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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Preliminary Analysis of Aircraft Loss of Control Accidents: Worst Case Precursor Combinations and Temporal Sequencing

Aircraft loss of control (LOC) is a leading cause of fatal accidents across all transport airplane and operational classes, and can result from a wide spectrum of hazards, often occurring in combination. Technologies developed for LOC prevention and recovery must therefore be effective under a wide variety of conditions and uncertainties, including multiple hazards, and their validation must provide a means of assessing system effectiveness and coverage of these hazards. This requires the definition of a comprehensive set of LOC test scenarios based on accident and incident data as well as future risks. This paper defines a comprehensive set of accidents and incidents over a recent 15 year period, and presents preliminary analysis results to identify worst-case combinations of causal and contributing factors (i.e., accident precursors) and how they sequence in time. Such analyses can provide insight in developing effective solutions for LOC, and form the basis for developing test scenarios that can be used in evaluating them. Preliminary findings based on the results of this paper indicate that system failures or malfunctions, crew actions or inactions, vehicle impairment conditions, and vehicle upsets contributed the most to accidents and fatalities, followed by inclement weather or atmospheric disturbances and poor visibility. Follow-on research will include finalizing the analysis through a team consensus process, defining future risks, and developing a comprehensive set of test scenarios with correlation to the accidents, incidents, and future risks. Since enhanced engineering simulations are required for batch and piloted evaluations under realistic LOC precursor conditions, these test scenarios can also serve as a high-level requirement for defining the engineering simulation enhancements needed for generating them.

Belcastro, Christine M.↗
NASA NTRS1989

Test Data of Flow Field of Shuttle SRM Nozzle Joint with Bond Defects, Using Unheated Air

The nozzle-to-case joint on the Shuttle SRM (as redesigned after the Challenger accident) features an adhesive sealant filling and bonding the joint, with a wiper O-ring to prevent the adhesive from reaching and disabling the closure O-ring. Flawless implementation of that joint design would ensure that hot, corrosive propellant combustion gases never reach the closure O-ring. However, understanding the flow field related to bonding defects is prudent. A comprehensive test program was conducted to quantify such flow fields and associated heating environments. A two-dimensional, full-scale model represented 65 inches of the nozzle joint, using unheated air as the test medium, in a blowdown mode. Geometry variations modeled RSRM assembly tolerances, and two types of bonding defects: pullaways and blowholes. A range of the magnitude of each type defect was tested. Also a range of operational parameters was tested, representative of the RSRM flow environment, including duplication of RSRM Mach and Reynolds numbers. Extensive instrumentation was provided to quantify pressures, heat rates, and velocities. The resulting data established that larger geometric defects cause larger pressure and larger heating, at the closure O-ring region. Velocity trends were not so straight-forward. Variations in assembly tolerances did not generally affect flow fields or heating. Operational parameters affected flow fields and heating as might be expected, increasing density or velocity increased heating. Complete details of this test effort are presented.

Hair, Leroy M.↗
DOE OSTI2023

Scoping Thermal Response Calculations of RNS Waste During Transport to and Disposal at the WIPP

Sandia National Laboratories (SNL) was contracted by the United States Department of Energy Environmental Management (DOE-EM), Los Alamos Field Office to perform mechanical and thermal scoping calculations as part of a study seeking to understand the ignitability risk of the Remediated Nitrate Salts (RNS) waste drums during transportation from the Waste Control Specialists (WCS) facility to Waste Isolation Pilot Plant (WIPP) and permanent disposal of the waste at WIPP. The scoping thermal simulations described in this report pertain to thermal calculations performed with a packaging system consisting of one Standard Waste Box (SWB) loaded with drums placed inside a Standard Large Box 2 (SLB2). During transportation, the SLB2 is inside Transuranic Package Transporter Model III (TRUPACT-III), which provides the third layer of the packaging. Once at the WIPP, it is assumed the SLB2 is extracted from the TRUPACT-III and maintained above ground, and then subsequently placed underground for permanent disposal. In these proposed configurations, the space between the SLB2 and the SWB is always filled by a layer of insulation consisting of air-filled glass microbubbles except for the bottom which rests directly on the SLB2. The thermal scoping calculations described in this report specifically address whether the introduction of external heat inputs, combined with the contributions from the internally generated radiolytic decay heat and chemical reactions, lead to an unstable thermal state during the time of its movement and placement in the permanent disposal location. The external heat inputs are of two forms: 1) ambient thermal irradiation (e.g., solar and ambient storage/disposal temperatures) and 2) accident-induced fire. Three scoping calculation scenarios were derived as representative, conservative scenarios: 1A) TRUPACT-III transient transportation, 1B) SLB2 48-hour outdoor storage with solar radiation, and 2) fully-engulfing fire during SLB2 handling or emplacement following a steady-state analysis in a 38 °C environment. All the simulated scenarios are conservative relative to the operational conditions expected for handling the waste package during transportation and placement in the WIPP underground disposal unit. The predictions obtained from simulating the three exposure scenarios revealed that adding the SLB2 and the air-filled glass microbubbles to the transport and storage/disposal configurations provides additional thermal protection of the drums beyond what the SWB provides alone, both during long-term above ground insolation and underground during a fire accident. Under the current transportation/storage/disposal concepts, the degree of protection provided by the packaging concept is sufficient to prevent the waste from being ignitable. The simulation results demonstrate that there is adequate margin to safely transport and place the RNS waste from WCS to the WIPP under the current operational concept.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS2004

Air Separation Using Hollow Fiber Membranes

The NASA Glenn Research Center in partnership with the Ohio Aerospace Institute provides internship programs for high school and college students in the areas of science, engineering, professional administrative, and other technical areas. During the summer of 2004, I worked with Dr. Clarence T. Chang at NASA Glenn Research Center s combustion branch on air separation using hollow fiber membrane technology. . In light of the accident of Trans World Airline s flight 800, FAA has mandated that a suitable solution be created to prevent the ignition of fuel tanks in aircrafts. In order for any type of fuel to ignite, three important things are needed: fuel vapor, oxygen, and an energy source. Two different ways to make fuel tanks less likely to ignite are reformulating the fuel to obtain a lower vapor pressure for the fuel and or using an On Board Inert Gas Generating System (OBIGGS) to inert the Central Wing Tank. goal is to accomplish the mission, which means that the Air Separation Module (ASM) tends to be bulky and heavy. The primary goal for commercial aviation companies is to transport as much as they can with the least amount of cost and fuel per person, therefore the ASM must be compact and light as possible. The plan is to take bleed air from the aircraft s engines to pass air through a filter first to remove particulates and then pass the air through the ASM containing hollow fiber membranes. In the lab, there will be a heating element provided to simulate the temperature of the bleed air that will be entering the ASM and analysis of the separated air will be analyzed by a Gas Chromatograph/Mass Spectrometer (GC/MS). The GUMS will separate the different compounds in the exit streams of the ASM and provide information on the performance of hollow fiber membranes. Hopefully I can develop ways to improve efficiency of the ASM. different types of jet fuel were analyzed and data was well represented on SAE Paper 982485. Data consisted of the concentrations of over 300 different hydrocarbons commonly found in JP- 8, Jet A, and JP-5 fuels. I researched the major hydrocarbons that has a concentration of greater than 50 parts per million and found the vapor pressure data coefficients for a specific temperature range. The coefficients were applied to Antoine s Equation and Riedel's Equation to calculate the vapor pressures for that specific hydrocarbon in the specific temperature range. With the vapor pressure data scientists can formulate a fuel composition that has a lower vapor pressure profile, therefore making jet fuels less flammable. work, learn how to operate and examine the data from Gas Chromatograph and Mass Spectrometer, and develop new ways in applying hollow fiber membrane technology to other areas of environmental engineering. The United States military currently uses air separation technology and their primary The other side of making air travel safer is to reformulate the fuel. Analyses of three My goal this summer is to learn about hollow fiber membrane technologies and how they

Huang, Stephen E.↗
NASA NTRS2003

Risk-based Classification of Incidents

As the penetration of software into safety-critical systems progresses, accidents and incidents involving software will inevitably become more frequent. Identifying lessons from these occurrences and applying them to existing and future systems is essential if recurrences are to be prevented. Unfortunately, investigative agencies do not have the resources to fully investigate every incident under their jurisdictions and domains of expertise and thus must prioritize certain occurrences when allocating investigative resources. In the aviation community, most investigative agencies prioritize occurrences based on the severity of their associated losses, allocating more resources to accidents resulting in injury to passengers or extensive aircraft damage. We argue that this scheme is inappropriate because it undervalues incidents whose recurrence could have a high potential for loss while overvaluing fairly straightforward accidents involving accepted risks. We then suggest a new strategy for prioritizing occurrences based on the risk arising from incident recurrence.

Greenwell, William S.↗
NASA NTRS2016

Aircraft Loss of Control: Problem Analysis for the Development and Validation of Technology Solutions

Aircraft loss of control (LOC) is a leading cause of fatal accidents across all transport airplane and operational classes. LOC can result from a wide spectrum of precursors (or hazards), often occurring in combination. Technologies developed for LOC prevention and recovery must therefore be effective under a wide variety of conditions and uncertainties, including multiple hazards, and the validation process must provide a means of assessing system effectiveness and coverage of these hazards. This paper provides a detailed description of a methodology for analyzing LOC as a dynamics and control problem for the purpose of developing effective technology solutions. The paper includes a definition of LOC based on several recent publications, a detailed description of a refined LOC accident analysis process that is illustrated via selected example cases, and a description of planned follow-on activities for identifying future potential LOC risks and the development of LOC test scenarios. Some preliminary considerations for LOC of Unmanned Aircraft Systems (UAS) and for their safe integration into the National Airspace System (NAS) are also discussed.

Belcastro, Christine M.↗
DOE OSTI2021

Development of Integrated Safety and Security Models for Comprehensive Reliability and Resiliency Evaluation

The security of the electric grid and supporting energy systems is crucial to national security. One of the complexities in analyzing the security of energy systems is the safety consequences that may result from accidents. For energy systems, the goal is to ensure that they operate as intended and that any consequences are mitigated or prevented. The integration of safety and security is paramount to protecting these systems from attacks and ensuring that large consequences are prevented. This report describes an integrated safety and security methodology to evaluate cybersecurity events that can lead to large consequences. This novel approach first describes how Systems-Theoretic Process Analysis (STPA) provides a digital causal analysis for Bayesian Networks (BNs). The use of STPA causal analysis provides a systematic approach to constructing BNs that adequately model cyber scenarios that result in consequences. When combined with the technical principles described in Risk-Informed Management of Enterprise Systems (RIMES), a comprehensive risk-informed cybersecurity analysis results that allows decision-makers to prioritize systems that most impact risk.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS2016

Humanoids and the Potential Role of Electroactive Materials/Mechanisms in Advancing Their Capability

Humanoids are increasingly becoming capable biologically inspired robots that are appearing and behaving lifelike. Making humanlike robots is the ultimate challenge to biomimetics and, while for many years they were considered a science fiction, such robots are increasingly becoming engineering reality. Progress in producing such robots are allowing them to perform impressive functions and tasks. In 2012, in an effort to promote significant advances in developing humanoids, DARPA (Defense Advanced Research Projects Agency) posed a Robotic Challenge to produce such robots that operate in disaster scenarios towards making society more resilient. The challenge was focused on the requirements that have been needed after the Fukushima accident in Japan, hoping to advance the field of disaster robotics. This disaster posed significant challenges to emergency responders since radiation prevented people from going into the station and venting the explosive gas. Another significant development in this field is the fact that major US corporations have entered into the race to produce commercial humanoids. As a result, one can expect significant and rapid progress in this field. Developing humanoids is critically dependent of the use of highly efficient, compact, lightweight actuators and electroactive materials are offering great potential. This paper reviews the state-of-theart of humanlike robots, potential applications and challenges, as well as the actuation materials that are used or could be used.

Electroactive Polymer Actuators↗
NASA NTRS2016

Humanoids and the Potential Role of Electroactive Materials/Mechanisms in Advancing Their Capability

Humanoids are increasingly becoming capable biologically inspired robots that are appearing and behaving lifelike. Making humanlike robots is the ultimate challenge to biomimetics and, while for many years they were considered a science fiction, such robots are increasingly becoming engineering reality. Progress in producing such robots are allowing them to perform impressive functions and tasks. In 2012, in an effort to promote significant advances in developing humanoids, DARPA posed a Robotic Challenge to produce such robots that operate in disaster scenarios towards making society more resilient. The challenge was focused on the requirements that have been needed after the Fukushima accident in Japan, hoping to advance the field of disaster robotics. This disaster posed significant challenges to emergency responders since radiation prevented people from going into the station and venting the explosive gas. Another significant development in this field is the fact that major US corporations have entered into the race to produce commercial humanoids. As a result, one can expect significant and rapid progress in this field. Developing humanoids is critically dependent of the use of highly efficient, compact, lightweight actuators and electroactive materials are offering great potential. This paper reviews the state-of-theart of humanlike robots, potential applications and challenges, as well as the actuation materials that are used or could be used.

Electroactive Polymer Actuators↗
NASA NTRS1987

Aircrew cooperation in the Royal Air Force

The progressive introduction of modern, high performance aircraft, coupled with a significant increase in the complexity of the operational environment, has highlighted crew co-operation as a critical factor in aircraft safety. Investigation into recent MAC aircraft accidents supports the conclusion reached by NASA and other U.S. research institutions that a positive training program is required to improve resource management in the cockpit and prevent a breakdown under stress of the crew process. Past training and regulation has concentrated on the attainment of individual flying skills, but group skills have been neglected through lack of knowledge and understanding of the group process. This long-standing deficiency is now being addressed in the U.S. by the progressive and widespread introduction of theoretical and practical training programs to improve crew co-operation. The RAF should provide similar training for its aircrews through the adaptation and development of existing training resources. Better crew co-operation would not only reduce the number of RAF aircraft accidents but also improve the morale of the Service.

Adcock, C. B.↗
DOE OSTI2025

Fuel Bonding and its Impact on Axial Gas Communication Behavior in Light-Water Reactor Fuel Rods

Axial gas communication concerns the flow along the axial axis of nuclear fuel rods during ramp and loss of coolant accident (LOCA) conditions. During power ramps, the higher linear heat generation rate may cause fuel-to-clad gap closure that may prevent transport of released fission gases to the plenum. Upon reduction in power the gas then can communicate to the plenum. This phenomenon has been experimentally observed by short power dips during ramp experiments completed at the Risø reactor. At higher burnups it is observed that the UO2 fuel and Zircaloy cladding forms a chemical bond. This bond results in complete closure of the gap. When these high burnup rods are subjected to a LOCA, the bond has implications on both the mechanical response (i.e., ballooning) of the cladding and subsequent fuel relocation and axial gas communication. In the LOCA scenario, gas communication is of interest in two different regimes: 1) pre-rupture communication from the plenum towards the lower pressure ballooning area and 2) the post-rupture depressurization of the plenum to the external system pressure. In both regimes the presence of a fuel-to-cladding bond will impact the rate of depressurization. In this work we present a fuel-to-clad bonding model that is coupled to an existing axial gas communication model framework in the BISON fuel performance code. The effect of considering the bond on fuel performance modeling predictions is presented through comparisons to existing experimental data. Experiments considered include several rods from the Halden IFA-650 test series. An evaluation on a full-length rod that explores the combined effect of plenum size and bonding status on axial gas communication behavior is also presented.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2000

An Overview of the NASA Aviation Safety Program Propulsion Health Monitoring Element

The NASA Aviation Safety Program (AvSP) has been initiated with aggressive goals to reduce the civil aviation accident rate, To meet these goals, several technology investment areas have been identified including a sub-element in propulsion health monitoring (PHM). Specific AvSP PHM objectives are to develop and validate propulsion system health monitoring technologies designed to prevent engine malfunctions from occurring in flight, and to mitigate detrimental effects in the event an in-flight malfunction does occur. A review of available propulsion system safety information was conducted to help prioritize PHM areas to focus on under the AvSP. It is noted that when a propulsion malfunction is involved in an aviation accident or incident, it is often a contributing factor rather than the sole cause for the event. Challenging aspects of the development and implementation of PHM technology such as cost, weight, robustness, and reliability are discussed. Specific technology plans are overviewed including vibration diagnostics, model-based controls and diagnostics, advanced instrumentation, and general aviation propulsion system health monitoring technology. Propulsion system health monitoring, in addition to engine design, inspection, maintenance, and pilot training and awareness, is intrinsic to enhancing aviation propulsion system safety.

Simon, Donald L.↗
NASA NTRS2005

Intelligent Engine Systems Work Element 1.2: Malfunction and Operator Error Reduction

Jet engines, although highly reliable and safe, do experience malfunctions that cause flight delays, passenger stress, and in some cases, in conjunction with inappropriate crew response, contribute to airplane accidents. On rare occasions, the anomalous engine behavior is not recognized until it is too late for the pilots to do anything to prevent or mitigate the resulting engine malfunction causing in-flight shutdowns (IFSDs), aborted takeoffs (ATOs), or loss of thrust control (LOTC). In some cases, the crew response to a myriad of external stimuli and existing training procedures is the source of the problem mentioned above. The problem is the reduction of jet engine malfunctions (IFSDs, ATOs, and LOTC) and inappropriate crew response (PSM+ICR) through the use of evolving and advanced technologies. The solution is to develop the overall system health maintenance architecture, detection and accommodation technologies, processes, and enhanced crew interfaces that would enable a significant reduction in IFSDs, ATOs, and LOTC. This program defines requirements and proposes a preliminary design concept of an architecture that enables the realization of the solution.

Wiseman, Matthew↗
NASA NTRS1997

Evaluation of Flight Attendant Technical Knowledge

Accident and incident reports have indicated that flight attendants have numerous opportunities to provide the flight-deck crew with operational information that may prevent or lessen the severity of a potential problem. Additionally, as carrier fleets transition from three person to two person flight-deck crews, the reliance upon the cabin crew for the transfer of this information may increase further. Recent research indicates that flight attendants do not feel confident in their ability to describe mechanical parts or malfunctions of the aircraft, and the lack of flight attendant technical training has been referenced in a number of recent reports. Chute and Wiener describe five factors which may produce communication barriers between cockpit and cabin crews: the historical background of aviation, the physical separation of the two crews, psychosocial issues, regulatory factors, and organizational factors. By examining these areas of division we can identify possible bridges and address the implications of deficient cockpit/cabin communication on flight safety. Flight attendant operational knowledge may provide some mitigation of these barriers. The present study explored both flight attendant technical knowledge and flight attendant and pilot expectations of flight attendant technical knowledge. To assess the technical knowledge of cabin crewmembers, 177 current flight attendants from two U.S. carriers voluntarily completed a 13-item technical quiz. To investigate expectations of flight attendant technical knowledge, 181 pilots and a second sample of 96 flight attendants, from the same two airlines, completed surveys designed to capture each group's expectations of operational knowledge required of flight attendants. Analyses revealed several discrepancies between the present level of flight attendant operational knowledge and pilots' and flight attendants' expected and desired levels of technical knowledge. Implications for training will be discussed.

Dunbar, Melisa G.↗
NASA NTRS1998

Evaluation of Cabin Crew Technical Knowledge

Accident and incident reports have indicated that flight attendants have numerous opportunities to provide the flight-deck crew with operational information that may prevent or essen the severity of a potential problem. Additionally, as carrier fleets transition from three person to two person flight-deck crews, the reliance upon the cabin crew for the transfer of this information may increase further. Recent research (Chute & Wiener, 1996) indicates that light attendants do not feel confident in their ability to describe mechanical parts or malfunctions of the aircraft, and the lack of flight attendant technical training has been referenced in a number of recent reports (National Transportation Safety Board, 1992; Transportation Safety Board of Canada, 1995; Chute & Wiener, 1996). The present study explored both flight attendant technical knowledge and flight attendant and dot expectations of flight attendant technical knowledge. To assess the technical knowledge if cabin crewmembers, 177 current flight attendants from two U.S. carriers voluntarily :ompleted a 13-item technical quiz. To investigate expectations of flight attendant technical knowledge, 181 pilots and a second sample of 96 flight attendants, from the same two airlines, completed surveys designed to capture each group's expectations of operational knowledge required of flight attendants. Analyses revealed several discrepancies between the present level of flight attendants.

Dunbar, Melisa G.↗
NASA NTRS2006

Multi-Dimensionality of Synthetic Vision Cockpit Displays: Prevention of Controlled-Flight-Into-Terrain

NASA's Synthetic Vision Systems (SVS) project is developing technologies with practical applications that will help to eliminate low visibility conditions as a causal factor to civil aircraft accidents while replicating the operational benefits of clear day flight operations, regardless of the actual outside visibility condition. The paper describes experimental evaluation of a multi-mode 3-D exocentric synthetic vision navigation display concept for commercial aircraft. Experimental results showed the situation awareness benefits of 2-D and 3-D exocentric synthetic vision displays over traditional 2-D co-planar navigation and vertical situation displays. Conclusions and future research directions are discussed.

Prinzel, Lawrence J., III↗
DOE OSTI2024

"Source Term Modeling for Advanced Gas Micro-Reactors"

Maintaining the safety of the public, environment, and operating personnel is the most important factor in designing, operating, maintaining, and decommissioning nuclear reactors. In recent years, there has been a growing interest in the development of micro-reactors employing TRi-structural ISOtropic (TRISO)-coated particle fuel. In gas reactors, TRISO fuel plays an important role in the safety case for high temperature reactors because of the fission product retention properties of the fuel. This ability enables the use of a functional containment strategy for the reactor where multiple barriers are used to prevent fission product release to the environment. Part of the safety analysis of these advanced reactors is the assessment of radionuclide releases under normal and accident conditions through the multiple credited safety barriers. Using conservative assumptions, a mechanistic analysis can be performed to quantify these releases that combines the probabilistic assessment of failure with analytic solutions to radionuclide transport equations. Source term modeling for TRISO fuel has been performed for previous reactor designs; however, these models are outdated, in many cases proprietary, and need updates to be applied to the current state of TRISO fuel technology and alternative gas reactor core configurations [1]. Currently, the only publicly available source term assessment for gas reactors is an expert-based Monte Carlo simulation based on the effectiveness of the fuel kernel, coating layers, and graphite block in a modular high temperature gas reactor [2]. Thus, there is a need to develop a simple, versatile, and mechanistic model of fission product release and transport in gas reactor cores that could be applied to a variety of reactors through user inputs and reactor-specific radionuclide inventories. The release is calculated by the diffusion of the key safety important fission products through the kernel, silicon carbide (SiC), graphite for both intact and defective TRISO particles based on fuel and graphite temperatures in the reactor under normal operation. These releases from the fuel enter the coolant where they can plate-out on cooler surfaces. A clean-up model is included for designs with a coolant purification system to remove fission gases. This initial distribution of fission products in the reactor serves as an initial condition for potential releases under postulated accident conditions. The model then can calculate the fission product release for any transient temperature profile and fission product releases can then be used to assess radiological dose to the workers and the public using conventional dose tools. Data on the diffusion of fission products is based on historic German TRISO experiments and the more current Department of Energy (DOE) Advanced Gas Reactor (AGR) TRISO fuel development program. The model is coded in python with inputs and outputs in excel spreadsheets, as well as python plotting utilities to aid in the interpretation of the results. References: [1] INL, NGNP Mechanistic Source Term White Paper, INL-10-17997, July 2010. [2] David A. Petti, Richard R. Hobbins, Peter Lowry, Hans Gougar, “Representative Source Terms and The Influence of Reactor Attributes on Functional Containment in Modular High Temperature Gas-cooled Reactors,” Nuclear Technology, Vol. 184, p. 181-197, Nov. 2013.

07 ISOTOPE AND RADIATION SOURCES↗
NASA NTRS2009

Evaluating Failures and Near Misses in Human Spaceflight History for Lessons for Future Human Spaceflight

There have been a number of studies done in the past drawn on lessons learned with regard to human loss-of-life events. Generally, the systemic causes and proximate causes for fatal events have both been examined in considerable detail. However, an examination of near-fatal accidents and failures that narrowly missed being fatal could be equally useful, not only in detecting causes, both proximate and systemic, but also for determining what factors averted disaster, what design decisions and/or operator actions prevented catastrophe. Additionally, review of risk factors for upcoming or future programs will often look at trending statistics, generally focusing on failure/success statistics. Unfortunately, doing so can give a skewed or misleading view of past reliability or a reliability that cannot be presumed to apply to a new program. One reason for this might be that failure/success criteria aren't the same across programs, but also that apparent success can hide systemic faults that, under other circumstances, can be fatal to a program with different parameters. A program with a number of near misses can look more reliable than a consistently healthy program with a single out-of-family failure and provide very misleading data if it is not examined in detail. This is particularly true for a manned space program where failure/success includes more than making a particular orbit. Augmenting reliability evaluations with this near miss data can provide insight and expand on the limitations of a strictly pass/fail evaluation. Even more importantly, a thorough understanding of these near miss events can identify conditions that prevented fatalities. Those conditions may be key to a programs reliability, but, without insight to the repercussions if such conditions were not in place, their importance may not be readily clear. As programs mature and political and fiscal responsibilities come to the fore, often there is considerable incentive to eliminate unnecessary conservatism, design margin, redundancy, operational support, testing, training, or safety oversight. An evaluation that demonstrates how these features and capabilities averted disaster can ensure processes that saved lives or missions are not discarded without appropriate review and understanding. Close examination of accidents that almost were can also highlight differences in design from one program to another, either justifying reliability comparisons or negating them. It can also provide considerable insight into how those saving factors were developed and implemented so that similar methods can be used to ensure appropriate life-saving and mission saving factors can be developed, even for a dissimilar space program. The lessons are appropriate for seasoned manned space programs and agencies, but crucial for untried agencies and organizations that are interested in sending man into space. The large body of publicly available near miss and accident data available provide invaluable insight into programmatic, technical, and even political issues that can be addressed before they impact safety. In this paper, we examine a number of these near misses and accidents and steps a program, agency, or potential spacefaring company might take to improve their chances of success and avoid mission or safety disasters using this data.

Barr, Stephanie↗