Research On ESD Of Manned Spaceflight Safety Risk Assessment And Software Realization

Based on the analysis of the characteristics of manned spaceflight risk assessment,this thesis compares the advantages and disadvantages of conventional risk assessment methodology and finds that applying event Sequence Diagram (ESD) to manned spaceflight risk assessment will effectively advance the level of risk assessment. Nevertheless,ESD has its own shortcomings and must be properly improved so that it can be more efficiently applied to manned spaceflight risk assessment.Through a deep research into the traditional ESD methodology and with the reference to the characteristics of manned spaceflight risk assessment,this thesis makes following improvements on ESD:1. To overcome the insufficiency of traditional ESD symbol dictionary,this thesis adds new logic modeling graphic symbols,such as CSP,WSP,"similitude transition symbol",etc.,enriching and perfecting the modeling elements of ESD.2. To overcome the limitation of ESD on model scale control,this thesis proposes a ESD-based modular theory and studies the method of transformation between ESD and probability influence diagram.3. This thesis proposes normalization theory of ESD model,which lays basis for computer-aided modeling.4. To meet the high level estimation of probability of occurrence and the high precision requirement of manned spaceflight risk assessment,this thesis studies the Bayesian modifying method that realizes the parameter probability through probability influence diagram transformation and also studies the method that combines the fuzzy set theory and ESD to handle accident probability of manned spaceflight.5. Bring forward the conception of"ESD Event Weightiness",and research the method of account of"the Structure Weightiness"and"the Property Weightiness".In order to apply ESD to practical engineering,the author develops Computer-Aided Events Sequence Diagram System (CAESDS).Taking the power failure of spaceship cooling circuit drove pump as an example,this thesis uses the improved ESD method and the ESD model constructed by CAESDS,drawing a conclusion that the improved method and CAESDS is valid in manned spaceflight risk assessment.