At NASA’s Kennedy Space Center (KSC), an engineering debris team performs a post-landing inspection of the space shuttle orbiter for debris and for anomalies in the thermal protection system. The areas of inspection and debris sampling include the orbiter windows, lower surface orbiter tiles, reinforced carbon-carbon panels of the orbiter wings, and the external tank (ET)/orbiter umbilicals.On October 18, 1989, the space shuttle Atlantis was launched from launch pad 39B at KSC. Atlantis landed on runway 23 at Edwards Air Force Base, California on October 23, 1989. During the post-landing inspection performed October 23-24, 1989, a washer, approximately 1/2 inch in diameter, was found embedded in one of the lower surface tiles forward of the LH2 ET/orbiter umbilical area. The washer was oriented perpendicular to the airflow, and approximately half of the washer protruded into the aerodynamic flow.The washer was submitted to the NASA KSC microchemistry laboratory for examination and elemental and phase analysis.