Quantifying the benefit of a developmental test program: Probabilistic Risk Assessment and Red Bull Stratos

Abstract Reaching new milestones in space, historically, has been achieved through the execution of a comprehensive developmental test program of increasing complexity, which validates engineering design models and provides operational experience. In this paper, the Red Bull Stratos program, which culminated with Felix Baumgartner's successful space dive on October 14, 2012, has been assessed in order to evaluate the quantitative enhancement to safety by its experimental test program. The analysis is carried out using Probabilistic Risk Assessment (PRA). 1 The PRA is a technique for mature systems to quantify complete system risk. Required inputs include numerical likelihood estimates for each individual failure mode or failure event; accurate results are dependent upon full and complete data sets, derived from the evaluation of mature systems. By contrast, test programs and one-off missions themselves frequently do not have the statistically significant number of past events and thus are not candidates for such evaluations. As such, this analysis is unable to reasonably quantify the absolute risk to the Red Bull Stratos mission. Instead, it is meant to show the relative value of enhancements to safety that were realized through the development program that follows a robust test program of increasing complexity in order to validate design models and reduce risks. The PRA is applied to the experimental test program and compared against the quantified results of the hypothetical test program that would have been performed had the project been completed in a single step, without the developmental test program. In addition to the planned test flights, the Stratos project also benefitted from past experience of other manned stratospheric balloon projects, including Project Manhigh (1955–58), Project Excelsior (1959–60), the Russian Volga (1962) and the Strato Jump project (1965–66). This study is attempting to quantify the safety benefit associated with a developmental test program and shows a marked improvement in quantified safety as a result of implementing lessons learned from testing and prior manned balloon flights. Initially, interest in a stratospheric jump program was from the US Air Force who was focused on the viability for a crew escape system from a reentry vehicle. There is renewed interest on this capability from the commercial industry that is looking to provide suborbital flight and access to Low Earth Orbit.