A program environment is presented that enables a co-operative design of high-technology products demanding interdisciplinary computer simulations for their optimisation. The system includes a multi-site, multi-machine, distributed data manager accessible by a data monitor. A client-server concept supports the user of massively parallel machines. The exchange of data between different executable scientific application modules is performed through the data base. Special modules to define the geometry, to decompose the domain in subdomains, to construct adaptive meshes in each subdomain, and to represent graphically the results run on workstations. Direct and iterative matrix solvers are embedded in the system. They optimally run on massively parallel machines. As a demonstration of the system, the high frequency wave generator (Gyrotron) application is presented.