An investigation of the flow field during eject of a cruise missile from the launch tube was undertaken using a "cold" flow simulation. A facility was developed whereby various design changes in the missile ejection apparatus, denoted the vertical support assembly, could be quickly and easily assessed in terms of the relative effects on the flow field. Flow visualization techniques using fluorescent dye allowed for documentation of flow patterns in the baseline configuration, such as backflow, jetting, and recirculation regions, as well as for the location of several potential hot spots. The mixing of the fuel-rich gas generator effulent and the air in the launch tube was assessed by thermocouple measurements; warm water was used to simulate the exhaust while ambient water represented the air initially contained in the launch tube. The results have shown that air is inefficiently mixed in large portions of the vertical support assembly volume. However, strong flameholding zones are established in the region vacated by the accelerating missile, where it is believed that secondary combustion could occur. The flow field characterization has shown that considerable improvements to system performance should be possible through geometrical changes to promote more efficient mixing. / M.S.