Off-nominal Situations Research Articles

Something's Not Right: How Thinking About Off-Nominal Situations Can Make Us Safer

Something's Not Right: How Thinking About Off-Nominal Situations Can Make Us Safer

Adequacy of in-mission training to treat tibial shaft fractures in mars analogue testing

Long bone fractures are a concern in long-duration exploration missions (LDEM) where crew autonomy will exceed the current Low Earth Orbit paradigm. Current crew selection assumptions require extensive complete training and competency testing prior to flight for off-nominal situations. Analogue astronauts (n = 6) can be quickly trained to address a single fracture pattern and then competently perform the repair procedure. An easy-to-use external fixation (EZExFix) was employed to repair artificial tibial shaft fractures during an inhabited mission at the Mars Desert Research Station (Utah, USA). Bone repair safety zones were respected (23/24), participants achieved 79.2% repair success, and median completion time was 50.04 min. Just-in-time training in-mission was sufficient to become autonomous without pre-mission medical/surgical/mechanical education, regardless of learning conditions (p > 0.05). Similar techniques could be used in LDEM to increase astronauts’ autonomy in traumatic injury treatment and lower skill competency requirements used in crew selection.

Single-Pilot Aircraft in Commercial Air Transport Operations: A Comparison of Potential Architectures

Single-pilot operations (SPOs) in commercial air transport present a range of benefits and challenges, but there is a need to define architectures and compare them in different operational contexts. Here, we identified various combinations of architectural decisions based on the literature, and we compared them to current operations (in different operating contexts) on a safety versus cost tradespace. Safety was defined as a function of the pilot nominal operations workload, handling of off-nominal situations, and pilot incapacitation; whereas the cost was defined as a combination of acquisition and operating costs. Our analysis suggests that different classes of aircraft (wide bodies, narrow bodies, and regional jets) have different levels of benefits and costs in moving to SPOs. The capabilities of automation need to improve drastically before the second human in the flight deck can be replaced, and this is borne out by the dominance of human-centered architectures in the tradespace. The analysis also reveals that regional aircraft may be prime candidates to move to SPOs first because most regional architectures generate positive savings.

Real-Time Power Quality Enhancement in a Hybrid Micro-Grid Using Nonlinear Autoregressive Neural Network

The extensive use of renewable energy sources (RESs) in energy sectors plays a vital role in meeting the present energy demand. The widespread utilization of allocated resources leads to multiple usages of converters for synchronization with the power grid, introducing poor power quality. The integration of distributed energy resources produces uncertainties which are reflected in the distribution system. The major power quality problems such as voltage sag/swell, voltage unbalancing, poor power factor, harmonics distortion (THD), and power transients appear during the transition of micro-grids (MGs). In this research, a single micro-grid is designed with PVs, wind generators, and fuel cells as distributed energy resources (DERs). A nonlinear auto regressive exogenous input neural network (NARX-NN) controller has been investigated in this micro-grid in order to maintain the above power quality issues within the specific standard range (IEEE/IEC standards). The performance of the NARX-NN controller is compared with PID and fuzzy-PID controllers. The single micro-grid is extended to design a three-phase large-scale realistic micro-grid structure to test the feasibility of the proposed controller. The realistic micro-grid is verified through addition of line-impedance, communication delay, demand response, and off-nominal situations. The proposed controller is also validated by simulating different test scenarios using MATLAB/Simulink and TMS320-based processor-in-loop (PIL) for real-time implementation.

Human-automation interaction for helicopter flight: Comparing two decision-support systems for navigation tasks

This paper investigates the effects of different automation design philosophies for a helicopter navigation task. A baseline navigation display is compared with two more advanced systems: an advisory display, which provides a discrete trajectory suggestion; and a constraint-based display, which provides information about the set of possible trajectory solutions. The results of a human-in-the-loop experiment with eight pilot participants show a significant negative impact of the advisory display on pilot trajectory decision-making: out of the 16 encountered off-nominal situations across the experiment, only 6 were solved optimally. The baseline and constraint-based display both lead to better decisions, with 14 out of 16 being optimal. However, pilots still preferred the advisory display, in particular in off-nominal situations. These results highlight that even when a support system is preferred by pilots, it can have strong inadvertent negative effects on their decision-making.

Toward Human–Autonomy Teaming in Single-Pilot Operations: Domain Analysis and Requirements

This paper aims to systematically analyze the needs for single-pilot and reduced crew operations in commercial air transportation, and to develop human–autonomy teaming requirements to support future operations. In reduced crew operations, the pilot-flying operates the flight alone in the cockpit while the pilot-not-flying rests outside of the cockpit unless needed in high-workload situations. In single-pilot operations, there is only one pilot onboard to manage the flight. Many of the functions performed by the second pilot in dual-pilot operations would be replaced with an autonomous teammate. These increasingly autonomous systems will have capabilities that require it to be treated more like a member of the crew. Enhanced ground support will also support these flights. The transition from dual-pilot to single-pilot operations will require the redesign of the roles and responsibilities of the air and ground crew, crew resource management, function allocation, human–autonomy teaming, and procedures for normal and off-nominal situations. Document analysis, subject-matter-expert interviews, and pilot evaluations were conducted to analyze and compare concepts of operation, develop domain knowledge models, and develop human–autonomy teaming requirements to support pilot decision making and operations.

On the development of testing facilities for the scientific testing center of the rocket and space industry for developmental testing of advanced cryogenic propulsion systems

The paper provides a review of materials on the development of testing facilities in the Scientific Testing Center of the Rocket and Space Industry and the issues involved in raising the efficiency and safety of experimental development of advanced cryogenic propulsion systems for launch vehicles intended for exploration of the near and deep space. It shows that the most dangerous tests are those that are conducted on engines and propulsion systems that use oxygen, methane and hydrogen as propellant components. They may involve containment failure in the propellant system in off-nominal situations — emergency releases of propellant components, explosions and fires. It provides calculation results for overpressure in the shock-wave front depending on the mass of the released hydrogen and the factor of its contribution to the explosion. It formulates special and additional safety measures for engine and propulsion system tests in a test facility. Key words: test facility (test stand), propulsion system, safety, off-nominal situation, cryogenic propellant components.

ON THE DEVELOPMENT OF TESTING FACILITIES FOR THE SCIENTIFIC TEST-ING CENTER OF THE ROCKET AND SPACE INDUSTRY FOR DEVELOPMENTAL TESTING OF ADVANCED CRYOGENIC PROPULSION SYSTEMS

The paper provides a review of materials on the development of testing facilities in the Scientific Testing Center of the Rocket and Space Industry and the issues involved in raising the efficiency and safety of experimental development of advanced cryogenic propulsion systems for launch vehicles intended for exploration of the near and deep space. It shows that the most dangerous tests are those that are conducted on engines and propulsion systems that use oxygen, methane and hydrogen as propellant components. They may involve containment failure in the propellant system in off-nominal situations — emergency releases of propellant components, explosions and fires. It provides calculation results for overpressure in the shock-wave front depending on the mass of the released hydrogen and the factor of its contribution to the explosion. It formulates special and additional safety measures for engine and propulsion system tests in a test facility. Key words: test facility (test stand), propulsion system, safety, off-nominal situation, cryogenic propellant components.

Human–Machine Interface Design for Monitoring Safety Risks Associated with Operating Small Unmanned Aircraft Systems in Urban Areas

The envisioned introduction of autonomous Small Unmanned Aircraft Systems (sUAS) into low-altitude urban airspace necessitates high levels of system safety. Despite increased system autonomy, humans will most likely remain an essential component in assuring safety. This paper derives, applies, and evaluates a display design concept that aims to support safety risk monitoring of multiple sUAS by a human operator. The concept comprises of five design principles. The core idea of the concept is to limit display complexity despite increasing the number of sUAS monitored by primarily visualizing highly abstracted information while hiding detailed information of lower abstraction, unless specifically requested by the human operator. States of highly abstracted functions are visualized by function-specific icons that change hue in accordance to specified system states. Simultaneously, the design concept aims to support the human operator in identifying off-nominal situations by implementing design properties that guide visual attention. The display was evaluated in a study with seven subject matter experts. Although preliminary, the results clearly favor the proposed display design concept. The advantages of the proposed design concept are demonstrated, and the next steps for further exploring the proposed display design concept are outlined.

Design and Evaluation of a Constraint-Based Head-Up Display for Helicopter Obstacle Avoidance

This paper investigates the effect of employing different display design principles for human–machine interaction in helicopters. Two obstacle avoidance support displays are evaluated during low-altitude forward flight. A baseline head-up display is complemented either by a conventional advisory display or a constraint-based display inspired by ecological interface design. The latter design philosophy has only been sparsely applied in the helicopter domain. Twelve helicopter pilots participated in an experiment in a research flight simulator. We found no significant effects of the displays on objective performance measures. However, there was a trend of decreasing pilot workload and increasing situation awareness when employing the support displays, as compared to the baseline display. The constraint-based display had the largest positive effect and increased the resilience of the pilot–vehicle system toward unexpected events when considering the safety of the flown trajectories. Pilots preferred the advisory display in nominal situations and the constraint-based display in off-nominal situations, reproducing similar findings from research in the fixed-wing domain. This experiment showed the potential of the developed constraint-based display to improve subjective pilot ratings, pilot preference, and safety during unexpected events. Future research will investigate more complex scenarios with longer time frames, possibly eliciting more divergent effects of different display design principles.

A method of using fuzzy hypergraphs to evaluate structural and technological survivability of attitude control systems for unmanned spacecraft

Successful completion of a mission by an unmanned spacecraft (USC), both under nominal operational conditions both under examined contingencies and unexamined off-nominal situations is possible through designing survivability into the USC onboard system (OS). An analysis of current methods for evaluating USC OS survivability during their configuration management and reconfiguration under conditions of examined in-flight contingencies widely used in the design and development of the said USC has shown that these methods are not acceptable for evaluating the USC OS survivability in case of unexamined off-nominal situations in flight. This calls for development of conceptually novel methodological and procedural framework for evaluating structural survivability of USC OS configurations that take into account the level of participation of functional elements (FE) and OS subsystems in the USC control operations under various scenarios of the mission plan implementation. The paper proposes an original approach to evaluating the structural and technological survivability of the USC OS based on a fuzzy hypergraph formal representation of the operations to control the USC attitude, where the edges of the hypergraph connect the FE and OS subsystems that support the implementation of this or that specific control process. The paper also shows how one could use for the quantitative evaluation of the structural and technological survivability of a specific USC OS configuration the results of differentiation of a fuzzy hypergraph that could be visualized as a fuzzy hypergraph of technological independence of OS FE. Such an approach makes it possible to analyze the effects of FE on OS, identify the most critical elements, which have the lowest technological independence under mission plan implementation conditions, which could be used for providing a rationale for the required level of structural and functional redundancy of USC elements and subsystems introduced during various phases in its life cycle. Keywords: unmanned spacecraft, onboard systems survivability, fuzzy hypergraph derivative.

Justification of the choice of the method and criterion of clustering for intelligent analysis in flight control spacecraft

The article examines the methods of intelligent analysis of telemetric information of spacecraft. The current state and main shortcomings of the control process during the spacecraft flight control are briefly given. It is proposed to eliminate the shortcomings by introducing intellectualization procedures in terms of telemetric information analysis. Based on the methods of cluster data analysis, a method is proposed for automatically determining the moment of occurrence of anomalies in the state of a spacecraft, which are precursors of off-nominal situations. A schematic diagram of the operation of an intelligent control system based on the use of the method of cluster analysis of the spacecraft telemetric information is presented. The conditions for choosing the method and criterion for clustering are substantiated, taking into account the goals pursued in solving control problems during flight control of the spacecraft. A mathematical description of the clustering methods and criteria selected for further practical testing is given. To test the proposed method of analysis for various methods and criteria of clustering, calculations were performed using archived telemetric information. From the point of view of the time of early detection of the anomaly in the state for a separate component of the spacecraft, the choice of the method and criterion of clustering is made for further research and experimental work.

Study of radial burning of holes in titanium shells of high-pressure tanks with oxygen containing gas

The paper presents the results of the experimental study of radial burning of holes in titanium samples simulating a fragment of the shell of a high-pressure tank filled with gaseous oxygen or oxygen-containing gas. The tests revealed the possibility of a large increase in the orifice area (140–2 250 times compared with the initial value) as a result of the burning of small through-holes when oxygen-containing gas of the increased pressure flows through them and allowed us to determine the apparent radial burning rate at various oxygen concentrations. The proposed mathematical dependence of the hole size in the titanium shell after their radial burning on the process parameters may be of interest for the analysis of processes occurring in engineering systems in case of some off-nominal and emergency situations. Key words: radial burning of holes, titanium tank, oxygen-containing gas, off-nominal and emergency situations.

An approach to mixed-fidelity system simulation of extravehicular activities

The National Aeronautics and Space Administration (NASA) is currently developing the next generation of spacesuits for use in future exploration missions. This effort, referred to as the Exploration Extravehicular Mobility Unit (xEMU), has been underway since 2015 with the goal of demonstrating the new technologies during a mission to the International Space Station (ISS).Due to the complexity of the xEMU system, and particularly its portable life support system (PLSS), computer simulations are heavily relied on in the development process, from dynamic loads analysis to software verification. The models of the physical systems that are currently being used for system-level simulations are mostly empirical, where the underlying formulas are mathematical fits to test or simulation data. An advantage of this approach is the fact that these models are very performant and can be used in real-time applications such as user interface testing and operator training.The research presented in this paper describes a different approach to modeling and simulation. A simulation tool focused on life support systems for human spaceflight in general and PLSSs in particular has been under development at the Technical University of Munich (TUM) since 2006. The spacesuit specific variant of this tool is called The Virtual Spacesuit (V-SUIT) and is now being utilized in the current spacesuit development process at the NASA Johnson Space Center (JSC). In contrast to the previously mentioned empirical models, V-SUIT uses a first-principles-based, bottom up modeling approach, where basic physical, chemical or biological effects are modeled at the lowest level and the component and system models are created using these fundamental building blocks. This enables the simulation to account for effects, and especially off-nominal situations, that may not be within the range of validity of the empirical models.This paper presents the structure of and the rationale behind V-SUIT itself as well as a status report on the ongoing effort to integrate it with the existing simulation systems in use at JSC, which is based on Trick/GUNNS. As a proof of concept, a single component model from V-SUIT, that of the spacesuit water membrane evaporator (SWME), has been integrated with NASA's simulation tool.Results include comparisons of the performance of the two simulation systems and a description of challenges that were encountered during implementation. The paper closes with an outlook towards the future developments that are planned for V-SUIT within the xEMU development program.

Systems for assuring safety of static firing tests of oxygen/hydrogen propulsion units

Static firing tests of oxygen-hydrogen propulsion units with propellant tank load of up to 2700 kg of hydrogen are run with special safety precautions and using emergency test protection system covering up to 60% of contingencies. Test on propulsion units with higher hydrogen propellant loads (up to 7000 kg) require additional safety measures, based on improved effectiveness of the fire and explosion prevention systems, emergency protection, and the coverage ratio for emergency (off-nominal) situations. The key factors for improving off-nominal situations coverage ratio during tests are research into systems for earlier detection of hydrogen leaks and the use of inhibitors with nitrogen as the phlegmatizing agent to prevent explosion of the hydrogen/air (oxygen) mixtures. The paper presents results of studies into systems for early detection of hydrogen leaks and design of monitoring equipment based on fiber optics and microcavity structures that have higher speed of response, selectivity, immunity to noise and reliability. Key words: propulsion system, safety, emergency protection system, off-nominal situation, hydrogen leak, fiber-optic technology.

Simulating splashdown of a re-entry vehicle with operating propulsion system on rough water

The re-entry vehicle included into the manned spacecraft Federatsiya that is being developed by RSC Energia, nominally lands on specially prepared solid ground landing sites using a parachute-jet system. In off-nominal situations the re-entry vehicle is capable of performing a splashdown. In that case, in order to properly take into account the loads and do strength analysis, one needs to know the levels of hydrodynamic loads on the spacecraft body and its dynamic behavior in water, factoring in all the possible weather conditions at the landing site and all possible operational modes of parachute-jet system in off-nominal situations. This paper presents the results of numerical simulation of a splashdown on rough water of the re-entry vehicle included in the crew transportation spacecraft Federatsiya. It discusses both the cases where the propulsion system is firing and where it is not. It provides data on changes in kinematic properties of the re-entry vehicle, in forces and torques it is subjected to, as well as g-loads it experiences. The obtained data are required for further loading and strength analyses of the spacecraft structure. Key words: numerical simulation, splashdown, re-entry vehicle, aerodynamic properties, rough seas

The Operational Issue of an Airliner’s Reduced-Crew Caused by Data-link Break-up to Remote Support

Different operational concepts for Single-Pilot and Reduced-Crew Operations (RCO) in commercial aviation include a ground based supportive component of a remote-copilot. The impact of an outage and break-up of the data-link connecting air and ground has not been investigated yet. Social Network Analysis (SNA) in combination with a Cognitive Work Analysis was used to compare the three crewing options of multi-crew, reduced-crew and a break-up of data-link in RCO in terms of social factors and interactions. A data-link loss decreased the networks density and its resilience to any off-nominal and emergency situations. The single-pilot suffers from higher functional loadings, is located more central and processes a higher information flow. A twofold degraded operational procedure was proposed to mitigate an outage and loss of data-link in combination with additional automation tools onboard. Nonetheless, further research is required to provide a data-link with a big bandwidth as reliable and secure as possible.

Development of Design Requirements for a Cognitive Assistant in Space Missions Beyond Low Earth Orbit

This study describes the development of requirements for a cognitive assistant (CA) for use onboard a space vehicle/station. For missions beyond low Earth orbit (LEO), delayed communication will limit mission control’s ability to support the space crew in real time. During off-nominal situations, where no procedures have been developed prior to missions, crews must develop responses in real time and may increasingly rely on automation. A systematic approach was used to model the domain knowledge of the collaborative decision-making process of current space operations, extrapolate to missions beyond LEO, and develop the design requirements for a CA. Document analysis and interviews were conducted to create an abstraction hierarchy and a decision-action diagram of the cognitive functions currently performed by space crew, mission control, and onboard automation. These domain models were extrapolated to missions beyond LEO by identifying the breakpoints where current decision-making processes would break down due to increased communication delay between mission control and the space crew. Design requirements were identified for future CA systems that offer real-time decision-making support to mitigate the negative effect of limited support in off-nominal situations. The approach developed for this research can be generalized to identify the design requirements for future support systems in domains beyond space operations.

Development of a Functionality Matrix for a Cognitive Assistant on Long Distance Space Missions

This paper discusses the development and application of a Functionality Matrix (FM) technique to design requirements for a Cognitive Assistant (CA) to aid future long distance space missions. Future far-Earth space missions pose challenges due to communication delays between Mission Control and space crew. As communication delays increase, Mission Control is less able to support space crew in off-nominal situations. The FM technique was used to extrapolate the joint decision-making functions performed in current near-Earth operations to functions performed in future, far-Earth space operations, allocated between Mission Control, space crew, and potential automation. Data gathered from document analysis and interviews with astronauts were consolidated to generate the domain knowledge models of the collaborative decision-making process for current space operations. Each function in the decision-making process was examined to extrapolate the current collaborative work of Mission Control and space crew to future space operations under long time delays, when the role of Mission Control must change. The domain knowledge models were also used to identify the functions performed to resolve off-nominal situations in current operations that are most affected by long communication delays. The identified functions constituted the input for the FM. The responsibilities of Mission Control, space crew and CA were categorized in the FM as current and/or future space operations. The FM describes the shared responsibilities between space crew and Mission Control with and without CA support in space operations. The FM was used to describe functional design requirements, and will lead to the development of function allocation rules.

Использование в оперативном контуре управления космическим аппаратом перспективного алгоритма выбора наиболее безопасного варианта спуска при возникновении нештатной ситуации

Использование в оперативном контуре управления космическим аппаратом перспективного алгоритма выбора наиболее безопасного варианта спуска при возникновении нештатной ситуации