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NASA NTRSDate not supplied

Hazard Perception & Avoidance (HPA), Assured Vehicle Automation 1 Simulation (AVA-1h) Results Outbrief

In late 2022, the Human Autonomy Teaming Lab (NASA Ames Research Center) conducted a manned, human-in-the-loop (HITL) simulation. This HITL was the lab’s second Hazard Perception and Avoidance (HPA) technical work under NASA’s Advanced Air Mobility (AAM), Automated Flight and Contingency Management (AFCM) Sub-Project. The goals were to assess detect and avoid technology for manned, electric vertical takeoff and landing (eVTOL) aircraft. This simulation tested Resolution Advisory (RA) responses and return-to-course (RTC) maneuvers for the second version of the Airborne Collision Avoidance System’s (ACAS) rotary-wing (Xr) variant. This was conducted at the center's Vertical Motion Simulator (VMS), on a motion-based platform, and was configured to fly eVTOL aircraft while maneuvering for intruding traffic. Variables for this study included ACAS Xr modes (i.e., TA/RA and DAA) and phases of flight (i.e., Cruise, Hover, and Approach). The data collected included response times, losses of well clear, and pilots' noncompliances to alerts and guidance as well as subjective ratings like acceptability and perceived workload. Additional details and future anticipations are also discussed.

ACAS Xr↗

NASA NTRS2019

Overview of Liner Activities in Support of the International Forum for Aviation Research

This paper provides an overview of liner research being conducted by members of the International Forum for Aviation Research (IFAR). The IFAR consists of representatives from a number of national research labs and is established to enable information exchange on aviation research activities. NASA has provided three challenges that explore different aspects of acoustic liner research, and will compile the results from each of the partners into a common database when the challenges are completed. The goal of the first challenge is to compare experimental methods applied at different national labs for acoustic liner evaluation, and to compare impedance eduction methodologies for uniform liners. The second challenge is to evaluate the ability of 3D propagation codes to predict the effects of spanwise variable-impedance liners on the acoustic pressure field. The third challenge is to explore different approaches to simultaneously educe the impedances for each zone of a three-zone liner. Each challenge is intended to be conducted as a blind test. Thus, only representative results achieved by the NASA Liner Physics Team for each of the three challenges are presented herein. When the results from all participants are available, the compiled results are intended to be provided in future reports.

Jones, Michael G.↗

NASA NTRS1990

Propulsion system filter sizing considerations for the Galileo spacecraft

Filtration capacity of the Galileo propulsion system has been investigated. Ground testing of flight spare components has been conducted to determine the representative number and size distribution of particulate matter collected in flow tests. For these tests and for filter qualification tests, a number of effects were examined. The influence of gravitational particle settling on ground test results vs the flight environment was considered. Centrifugal effects inherent in the test apparatus and/or the propulsion system could have an influence. Variability among particle sizing techniques was explored. The influence of size distribution, particle shape, and density in the choice of a particulate test material was studied. Characteristics for AC Coarse Dust (an industry standard filter test media), microscopic polymer beads, and aluminum oxide particulate test matter are listed. Filtration tests were conducted using AC Coarse Dust and mixtures containing components of AC Coarse Dust. These results are expected to be useful data for filter sizing of future spacecraft.

Jan, Darrell L.↗

NASA NTRS2010

Comparison of Airborne and Ground-Based Function Allocation Concepts for NextGen Using Human-In-The-Loop Simulations

This paper presents an air/ground functional allocation experiment conducted by the National Aeronautics and Space Administration (NASA) using two human-in-the-Loop simulations to compare airborne and ground-based approaches to NextGen separation assurance. The approaches under investigation are two trajectory-based four-dimensional (4D) concepts; one referred to as "airborne trajectory management with self-separation" (airborne) the other as "ground-based automated separation assurance" (ground-based). In coordinated simulations at NASA's Ames and Langley Research Centers, the primary operational participants -controllers for the ground-based concept and pilots for the airborne concept - manage the same traffic scenario using the two different 4D concepts. The common scenarios are anchored in traffic problems that require a significant increase in airspace capacity - on average, double, and in some local areas, close to 250% over current day levels - in order to enable aircraft to safely and efficiently traverse the test airspace. The simulations vary common independent variables such as traffic density, sequencing and scheduling constraints, and timing of trajectory change events. A set of common metrics is collected to enable a direct comparison of relevant results. The simulations will be conducted in spring 2010. If accepted, this paper will be the first publication of the experimental approach and early results. An initial comparison of safety and efficiency as well as operator acceptability under the two concepts is expected.

Wing, David J.↗

NASA NTRS1975

Airloads investigation of an 0.030 scale model of the space shuttle vehicle 140A/B launch configuration (model 47-OTS) in the ARC 9 by 7 foot unitary plan wind tunnel for Mach 1.55 and 2.2 (iA14B), volume 1

Tests were conducted in September, 1973 on a launch vehicle configuration consisting of a space shuttle orbiter, an external tank, two solid rocket boosters, and associated intercomponent attach hardware. Model variables included elevon, rudder, and speed brake deflections. Aerodynamic loads were measured and surface pressure distributions were obtained simultaneously with six-component stability and control force data on the complete configuration. Angles of attack and sideslip were also investigated.

Gillins, R. L.↗

NASA NTRS1976

Thermal analysis of PMR-polyimides by dielectrometry

A preliminary study was conducted to determine the dielectric properties of glass fabric reinforced composites as influenced by the reactions occurring during the preparation of crosslinked polyimides by the PMR process. The variables studied included: formulated molecular weight, staging temperature and time; rate of temperature increase to cure temperature; and cure temperature and time. The changes of capacitance and, particularly, of dissipation factor were found to be strongly dependent on each of the variables studied.

Gluyas, R. E.↗

NASA NTRS1976

Development testing of a self-contained heat rejection module

This paper discusses the thermal vacuum testing of a Self-Contained Heat Rejection Module (SHRM) currently being developed for use with Shuttle payloads and future spacecraft. Two weeks of testing were conducted in the NASA Johnson Space Center Space Environment Simulator Laboratory in October and November of 1975. The testing included demonstration of deployable spacecraft radiators with fluid swivels, variable return temperatures, and a dual-mode pumped fluid radiator/vapor compression refrigeration system. In addition, an evaluation was made of a contact heat exchanger used as the intercooler. The test articles and systems are described and the test planning and objectives discussed. A summary of the significant results of the testing and conclusions drawn from the testing are presented.

Fleming, M. L.↗

NASA NTRS1978

The effects of design and operating variables on the response of an axial flow fan to inlet flow distortions

The results of a study of total pressure and velocity circumferential distortions in an axial-flow fan are presented. Some of the fundamental experimental data needed to understand distorted flow phenomena as affected by design and operating variables are provided. The flow through an isolated rotor was examined at various operating conditions with six different distortions and three different blade stagger angles. Circumferential surveys were conducted upstream and downstream of the rotor using five-hole probes in the nonnulling mode. The total pressure and axial velocity distortion data were analyzed to determine the degree of distortion attenuation as a function of blade stagger angle, mean incidence angle, and reduced frequency. The results indicate that, for the rotors tested, the mean incidence or loading has very little effect on the distortion attenuation.

Yocum, A. M., II↗

NASA NTRS1980

Application of high-alpha control system concepts to a variable-sweep fighter airplane

The use of control system design to enhance high-angle-of-attack flying qualities and departure/spin resistance has become an accepted and widely used approach for modern fighter aircraft. NASA and the Navy are currently conducting a joint research program to investigate the application of this technology to the F-14. The paper discusses the results of this program within the context of its contributions to advancing high-alpha control system technology. General topics covered include (1) analysis and design tools, (2) control system design approach, and (3) flight test approach and results.

Nguyen, L. T.↗

NASA NTRS1983

Advanced microwave soil moisture studies

Comparisons of low level L-band brightness temperature (TB) and thermal infrared (TIR) data as well as the following data sets: soil map and land cover data; direct soil moisture measurement; and a computer generated contour map were statistically evaluated using regression analysis and linear discriminant analysis. Regression analysis of footprint data shows that statistical groupings of ground variables (soil features and land cover) hold promise for qualitative assessment of soil moisture and for reducing variance within the sampling space. Dry conditions appear to be more conductive to producing meaningful statistics than wet conditions. Regression analysis using field averaged TB and TIR data did not approach the higher sq R values obtained using within-field variations. The linear discriminant analysis indicates some capacity to distinguish categories with the results being somewhat better on a field basis than a footprint basis.

Dalsted, K. J.↗

NASA NTRS1984

Mechanisms of interannual ocean-atmosphere interactions

Results of an investigation to study the interaction between ocean and atmosphere on the annual to decadal time scale are reported. Separate studies of the ocean response to atmospheric forcing, and of atmospheric response to ocean forcing were also conducted. The main findings are the dynamics of sea surface temperature anomalies, the role of short time scale weather fluctuations in the seasonal cycle of the upper ocean variability, and the planetary wave response to sea surface temperature anomalies. A numerical model of the ocean atmosphere continent system and a two layer quasi-geostropic ocean model is discussed.

Frankignoul, C.↗

NASA NTRS1984

Seasonal variations of Pb-210 and Po-210 concentrations in an oligotrophic lake

In order to examine spatial and temporal variability during the seasonal cycle of the oligotrophic Crystal Lake, Wisconsin, vertical distribution measurements of Pb-210 and Po-210 in both the dissolved and particulate phases were conducted. Mass balance considerations indicate that the removal rates of the two isotopes from the water column to the sediment vary temporally by nearly an order of magnitude. The mean removal residence time was estimated to be 0.095 yr for Pb-210 and 0.26 yr for Po-210, suggesting a difference in the extent of water column recycling. Calculations indicate a cyclic response of the water column Po-210 inventory which corresponds to successive time periods when there were net losses or gains; this response may be due to rapid biological removal and subsequent release from the sediment of freshly deposited Po-210.

Talbot, R. W.↗

NASA NTRS1986

Simulation studies of alternate longitudinal control systems for the space shuttle orbiter in the landing regime

Simulations of the space shuttle orbiter in the landing task were conducted by the NASA Ames-Dryden Flight Research Facility using the Ames Research Center vertical motion simulator (VMS) and the total in-flight simulator (TIFS) variable-stability aircraft. Several new control systems designed to improve the orbiter longitudinal response characteristics were investigated. These systems improved the flightpath response by increasing the amount of pitch-rate overshoot. Reduction in the overall time delay was also investigated. During these evaluations, different preferences were noted for the baseline or the new systems depending on the pilot background. The trained astronauts were quite proficient with the baseline system and found the new systems to be less desirable than the baseline. On the other hand, the pilots without extensive flight training with the orbiter had a strong preference for the new systems. This paper presents the results of the VMS and TIFS simulations. A hypothesis is presented regarding the control strategies of the two pilot groups and how this influenced their control systems preferences. Interpretations of these control strategies are made in terms of open-loop aircraft response characteristics as well as pilot-vehicle closed-loop characteristics.

Powers, B. G.↗

NASA NTRS1986

Simulation studies of alternate longitudinal control systems for the Space Shuttle Orbiter in the landing regime

Simulations of the Space Shuttle Orbiter in the landing task were conducted by the NASA Ames-Dryden Flight Research Facility using the Ames Research center vertical motion simulation (VMS) and the total in-flight simulator (TIFS) variable-stability aircraft. Several new control systems designed to improve the orbiter longitudinal response characteristics were investigated. These systems improved the flightpath response by increasing the amount of pitch-rate overshoot. Reduction in the overall time delay was also investigated. During these evaluations, different preferences were noted for the baseline or the new systems depending on the pilot background. The trained astronauts were quite proficient with the baseline system and found the new systems to be less desirable than the baseline. On the other hand, the pilots without extensive flight training with the Orbiter had a strong preference for the new systems. This paper presents the results of the VMS and TIFS simulations. A hypothesis is presented regarding the control strategies of the two pilot groups and how this influenced their control system preferences. Interpretations of these control strategies are made in terms of open-loop aircraft response characteristics as well as pilot-vehicle closed-loop characteristics.

Powers, B. G.↗

NASA NTRS1987

Off-design analysis of counter-rotating propeller configurations

An analysis is conducted to determine whether the counterrotating propeller configuration maintains, and perhaps improves, its excellent performance in the off-design mode for the constant-speed or variable-pitch case. While the twist distribution is maintained, the blade angle is changed to absorb shaft horsepower as a constant rpm setting is maintained under varying freestream velocities. A relatively flat propeller efficiency curve is obtained for advance ratios of 1.5-5.0.

Korkan, K. D.↗

NASA NTRS1986

A conceptual design for a microwave active phased array SAR

The active phased array radar is well known for its assets of rapid electronic beam steering and adaptability to limited degrading influences. In a spaceborne synthetic aperture radar (SAR) application, therefore, it should be possible to provide for rapid beam control in the cross-track (variable incidence angle) and along-track (spot-light mode) directions, as well as allowing for possible relaxation of antenna structural requirements. A design study has been conducted at Stanford University for a conceptual spaceborne C-band SAR application operating in the early to mid-1990's time frame. This study was intended to identify principal design issues, as well as unique features associated with an active phased array antenna SAR. A hypothetical design is used to illustrate these issues. Some of this work should have generic application to space-based communications activities.

Gilchrist, Brian E.↗

NASA NTRS1989

Energy-absorption capability of composite tubes and beams

In this study the objective was to develop a method of predicting the energy-absorption capability of composite subfloor beam structures. Before it is possible to develop such an analysis capability, an in-depth understanding of the crushing process of composite materials must be achieved. Many variables affect the crushing process of composite structures, such as the constituent materials' mechanical properties, specimen geometry, and crushing speed. A comprehensive experimental evaluation of tube specimens was conducted to develop insight into how composite structural elements crush and what are the controlling mechanisms. In this study the four characteristic crushing modes, transverse shearing, brittle fracturing, lamina bending, and local buckling were identified and the mechanisms that control the crushing process defined. An in-depth understanding was developed of how material properties affect energy-absorption capability. For example, an increase in fiber and matrix stiffness and failure strain can, depending upon the configuration of the tube, increase energy-absorption capability. An analysis to predict the energy-absorption capability of composite tube specimens was developed and verified. Good agreement between experiment and prediction was obtained.

Farley, Gary L.↗

NASA NTRS1992

Directional and temporal variability of the APAR/VI relationships - The case of a sunflower canopy

Detailed biomass and structure measurements as well as photosynthetically active radiation (PAR) balance and bidirectional and polarized reflectances in various wavebands from 450 nm to 1750 nm have been conducted over a sunflower canopy in France. Preliminary results show that the vegetation indices (NDVI or TSAVI) computed from the red and near-infrared reflectances exhibit strong directional and temporal (variation with the sun zenith angle) features. The relationship between the vegetation indices and the PAR fraction absorbed or intercepted by the canopy is likely to vary greatly with these factors.

Baret, F.↗