Researchers at the Department of Energy’s Oak Ridge National Laboratory have taken additive manufacturing to the final frontier as they 3D print moon rover wheel prototype in collaboration with NASA. This is the same design as NASA’s robotic lunar rover, demonstrating the technology for specialised parts required for space exploration.
The additively manufactured wheel was modelled after the existing, light-weight wheels of the Volatiles Investigating Polar Exploration Rover, or VIPER, a mobile robot NASA plans to send to the moon’s south pole in 2024 to map ice and other potential resources. The mission’s goal is to determine the origin and distribution of the moon’s water, as well as whether enough water can be harvested from the moon’s surface to sustain people living there.
Researchers 3D Print Moon Rover Wheel Prototype
While the prototype wheel printed at DOE’s Manufacturing Demonstration Facility at ORNL will not be used on the NASA Moon mission, it was designed to meet the same design specifications as the wheels used on NASA’s VIPER. More testing is planned to validate the design and fabrication method before applying it to future lunar or Mars rovers or considering it for other space applications such as large structural components.
Additive manufacturing can reduce energy consumption, material waste, and lead time while increasing design complexity and material property tailoring. MDF has been at the forefront of this effort for over a decade, developing the technology for a wide range of applications in the clean energy, transportation, and manufacturing sectors. In the autumn of 2022, MDF researchers will print the rover wheel prototype at ORNL. To selectively melt metal powder into the designed shape, a specialised 3D printer used two coordinated lasers and a rotating build plate.
“This dramatically increases the production rate with the same amount of laser power. We’re only scratching the surface of what the system can do. I really think this is going to be the future of laser powder bed printing, especially at large scale and in mass production.”
– Peter Wang, who leads MDF development of new laser powder bed fusion systems
The prototype wheel is about 8 inches wide and 20 inches in diameter, which is much larger than typical parts printed with metal powder bed systems. Its creation necessitated the ability to print small geometric features spread across a large work area. The use of additive manufacturing allowed for greater complexity in the rim design without increasing the cost or manufacturing difficulty.
In comparison, the four VIPER wheels that will churn through moon dust next year necessitated numerous manufacturing and assembly steps. The 50-piece wheel rim of VIPER is held together by 360 riveted joints. To meet the mission’s stringent requirements, the manufacturing process required complex and time-consuming machining.
If NASA testing shows that the 3D printed prototype is as strong as conventionally built wheels, future rovers could use a single printed wheel rim, which took ORNL 40 hours to create. ORNL and NASA engineers also investigated printing precise design features such as angled sidewalls, a domed shape, and wavy tread to increase the wheel’s stiffness during the project.
Traditional fabrication methods make it difficult to incorporate these characteristics into the current VIPER wheel design. Despite the fact that 3D printing allows for a more complex spoke pattern and spoke locking features on the wheel, it simplifies and reduces the cost of the wheel design and makes final assembly easier.
The specialised printer only builds with specific materials – in this case, a nickel-based alloy – so the 3D-printed wheel is 50% heavier than the aluminium VIPER wheel despite being printed at the same thickness.
NASA intends to test the performance of the 3D-printed wheel on a rover in the rock yard at NASA’s Johnson Space Centre or in a massive “sandbox” of simulated lunar rocks and soil at a contracted test facility. The wheel’s manoeuvrability, pivoting resistance, sideways slippage, slope climbing, and other performance metrics will be evaluated.
“Crewed research stations placed on the moon as part of the agency’s Artemis Program will need off-planet manufacturing capability. Being able to build parts in space for repairs will be important, because you just can’t take enough spares. Powder, pellets or filament for printing are a lot easier to pack and would allow for more flexibility.”
– Richard Hagen, a mechanical design engineer for NASA and additive manufacturing lab manager at NASA’s Johnson Space Center in Houston
Jay Reynolds, Gordon Robertson, Greg Larsen, Jamie Stump, Michael Borish, Chris Ledford, Ryan Dehoff, and former ORNL staff member Charles Wade are also involved in the project, with technical assistance from Ryan Duncan and Jeremy Malmstead.
