Breakthroughs noted in space debris propagation, aircraft vulnerability and high-speed X-ray imaging
By Dominic A. Pena|December 2024
The Survivability Technical Committee promotes air and spacecraft survivability as a design discipline that includes such factors as crashworthiness, combat and repairability.
At the Air Force Research Laboratory at Wright-Patterson Air Force Base in Ohio, research conducted between January and September focused on modeling debris propagation physics and space system survivability from catastrophic breakups in multibody gravitational systems. One segment examined debris risks from spacecraft breakups in disposal and reconstitution parking orbits in sun-Earth Lagrange-point orbits, updating debris models for this regime for the first time since 2001. Another segment conducted large-scale Monte Carlo simulations to assess debris risks in Martian orbits for operational and disposed vehicles. Additionally, researchers tested the survivability of aerospace-grade aluminum honeycomb panels of varying thicknesses, firing projectiles from AFRL’s cold gas gun at them to simulate high-speed impacts from debris fragments. Future research will focus on enhancing debris modeling fidelity in cislunar space and assessing debris risks to spacecraft operating in the Earth-moon corridor.
In the air domain, the U.S. Air Force’s 704th Test Group in August conducted tests to quantify ullage ignition probabilities and overpressures under varying operational conditions, oxygen concentrations and ignition energy. They mapped the relationship between ballistic threat levels, ignition energy and overpressure, providing critical data for aircraft fuel system designers to reduce vulnerability while optimizing weight and cost. From February to August, graduate students at the Air Force Institute of Technology, AFIT, at Wright-Patterson completed research projects focused on reducing aircraft vulnerability to kinetic and nonkinetic threats. They analyzed results of fuel tank ballistic impact tests, measuring the time delay from impact to the first instance of fluid spurting out of the impact point — known as shallow jet spurt. This analysis considered the structural dynamics and material properties of the impacted fuel tank panel, and researchers found a correlation between the fluid-back natural frequency and the time delay for shallow jet spurt. This illustrated the importance of matching structural dynamic properties between the test article and the modeled aircraft of interest when designing future ballistic tests to mitigate fire hazards.
In May, AFIT researchers with SURVICE Engineering Co. of Virginia designed a composite-copper component to shield small unoccupied rotorcraft from electromagnetic energy attacks. The design incorporates heat transfer and electromagnetic shielding analyses to ensure functionality in contested airspace. Researchers also conducted ballistic impact tests on composite armor panels made from glass or aramid fibers, paired with different thermoplastic matrix options. The combination of aramid fibers and a high-density polyethylene matrix displayed the highest ballistic strength among the materials tested, highlighting the importance of material selection in armor design.
In March, researchers at the Fraunhofer Institute for High-Speed Dynamics in Germany achieved a milestone in high-dynamic X-ray imaging, creating the first continuous depiction of internal deformations of crash safety components not visible during high-speed events. This was possible with a new high-speed X-ray technology, capable of capturing 1,000 images per second. Traditionally, X-ray techniques have been applied statically to non-moving objects, while flash X-ray provided only limited images during high-speed events. They tested the new approach in a crash scenario, in which a deformable barrier collided with the side of a vehicle, while a custom-built linear accelerator by Siemens captured X-ray images at 1,000 Hertz. The 9-megaelectronvolt energy from the accelerator allows the X-ray to penetrate dense structures, requiring enhanced radiation protection. Laboratories at Fraunhofer were modified for X-ray and radiation safety to ensure controlled testing. This technology could enrich data collected during testing and improve the predictive capabilities of simulation methods. Future applications could include analyzing thermal runaway processes in battery packs for urban air mobility, as well as providing insights into internal processes during impact events like bird strikes on aircraft.
Contributors: Air Force Lt. Col. Robert Bettinger, Air Force Maj. John Hansen, Colton Lapworth and Michael May
