Fifty-plus years after astronauts last set foot on the Moon, the space industry is gearing up to return, with ambitious plans to build habitable structures, mining operations, and other facilities. The lunar missions may also pave the way for future missions to Mars, where additional opportunities beckon.
In both lunar and Mars missions, as well as other space construction activities, AEC professionals play key roles. Architects, engineers, scientists, and construction professionals from government, academia, and private industry are joining forces to pursue ambitious goals and address numerous challenges of building in space.
Image source: Romolo Tavani/stock.adobe.com.
While some construction methods are similar to those conducted on Earth, new approaches are needed to address extraterrestrial challenges, such as material availability, equipment capabilities, and construction techniques in harsh, low-gravity environments. The myriad issues are resulting in ongoing technological developments and collaboration amongst public and private agencies.
“There’s a lot of strength in having multiple companies building things together,” said Jennifer Edmundson, geologist at the National Aeronautics and Space Administration (NASA), the agency that oversees U.S. space exploration and research. ”I’m really excited to see all of the companies looking at this.” Edmundson, based at NASA’s Marshall Space Flight Center in Alabama, is also the project manager for NASA’s Moon-to-Mars Planetary Autonomous Construction Technology (MMPACT) project, which is exploring the use of robotic technology to build structures on the Moon and Mars.
Getting Off the Ground
One of the first challenges to conquer is transforming launch facilities to accommodate a new, diverse range of space vehicles, such as NASA’s Space Launch System (SLS) rocket and Orion spacecraft for the Artemis program, along with various vehicles being developed by private sector partners. To handle the new line of vehicles, NASA has been upgrading its historic Launch Pad 39B, along with mobile launchers and other facilities at the Kennedy Space Center in Florida.
Teams from NASA and Bechtel moved the base structure of ML2 to a permanent mount structure at Kennedy Space Center in Florida. Image source: NASA/Madison Tuttle. Click image to enlarge.
The first mobile launcher (ML1) was used to assemble, process, and launch the SLS rocket and Orion spacecraft for Artemis I — a 2022 uncrewed mission that traveled beyond the Moon and back, setting the stage for future crewed missions. ML1 will also be used to launch Artemis II, designed to carry a crewed mission around the moon to test human deep space exploration capabilities, and Artemis III, designed to land on the moon and send humans to explore the lunar South Pole region, where ice has been observed.
For Artemis IV, destined for the Gateway lunar space station, and future missions potentially destined for Mars and beyond, NASA is building a replacement mobile launcher — ML2 — to launch the SLS Block 1B rocket, which can carry heavier cargo than its predecessor. The 355-foot–tall ML2 will be used to assemble and process the rocket and spacecraft in NASA’s Vehicle Assembly Building (VAB), support the vehicles as they are moved onto the launch pad, and ultimately support the launch process.
In May, NASA and primary contractor, Bechtel National, Inc., achieved a major milestone when they moved the two-story ML2 base structure to a permanent mount structure where assembly will be completed. The complex “jack and set” process, featured four self-propelled motor transporters and eight jacks placed around the outside of the base steel. “Lifting a 2.6-million-pound launcher base more than 20 feet into the air, moving it nearly the length of a football field, and then setting it down safely at a height of 25 feet, requires both great skill and careful planning,” said Mike Costas, Bechtel’s General Manager of Defense and Space in a statement.
The four-year design of the ML2 structure was also extremely complex. “It is one of the most fascinating steel structures I’ve ever worked on,” said Pete Carrato, a Bechtel fellow emeritus who now works as an independent consulting engineer. “It has many different design considerations.”
As a portable structure, ML2 must be designed for multiple support conditions, explained Carrato. Initial conditions occur during construction, followed by different loading conditions as NASA’s crawler-transporter moves it to the VAB and other locations and then out onto the launch pad. During launch, the SLS rocket will exert 9.5-million pounds of thrust and generate temperatures up to 2,200°F.
The complexity of launch facilities also creates other design challenges. “When you have a 20- to 30-story building that moves, all the [conventional] design practices go out the window,” said Andrew Nelson, vice president, aerospace at consultant RS&H. Design considerations include emergency egress systems to carry astronauts away from the vehicle and movable bridges that swing out of the way during launch. RS&H was the designer of record for ML1 and designed the vertical stabilizer for ML2. They have also provided various consulting services to NASA for other facilities.
NASA’s ML1 was used to launch the Artemis I vehicles and will also be used for Artemis II and III missions. Image source: RS&H. Click image to enlarge.
Next Stop, the Moon
With the Moon targeted as the next destination for the U.S. and other nations, space professionals are formulating plans to build on the lunar surface. In addition to its low gravity — approximately one-sixth of Earth’s gravity — the Moon imposes challenges due to its lack of atmosphere, extreme temperature swings, and exposure to radiation and micrometeorites.
Material availability is also a key consideration. Lunar soil — particularly the upper layer called regolith — offers potential as a building material and is one of several materials being considered for in-situ resource utilization (ISRU). The use of on-site material minimizes transport of equipment and materials from Earth, which could cost more than $1-million per kg according to some estimates, and is key to sustainable construction.
“It really turns into a logistics challenge,” said Patrick Suermann, interim dean of the School of Architecture at Texas A&M. “How can you get the most [material and equipment] up there for the least cost? And, how can you have small progress over long periods of time versus the way we do construction now [relying on heavy equipment]?” Suermann is a former associate professor of civil engineering at the U.S. Air Force Academy and retired U.S. Air Force officer who oversaw major military construction projects.
Texas A&M is one of many universities researching space construction for NASA. Research has included such areas as construction materials, techniques, and equipment, solar energy on the Moon, spacesuits, space architecture, and others. The Texas Legislature also allocated $350-million for creation of the Texas A&M Space Institute and $200-million for construction of a Texas A&M facility next to NASA’s Johnson Space Center in Houston.
Autonomous Construction
With transporting humans to the Moon also a costly and complex endeavor, autonomous construction techniques such as 3D printing will be critical to building on the Moon and Mars. In 2022, NASA awarded a $57-million contract to ICON Technology, Inc., to develop construction technologies for building landing pads, habitats, roads, and other facilities on the lunar surface. ICON has used its 3D printing technology to build homes in the southwestern U.S,. as well as experimental structures for off-earth locations, such as their collaboration with the Colorado School of Mines in a 2019 NASA challenge to develop a sample habitat structure suitable for the Moon or Mars.
ICON’s space technology is focused on using local materials on the moon, and eventually Mars, to create structures, according to Melodie Yashar, ICON vice president for building design and performance. ICON researchers are exploring how to fuse regolith with laser energy and create small samples of concrete-like material. They are also developing a robotic manipulator that can scoop, sieve, and evaluate regolith, then lase samples of the material onto itself.
One of the key challenges ICON faces is the large temperature differentials in shadowed and lit regions of the Moon. “The temperature swings are extremely unforgiving,” said Yashar. “We have to think about what that means both for the hardware we’re engineering and the structures we’re creating.”
Also under consideration are how to adapt the company’s proprietary software to guide robotic equipment on extraterrestrial locations. The company’s G-code — software instructions that tell 3D printers what to do — recognizes ambient conditions while printing and leverages project-specific data to guide equipment. The unique environments on the Moon and Mars will “almost certainly” require unique software modifications for each environment, noted Yashar.
ICON’s Olympus construction system is designed to construct landing pads, roadways, non-pressurized structures, and pressurized habitats. Image source: ICON. Click image to enlarge.
A Texas A&M architectural and construction robotics class led by Ph.D. student Mehdi Farah Bakhsh used a slurry mix to test nested 3D printing, which enables the creation of large-scale structures with smaller 3D printers. This reduces weight while increasing the reach of the printing robot in extraterrestrial 3D printing processes. Image source: Texas A&M School of Architecture/Mehdi Farah Bakhsh. Click image to enlarge.
In another approach to lunar construction, researchers at Louisiana State University are exploring how to use lunar sulfur and regolith to develop 3D-printed waterless concrete. “Molten sulfur is the binder and regolith acts as the filler material,” said Ali Kazemian, LSU construction management assistant professor. Initial findings indicate sulfur regolith concrete (SRC) outperforms water-based concrete in some ways, such as cure time—10 hours instead of four weeks—though the SRC material melts at 120 to 130°C, so it would not be effective for high-temperature environments, such as launch pads, he said.
The LSU team is also working on refinements to 3D printing processes by using LiDAR sensors and data processing algorithms for automated inspection. “We can be fully digitized from design through construction and inspection,” Kazemian said. “We cannot rely on human construction workers because of the harsh environment and motion limitations of astronauts.”
LSU researchers have developed systems and algorithms for inline automated inspection during 3D printing using LiDAR data. Image source: LSU Department of Construction Management. Click to enlarge.
A host of other research is underway as part of NASA’s MMPACT project and other programs. A recent Break the Ice Lunar Challenge invited competitors to develop robotic equipment for excavating and transporting icy regolith on the Moon. To simulate microgravity conditions, NASA lifted the rovers slightly off the ground as they attempted to excavate pads of low-strength concrete. “The point was to look at different excavation technologies to see which ones handle gravity offload better than others,” said Mike Fiske, technical fellow at Jacobs Space Exploration Group and a judge in the competition.
The winning team in the challenge was Terra Engineering, a husband-wife team from California that developed a rover with a series of rotating blades that scraped material into a hopper. As the machine dug deeper, it gained more leverage to excavate material. The rover excavated more than 300 kg of material, far more than the competition, according to Fiske.
Other research is focused on the suitability of different lunar materials. Because lunar regolith is highly abrasive, research is needed on how to protect astronauts and equipment, as well as how to use the material for construction. NASA’s Edmundson, who has analyzed lunar material from the Apollo missions, said the Artemis III mission could provide valuable insight into different materials and future capabilities. “It’s going to be some of the oldest material we’ve ever collected,” she said.
Texas A&M’s Suermann said additional research is needed on developing standards for lunar pavement and other structures. He also said areas such as georeferencing and telemetry need additional research, noting that “there’s no GIS or GPS on the Moon.”
A New World
Meanwhile, other nations besides the U.S. have completed or are planning trips to the Moon. Russia, China, India, and Japan have completed successful “soft landings” where the spacecraft touches down at a speed suitable for crewed or exploratory missions. A handful of others have similar plans.
Privatization of the U.S. space program adds another intriguing twist. SpaceX, Boeing, Blue Origin, Virgin Galactic, and other companies are developing programs that promise to accelerate the pace of space exploration. “It’s a new world,” said Jacobs’ Fiske.
NOTE: Article edited for clarity, August 6, 2024.
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In Part 2 of this series, we will further explore challenges in establishing habitable facilities and mining facilities on the Moon and Mars, as well as other related topics.
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