Abstract
The motivation of this manuscript is feeling of strangeness that words of security and safety are widely used as a pair word in Japan. In addition, for a large-scale and complicated system such as a spacecraft system, safety requirement should be defined not only in the field of engineering, but also in the field of social science. It means that social attitude to safety, security and risk has a large effect on the large-scale and complicated system. This manuscript discusses the attitude to safety, security and risk on development of a spacecraft system.
