For thousands of aspiring engineers, the NASA Human Exploration Rover Challenge is the highlight of their student careers. The competition invites high school and college teams to design, build and test technologies that enable rovers to operate in a range of harsh environments. The Human Exploration Rover Challenge, a follow-up to NASA’s Great Moonbuggy Race, which had a successful 20-year run through 2014, was hosted by NASA’s Marshall Space Flight Center at the U.S. Space & Rocket Center (Huntsville, AL).
The rover competition’s mission is to inspire participants to become engineers who may one day design NASA’s next-generation space systems. Traditionally, the contest was a race across difficult terrain but, beginning in 2018, it mimicked actual conditions and critical decisions that explorers face in interplanetary space. NASA’s Rover Challenge requires entries to be a two-person, collapsible, pedal-powered vehicle.
Within the college-level challenge, 114 teams from around the globe registered, including a team from Central Connecticut State University (CCSU; New Britain, CT). It was assisted by engineers from neighboring CNC Software Inc. (Tolland, CT), developer of Mastercam CAD/CAM software, which has aided CCSU’s rover team for the past three years.
Understanding the terrain and course requirements of the challenge was critical. According to Tristian Sudac, CCSU student and project leader of the 12-person rover team, his group focused on a vehicle with a bicycle-like drive train. It employs a chain moving between two sprockets. The rover is about 5′ (1.52 m) in length and constructed almost entirely of carbon fiber.
The rugged, half-mile course featured 14 obstacles and five tasks, all required to be performed while operating on a virtual six-minute supply of oxygen. Choosing a strong, lightweight material was crucial. To the delight of entrants, museum exhibits were incorporated into the race course.
“We actually drove through the moon crater exhibit, which is pretty cool because it’s the closest thing to driving on the moon,” said Sudac. “There was a specific area to mimic the terrain of Mars. It had giant boulders and, if you weren’t careful or didn’t have a good enough suspension system, you could hit a boulder and destroy your vehicle.”
If the moon craters and boulders were not enough, the course also featured sand pits, rock beds, speed bumps, erosion ruts, a simulated field of asteroid debris and a 4′ (1.22 m) hill nicknamed Hell’s Hill. Two-person teams had objectives such as collecting water and ground samples or taking photos. With the new obstacles and requirements added to the 2018 competition, the CCSU team knew it had to incorporate a more robust rover design than in previous years. All vehicle entries had to fit in a 5′-cube lander equipment bay.
The CCSU team used CAD software to design its rover. One component required special attention. “We used Mastercam CAD software to design the crucial axle part,” said Sudac. In the past, the team had performance issues with its rover axle. Over the previous three competitions, it was made with two or three pieces of steel. In the 2017 race, the axle sheared on both sides due to force. This year, the team designed a similar shaft from one solid piece of steel. “That way, it wouldn’t break,” said Sudac. “And it didn’t.”
Sudac, a fourth-year CCSU student at the time of the rover challenge, is not new to Mastercam. As a high schooler, he used it to create CNC programs for manufacturing shop class. For the rover, he and his team modeled the blind shaft in Mastercam. The Edit Spline function was used to refine splines, while the Sprocket feature helped create geometries for sprockets to ensure that they would fit into the base of the transmission. Because they were unable to manufacture a four-axis part with machine tools at CCSU, the students sought help from CNC Software engineers who created G-code and produced the rover axle in the company’s machine shop.
“When it comes to voluntary machine time for schools, we very rarely say no,” said Mark Baker, CNC Software Inc. applications engineer.
After their previous design failed, CCSU team members agreed upon a more flexible yet durable configuration. Producing the axle from one solid piece of chromoly steel proved to be a wise choice. Machining of the ¾” × 10″ (19 × 254 mm) part took two hours. “The part was done on our Integrex i100 ST Mill Turn from Mazak,” said Baker. “We started off on the main spindle. We had multiple stock pulls to cut the part plus the pickoff.”
After using the same vehicle for three previous challenges, Sudac felt the team would benefit from building a completely new model. The bold approach paid off. Though the team did not place among the top 10 finishers, it designed and built the first composite leaf-suspension system in the NASA Human Exploration Rover Challenge and eliminated 40 lb (18.14 kg) of weight from its previous version. Thanks to a streamlined CAD engine, the students benefitted from the software’s ease-of-use and plan to use it for future projects. With traditional functions consolidated into a few clicks, creating even the most complex parts was simplified. Wireframe, surface and solid modeling allow straightforward geometry modeling and editing. “Mastercam made it easy for us to make something that would not fail when we needed it to succeed,” said Sudac. “It pulled through tremendously. Also, we really do enjoy having the software output G-code for us.”
Ke Wang, manager of applications engineering for CNC Software Inc., said that he and his team don’t get involved on the design side of student projects unless they detect a design failure that could impede manufacturing. In most cases they use student designs as-is.
The collaboration between CNC Software and Central Connecticut State University was mutually beneficial. Rover team members improved the design and durability of their vehicle and CNC engineers had a close-up view of the next generation of CAD/CAM software users.
“Working with students provides us with different perspectives on how to use machining and software in the design,” said Wang. “It really opens our minds about how the young generation interacts with the software. We work with several student groups and we found that they really think outside of the box.”
For more information from Mastercam/CNC Software Inc., go to www.mastercam.com, or phone 860-875-5000.
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