Landing rovers and helicopters on Mars is a challenge. It’s even more of a challenge when you don’t have enough information about how the parachutes bear the load when descending to the surface. Researchers at NASA’s Armstrong Flight Research Center in Edwards, Calif., are experimenting with readily available, highly elastic sensors that can be attached to a parachute during testing to provide missing data.
Knowing how the canopy material stretches during deployment can improve safety and performance by quantifying fabric limits and improving existing computer models for more reliable parachutes for tasks such as landing astronauts on Earth or delivering scientific instruments and cargo to Mars. This is the work Enhancing Parachutes by Instrumenting the Canopy, or EPIC, seeks to advance the ability to measure parachute tension.
“Our goal is to demonstrate which sensors will work to determine the stress on the parachute canopy material without compromising that,” said LJ Hantsche, project manager. NASA’s Space Technology Mission Directorate is funding the team’s work through the Early Career Initiative.
Starting with 50 potential sensor candidates, the team narrowed down and tested 10 types of different sensors, including commercially available and development sensors. The team selected the three most promising sensors for further testing. These include a silicon-based sensor that measures the change in electrical charge storage as the sensor is stretched. It’s also easy to connect to data logging systems, Hantsche explained. The second sensor is a small, stretchable braided sensor that measures the change in electrical memory. The third sensor is made by printing with metallic ink on a thin and flexible plastic.
Determining methods for attaching each of the sensors to the super-thin and slippery canopy material was difficult, Hantsche said. Once the team figured out how to attach the sensors to the fabric, they were ready to start testing.
“We started with uniaxial testing, where each end of the parachute material is secured and then pulled to failure,” she said. “The test is important because stretching the sensor causes its electrical response. Determining the correlation between the voltage and the response of the sensor when it is on the fabric is one of our main measurement goals.”
This phase of testing was conducted in collaboration with NASA’s Jet Propulsion Laboratory in Pasadena, California. A high-speed version of this test, which simulates the speed of parachute deployment, was conducted at NASA’s Glenn Research Center in Cleveland.
The team used a bubble test for the sensors, which simulates 3D parachute testing. It consists of a fabric sample and a silicone membrane sandwiched between a 4-inch diameter ring and a test structure. When pressurized from the inside, the silicone membrane expands the fabric and sensor into a bubble shape. The test is used to verify the sensor’s bending performance and is compared to the results of other tests.
With the EPIC project nearing completion, further work could include temperature tests, development of a data collection system for flight, determining whether the sensor can be packed with a parachute without adverse effects, and operating the system in flight. The EPIC team is also working with researchers at NASA’s Langley Research Center in Hampton, Va., to test its sensors later this year using the center’s drone test, which will drop a parachute capsule.
In addition, the EPIC team is collaborating with the Entry Systems Modeling Group at NASA Ames Research Center in Silicon Valley, California, to design a comprehensive parachute project aimed at better understanding parachutes through modeling and test flights. The joint NASA project could result in better parachutes that are safer and more reliable for the approaching era of exploration.