By Denise M. Stefula
The Pop-Up Flat Folding Explorer Robots technology, or PUFFER, is readying a prototype for field testing in Southern California’s Mojave Desert through this summer and into the fall.
PUFFER is a low-cost pop-up rover that folds compactly—near the size of a smartphone—into a parent spacecraft and can then unfold when needed for exploring and gathering science from the extreme terrains of other planets, like Mars, or those here on Earth, such as on the polar ice sheets. As part of Space Technology’s Game Changing Development Program, PUFFER has completed its field test plan, prepared a technical report on component-level testing of cold-tolerant batteries and brushless motors, and conducted a peer review, all important milestones for the project.
“The PUFFER team is off to an excellent start developing and testing designs for the robot’s subsystems and in defining how these will come together in our next prototype,” says Jaakko Karras, PUFFER project manager at NASA’s Jet Propulsion Laboratory (JPL). “PUFFER’s compact origami-inspired design requires that every component integrate very closely with the rest of the system. Our initial work is important for ensuring that everything comes together to provide the greatest new science and exploration capabilities possible.”
In April, the PUFFER team made a preliminary visit to the Rainbow Basin field test site in the Mojave Desert to identify specific terrain features for testing, including four inclines of varying slope featuring sedimentary rock structure, two natural overhangs, and a large level region for general mobility testing. Observing the PUFFER prototype’s capabilities as it navigates the natural terrain features will provide important data supplementing lab testing already underway.
“Our current testing is evaluating PUFFER’s mobility in a lab setting at JPL, testing the platform’s mobility on steep inclines and beneath confined overhangs. These early tests are excellent for initial prototyping of things like PUFFER’s wheels and actuators, and for getting a sense of how energy efficient these types of maneuvers are,” says Karras. “These findings will be compared against field test data to determine how our performance changes in ‘real-world’ conditions, which will allow us to better tune our designs for the natural terrain.”
While testing in Rainbow Basin, the team hopes to see PUFFER use its small size and unique mobility architecture to drive up steep sedimentary rock slopes as well as beneath eroded rock overhangs, places that often present challenges for larger spacecraft. “These types of terrains are of high interest to Mars scientists, and we hope to one day use teams of PUFFERs to provide access into unexplored areas,” says Karras.
The PUFFER team is currently finalizing with industry partner Pioneer Circuits, Inc., its latest production run of rigid yet flexible printed circuit board (PCB) structures, from which prototypes are being constructed for use as the field test articles. These circuit boards are unique in that they incorporate new materials, such as woven textiles, that can fold into the PUFFER robot’s body.
“These new materials did present some early challenges because nobody had produced PCBs quite like this before, and we had to work with Pioneer Circuits to figure out how to get them manufactured. In the end, though, the process that we’ve come up with is perfect for these types of origami-inspired robots,” says Karras.
Component-level testing reported on in May revealed very promising results, showing that both the batteries and actuators can survive the full –135 to 30 ˚C Martian thermal cycle. In order to maximize the science return PUFFER is capable of, Karras wants to see as much of the power budget as possible dedicated to driving and instruments. A good way to do this, he explains, is to operate PUFFERs without any onboard heating because heaters consume large amounts of power.
“By showing that our key components, such as the batteries and motors, can operate in cold environments without heating, we’ve taken an important first step toward our envisioned heaterless robot,” Karras says.
Also in May, a peer review was conducted including 11 reviewers at JPL outside the core PUFFER team. Current progress toward the next generation of instrumented prototypes, as well as work being done to identify future mission opportunities, was presented. These reviews are an exciting time for projects because it brings together elements from many different disciplines, spanning both engineering and science.
“Getting together with experts from these disciplines, like we did at our peer review, is an important way to get feedback to ensure that we bring all the different elements together effectively.” says Karras. “Our team received a number of good inputs regarding wheel design for mobility in the types of rough terrains that we are targeting. We are incorporating these inputs into the design and iteration of our wheels as we prepare for field testing on the natural rock features at Rainbow Basin.”
“Many of our reviewers have extensive experience from designing, testing, and operating past and present Mars rovers,” Karras continues. “They pointed us to good resources on topics such as operating electronics in the Mars environment and qualifying future designs for flight. Our reviewers also provided good inputs on formulating PUFFER mission scenarios to identify new mission infusion opportunities.”
Many of the most scientifically intriguing destinations in our solar system, such as caves and lava tubes on Mars or the “chaos terrains” on Europa, will require maneuvering over challenging extreme terrains. This makes extreme terrain mobility a high priority for NASA and its missions, particularly those with science objectives requiring craft to travel highly rugged, adverse surroundings. The PUFFER technology will provide future NASA missions with a low payload cost mission enhancement to explore these types of environments.
- Folds flat and stacks as a compact secondary payload
- Pops up without assistance from parent
- Sprawls to fit in confined spaces or position instruments
- Integrates electronics and sensors with structure
- Explores previously inaccessible terrain
- Images steep slope stratigraphy with ground-facing microscope
- Adjusts shape to fit under rock outcrops and measure microenvironments
- Survives falls from cliffs with compliant structure and ability to operate inverted