Methodology for the Safety and Reliability assessment of hypersonic transportation systems in conceptual design activities

摘要

This paper suggests a methodology to support the safety and reliability assessment of hypersonic transportation systems in conceptual design activities. In particular, this research activity aims at overcoming the noticeable lack of statistical data related to safety and reliability characteristics of hypersonic transportation systems. At the beginning of the paper, a review of the existing methodologies currently in use for the safety and reliability assessment in conceptual and preliminary design of aeronautical and space systems is presented. In particular, the proposed methodology starts from an estimation algorithm already developed within the reaseach group which the authors belong to. This approach is based on a semi-empirical formulation that would allow to estimate Reliability, Availability, Maintainability and Safety characteristics for the entire transportation system and to allocate them on subsystems, equipment and component. Proper trend lines and interpolative polynomials are obtained for different aircraft category, based on the statistical available. The challenge faced in this paper is to suggest a way to generate and update of these semi-empirical models for the peculiar class of the hypersonic transportation systems, overcoming the noticeable problem of lack of statistical data at vehicle level. Considering the high level of complexity and integration of the hypersonic transportation systems and the mukidisciplinarity of the design activities, the presented methodology is fully integrated within a novel conceptual design workflow based on a Systems Engineering approach. In addition the paper reports, as case-study, the application of such a methodology at subsystem level. In particular, the example deals with the safety and reliability of a complex propulsion system guaranteeing vertical take-off capabilities to a trans-atmospheric vehicle aimed at performing parabolic flights (recognized to be a possible technological demonstrator of enabling technologies for hypersonic). Eventually, a massive application of the presented methodology to different test-cases for different families of hypersonic vehicles, will contribute to the characterization of an under-development database (HyDat) with the ultimate aim of increasing the confidence level of the new semi-empirical models.