Materials and coatings created for aerospace systems that travel at high rates of speed are repeatedly exposed to rain droplets could make the systems, materials and coatings susceptible to damage or erosion.
Engineers from the Air Force Research Laboratory Materials and Manufacturing Directorate’s Systems Support Division conducted testing on mission critical components for a Navy aircraft system that were experiencing premature erosion in flight.
Conducted in late-August 2013, RX engineers, in cooperation with peers from the Navy, tested the components in their unique, one-of-a-kind supersonic rain erosion (SURE) testing rig, which simulates the impact of rain on aerospace systems travelling at transonic and supersonic speeds.
The SURE capability (nicknamed “The Supersoaker”), which was installed at RX’s Coatings Technology Integration Office facility in 2011, enables researchers to conduct both predictive modeling of material behaviors, and large- and full-scale component rain erosion testing. The testing rig appealed to Navy personnel, because it allowed them to recreate in flight conditions in a laboratory environment where they could closely monitor the impact of erosion on identical components several times.
The SURE capability allows researchers to test systems, materials and new technologies for missile materials, coatings for aircraft leading edges, optical materials, rotor blades, radomes, antennas and other commercial technologies at speeds up to Mach 2.5. Because the SURE operates at speeds that are not already offered by the AFRL Rain Erosion Test Facility or the Holloman High Speed Test Track (HHSTT), material and system developers can use the SURE capability to establish a testing baseline in the mid-range, which was unavailable before development of the SURE apparatus.
The SURE apparatus produces 1-2 mm diameter water droplets, and achieves 12 gallons of output a minute at 50,000 pounds per square inch. Droplet size is controlled by the size of an interchangeable nozzle used in the system. Droplet speed is independently controlled by pump pressure.
During the testing, erosion damage was capture using a high speed camera monitoring components through a window to the chamber. This allowed Navy personnel to review the results of the testing on a video monitor in another part of the facility immediately following testing.
The SURE capability is operated and maintained by personnel from the University of Dayton Research Institute (UDRI) by-way-of an on-site contract with the CTIO. A cooperative research and development agreement between RX and UDRI accommodates testing for commercial and industrial customers.
Navy counterparts were pleased with the results of the testing and are currently discussing their return for follow on testing, which will allow them to determine preventative maintenance or design changes to safeguard their system from the affects of rain erosion.
Additionally, this testing was the first full-scale component testing conducted using the SURE capability at CTIO, which provides confidence in its ability to handle full-scale component testing for other DoD, Air Force, commercial and industry customers in the future.