need more spare parts and maintenance. An open-loop life support architecture will require much more water and gas to be delivered than a system that could recycle most of those commodities. EVAs are very intensive on both hardware and life support systems, so the number of EVAs can significantly compound the other factors as well.

Proving out sustainable lunar exploration is critical to extending the longevity of Artemis as a program but is even more critical to the program’s ultimate goal: enabling human exploration of Mars. Mars exploration will require precise navigation, long distance communications, advanced mobility, extraordinarily large logistics quantities, and the ability to maintain systems in situ. Astronauts will need to be independent and autonomous with no real time ground support in order to meet objectives and stay safe. The ability to operate quickly and independently is key to surviving on Mars and for maximizing science return in the limited time available. We will need to be able to live and explore for extended durations far from Earth, assemble outposts, and build sustainably.

A New Path Forward

Artemis represents a unique departure from previous lunar exploration initiatives in that it is incredibly international. Beginning with the Artemis Accords in 2020, several partner nations have anchored themselves to the program’s execution – a notable carryover from the lessons learned on ISS. This cooperative landscape, however, is much more open ended, drawing on new frameworks drafted in a post ISS environment. One of the key elements in the initial phases of Artemis will be the establishment of working relationships beyond Earth, forging ahead into this new frontier. At the 2024 Humans to Mars summit, NASA and partner leadership highlighted that this new approach would enable more collaboration through more open dialogues, and less emphasis on initial capability. It is through this lens that the weight of Artemis can be distributed across multiple partners, ensuring the program’s longevity. The return to the Moon also opens new doors for a changing political landscape on the lunar surface. Alongside Artemis, China has set their sights on the moon, with the intention of a crewed landing by 2030. Artemis, with perhaps no intention of initially doing so, has become a program which will have to learn about the nature of politics and policy beyond a planetary surface, proving out the future of human diplomacy in space. One of these key areas of interest is deconfliction, the enabling of multiple participants in similar geographical regions, one that may prove contentious with the discovery of water ice. 

The first two phases of Artemis represent a quantum leap for not just how we conduct exploration, but doing so sustainably and with various parties’ interests in mind. Human Lunar Return is the ultimate test of our mettle, an incremental system that builds up our capability as we set our sights on the future. With the completion of all of the required testing, the Artemis program can move into Foundational Exploration – a key stretch of capabilities across the lunar surface. All of this acts as part of a chain, a system that links work being done on the moon with challenges to come on the journey to Mars. But every element remains crucial, a testament to the hard work and pride of every Artemis contributor. 

Acronyms

SLS – Space Launch System

PPE – Power and Propulsion Element 

HALO – Habitation and Logistics Outpost

ESPRIT – European System Providing Refuelling, Infrastructure, and Telecommunications

LTV – Lunar Terrain Vehicle

MBRSC – Mohammed Bin Rashid Space Centre

LCRNS – Lunar Communications Relay and Navigation Services