Inspection of Rocket Engine Components Using Laser-Based Ultrasound

Abstract

High-performance rocket engines, which require active cooling of the thrust surfaces, are being developed for the next generation of reusable launch vehicles. These engines require an effective and rapid method for inspecting the critical braze bond between the liner assembly and the stainless steel outer jacket of the thrust chamber, to determine its integrity and prevent catastrophic failure during hot fire testing. Currently, a series of conventional ultrasonic techniques are used to inspect the thrust cell chamber. However, the complexly contoured surfaces prevent 100% inspection. Laser-based ultrasound (LBU) techniques have previously been shown to be an effective method for rapid inspection of contoured polymer-matrix composite structures^1–3. The transition to inspection of metallic components requires increased spatial resolution to resolve defects on the order of 1 mm diameter, in addition to modification for limited access inspection from inside the thrust cell chamber. This paper reports progress on inspection of a heat exchanger NDE standard which demonstrates the resolution capability of the LBU system. In addition, C-scan results for LBU inspection of a three-quarter section aluminum rocket nozzle proof part and a quarter-section throat bond demonstrator are presented.