Aerospace Design and Structures

U.S. Defense Department researchers improve survivability in the air and in space

The Survivability Technical Committee promotes air and spacecraft survivability as a design discipline that includes such factors as crashworthiness, combat and repairability.

During May and June, the U.S. Air Force 704th Test Group’s Aerospace Survivability and Safety Office at Wright-Patterson Air Force Base in Ohio conducted polyalphaolefin oil fire-mitigation testing. PAO is commonly used in aircraft as coolant, lubricant and hydraulic fluid. With these fluid lines positioned throughout aircraft, PAO fires are large sources of uncertainty in aircraft vulnerability analyses. A fire-mitigating additive was developed that mixes with PAO to reduce the probability of ignition due to ballistic threats. This test program, conducted with the Joint Aircraft Survivability Program Office, aimed to quantify the effectiveness of the additive against ballistic fragment impacts, comparing results to baseline ballistic testing of standard PAO. The results contributed to ongoing research into PAO fires by improving the accuracy and reducing the uncertainty of vulnerability assessment models. Plans call for additional testing with fragments in 2024 to further characterize the treated PAO.

From May through July, the U.S. Air Force Institute of Technology at Wright-Patterson conducted simulation-based research to analyze the debris risk from spacecraft breakups in disposal and reconstitution parking orbits in a variety of cislunar and sun-Earth orbits. With super-computing resources, researchers conducted large-scale Monte Carlo debris impact simulations to also investigate debris risks in low lunar orbit. For future tests, plans call for firing a cold gas gun at aerospace-grade aluminum honeycomb panels and additively manufactured components of varying thickness to simulate high-speed impacts of debris fragments. Also next year, researchers are to examine debris risks to the lunar surface, as well multibody planetary systems, including Mars-Deimos-Phobos.

In July, the U.S. Army Aviation Survivability Integrated Product Team met at Fort Belvoir in
Virginia. Organized by the Aviation Survivability Branch of DEVCOM, the U.S. Army Combat Capabilities Development Command, the event brought together an unprecedented group of Defense Department organizations studying aviation survivability. Key participants included the Joint Aircraft Survivability Program Office; U.S. Marine Corps Aviation; Naval Air Systems Command and the Naval Research Laboratory; and the U.S. Army Futures Command Future Vertical Lift Cross-Functional Team. Participants presented and discussed cutting-edge survivability science, technologies and capabilities, with a focus on sharing essential capabilities for future and current Army aircraft and those for other service branches. Specific topics addressed threat sensing, imaging, modeling and simulation.

Researchers in the University of Texas Arlington’s Advanced Materials and Structures Laboratory made progress toward breaking through object size limitations of X-ray computed tomography, or CT, which makes possible high-resolution nondestructive inspection, or NDI, of large aerospace composite structures. X-ray CT has proven to be the only three-dimensional NDI technique with sufficient resolution and objectivity for automated interpretation of inspection results, including manufacturing flaws and damage affecting aircraft survivability. The main challenge is that traditional CT methods and equipment are based on generating X-ray projections all around the inspected object, limiting the methods to high-fidelity inspection of small parts. Simply scaling traditional X-ray CT systems to fit aircraft structure is not the solution, as this makes it nearly impossible to detect critical flaws or damage in composites. The Texas researchers developed reconstruction algorithms and software tools for expanding X-ray CT to high-resolution NDI of large structures and paired these with new CT scanning hardware developed by Japanese company Shimadzu Corp. The result was a prototype CT NDI system that can conduct high-    resolution three-dimensional NDI not possible with conventional methods. From June to November, the prototype inspected large aerospace composite structures with the fidelity required to detect and assess flaws and damage affecting aircraft survivability.

Contributors: Robert Bettinger, Andrew Makeev, Brad Snowden and Carlos Suarez

U.S. Defense Department researchers improve survivability in the air and in space