An experimental technique for determining the velocity of individual debris fragments from hypervelocity impacts and correlating these velocity data to fragment size is presented. Design trades and experimental results for fragment spin velocimeters based on this technique are also presented. Validation tests were conducted to verify and optimize the performance of these instruments, and they were subsequently used to collect data for four hypervelocity impact tests. Such data are critical to the development of accurate debris environment models and to support safety hazard analyses of flight tests involving impacts. Comparisons with model predictions are presented.