The training systems industry has long recognized the need to base the design of complex and expensive training devices on specific training requirements. The numerous efforts that have been made to achieve this goal have encountered problems across a range of areas. User communities and procuring agencies have in the past been forced to struggle with these problems alone, but with the advent of total training systems acquisition, the system supplier must face this problem directly. Functional design techniques from engineering disciplines have proved insufficiently sensitive to required student behavior. Media selection models from ISD, on the other hand, are not optimized to support the development of a new device. The use of ISD media models has identified training requirements for which simulation is needed but without sufficient detail to support engineering decisions. There is a clear need for a media design process which is oriented around training requirements and which yields information required for device engineering. This paper outlines a process which appears to have promise as a response to these needs.