NASA scientists are developing a new family of flexible heat-shield systems that can survive re-entry from low-Earth orbit.
NASA Ames Research Center (NASA ARC)— which developed the Phenolic Impregnated Carbon Ablator (PICA) material utilized on the Curiosity Rover on Mars and the Stardust spacecraft—is now developing a new family of flexible heat-shield systems. While traditional heat shields form a rigid structure, scientists from NASA ARC have developed ADEPT (Adaptive Deployable Entry and Placement Technology) using a woven carbon-fiber substrate or base material.
The material’s heat-resistance and structural properties can be fine-tuned by adjusting the weaving techniques. The flexible nature of the woven materials can accommodate the design of large-profile spacecraft capable of landing heavier payloads, including human crews.
ADEPT would be stowed inside the spacecraft and deployed like an umbrella prior to atmospheric entry. The new system is supported by an array of sturdy metallic struts and could also serve to steer the spacecraft during descent.
Unlike the reusable ceramic tiles used on NASA’s space shuttles to survive reentry from low-Earth orbit, the lighter PICA material and woven carbon materials are designed for single use, protecting their payload while they slowly burn up during the rigors of atmospheric entry.
NASA research scientists are conducting X-ray experiments at the Lawrence Berkeley National Laboratory to track the material’s response to extreme temperatures and pressures.
“We’ve been working on studies of various heat-shield materials for the past three years,” Harold Barnard, a scientist at Berkeley Lab’s Advanced Light Source (ALS), said in a statement. “We are trying to develop high-speed X-ray imaging techniques so we can actually capture these heat-shield materials reacting and decomposing in real time.”
During an atmospheric entry into Mars, there is substantial heat load on the shielding material with surface temperatures approaching 4,000 degrees Fahrenheit.
“We are developing methods for recreating those sorts of conditions, and scanning materials in real time as they are experiencing these loads and transitions,” Barnard said. A test platform now in development uses a pneumatic piston to stretch the material, in combination with heat and gas-flow controls to simulate entry conditions.
“X-rays enable new simulations that we were not able to do before,” Francesco Panerai, a scientist with AMA Inc. at NASA ARC and the lead experimentalist for NASA’s X-ray studies at Berkeley Lab’s ALS, said in a statement. “X-rays enable new simulations that we were not able to do before.
“Before we were using X-rays, we were limited to 2D images, and we were trying to mimic these with computer simulations. X-ray tomography enables us to digitize the real 3-D microstructure of the material.”
Joseph Ferguson, a researcher with Science and Technology Corp. at NASA ARC, led the development of a software tool—PuMA (Porous Materials Analysis)—that can extract information about a material’s properties from the ALS X-ray imaging data, including details about how porous a material is, how it conducts heat and how it decomposes under entry conditions.
According to Barnard, the software tool has pushed ALS researchers to develop faster microtomography imaging methods that capture how materials respond over time to stress.
“We have been able to push the imaging speed down to between 2.5 to 3 seconds per scan,” Barnard said. “Normally these scans can take up to 10 minutes. It has been good for us to work on this project. We want better instrumentation and analysis techniques for the experiments here, and we are pushing our instrumentation boundaries while helping NASA to develop heat shields.”
Dula Parkinson, a research scientist who works with Barnard at the ALS on microtomography experiments, said the faster imaging speeds, which can produce about 2,000 frames per second, are generating a high volume of data.
“The capabilities of our detectors and other instruments over the past five years have improved orders of magnitude,” Parkinson said in a statement. “It has increased our needs for data management and computing power.”