Results for “Safety parameters” — Page 4

NASA NTRS1986

System identification for modeling for control of flexible structures

The major components of a design and operational flight strategy for flexible structure control systems are presented. In this strategy an initial distributed parameter control design is developed and implemented from available ground test data and on-orbit identification using sophisticated modeling and synthesis techniques. The reliability of this high performance controller is directly linked to the accuracy of the parameters on which the design is based. Because uncertainties inevitably grow without system monitoring, maintaining the control system requires an active on-line system identification function to supply parameter updates and covariance information. Control laws can then be modified to improve performance when the error envelopes are decreased. In terms of system safety and stability the covariance information is of equal importance as the parameter values themselves. If the on-line system ID function detects an increase in parameter error covariances, then corresponding adjustments must be made in the control laws to increase robustness. If the error covariances exceed some threshold, an autonomous calibration sequence could be initiated to restore the error enveloped to an acceptable level.

Mettler, Edward↗

NASA NTRS1993

Parallel runway requirement analysis study. Volume 1: The analysis

The correlation of increased flight delays with the level of aviation activity is well recognized. A main contributor to these flight delays has been the capacity of airports. Though new airport and runway construction would significantly increase airport capacity, few programs of this type are currently underway, let alone planned, because of the high cost associated with such endeavors. Therefore, it is necessary to achieve the most efficient and cost effective use of existing fixed airport resources through better planning and control of traffic flows. In fact, during the past few years the FAA has initiated such an airport capacity program designed to provide additional capacity at existing airports. Some of the improvements that that program has generated thus far have been based on new Air Traffic Control procedures, terminal automation, additional Instrument Landing Systems, improved controller display aids, and improved utilization of multiple runways/Instrument Meteorological Conditions (IMC) approach procedures. A useful element to understanding potential operational capacity enhancements at high demand airports has been the development and use of an analysis tool called The PLAND_BLUNDER (PLB) Simulation Model. The objective for building this simulation was to develop a parametric model that could be used for analysis in determining the minimum safety level of parallel runway operations for various parameters representing the airplane, navigation, surveillance, and ATC system performance. This simulation is useful as: a quick and economical evaluation of existing environments that are experiencing IMC delays, an efficient way to study and validate proposed procedure modifications, an aid in evaluating requirements for new airports or new runways in old airports, a simple, parametric investigation of a wide range of issues and approaches, an ability to tradeoff air and ground technology and procedures contributions, and a way of considering probable blunder mechanisms and range of blunder scenarios. This study describes the steps of building the simulation and considers the input parameters, assumptions and limitations, and available outputs. Validation results and sensitivity analysis are addressed as well as outlining some IMC and Visual Meteorological Conditions (VMC) approaches to parallel runways. Also, present and future applicable technologies (e.g., Digital Autoland Systems, Traffic Collision and Avoidance System II, Enhanced Situational Awareness System, Global Positioning Systems for Landing, etc.) are assessed and recommendations made.

Ebrahimi, Yaghoob S.↗

NASA NTRS2006

Stardust Entry: Landing and Population Hazards in Mission Planning and Operations

The 385 kg Stardust mission was launched on Feb 7, 1999 on a mission to collect samples from the tail of comet Wild 2 and from interplanetary space. Stardust returned to Earth in the early morning of January 15, 2006. The sample return capsule landed in the Utah Test and Training Range (UTTR) southwest of Salt Lake City. Because Stardust was landing on Earth, hazard analysis was required by the National Aeronautics and Space Administration, UTTR, and the Stardust Project to ensure the safe return of the landing capsule along with the safety of people, ground assets, and aircraft. This paper focuses on the requirements affecting safe return of the capsule and safety of people on the ground by investigating parameters such as probability of impacting on UTTR, casualty expectation, and probability of casualty. This paper introduces the methods for the calculation of these requirements and shows how they affected mission planning, site selection, and mission operations. By analyzing these requirements before and during entry it allowed for the selection of a robust landing point that met all of the requirements during the actual landing event.

Desai, P.↗

NASA NTRS2011

Swingbed Amine Carbon Dioxide Removal Flight Experiment - Feasibility Study and Concept Development for Cost-Effective Exploration Technology Maturation on The International Space Station

The completion of International Space Station Assembly and transition to a full six person crew has created the opportunity to create and implement flight experiments that will drive down the ultimate risks and cost for human space exploration by maturing exploration technologies in realistic space environments that are impossible or incredibly costly to duplicate in terrestrial laboratories. An early opportunity for such a technology maturation experiment was recognized in the amine swingbed technology baselined for carbon dioxide and humidity control on the Orion spacecraft and Constellation Spacesuit System. An experiment concept using an existing high fidelity laboratory swing bed prototype has been evaluated in a feasibility and concept definition study leading to the conclusion that the envisioned flight experiment can be both feasible and of significant value for NASA s space exploration technology development efforts. Based on the results of that study NASA has proceeded with detailed design and implementation for the flight experiment. The study effort included the evaluation of technology risks, the extent to which ISS provided unique opportunities to understand them, and the implications of the resulting targeted risks for the experiment design and operational parameters. Based on those objectives and characteristics, ISS safety and integration requirements were examined, experiment concepts developed to address them and their feasibility assessed. This paper will describe the analysis effort and conclusions and present the resulting flight experiment concept. The flight experiment, implemented by NASA and launched in two packages in January and August 2011, integrates the swing bed with supporting elements including electrical power and controls, sensors, cooling, heating, fans, air- and water-conserving functionality, and mechanical packaging structure. It is now on board the ISS awaiting installation and activation.

Hodgson, Edward↗

NASA NTRSDate not supplied

Using Holey Graphene for Improved Interfacial Contact in Solid Electrolyte Ionic Conductivity Measurements

Solid-state batteries (SSBs) are poised to become the batteries of the future with advantages such as higher energy density, lighter weight, versatile geometry, and greater safety due to low flammability risk. An important parameter of the solid electrolyte (SE) used is its ionic conductivity. The ionic conductivity is generally calculated from the bulk resistance of a SE pellet, measured from the electrochemical impedance spectroscopy data. The SE pellet is typically prepared from the electrolyte powder by dry compression and is sandwiched between two blocking current collectors to obtain the impedance spectroscopy data. One of the challenges in conducting this measurement is poor interfacial contacts between the SE pellet and the current collector surfaces. Therefore, measurements reported in the literature may underestimate the true ionic conductivity of a given electrolyte. Holey graphene is a carbon nanomaterial with high electrical conductivity and unique dry compressibility, which is unusual for carbon materials but similar to many oxide and sulfide SEs. In this work, it is demonstrated that adding a thin layer of holey graphene between the electrolyte and the stainless steel current collectors significantly improves the interfacial contact. The ionic conductivity values obtained in the effort were sometimes several times higher than the data measured for SEs without the holey graphene layers. This work calls for more standardized measurement procedures to reduce the discrepancies in reported ionic conductivity values.

Solid state battery↗

NASA NTRS2011

Negative Stress Margins - Are They Real?

Advances in modeling and simulation, new finite element software, modeling engines and powerful computers are providing opportunities to interrogate designs in a very different manner and in a more detailed approach than ever before. Margins of safety are also often evaluated using local stresses for various design concepts and design parameters quickly once analysis models are defined and developed. This paper suggests that not all the negative margins of safety evaluated are real. The structural areas where negative margins are frequently encountered are often near stress concentrations, point loads and load discontinuities, near locations of stress singularities, in areas having large gradients but with insufficient mesh density, in areas with modeling issues and modeling errors, and in areas with connections and interfaces, in two-dimensional (2D) and three-dimensional (3D) transitions, bolts and bolt modeling, and boundary conditions. Now, more than ever, structural analysts need to examine and interrogate their analysis results and perform basic sanity checks to determine if these negative margins are real.

Raju, Ivatury S.↗

NASA NTRS2011

Negative stress margins – are they real?

Advances in modeling and simulation, new finite element software, modeling engines and powerful computers are providing opportunities to interrogate designs in a very different manner and in a more detailed approach than ever before. Margins of safety are also often evaluated using local stresses for various design concepts and design parameters quickly once analysis models are defined and developed. This paper suggests that not all the negative margins of safety evaluated are real. The structural areas where negative margins are frequently encountered are often near stress concentrations, point loads and load discontinuities, near locations of stress singularities, in areas having large gradients but with insufficient mesh density, in areas with modeling issues and modeling errors, and in areas with connections and interfaces, in two-dimensional (2D) and three-dimensional (3D) transitions, bolts and bolt modeling, and boundary conditions. Now, more than ever, structural analysts need to examine and interrogate their analysis results and perform basic sanity checks to determine if these negative margins are real.

Raju, Ivatury S.↗

NASA NTRSDate not supplied

Moon to Mars (M2M): Exploration Atmosphere

As humans leave the bounds of Earth to explore the lunar surface and beyond, crew will don extravehicular activity (EVA) suits to learn more about these extraterrestrial environments, establish sustained presence, and perform needed upgrades and maintenance to their space vehicle and habitation systems. Spacefaring vehicle and habitation design will need to support these EVA excursions while ensuring crew health and safety. A crucial technological design advancement towards this goal is the use of a lower pressure exploration atmosphere (EA) that enables high efficiency EVA, rather than the sea level atmosphere of 14.7 psia, 21% oxygen (O 2 ) found on the International Space Station, Shuttle, and most other Russian and Chinese space vehicles and stations. Early space vehicles (Mercury through Apollo Programs) used a 5 psia, 100% O 2 environment, which eliminated the need for pre-EVA denitrogenation protocols, simplified the life support system to a single gas, and saved structural mass. For longer duration missions (Skylab), a diluent gas was added, changing the atmosphere to 5 psia, 70-74% O 2 to prevent atelectasis while remaining normoxic. As in-flight science became a top priority, Shuttle and ISS atmospheres were chosen to operate at sea level allowing for simpler ground-based study control conditions. Consequently this led to long pre-EVA denitrogenation protocols involving up to 4 hours of O 2 prebreathe because the EVA suit still operated at a low pressure of 4.3 psid. To increase operational efficiency, the Shuttle was retroactively certified to operate using 10.2 psia, 26.5% O 2 , reducing O 2 prebreathe time to 40-75 min. Current plans for M2M habitats on the Lunar surface require EVA, thus EA recommendation became 8 psia and 32% O 2 but was revised to 8.2 psia and 34% O 2 to decrease hypoxia exposure. Unfortunately, the benefits of EA in support of safe and efficient EVAs comes with the challenge of fire management in a higher-than-normal O 2 % environment. Although known for decades, the recommended forward work to address fire management has only recently begun. Current flammability tests include examining material propagation and ignition sources as well as fire mitigation processes to better understand these properties for proposed new EA environments. Fire safety, DCS risk, and mission design all contribute to the multifaceted parameters of EA. Thus while it is clear that EA is required to achieve the goals of future exploratory space missions, final specifications are still being evaluated for optimizing crew health and safety.

space atmosphere↗

NASA NTRSDate not supplied

Roughness Parameter Optimization of the McClain Model in GlennICE

Aircraft icing remains a significant threat to aviation safety. Software that predicts the impingement and ice accretion on full aircraft geometries and aircraft components are in demand and NASA Glenn is committed to produce software that meets this need. One of the key parameters affecting an accurate prediction of iced geometry is the effect of ice roughness on the heat transfer coefficient. While many efforts have been made to implement the roughness in the flow solver, this report takes a correlation for roughness height distribution that is based on experimental measurements and demonstrates how to relate those measurements to an augmentation to the heat transfer coefficient provided by the flow solution. The outcome of this effort was the calibration of defaults for user supplied parameters to this correlation through comparison with 95 large glaze conditions from experiment by adjusting user-supplied parameters in the roughness augmentation equation.

Aircraft Icing↗

NASA NTRS1998

Preliminary Study of Relationships between Stability and Control Characteristics and Affordability for High-Performance Aircraft

This paper describes a study that is being done as part of the Methods for Affordable Design (MAD) program within the National Aeronautics and Space Administration (NASA), for which the goal is to develop design methods and information that contribute to reductions in the aircraft development cycle time while increasing design confidence throughout the design cycle. The product of the study will be a database of information that relates key stability and control parameters to affordability considerations such as air combat exchange ratio, safety of flight, and probability of loss of the aircraft or pilot. The overall background and methodology are described, and preliminary results are shown for the first phase of the study to evaluate characteristics in the longitudinal axis. For these preliminary results a simplified analytical model of the aircraft response to uncommanded nose-up pitching moments was developed and used to characterize the requirements for recoveries to controlled flight conditions and to evaluate some parameters that affect the survivability of the aircraft and the pilot.

High performance aircraft↗

NASA NTRS2014

MARGInS: Model-Based Analysis of Realizable Goals in Systems

Under NASAs Constellation effort, the Exploration Technology Development Program funded research toward a system validation capability that applied machine learning and test-case generation techniques to the analysis of black-box system behavior. The behavior analysis capability scaled to spaces of hundreds of input parameters and tens of thousands of test cases. Aerospace systems at the vehicle level, especially those systems which contain some level of autonomy, are best described by hybrid and non-linear mathematics. Even simplified models of such systems need parameter dimensionalities in the hundreds or thousands of parameters in order to capture sufficient fidelity. The System Safety Assessments (such as those described in the SAE ARP 4761A Safety Assessment Process guidelines) for these systems are prone to errorinteractions between the vehicles subsystems are complex, and can display emergent behaviors. NASA captured this new analysis in the Model-based Analysis of Realizable Goals in Systems (MARGInS) tool and applied it to the Pad Abort 1 (PA-1) simulation as part of the independent validation and verification cycle before the PA-1 flight test in May of 2010. MARGInS evaluated the adherence of the high-fidelity simulation to its requirements, and deter- mined the margins to failure from the expected nominal input conditions. Following the PA-1 test, the capabilities within the MARGInS framework have been extended with sophisticated statistical and white-box test case generation techniques and applied to other NASA missions. The frame- work now includes a critical factors analysis that was applied to NASAs Orion simulation and design. NASAs Aeronautics Research Mission Directorate (ARMD) leveraged the existing MARGInS framework for work on aviation safety for civil transport vehicles and for research on autonomy issues. The NASA ARMD effort created a time series output prediction capability that has been used to characterize trajectories for a plane with an adaptive control system, and a safety boundary detection capability that has been applied to an air traffic control concept of operation for the Federal Aviation Administration. The statistical and machine- learning based techniques within MARGInS have been successfully combined with concolic execution to improve the coverage of a critical unit by driving system-level inputs. The use case driving the concolic execution and MARGInS integration was inspired by the Air France 447 disaster in which the loss of a critical functionality (the airspeed calculation from the pitot tubes) led to loss of the entire plane with the people aboard. To illustrate capabilities and limitations, we will highlight the analyses for the applications listed above. We will then discuss the future plans for MARGInS and its interfaces with other tools.

Validation↗

NASA NTRSDate not supplied

A Concept of Operations for Power Beaming of Electric Air Vehicles

A concept of operations is presented for power beaming of microwaves to extend battery charge of an electric air vehicle. Critical aspects of airspace operations and power beam charging are addressed. Three classes of electric Vertical Take-Off and Landing vehicle models are considered for recharging. The effects of transmitter frequency, antenna size, and beam width are analyzed. Based on past experiments in the industry, a 2.5 kW power beam is selected. A no-drag rectifying antenna under the belly of the vehicle is selected along with the conversion efficiency, power density, and its size. The combined efficiency of the transmit/receive system as well as the beam containment values are addressed. These parameters are chosen to assess viability and feasibility of the energy augmentation method to establish safety for humans on-board from exposure to the transmitted energy. NASA will test the concept of operations in a laboratory experiment with parameters selected and presented in this paper.

eVTOL vehicles↗

NASA NTRSDate not supplied

A Concept of Operations for Power Beaming of Electric Air Vehicles

A concept of operations is presented for power beaming of microwaves to extend battery charge of an electric air vehicle. Critical aspects of airspace operations and power beam charging are addressed. Three classes of electric Vertical Take-Off and Landing vehicle models are considered for recharging. The effects of transmitter frequency, antenna size, and beam width are analyzed. Based on past experiments in the industry, a 2.5 kW power beam is selected. A no-drag rectifying antenna under the belly of the vehicle is selected along with the conversion efficiency, power density, and its size. The combined efficiency of the transmit/receive system as well as the beam containment values are addressed. These parameters are chosen to assess viability and feasibility of the energy augmentation method to establish safety for humans on-board from exposure to the transmitted energy. NASA will test the concept of operations in a laboratory experiment with parameters selected and presented here.

eVTOL vehicles↗

NASA NTRSDate not supplied

Quantifying Effects of Departure and Flight Time Uncertainty on Urban Air Mobility Operations

Demand capacity balancing is a key mechanism for maintaining safe and efficient Urban Air Mobility (UAM) operations. However, uncertainties such as departure delays and flight time variation may reduce the effectiveness of algorithms used for balancing and detrimentally impact the safety and efficiency of UAM operations. In this paper, the effects of these uncertainties on UAM operations are quantified by modeling a distribution of departure and flight time errors. A route network in the Dallas/Fort Worth metropolitan area was used to simulate traffic demand with and without uncertainty. Simulations were conducted with three main models of uncertainty – first uncertainty in departure time delay resulting in late takeoffs, second with uncertainty in flight times in addition to departure delays, and finally, uncertainty in departure times that cause either late or early takeoffs. Each of these simulations were performed using varied standard deviations to fully understand the effects of uncertainties. Results from these simulations were compared to a baseline simulation using the same parameters, but without any uncertainty. The results suggest that both safety and efficiency are significantly impacted by uncertainty even with relatively low uncertainty introduced. These results work towards quantifying the effects of uncertainty in flight scheduling for UAM. They will also aid in the further development of the demand capacity balancing algorithms for UAM operations and associated air traffic management.

Urban Air Mobility↗

NASA NTRSDate not supplied

Quantifying the Effects of Departure and Flight Time Uncertainty on Urban Air Mobility Operations

Demand capacity balancing is a key mechanism for maintaining safe and efficient Urban Air Mobility (UAM) operations. However, uncertainties such as departure delays and flight time variation may reduce the effectiveness of algorithms used for balancing and detrimentally impact the safety and efficiency of UAM operations. In this paper, the effects of these uncertainties on UAM operations are quantified by modeling a distribution of departure and flight time errors. A route network in the Dallas/Fort Worth metropolitan area was used to simulate traffic demand with and without uncertainty. Simulations were conducted with three main models of uncertainty – first uncertainty in departure time delay resulting in late takeoffs, second with uncertainty in flight times in addition to departure delays, and finally, uncertainty in departure times that cause either late or early takeoffs. Each of these simulations were performed using varied standard deviations to fully understand the effects of uncertainties. Results from these simulations were compared to a baseline simulation using the same parameters, but without any uncertainty. The results suggest that both safety and efficiency are significantly impacted by uncertainty even with relatively low uncertainty introduced. These results work towards quantifying the effects of uncertainty in flight scheduling for UAM. They will also aid in the further development of the demand capacity balancing algorithms for UAM operations and associated air traffic management.

Urban Air Mobility↗

NASA NTRS2013

An Indirect System Identification Technique for Stable Estimation of Continuous-Time Parameters of the Vestibulo-Ocular Reflex (VOR)

The vestibulo-ocular reflex (VOR) is a well-known dual mode bifurcating system that consists of slow and fast modes associated with nystagmus and saccade, respectively. Estimation of continuous-time parameters of nystagmus and saccade models are known to be sensitive to estimation methodology, noise and sampling rate. The stable and accurate estimation of these parameters are critical for accurate disease modelling, clinical diagnosis, robotic control strategies, mission planning for space exploration and pilot safety, etc. This paper presents a novel indirect system identification method for the estimation of continuous-time parameters of VOR employing standardised least-squares with dual sampling rates in a sparse structure. This approach permits the stable and simultaneous estimation of both nystagmus and saccade data. The efficacy of this approach is demonstrated via simulation of a continuous-time model of VOR with typical parameters found in clinical studies and in the presence of output additive noise.

Kukreja, Sunil L.↗

NASA NTRS1990

Interdependence of science requirements and safety limitations on the space station

One of the benefits of experimentation on the Space Station is the ability to carry out the experiment, to immediately analyze the results, to calculate improved experimental parameters, and to quickly repeat the experiment. In this improved mode of operation there are new safety considerations that must be addressed in the design stages of both the station and the experiments. Some of the chemical and procedural requirements are shared, and some of the earth-bound storage, dispensing, and disposal techniques that may assist in the development of analogous procedures for the Space Station are discussed.

Barber, Patrick G.↗

NASA NTRSDate not supplied

Establishing the Assurance Efficacy of Automated Risk Mitigation Strategies

Verification and validation of increasingly autonomous aviation systems is a major challenge. Traditional techniques for the assurance of high-confidence, safety-critical systems are not equipped to handle the complexity, uncertainty, and lack of predictability inherent in non-deterministic systems. Techniques such as run time monitoring, formal methods, and testing and simulation have been applied to some effect, but it is difficult to properly assess the success of such measures. The authors propose the concept of Assurance Efficacy to address this gap. Assurance Efficacy is seen as a parameter, criteria, or perspective by which to evaluate, identify and explore safety risk mitigation strategies and operational assurance architectures. Validation of the utility of this concept through flight testing is a first step in determining its potential role in assessing the overall safety of complex, increasingly autonomous systems that cannot be fully assured in the design phase.

system safety↗