Lunex II - A study on manned lunar exploration.
Crew performance evaluation via behavioral and psychophysiological tests in Lunex 2 simulated lunar mobile laboratory
Burns, N. M.↗
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Rapid Aero Modeling for Urban Air Mobility Aircraft in Wind-Tunnel Tests
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Aerodynamics↗
FT - 06 - Advanced Air Mobility Operation & Automation: National Campaign Simulation Activity with Joby Aviation
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David Zahn↗
Initial Testing the Exploration Extravehicular Mobility Unit (xEMU) in Lunar Environment Simulation at the Neutral Buoyancy Lab (NBL) in 2022
Understanding how to effectively train for Extravehicular Activities (EVAs) for Artemis missions is critical. Tasked by the new Extravehicular Activity and Human Surface Mobility Program(EHP), a team of stakeholders from engineering and flight operations worked together to test the Exploration Extravehicular Mobility (xEMU) in the Neutral Buoyancy Lab(NBL) simulating the lunar environment. The NBL is a pool in which astronauts are typically trained to complete simulated International Space Station (ISS) EVA tasks in a neutral weigh-out. The overall focus for this test series was evaluating how well the NBL could be used as an effective simulated environment for Artemis lunar EVAs. New NBL support hardware was manufactured to support this test series and update the interfaces to be more representative of xEMU hardware such as a new NBL Portable Life Support System(PLSS)mock-up and umbilical, lights and cameras, and display and control unit (DCU).To simulate the 1/6th-gravity (1/6-g) environment, extra weights were added around the suit to create an accurate center of gravity representation. The Partial Gravity Weigh-out Stand (PGWS) predicted where and how much weight would be required for the 1/6th-G simulation and predicted the center of gravity placement. After the weigh-out attempt was completed, the suited participant would complete a set of directed tasks such as kneeling, object pick-up, and walking to evaluate the weigh-out. To create the lunar environment, sand, boulders, and ramps were added to the pool floor. If time allowed after weigh-out was determined acceptable, the flight operations team would direct the suited participants to complete simulated Artemis EVA tasks using flight-like tools and tool cart. The team also evaluated turning out the overhead lights in the NBL for a portion of some of the test runs and using a solar simulator to create amore realistic lunar south pole lighting environment. The test series completed one unmanned test and nine manned tests. With four of the tests, dual xEMU suited operations were completed with subjects in both the small and large xEMU sizes. Overall, the NBL was able to create an acceptable lunar landscape and ability to have two subjects work side by side in pressurized xEMUs which currently cannot be achieved in other test environments. Achieving a stable 1/6th-G lunar weigh-out and clear, consistent dual suit communications was a challenge for this series. Future work is planned to continue to improve this simulation environment.
spacesuit↗
Initial Testing of the Exploration Extravehicular Mobility Unit (xEMU) in Lunar Environment Simulation at the Neutral Buoyancy Lab (NBL) in 2022
Understanding how to effectively train for Extravehicular Activities (EVAs) for Artemis missions is critical. Tasked by the new Extravehicular Activity and Human Surface Mobility Program(EHP), a team of stakeholders from engineering and flight operations worked together to test the Exploration Extravehicular Mobility (xEMU) in the Neutral Buoyancy Lab(NBL) simulating the lunar environment. The NBL is a pool in which astronauts are typically trained to complete simulated International Space Station (ISS) EVA tasks in a neutral weigh-out. The overall focus for this test series was evaluating how well the NBL could be used as an effective simulated environment for Artemis lunar EVAs. New NBL support hardware was manufactured to support this test series and update the interfaces to be more representative of xEMU hardware such as a new NBL Portable Life Support System(PLSS)mock-up and umbilical, lights and cameras, and display and control unit (DCU).To simulate the 1/6th-gravity (1/6-g) environment, extra weights were added around the suit to create an accurate center of gravity representation. The Partial Gravity Weigh-out Stand (PGWS) predicted where and how much weight would be required for the 1/6th-G simulation and predicted the center of gravity placement. After the weigh-out attempt was completed, the suited participant would complete a set of directed tasks such as kneeling, object pick-up, and walking to evaluate the weigh-out. To create the lunar environment, sand, boulders, and ramps were added to the pool floor. If time allowed after weigh-out was determined acceptable, the flight operations team would direct the suited participants to complete simulated Artemis EVA tasks using flight-like tools and tool cart. The team also evaluated turning out the overhead lights in the NBL for a portion of some of the test runs and using a solar simulator to create amore realistic lunar south pole lighting environment. The test series completed one unmanned test and nine manned tests. With four of the tests, dual xEMU suited operations were completed with subjects in both the small and large xEMU sizes. Overall, the NBL was able to create an acceptable lunar landscape and ability to have two subjects work side by side in pressurized xEMUs which currently cannot be achieved in other test environments. Achieving a stable 1/6th-G lunar weigh-out and clear, consistent dual suit communications was a challenge for this series. Future work is planned to continue to improve this simulation environment.
spacesuit↗
Evaluation of Heave Disturbance Rejection and Control Response Criteria on the Handling Qualities Evaluation of Urban Air Mobility (UAM) eVTOL Quadrotors Using the Vertical Motion Simulator
The first piloted handling qualities study of an urban air mobility (UAM) vehicle leveraging the Vertical Motion Simulator (VMS) at NASA Ames Research Center was conducted in Spring 2021. The VMS provides a unique capability to reduce risk by assessing and iterating control designs. Minimal sources currently exist to provide performance and handling qualities data for large, rotor speed-controlled vehicles outside of the software environment. The study compares multiple handling qualities performance configurations for rotor speed and blade pitch-controlled variants of a six-passenger quadrotor conceptual design model developed by the NASA Revolutionary Vertical Lift Technology (RVLT) Project. Additionally, both ADS-33 and a tailored set of performance standards (notionally representing the agility required of a UAM mission) are examined under conditions with and without light turbulence. Preliminary results did show significant variation in ratings based on the set of standards utilized, controller tuning to either Level 1 or boundary Level 1/ Level 2 conditions, and presence or lack of turbulence. A custom approach and landing maneuver was also designed to bring these evaluation tasks together in a more comprehensive application.
Handling Qualities↗
High-Fidelity Simulations of Lift+Cruise VTOL Urban Air Mobility Concept Aircraft in Hover
This paper presents progress of high-fidelity multidisciplinary simulations for the NASA lift+cruise vertical takeoff and landing (VTOL) urban air mobility concept aircraft in hover. The study focuses on the unsteady flow solutions featuring strong wake interactions between rotors and the airframe. The simulations couple a high-fidelity aerodynamic model with a comprehensive rotorcraft aeromechanics tool with rotor rotation-speed trim. The aerodynamic model is based on the Reynolds-averaged Navier-Stokes equations using the one-equation Spalart-Allmaras turbulence model with rotation correction. Unsteady aerodynamic flows are computed on a dynamic, deformable, unstructured, overset grid system. An integrated overset-grid assembler is used to construct the composite grid from 23 component grids and facilitate communications between individual component grids. Rotor performance and airframe forces and moments are computed and compared on two unstructured grids. The study demonstrates capabilities of high-fidelity multidisciplinary analysis tools to capture the strong unsteady flowfield around this multi-rotor aircraft in hover.
CFD↗
High-Fidelity Simulations of Lift+Cruise VTOL Urban Air Mobility Concept Aircraft in Hover
This presentation presents progress of high-fidelity multidisciplinary simulations for the NASA lift+cruise vertical takeoff and landing (VTOL) urban air mobility concept aircraft in hover. The study focuses on the unsteady flow solutions featuring strong wake interactions between rotors and the airframe. The simulations couple a high-fidelity aerodynamic model with a comprehensive rotorcraft aeromechanics tool with rotor rotation-speed trim. The aerodynamic model is based on the Reynolds-averaged Navier-Stokes equations using the one-equation Spalart-Allmaras turbulence model with rotation correction. Unsteady aerodynamic flows are computed on a dynamic, deformable, unstructured, overset grid system. An integrated overset-grid assembler is used to construct the composite grid from 23 component grids and facilitate communications between individual component grids. Rotor performance and airframe forces and moments are computed and compared on two unstructured grids. The study demonstrates capabilities of high-fidelity multidisciplinary analysis tools to capture the strong unsteady flowfield around this multi-rotor aircraft in hover.
CFD↗
Feasibility study of automatic control of crew comfort in the shuttle Extravehicular Mobility Unit
Computer simulation is used to demonstrate that crewman comfort can be assured by using automatic control of the inlet temperature of the coolant into the liquid cooled garment when input to the controller consists of measurements of the garment inlet temperature and the garment outlet temperature difference. Subsequent tests using a facsimile of the control logic developed in the computer program confirmed the feasibility of such a design scheme.
Cook, D. W.↗
Simulation Study for Interoperability of Urban Air Mobility Scheduling and Separation Services in Ideal Conditions
Provision of strategic scheduling and tactical separation services is vital to the safe and efficient operation of vehicles in the urban airspace. This paper describes the efforts made towards the integration of two such services in a simulation environment under ideal conditions and the subsequent studies done on evaluation of system performance. The scheduling and separation services are set up to complement each other to ensure safe separation between airborne aircraft. The utility of these services will become important as the level of traffic increases. This paper describes the simulation experiments conducted to identify cases where the system performance measured by the number of observed losses of separation degrades even with the scheduling and separation services active. From the results obtained, we identify conditions under which the required maneuvers increase and when we observe airborne conflicts even with separation service active. Results obtained will inform requirements for future advancements both in these services independently and in their joint operations.
Urban Air Mobility↗
Simulation Study for Interoperability of Urban Air Mobility Scheduling and Separation Services in Ideal Conditions
Provision of strategic scheduling and tactical separation services is vital to the safe and efficient operation of vehicles in the urban airspace. This paper describes the efforts made towards the integration of two such services in a simulation environment under ideal conditions and the subsequent studies done on evaluation of system performance. The scheduling and separation services are set up to complement each other to ensure safe separation between airborne aircraft. The utility of these services will become important as the level of traffic increases. This paper describes the simulation experiments conducted to identify cases where the system performance measured by the number of observed losses of separation degrades even with the scheduling and separation services active. From the results obtained, we identify conditions under which the required maneuvers increase and when we observe airborne conflicts even with separation service active. Results obtained will inform requirements for future advancements both in these services independently and in their joint operations.
Urban Air Mobility↗
Simulation Studies for an Urban Air Mobility Aircraft using Hardware-In-Loop Experiments
This presentation is for the submitted manuscript for AIAA Aviation 2022 (20220006457)
UAM↗
Mobility of a spatially modulated electron liquid on the helium surface
Here, we present the results of large-scale numerical simulations of the mobility of a two-dimensional electron liquid on the helium surface in the presence of a one-dimensional periodic potential. Even where the potential is much weaker than the electron-electron interaction, it can strongly change the mobility. The effect depends on the interrelation between the potential period and the mean interelectron distance. It is most pronounced where the period is close to the period of the Wigner crystal that would form if the liquid were cooled to a lower temperature. The results suggest, in particular, that the correlation length in the electron liquid can be found by measuring the mobility in a weak periodic potential. The simulations are based on the microscopic model of the electron scattering by the excitations in helium.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
The {10$\overline{1}$2} non-cozone twin-twin interactions in Mg: A stability and mobility study using 3-D atomistic simulations
Due to easy activation of tensile twinning in Mg, multiple {10$\overline{1}$2} twin variants can interact with each other and form twin-twin boundaries over the course of plastic deformation. Previous studies using 2-D settings provide only a partial understanding of these interactions, especially the non-cozone ones. Here, atomistic simulations are used to study the 3-D structural characteristic and evolution of the non-cozone {10$\overline{1}$2} twin-twin junctions. The study reveals the existence of new twin-twin boundaries (TTBs) such as TTB BP and TTB K2 , formed after the interaction between the basal prismatic and conjugate twin interfaces with the coherent twin boundary. Here, for both non-cozone twin-twin interactions, the {10$\overline{1}$2} TTB and its associated twin-twin junctions are found to play a major role in the {10$\overline{1}$2} twin's stability and mobility. Specifically, they promote the growth of the 3-D twin in both the normal and forward directions during the interaction and hinder the detwinning process upon unloading.
36 MATERIALS SCIENCE↗
A method for modelling peak signal statistics on a mobile satellite transponder
A simulation method is proposed. The simulation was developed to model the peak duration and energy content of signal peaks in a mobile communication satellite operating in a Frequency Division Multiple Access (FDMA) mode and presents an estimate of those power peaks for a system where the channels are modeled as band limited Gaussian noise, which is taken as a reasonable representation for Amplitude Commanded Single Sideband (ACSSB), Minimum Shift Keying (MSK), or Phase Shift Keying (PSK) modulated signals. The simulation results show that, under this hypothesis, the level of the signal power peaks for 10 percent, 1 percent, and 0.1 percent of the time are well described by a Rayleigh law and that their duration is extremely short and inversely proportional to the total FDM system bandwidth.
Bilodeau, Andre↗
Simulation Studies for an Urban Air Mobility Aircraft using Hardware-In-Loop Experiments
Urban Air Mobility seeks to transport passengers, deliver cargo, and provide emergency transportation in major metropolitan areas. This will be accomplished with distributed electric-powered vertical takeoff and landing aircraft. The low specific energy of the current generation lithium-ion battery packs limit the operational range of electric aircraft. Limited range impacts safety by reducing the time available for analyzing and responding to errors and failures, and limiting the ability to fly to an alternative landing area or return to base. It is therefore critical to understand flight operational and environmental conditions that impact the onboard lithium-ion polymer battery pack’s health. With this as the motivation, experimental procedure in a laboratory setting, and results of the experiments performed on battery packs subject to power draw corresponding to power required during the different phases of flight of a NASA conceptual quadrotor aircraft in simulation are described. The fully charged battery is allowed to discharge at specific C-rates based on the power draw profile and the current and voltages are recorded. Observed results under different operating conditions and mission profiles are discussed.
UAM↗
Simulation Studies for an Urban Air Mobility Aircraft using Hardware-In-Loop Experiments
Urban Air Mobility seeks to transport passengers, deliver cargo, and provide emergency medical transportation in major metropolitan areas. This will be accomplished with distributed electric powered vertical takeoff and landing aircraft vehicles. The low specific energy of the current generation lithium-ion battery packs limit the operational range of the electric aircraft. Limited range impacts safety by reducing the amount of time available for analyzing the potential impact of errors and failures and responding to them, and for flying to an alternative landing area or returning to the base. It is therefore critical to understand the impact of flight and environmental conditions on the onboard lithium-ion battery pack’s health. With this as the motivation, the procedure for evaluating the performance of battery packs in a laboratory setting and the results obtained using this procedure on battery packs subject to power draw characteristics of a simulated flight of a NASA conceptual quadrotor aircraft model are described. The fully charged battery is allowed to discharge at specific C-rates based on the power draw profile during the experiment, and the current and voltages are recorded as a function of time. Observed results under different operating conditions and mission profiles are discussed.
UAM↗
Developing an Automated Microscopic Traffic Simulation Scenario Generation Tool
Traffic simulation is an effective tool for urban planners, traffic engineers, and researchers to study traffic. In particular, microscopic traffic simulation, which simulates individual vehicles’ movements within a transportation network, has demonstrated its importance in analyzing and managing transportation systems. However, integrating data from various sources, generating traffic scenarios, and importing information into traffic simulators to conduct microscopic simulations have always been a challenge. This paper presents a solution to overcome this challenge: RealTwin, a comprehensive tool for automated scenario generation for microscopic traffic simulation. Following a streamlined scenario generation and calibration workflow, RealTwin effectively bridges gaps between traffic data from various sources and traffic simulators, making microscopic traffic simulation more accessible for researchers and engineers across various levels of expertise. Using RealTwin to generate a real-world traffic scenario in Simulation of Urban Mobility (SUMO), VISSIM, and AIMSUN, RealTwin’s ability is demonstrated in the construction of realistic and consistent traffic scenarios in different simulators. Furthermore, this paper introduces and illustrates RealTwin’s capability for technology (e.g., autonomous vehicle) scenario generation. This feature can contribute to more comprehensive microscopic simulations, facilitating the analysis of potential effects of various technological innovations on mobility, energy efficiency, and safety. Finally, RealTwin is used to calibrate a simulation in SUMO. In conclusion, the calibration module enhances RealTwin’s ability to generate consistent simulations across different platforms and more realistic simulations that reflect real-world traffic operations.
autonomous vehicle↗