Overview of NASA’s System Safety Requirements in the Context of Risk-informed Decision Making
Dezfuli, Homayoon
NASA

“Risk-informed” is used nowadays to refer to a decision process that accepts modern risk analysis results as an input to a process that traditionally relied on engineering metrics. In the context of safety, “risk-informed” means consideration of a blend of high-level integrated risk metrics (such as probability of loss of crew), traditional safety metrics (such as safety margin), and applicable deterministic safety requirements (such as fault tolerance). This presentation will provide an overview of NASA’s system safety (SS) requirements and discuss how and why these requirements collectively promote a risk-informed decision making process. The SS requirements are designed to ensure that the system safety technical processes have the following characteristics:

  • Safety-related performance measures (PMs) are formulated to support risk trade studies
  • Hazard identification and characterization is model-based using accident scenario modeling technique
  • Modern risk analysis techniques are used to quantify PMs
  • Uncertainties are evaluated and characterized
  • Elements that have not been captured by the formal analysis (e.g., compliance with deterministic safety requirements) are dealt with through the deliberation process.

    The implementation of system safety requirements in this way couples system safety with system engineering and risk management processes. This coupling is essential to the attainment of a risk-informed decision-making environment that NASA intends to achieve.