A Ski Lift on the Moon
Deep in the sub-basement of the Keck Engineering Laboratories, a team of 56 Caltech undergraduates is engineering a new way to explore the moon. The team is among seven finalists in the 2022 NASA Breakthrough, Innovative, and Game-Changing (BIG) Idea Challenge, which asks university teams to design new ways of traversing lunar craters that do not rely on wheels.
Lunar craters contain valuable materials able to support human settlements on the moon, but the steep slopes and fluffy surface textures of the craters wreak havoc on traditional wheeled rovers. The Caltech team's concept, called LATTICE (Lunar Architecture for Tree Traversal in-service-of Cable Exploration), uses a self-deploying distributed robotic system able to transport materials in and out of lunar craters, like a ski lift. The team was named a NASA BIG Idea finalist earlier this year, and the project will culminate in a tech-demo planned for mid-November.
Along with the fluffy and asbestos-like composition of the moon's regolith—the broken-down rocks covering the moon—lunar craters are massive. "The depth of these craters is like the top of Mount Everest to the sea, with widths that can span five times wider than the Grand Canyon," says Lucas Pabarcius, a third-year undergraduate student and project lead.
To manage the scope of the challenge, the LATTICE project team is comprised of three different technical sections: the design of the stakes and cable system; the system for driving those stakes into the moon's surface; and the autonomous robotic shuttle traversing the stakes via cables. The LATTICE design was finalized in May, but the project expanded from around 25 to 56 throughout the spring and summer.
"This summer we had 12 SURF students (Summer Undergraduate Research Fellows) and 6 FSRI students (First-Year Success Research Institute) work full time on this project," says Kaila Coimbra, a fourth-year undergraduate and lead of the stake-driving sub team. "This project has given so many students meaningful opportunities on campus and a really great learning experience." Along with mentorship from fourth-year students and Professor Soon-Jo Chung, Bren Professor of Aerospace and Control and Dynamical Systems and JPL Senior Research Scientist, the LATTICE team receives guidance from space robotics experts at JPL and NASA.
While the other BIG Idea Challenge finalist teams include a mixture of undergraduate and graduate students, the LATTICE team is the only one comprised entirely of undergraduates. "Because our team is so big, the SURF and FSRI students were able to get super invested and involved," says Pabarcius. "These students clearly gained a lot of experience and were even picking up on advanced theory."
Since hands-on projects don't usually begin until the end of the second year, the LATTICE project offers students an unprecedented early opportunity to get involved in a real-world set of challenges that not even NASA has solved.
"We are trying to do something nobody has ever done before," says Winter Pearson, a third-year undergraduate student and SURF 2022 participant. "We're working at the cutting edge of engineering because we want to be as light, efficient, and effective as possible. Nobody really knows what will happen when you drive a stake into the surface of the moon a meter deep. It's extraordinarily fascinating and a brilliant opportunity, but definitely a challenge."
A significant challenge of the stake-and-cable system involves the fluctuating tension of the cables. Since the moon experiences huge thermal swings from day to night, the cables involved in the LATTICE design can tense, stretch, and droop over time. When the autonomous shuttle traverses the cables, the system droops even further. The team's solution was to tension the cables as the shuttle rides across them.
"This required some very high forces," says Kemal Pulungan, a second-year undergraduate focusing on the robotic shuttle sub-team. "We couldn't find any gearbox with a high enough torque that was also light enough for our Earth demonstration. So, we discovered a company that specializes in high torque drills, which can output 900 Newton-meters while only weighing three kilograms." This high-torque drill allows the shuttle to successfully traverse the cables and carry heavy payloads on Earth, where the gravity is six times that on the moon.
"This is one of the few problems where the solution is slightly easier on the moon because of the 1/6th gravity," adds Coimbra. "Because the shuttle is so heavy on Earth, it is difficult to show that it can carry a payload as the shuttle itself is its own payload."
To simulate the conditions of the moon on Earth, the LATTICE team made several excursions to Lucerne Valley in the southern region of the Mojave Desert. While not a perfect match, the sandy conditions of Lucerne Valley act as a close approximation of the conditions near and inside of lunar craters—this is where the team is testing the LATTICE prototype and will ultimately conduct the final tech-demo for the BIG Idea Challenge.
In the desert, the team uses a small, twenty-year-old red robotic rover, which they've nicknamed Clifford. Attached to the back of the rover is the team's stake-driving mechanism. The rover then drives down a hill to drive the stakes into the ground, creating a connecting cable line between the stakes. In the final tech-demo in Lucerne Valley, the team will demonstrate the robotic shuttle traversing up and down the cable line. This will show the feasibility of the LATTICE design when transposed to the conditions present on the moon.
"It is really cool to see an idea become something physical and something you can inspire other people with," says Coimbra. "As a lead for this year's BIG Idea Challenge, I learned how to deal with technical challenges as well as how to better manage and communicate with such a large group of people."
"We've already made a lot of connections with our partners at JPL and within industry," adds Pulungan. "I feel that this is very beneficial to the students working on this project; building those connections can help start people in the realm of space exploration."
Although the final tech demo will take place in late November, the team is already thinking of future implications for the LATTICE concept. "This is a good first step for lunar infrastructure, but this kind of concept has the potential for the moon, Mars, and any other planet," says Coimbra.
"This concept could reduce dependence on Earth resupply," adds Pulungan. "The cost of operating missions and bases on the moon would go down because you can just rely on what's on the moon."
Pearson, a computation and neural systems major confesses a deep love for robotics but was not previously interested in aerospace. "Certainly, everyone was extremely welcoming. If anything, this project is sparking a strong interest in aerospace, and I suppose I'll see where that takes me in the future," Pearson says. "There are very few chances that people get in their lives, not just limited to Caltech, to work with a team of other undergrads who are super excited about something this big and cutting edge."
The full list of LATTICE team members (past and present) include: Jedidiah Alindogan, Matthew Anderson (advising Grad), Mars Arechavala, Diego Attra, Sammy Binkin (ArtCenter), Sravani Boggaram, Matticus Brown, Kevin Cai, Enzo Celis, Sujay Champati, Sean Chang, Norman Chung, Tommy Clark, Lily Coffin, Kaila Coimbra, Tyler Colenbrander, Caitlyn Coloma, Robert Daigle, Gerard Decker, Philippe des Boscs, Juan Escobar, Yao Huang, Nicolas Jimenez-Lozano, Colton Johnston, Calle Junker, Matteo Kimura, Sulekha Kishore, Alec Laprevotte, Eric Lee, Joshua Lee, Sorina Lupu (advising Grad), Moya Ly, Fernando Matias, Amrita Mayavaram, Aramis Mendoza, Robert Menezes, Esmir Mesic, Frida Moreno, Rithvik Musuku, Nathan Ng, Tyler Nguyen, Dilichi Nwankwo, Lucas Pabarcius, Luis Pabon, Andrew Pasco, Winter Pearson, Jules Penot, Geoffrey Pomraning, Kemal Pulungan, Rasool (Isaac) Ray (WAVE), Kellen Rodriguez, Purvi Sehgal, Parul Singh, Aiden Swann, Ellande Tang (advising Grad), Malcolm Tisdale, Priscilla Vazquez, Polina Verkhovodova , Kenadi Waymire, Tomás Wexler, Brooklyn Williams, Brit Wylie, Jonah Yoshida, Benjamin Zeng, and Isabella Zuñiga.
This story is a follow up to a story originally published in April. Read that story here.
