Laser-Based Ultrasonic Inspection of Complexly Contoured Rocket Engine Components

McKie, A.
Addison, R.
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High-performance rocket engines, that are being developed for the next generation reusable launch vehicles, require active cooling of the thrust surfaces. An effective and rapid method is needed to inspect the critical bond between the liner assembly and the jacket of the thrust cell chamber, to determine its integrity prior to the expense of 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. The use of laser-based ultrasound (LBU) techniques have previously been shown to be an effective method for rapid inspection of contoured polymer-matrix composite structures[l–3]. The transition to inspection of metallic components requires increased spatial resolution to resolve defects of ∼1.2 mm diameter, in addition to modification for limited access inspection from inside the thrust cell. This paper reports progress on inspection of a heat exchanger NDE standard which demonstrates the resolution capability of the LBU system. LBU inspection of a three-quarter section aluminum rocket nozzle proof part is presented, in addition to data showing the dependence of the thermoelastic generation efficiency as a function of the applied paint thickness.