[en] Two aerodynamic separation techniques for uranium enrichment were investigated for technical feasibility and economic viability. These techniques are known as the Jet Membrane and Velocity Slip Processes. Both analytical and laboratory studies were conducted to explore the technical feasibility of the subject processes. The Jet Membrane Process Studies demonstrated that the process was feasible and that a condensable gas carrier is available. The Velocity Slip Studies demonstrated the predicted effects and did not identify a suitable condensable gas carrier. Hence the Velocity Slip Process exhibited a larger power consumption than did the Jet Membrane Process. An independent contractor prepared detailed cost estimates of the process. The independent results indicated that, based on the same costing ground rules, the Velocity Slip process would require 16 times the fixed capital costs and 12 times the cost per separative work unit as compared to the Jet Membrane Process. The same cost structure indicated that the cost per separative work unit for the Jet Membrane process would be two to three times that for the Gas Centrifuge process. There are a number of uncertainties associated with these cost estimates, such that, in the extreme, the costs might be the same. Further, more detailed cost analysis would be required to resolve the uncertainties associated with the initial cost estimates. The conduct of new studies was not considered to be appropriate for EPRI because of the changes in enrichment program management and security philosophy discussed in the text