Next: Displays Supported Up: INTRODUCTION Previous: INTRODUCTION

# Philosophy

The role of CAD models at BRL differs somewhat from that of CAD models being built in the automobile and aerospace industries, resulting in some different design choices being made in the BRL CAD software. Because BRL's main use for these models is to conduct detailed performance and survivability analyses of large complex vehicles, it is required that the model of an entire vehicle be completely contained in a single database suitable for interrogation by the application codes. This places especially heavy demands on the database software. At the same time, these analysis codes require less detail than would be required if NC machining were the primary goal.

At BRL, there are only a small number of primary designers responsible for the design of a vehicle, and for the construction of the corresponding solid model. Together they decide upon and construct the overall structure of the model, then they perform the work of building substructures in parallel, constantly combining intermediate results into the full model database. Because of the need to produce rapid prototypes (often creating a full design within a few weeks), there is no time for a separate integration stage; subsystem integration must be an ongoing part of the design process.

Once an initial vehicle design is completed, there is usually the need for exploring many alternatives. Typically, between three and twelve variations of each design need to be produced, analyzed, and optimized before recommendations for the final design can be made. Also, there is a constantly changing definition of performance; new developments may necessitate rapidly re-evaluating all the designs of the past several years for trouble spots.

The user interface is designed to be powerful and ``expert friendly'' rather than foolproof for a novice to use. However, it only takes about two days for new users to start doing useful design work with MGED. True proficiency comes with a few months practice.

Finally, it is vitally important that the software offer the same capabilities and user interface across a wide variety of display and processor hardware. Government procurement regulations make single-vendor solutions difficult. The best way to combat this is with highly portable software.

Next: Displays Supported Up: INTRODUCTION Previous: INTRODUCTION