Calculation of Unsteady Aerodynamic Loads Using Fast-Response Pressure-Sensitive Paint (PSP)

The improved uPSP relies on a specific combination of TiO2 particle grades and dispersants. The formulation improves the dispersion of the TiO2 particles within the polymer/ceramic binder, reducing particle agglomeration and allowing thinner, smoother coatings to be applied. The new coating exhibited linear calibrations and retained the fast pressure response required for unsteady measurements while reducing surface roughness and coating thickness compared to traditional uPSP formulations. The improved formulation also provides greater stability with age, allowing the coating to retain its pressure sensitivity for longer periods after application. Calibration chamber testing conducted from vacuum conditions to 100 kPa, highlights substantial improvements over baseline formulations. Compared to traditional mixes, the optimized formulation delivers highly linear oxygen sensitivity, enhanced overall responsiveness, and superior thermal stability. Frequency response characterization confirms the uPSP reliably captures high-speed transient aerodynamic phenomena up to 12 kHz. While NASA's Langley Research Center originally developed this uPSP for testing launch vehicle buffeting, rotorcraft, and transonic fluid dynamics, it offers value across multiple industries. Automotive and wind energy sectors can utilize this stable, thin-profile coating to map high frequency aerodynamic loads on vehicle prototypes or turbine blades, and its ability to capture dynamic pressure changes makes it ideal for structural monitoring and real-time pressure mapping in commercial machinery. This technology is currently available for patent licensing.

Axial force is a key parameter for many aeroscience R&D applications. Axial force is the dominant component used to measure aircraft drag (for fuel efficiency purposes) and provides important control information (such as vehicle deceleration rate). Integration of Axial force measurement into this design enables a direct measure of the drag force, while simultaneously providing a fluid flow path for powered simulation in wind tunnel testing. Current state-of-the art alternatives (i.e., flow-through balances without axial force) either require investigators to infer the drag force by integrating pressure taps on the test article (which further increases axial force measurement uncertainty) or run a redundant, second wind tunnel entry with a standard six-component balance without the flow-through capability (which is not desirable because they are expensive, time consuming, and impede efficiency). While NASA’s flow-through transducer technology could be manufactured using conventional fabrication methods, additive manufacturing is expected to be preferred as it enables relatively simple incorporation of the flow-through axial element into the design without increasing manufacturing complexity or costs.

The heating layer uses a polyurethane binder loaded with carbon-based conductive filler, formulated to remain stable and crack-free across a wide temperature range. Applied as a thin film with copper-tape electrodes, it generates heat through electrical resistance when energized, functioning as a spray-on electric blanket that produces a precise, localized temperature step. The resistance can be tuned to match specific power and geometry requirements, offering a scalable alternative to the traditional temperature step method with lower energy consumption, faster setup, and reduced maintenance. The layer has been tested at NASA's National Transonic Facility (NTF), integrated into the CATNLF wing, and installed on test aircraft. The silicon carbide protective coating was developed after flight demonstrations revealed that minor surface damage from debris caused premature flow transition and compromised data quality. By incorporating beta silicon carbide into a polyurethane binder, the coating significantly increases surface hardness and abrasion resistance while retaining flexibility. It applies over the heating layer to protect against debris, water, and oil, and has demonstrated superior durability during surface preparation on in-flight models requiring infrared imaging. Together, the two coatings improve the accuracy, durability, and efficiency of aerodynamic testing in extreme environments. The heating layer is a TRL 6 and the silicon carbide coating is a TRL 4. The coatings are available for patent licensing.

In order to maintain the low cost, simplicity, and quick turnaround of cold-flow testing while improving accuracy, NASA evaluated unconventional gases for use as simulants. During such evaluations, NASA discovered that by adjusting stagnation temperature, the isentropic exponent of ethane can be tuned to approximate those of common rocket propellants (e.g., hydrogen, hypergols, alcohols, and hydrocarbons). Furthermore, due to ethane’s high auto-ignition temperature and resistance to condensation, tuned ethane enables testing of expansion ratios much larger than conventional inert-gas testing. To leverage this discovery, NASA developed a hardware-based system to treat ethane and obtain nozzle chamber conditions that match the appropriate aerodynamics for a specific test. The system, named HYPERFIRE, works in the following manner. Liquid ethane is transferred to a piston-style run tank, where it is pressurized. Then, the ethane is run through two insulated pebble beds where it is heated, vaporized, and stabilized. Finally, the treated ethane is transferred from the second pebble bed to a small thrust takeout structure, and through the test article. Control of valves and regulators is managed by an onboard computer, accessed via a LabVIEW™ interface. The system is mounted on a hurricane-resistant steel frame to enable transportation via forklift. Heated ethane reproduces the aerodynamics of combustion products at low temperatures relative to alternative testing methods. Thus, test articles can be manufactured using low-cost, low temperature rated, transparent materials (e.g., acrylic). In addition to reducing testing cost, this grants optical access to internal flowfields, enabling advanced diagnostic techniques (e.g., Schlieren imaging, particle image velocimetry) not possible with hot-fire testing and less meaningful with conventional cold-flow testing.

The disclosed technology provides a multistage system for evaluating the free-flight behavior of test articles across of the supersonic, transonic, and subsonic regimes. First, a drop platform is lifted to high altitudes using a lifting device, such as a stratospheric balloon. The drop platform houses multiple projectiles, each containing an ejection mechanism, an on-board avionics suit, and an instrumented test article. Upon reaching the target altitude via the lifting device, the drop platform releases the projectiles sequentially. Each projectile accelerates to a target speed and altitude before ejecting its test article into the freestream. The test articles, such as a scaled re-entry capsule, then collect flight data during their descent through the various Mach regimes, providing valuable insights into their flight performance under mission-relevant conditions. This innovative testing system offers several benefits. It enables the simultaneous testing of multiple vehicles, facilitating the evaluation of design variations as well as statistical analyses of vehicle behavior. This system also provides significant cost savings in comparison to other state-of-the-art testing methods, such as ballistic range testing. Additionally, the test articles within each projectile are easily interchangeable through a simple, modular change of a support surface in the ejection mechanism. This flexibility enables the system to accommodate a range of other aerodynamic technologies, including other vehicles, parachutes, propulsion systems, and defense technologies. This system can enhance the efficiency and robustness of reentry vehicle design, testing, and simulation operations through the collection of rich, flight-relevant data.