A pulsed high flux source of nearly monoenergetic atomic oxygen has been developed at Physical Sciences Inc. (PSI) to perform accelerated erosion testing of spacecraft materials in a simulated low earth orbit (LEO) environment. Molecular oxygen is introduced into an evacuated conical expansion nozzle at several atmospheres pressure through a pulsed molecular beam valve. A laser induced breakdown is generated in the nozzle throat by a pulsed CO2TEA laser focused to intensities ≳109W/cm2. The resulting plasma is heated in excess of 20,000 K by the ensuing laser supported detonation wave, and then rapidly expands and cools. The nozzle geometry confines the expansion to promote rapid electron‐ion recombination into atomic oxygen. The source generates an atomic oxygen beam with fluxes ≳1018atoms per pulse at 8±1.6 km/s with an ion content below 1% for LEO testing. For other applications the beam velocity can be varied over a range from 5 to 13 km/s by changing the discharge conditions. Materials testing has obtained the same surface oxygen enrichment in polyethylene samples as observed on the STS‐8 mission, and scanning electron micrographs of the irradiated polymer surfaces reveal an erosion morphology similar to that obtained on low earth orbit.