X-ray Computed Tomography (CT) has been used for several years as an inspection technique in the rocket nozzle industry, but only recently has it been examined as an instrumentation technique. Boeing pioneered the use of CT in the rocket nozzle industry when it began to use medical CT systems to evaluate exit cones [1]. Recently, Boeing has conducted experiments using CT to instrument high temperature testing of composite parts. We have successfully conducted real-time tests of ablating thick (>25 mm) carbon phenolic (C-P) material using a high framing rate CT system. Ablation, charring, and thermal cracking can be quantified over the time of the burn, at scan times as short as 0.06 sec as allowed by special purpose medical systems developed to image the human heart.