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

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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

UAS Integration in the NAS: Encounter Rate Simulation Study with UAS Missions

This study investigates the effects that different parameters of a given well clear metric has on the rate of well clear violations (WCV) in Class E airspace. The proposed metrics are taken from variations on methods used by TCAS IIand also considers different alerting schemes against the well clear metric. This presentation is divided into three analysis. The first analysis presented investigates the effect of well clear definitions on the rate of WCV occurrence. The second analysis characterises encounters at the WCV and the third analysis evaluates the alerting threshold definition and criteria. This study should inform refinement of an appropriate definition of well clear for UAS sense and avoid systems and motivate further research on exploring alerting definitions and criteria for a given well clear definition.

Johnson, Marcus↗
NASA NTRSDate not supplied

Retrieving DSD Moments from GPM-DPR: A Simulation Study Based on the Full DSD Spectra Characterized by the Generalized Gamma Model

Recently, a method to retrieve rain drop size distribution (DSD) moments from X-band dual polarization radar measurements has been developed using copolar reflectivity, differential reflectivity and specific attenuation. Two reference moments are retrieved first, followed by reconstructing the DSDs and calculating other moments using a generalized gamma model to represent the underlying shape, h(x), corresponding to the pair of chosen reference moments. Here we explore a similar approach but the retrieval method in this study uses dual-frequency radar measurements. In the case of GPM-DPR, the two frequencies are 13.8and 35 GHz, and their products include attenuation corrected reflecivities at both frequencies (Z and Z) and the specific attenuation (k, k, if available). Our approach is to use these products to determine two reference moments, namely M3 andM6 representing the third and the sixth moments respectively. Then, as with the polarimetric radar retrievals, we use the most probable h(x) to reconstruct the full DSD spectra, from which other moments are calculated. The best two DPR products for estimating M3 and M6 appear to be A and Z. Figure 1 shows the retrievals versus the ‘true’ moments. 2930 three-minute DSDs were used for the (T-matrix) scattering calculations at Ku and Ka bands but only cases with A > 0.5 dB/km were chosen. For the retrieved moments, the integration was performed only up to 6 mm drop diameter. The [1:1] line is included in Fig. 1. Even with just two DPR products as input the results seem promising, although the lower order moments show somewhat more scatter, especially the zeroth moment, M0. We will quantify the retrieval errors, and additionally examine the stability of h(x). For the latter, data from (i) Greeley, Colorado, (ii) Huntsville, Alabama, and (iii)Wallops, Virginia, will be used. Finally, a GPM overpass case over Huntsville, during a widespread rain event on 11 April 2016, will be considered as an initial test case.

precipitation↗
NASA NTRSDate not supplied

Define Minimum Safe Operational Volume for Aerial Vehicles in Upper Class E Airspace

This work presents both analytical and simulation studies for defining the minimum safe operational volume needed for aerial vehicles operating in upper Class E airspace. The analytical study is conducted first to investigate factors that affect the minimum safe operational volume, such as position errors, wake/vortex, vehicle maneuverability, communication and surveillance, control/operator response time. A mathematical approach is developed to compute the boundary of the safe operational volume required by the limited aircraft maneuverability and an analytical sensitivity study is then performed with varying parameters. After the analytical study, simulations are then conducted to verify the results from the analytical study. Simulation results will be included in the final paper.

Separation standard, well-clear definition, upper ↗
NASA NTRS1974

Simulator verification techniques study. Integrated simulator self test system concepts

Software and hardware requirements for implementing hardware self tests are presented in support of the development of training and procedures development simulators for the space shuttle program. Self test techniques for simulation hardware and the validation of simulation performance are stipulated. The requirements of an integrated simulator self system are analyzed. Readiness tests, fault isolation tests, and incipient fault detection tests are covered.

Montoya, G.↗
NASA NTRS1974

Simulation verification techniques study. Subsystem simulation validation techniques

Techniques for validation of software modules which simulate spacecraft onboard systems are discussed. An overview of the simulation software hierarchy for a shuttle mission simulator is provided. A set of guidelines for the identification of subsystem/module performance parameters and critical performance parameters are presented. Various sources of reference data to serve as standards of performance for simulation validation are identified. Environment, crew station, vehicle configuration, and vehicle dynamics simulation software are briefly discussed from the point of view of their interfaces with subsystem simulation modules. A detailed presentation of results in the area of vehicle subsystems simulation modules is included. A list of references, conclusions and recommendations are also given.

Duncan, L. M.↗
NASA NTRS2014

Usability of EFBs for Viewing NOTAMs and AIS/MET Data Link Messages

Electronic Flight Bags (EFB) are increasingly integral to flight deck information management. A piloted simulation study was conducted at NASA Langley Research Center, one aspect of which was to evaluate the usability and acceptability of EFBs for viewing and managing Notices to Airmen (NOTAMs) and data linked aeronautical information services (AIS) and meteorological information (MET). The study simulated approaches and landings at Memphis International Airport (KMEM) using various flight scenarios and weather conditions. Ten two-pilot commercial airline crews participated, utilizing the Cockpit Motion Facility's Research Flight Deck (CMF/RFD) simulator. Each crew completed approximately two dozen flights over a two day period. Two EFBs were installed, one for each pilot. Study data were collected in the form of questionnaire/interview responses, audio/video recordings, oculometer recordings, and aircraft/system state data. Preliminary usability results are reported primarily based on pilot interviews and responses to questions focused on ease of learning, ease of use, usefulness, satisfaction, and acceptability. Analysis of the data from the other objective measures (e.g., oculometer) is ongoing and will be reported in a future publication. This paper covers how the EFB functionality was set up for the study; the NOTAM, AIS/MET data link, and weather messages that were presented; questionnaire results; selected pilot observations; and conclusions.

Evans, Emory T.↗
NASA NTRS2005

Mars Atmospheric Chemistry in Electrified Dust Devils and Storms

Laboratory studies, simulations and desert field tests all indicate that aeolian mixing dust can generate electricity via contact electrification or "triboelectricity". In convective structures like dust devils or storms, grain stratification (or charge separation) occurs giving rise to an overall electric dipole moment to the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous simulation studies [1] indicate that this storm electric field on Mars can approach atmospheric breakdown field strength of 20 kV/m. In terrestrial dust devils, coherent dipolar electric fields exceeding 20 kV/m have been measured directly via electric field instrumentation. Given the expected electrostatic fields in Martian dust devils and storms, electrons in the low pressure CO2 gas can be energized via the electric field to values exceeding the electron dissociative attachment energy of both CO2 and H2O, resulting in the formation of new chemical products CO and O- and OH and H- within the storm. Using a collisional plasma physics model we present a calculation of the CO/O- and OH/H- reaction and production rates. We demonstrate that these rates vary geometrically with ambient electric field, with substantial production of dissociative products when fields approach breakdown levels of 20-30 kV/m.

Farrell, W. M.↗
NASA NTRS1970

Simulated GARP studies

Computerized simulation of wind velocity using Nimbus 3 infrared sounding data

Jastrow, R.↗