In April, Tennessee Tech University’s Lunar Rover team placed seventh in the first NASA Human Exploration Rover Challenge in Huntsville, Ala. The event brings together 70 high school, college and university teams from the United States and as far away as Canada, Puerto Rico, India, Russia, Mexico and Germany.
The challenge involves two-person human-powered vehicles traversing a half-mile obstacle course. The course features simulated extraterrestrial terrain such as craters, crevasses, ridges, inclines, boulders and ruts.
“We accumulated zero penalties on obstacle times,” said team member Demanuel Boyd, of Chattanooga. “We also did great on tech inspection and safety issues. We designed a really light vehicle this time, starting with an extremely light steel frame, and we’re pretty sure that had a lot to do with us performing as well as we did in the event.”
Since 1999, TTU has competed in the NASA Great Moonbuggy Race; the Human Exploration Rover Challenge has taken the place of that event, with tougher, more complex challenges and requirements. Differences include new obstacles on the course that teams will traverse with their student-designed, built and powered rovers.
To simulate conditions on Mars, for example, the course now features "a simulated field of asteroid debris - boulders from 5-15 inches across; an ancient stream bed with pebbles about 6 inches deep; and erosion ruts and crevasses in varying widths and depths," according to NASA.
Rules also specify that the disassembled rover must measure no more than 5 feet by 5 feet by 5 feet; the team must carry the rover to the course’s starting line and assemble it on the spot. Assembly time counts toward final results as well; Tech’s team lagged behind, with an assembly time of 11 seconds.
The goal of the redesign is "to engage students worldwide in the next phase of human space exploration," NASA said in a late November news release. Students will get an authentic engineering experience with the new event.
NASA is taking steps to ultimately send humans to Mars, so broadening this student design challenge represents a logical next step. It also continues NASA's effort to use the appeal and intrigue of its space missions and programs as catalysts for engaging students in STEM - science, technology, engineering and mathematics.
“I’m very pleased with the way things turned out at this year’s Rover Challenge,” said manufacturing and engineering technology professor Ahmed Elsawy. “Our team built a great rover, which held up under the punishment of a really grueling course, and came to the event totally prepared and ready to compete.”
This year’s rover incorporates a number of innovations, such as airless tires on custom-fabricated aluminum rims, coil-over shock absorbers, an infinitely-adjustable hub akin to an automotive CVT transmission and a lightweight chromoly frame. Previous teams discovered that conventional mountain-bike spoked wheels couldn’t hold up to hard use on the course; this year’s team had forged-aluminum 29-inch wheels fabricated by Calsonic Kansei.
A new requirement this year is for non-pneumatic tires; conventional tires with inner tubes would explode from the lack of atmospheric pressure in an outer-space environment. That meant the team had to locate tires with an airless inner structure that could still provide the shock absorption, handling and load carrying of a conventional tire. The tough and resilient airless designs are already in use for military vehicles, off-road applications and industrial tires.
“The tough part was getting the tire affixed to the rim,” said Evan Richards, of Celina. “We ended up using a series of hose clamps and zip ties to fasten the tire securely to the rim – anything else ended up getting thrown off the rim too easily, which would of course be a race-losing event.”