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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.

The behaviour of fluids in microgravity imposes a risk to an Extravehicular Activity (EVA) crewmember. The intrusion of water into air conduits used for pressurization and breathing would flow with minimum resistance in the direction of pressure differential. Such an intrusion would cause water to enter into the helmet breathing space and could cause suffocation and drowning in addition to loss of vision and loss of communication. It is hence prudent to detect this water intrusion before it accumulates undetected to a dangerous level. This paper offers a design to address this risk. A sensor system is described that detects the water intrusion into the air lines that are part of the Extravehicular Mobility Unit (EMU) life support system. Upon detection, the EVA can be terminated before a harmful state is reached.

The Red Bull Stratos and Paragon StratEx were ground breaking projects in terms of pushing the human envelope for survivability. The data collected is of great value for future development of manned space programs. They showed among other things that it is possible for a human to survive transonic and supersonic speeds without a vehicle protection. One of the ways the two projects will be used is by evaluating the reliability of the systems and defining the parameters that are of high criticality during a crew escape. The PRA on mission architectures also helps in determining the safest mission hardware and human operations, leading to a more successful crew escape outcome. An after the fact PRA was performed by Teri Hamlin on the Space Shuttle program for all flights. The intent was to study the change in risk with changes in flight hardware and procedures [1]. This could be used to establish safety recommendations and flight procedures on future human spaceflight missions. A similar study is being carried out on the recent stratospheric balloon jumps, the Red Bull Stratos and StratEx in conjunction with Paragon Space Development Corporation. The two missions are being studied in detail for failure modes inherent in design and procedures and a risk analysis will be performed. The safety of high altitude bailout systems and procedures will be validated and the risk drivers hence found will be addressed for such a bailout. Due to different mission architectures used in the two jumps, a direct comparison between systems will be made which would help in a trade studies of such systems. Furthermore, the results found will be a design driver in stratospheric balloon programs for scientific and commercial applications.