The conceptual design of a space power reactor core requires cooperative work by a group of experts from various fields. It is necessary to implement mechanisms to realize an effective computerized support system for group activity by different engineers. We aimed at incorporating tasks into a workable human interface system based on virtual reality technology with the full usage of advanced information technology on 3D graphics, numerical calculation and AI processing. We also aimed at developing a WWW-based design support system for the same work domain for higher levels of flexibility in cooperative work using distributed computer systems. In this paper, we describe the structure of the space reactor as a conceptual design target, a VR-based design support system to realize an effective human interface and WWW-based design support system for effective cooperative work.