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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Low-Speed Flight Dynamic Tests and Analysis of the Orion Crew Module Drogue Parachute System

A test of a dynamically scaled model of the NASA Orion Crew Module (CM) with drogue parachutes was conducted in the NASA-Langley 20-Foot Vertical Spin Tunnel. The primary test objective was to assess the ability of the Orion Crew Module drogue parachute system to adequately stabilize the CM and reduce angular rates at low subsonic Mach numbers. Two attachment locations were tested: the current design nominal and an alternate. Experimental results indicated that the alternate attachment location showed a somewhat greater tendency to attenuate initial roll rate and reduce roll rate oscillations than the nominal location. Comparison of the experimental data to a Program To Optimize Simulated Trajectories (POST II) simulation of the experiment yielded results for the nominal attachment point that indicate differences between the low-speed pitch and yaw damping derivatives in the aerodynamic database and the physical model. Comparisons for the alternate attachment location indicate that riser twist plays a significant role in determining roll rate attenuation characteristics. Reevaluating the impact of the alternate attachment points using a simulation modified to account for these results showed significantly reduced roll rate attenuation tendencies when compared to the original simulation. Based on this modified simulation the alternate attachment point does not appear to offer a significant increase in allowable roll rate over the nominal configuration.

Hahne, David E.↗
DOE OSTI2024

Quantifying spectral albedo effects on bifacial photovoltaic module measurements and system model predictions

We provide a comprehensive analysis of the effect of spectral albedo on photovoltaic (PV) module measurements and system model predictions. We demonstrate how to account for albedo in indoor bifacial device measurements by adjusting the applied irradiance using the scaled rear irradiance method, exemplified on fabricated silicon heterojunction (SHJ) modules. System model performance is studied using a detailed 3D finite-element model, DUET, for fixed-tilt and horizontal single-axis tracked (SAT) arrays between 15 and 75°N. Spectral effects cause variations in measured SHJ module short-circuit current up to 2% and efficiency variation up to 0.3% abs. We further demonstrate that rear-side spectral mismatch factors (SMMs) resulting from including or omitting spectral albedo in PV system modeling vary between ±13%, while total (front+rear) SMMs vary up to 3%, depending on the deployment configuration and latitude. SAT array SMMs are weakly correlated with latitude, while fixed-tilt array SMMs increase with latitude, driven by an increasing proportion of ground-reflected light on the front-side of modules. Ground-reflections can constitute between 2% and 32% of total incident module irradiance, with notably high (>10%) contributions for fixed-tilt arrays at high latitude. Effects of spectral albedo are most significant for: (1) fixed-tilt deployments at high latitudes, (2) wide bandgap technologies such as perovskite and cadmium telluride cells, (3) albedos which vary steeply over the technology's absorption range, and (4) high albedo ground covers. Overall, we demonstrate that omitting spectral albedo effects can result in PV measurement and system-level modeling uncertainties on the order of several percent in these cases.

14 SOLAR ENERGY↗
NASA NTRS2002

Approximating Fluid Flow from Ambient to Very Low Pressures: Modeling ISS Experiments that Vent to Vacuum

Two ISS (International Space Station) experiment payloads will vent a volume of gas overboard via either the ISS Vacuum Exhaust System or the Vacuum Resource System. A system of ducts, valves and sensors, under design, will connect the experiments to the ISS systems. The following tasks are required: Create an analysis tool that will verify the rack vacuum system design with respect to design requirements, more specifically approximate pressure at given locations within the vacuum systems; Determine the vent duration required to achieve desired pressure within the experiment modules; Update the analysis as systems and operations definitions mature.

Minor, Robert↗
NASA NTRS2005

Tributary Analysis Monitoring System

A monitoring system for a fleet of vehicles includes at least one data acquisition and analysis module (DAAM) mounted on each vehicle in the fleet, a control module on each vehicle in communication with each DAAM, and terminal module located remotely with respect to the vehicles in the fleet. Each DAAM collects/analyzes sensor data to generate analysis results that identify the state of a plurality of systems of the vehicle. Each vehicle's control module collects/analyzes the analysis results from each onboard DAAM to generate vehicle status results that identify potential sources of vehicle anomalies. The terminal module collects/analyzes the analysis results and vehicle status results transmitted from each control module from the fleet of vehicles to identify multiple occurrences of vehicle anomalies and multiple occurrences of those vehicle systems operating at a performance level that is unacceptable. Results of the terminal module's analysis are provided to organizations responsible for the operation, maintenance and manufacturing of the vehicles in the fleet as well as the plurality of systems used in the fleet.

Stanley E Woodard↗
NASA NTRS1995

Line group techniques in description of the structural phase transitions in some superconductors

The main features of the theory of line groups, and their irreducible representations are briefly discussed, as well as the most important applications of them. A new approach in the general symmetry analysis of the modulated systems is presented. It is shown, that the line group formalism could be a very effective tool in the examination of the structural phase transitions in High Temperature SUperconductors. As an example, the material YBa2Cu3O(7-x) is discussed briefly.

Meszaros, CS.↗
NASA NTRS1982

Role of IAC in large space systems thermal analysis

Computer analysis programs to evaluate critical coupling effects that can significantly influence spacecraft system performance are described. These coupling effects arise from the varied parameters of the spacecraft systems, environments, and forcing functions associated with disciplines such as thermal, structures, and controls. Adverse effects can be expected to significantly impact system design aspects such as structural integrity, controllability, and mission performance. One such needed design analysis capability is a software system that can integrate individual discipline computer codes into a highly user-oriented/interactive-graphics-based analysis capability. The integrated analysis capability (IAC) system can be viewed as: a core framework system which serves as an integrating base whereby users can readily add desired analysis modules and as a self-contained interdisciplinary system analysis capability having a specific set of fully integrated multidisciplinary analysis programs that deal with the coupling of thermal, structures, controls, antenna radiation performance, and instrument optical performance disciplines.

Jones, G. K.↗
NASA NTRS1975

Error Analysis of the Shuttle Reaction Control System Propellant Gaging Module

An investigation of the Shuttle Reaction Control System (RCS) propellant gaging module has revealed that the gaging errors due to the combined effects of random instrumentation measurement errors and propellant loading uncertainties are non-linear over the range of the propellant quantity gage (0-100%), with the largest error occurring at the zero point. When the RCS propellant tanks are filled to contain 100% of the maximum usable propellant, the largest gaging error was determined to be 3.9% for the fuel and 5.4% for the oxidizer. When the RCS propellant tanks initially contain 50% of the maximum usable propellant, the largest gaging error increases to 4.0% for the fuel and 5.6% for the oxidizer.

Duhon, D. D.↗
NASA NTRS1989

Pulse modulated control synthesis for a flexible spacecraft

The describing function method is employed for the nonlinear control analysis and design of a flexible spacecraft equipped with pulse modulated reaction jets. The method provides a means of characterizing the pulse modulator in terms of its gain and phase for structural mode limit cycle analysis. Although the describing function method is inherently inexact and is not widely used in practice, a new way of utilizing it for practical control design problems is presented. It is shown that the approximations inherent in the method can be accounted as a modeling uncertainty for the nonlinear control robustness analysis. The pulse modulated control system of the Intelsat 5 spacecraft is used as an example to illustrate the concept and methodology developed in the paper. The nonlinear stability margins predicted by the describing function analysis are verified from nonlinear simulations.

Anthony, Tobin C.↗
NASA NTRS1972

Reaction control system helium pressure regulator filter failure

The failure analysis of the command module reaction control system helium pressure regulators revealed that the filter element end caps were bulged by the helium pressure surge during activation. Some end caps may bulge and also some wire separation may occur during command module reaction control system activations; however, system performance should not be affected. The reaction control system design is acceptable and no change in hardware, system, or activation procedures is required.

Source record↗
NASA NTRS1989

Requirements for implementing real-time control functional modules on a hierarchical parallel pipelined system

Analysis of a robot control system leads to a broad range of processing requirements. One fundamental requirement of a robot control system is the necessity of a microcomputer system in order to provide sufficient processing capability.The use of multiple processors in a parallel architecture is beneficial for a number of reasons, including better cost performance, modular growth, increased reliability through replication, and flexibility for testing alternate control strategies via different partitioning. A survey of the progression from low level control synchronizing primitives to higher level communication tools is presented. The system communication and control mechanisms of existing robot control systems are compared to the hierarchical control model. The impact of this design methodology on the current robot control systems is explored.

Wheatley, Thomas E.↗