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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

A tool for modeling concurrent real-time computation

Real-time computation is a significant area of research in general, and in AI in particular. The complexity of practical real-time problems demands use of knowledge-based problem solving techniques while satisfying real-time performance constraints. Since the demands of a complex real-time problem cannot be predicted (owing to the dynamic nature of the environment) powerful dynamic resource control techniques are needed to monitor and control the performance. A real-time computation model for a real-time tool, an implementation of the QP-Net simulator on a Symbolics machine, and an implementation on a Butterfly multiprocessor machine are briefly described.

Sharma, D. D.↗
NASA NTRS1990

Numerical evaluation of the performance of active noise control systems

This paper presents a generalized numerical technique for evaluating the optimal performance of active noise controllers. In this technique, the indirect BEM numerical procedures are used to derive the active noise controllers for optimal control of enclosed harmonic sound fields where the strength of the noise sources or the description of the enclosure boundary may not be known. The performance prediction for a single-input single-output system is presented, together with the analysis of the stability and observability of an active noise-control system employing detectors. The numerical procedures presented can be used for the design of both the physical configuration and the electronic components of the optimal active noise controller.

Mollo, C. G.↗
NASA NTRS2007

Analytical Approach for Estimating Preliminary Mass of ARES I Crew Launch Vehicle Upper Stage Structural Components

In January 2004, President Bush gave the National Aeronautics and Space Administration (NASA) a vision for Space Exploration by setting our sight on a bold new path to go back to the Moon, then to Mars and beyond. In response to this vision, NASA started the Constellation Program, which is a new exploration launch vehicle program. The primary mission for the Constellation Program is to carry out a series of human expeditions ranging from Low Earth Orbit to the surface of Mars and beyond for the purposes of conducting human exploration of space, as specified by the Vision for Space Exploration (VSE). The intent is that the information and technology developed by this program will provide the foundation for broader exploration activities as our operational experience grows. The ARES I Crew Launch Vehicle (CLV) has been designated as the launch vehicle that will be developed as a "first step" to facilitate the aforementioned human expeditions. The CLV Project is broken into four major elements: First Stage, Upper Stage Engine, Upper Stage (US), and the Crew Exploration Vehicle (CEV). NASA's Marshall Space Flight Center (MSFC) is responsible for the design of the CLV and has the prime responsibility to design the upper stage of the vehicle. The US is the second propulsive stage of the CLV and provides CEV insertion into low Earth orbit (LEO) after separation from the First Stage of the Crew Launch Vehicle. The fully integrated Upper Stage is a mix of modified existing heritage hardware (J-2X Engine) and new development (primary structure, subsystems, and avionics). The Upper Stage assembly is a structurally stabilized cylindrical structure, which is powered by a single J-2X engine which is developed as a separate Element of the CLV. The primary structure includes the load bearing liquid hydrogen (LH2) and liquid oxygen (LOX) propellant tanks, a Forward Skirt, the Intertank structure, the Aft Skirt and the Thrust Structure. A Systems Tunnel, which carries fluid and electrical power functions to other Elements of the CLV, is included as secondary structure. The MSFC has an overall responsibility for the integrated US element as well as structural design an thermal control of the fuel tanks, intertank, interstage, avionics, main propulsion system, Reaction Control System (RCS) for both the Upper Stage and the First Stage. MSFC's Spacecraft and Vehicle Department, Structural and Analysis Design Division is developing a set of predicted mass of these elements. This paper details the methodology, criterion and tools used for the preliminary mass predictions of the upper stage structural assembly components. In general, weight of the cylindrical barrel sections are estimated using the commercial code Hypersizer, whereas, weight of the domes are developed using classical solutions. HyperSizer is software that performs automated structural analysis and sizing optimization based on aerospace methods for strength, stability, and stiffness. Analysis methods range from closed form, traditional hand calculations repeated every day in industry to more advanced panel buckling algorithms. Margin-of-safety reporting for every potential failure provides the engineer with a powerful insight into the structural problem. Optimization capabilities include finding minimum weight panel or beam concepts, material selections, cross sectional dimensions, thicknesses, and lay-ups from a library of 40 different stiffened and sandwich designs and a database of composite, metallic, honeycomb, and foam materials. Multiple different concepts (orthogrid, isogrid, and skin stiffener) were run for multiple loading combinations of ascent design load with and with out tank pressure as well as proof pressure condition. Subsequently, selected optimized concept obtained from Hypersizer runs was translated into a computer aid design (CAD) model to account for the wall thickness tolerance, weld land etc for developing the most probable weight of the components. The flow diram summarizes the analysis steps used in developing these predicted mass.

Aggarwal, Pravin↗
NASA NTRSDate not supplied

History, Current Operations and Management of Water Systems on the International Space Station

In November 2000, the Expedition 1 crew to the International Space Station (ISS) arrived onboard, thus beginning a 19+ year need to provide potable water to the crew, as well as water to key life support systems. For the first 8 years of ISS operations, the water systems' operations were relatively simple. It consisted of manifesting water via cargo ships or generated via the Space Shuttle fuel cells and stored on ISS to supplement the water processing systems on the Russian segment of the ISS. In 2008, the Water Processor Assembly (WPA), Urine Processor Assembly (UPA), along with a U.S. provided toilet arrived onboard, supplementing the Oxygen Generator Assembly (OGA). This new equipment, known as Regen ECLSS (Regenerative Environmental Control and Life Support Systems), provided a significant capability in recycling fluid within the ISS and minimized manifestation needs. Early in the operations of the Regen ECLSS system, it became clear that the tank capacities were under sized. This led to excessive use of costly crew time to perform water operations. In 2012, a group of ISS flight controllers and engineers proposed and developed a new system that would provide integrated water tanks that could be fully operated from Mission Control on the ground to move water around within the systems. This system has very recently been installed on the ISS and commissioning operations have occurred. This paper will provide a general history of water operations on the ISS, as new systems arrived, and new operations were required. Challenges with water balance, to both avoid overfilling the system as well as avoid running out of water, will be discussed, along with touching on the convoluted steps the Flight Control team had to perform daily to predict future water needs. Finally, the new water storage system will be discussed and the benefits it brings to ISS water operations.

Christopher A Brown↗
NASA NTRS1982

Telecommunications systems design

The general configuration of deep space telecommunication systems is reviewed with regard to the design criteria necessary to insure the integrity of the system's telemetry, command, and tracking functions. The signal to noise spectral density ratios that characterize telecommunications performance are defined in terms of the link parameters. For design control, a statistical approach to predict link performance and to assess its uncertainty is described.

Yuen, J. H.↗
NASA NTRS2012

An Update on Design Tools for Optimization of CMC 3D Fiber Architectures

Objective: Describe and up-date progress for NASA's efforts to develop 3D architectural design tools for CMC in general and for SIC/SiC composites in particular. Describe past and current sequential work efforts aimed at: Understanding key fiber and tow physical characteristics in conventional 2D and 3D woven architectures as revealed by microstructures in the literature. Developing an Excel program for down-selecting and predicting key geometric properties and resulting key fiber-controlled properties for various conventional 3D architectures. Developing a software tool for accurately visualizing all the key geometric details of conventional 3D architectures. Validating tools by visualizing and predicting the Internal geometry and key mechanical properties of a NASA SIC/SIC panel with a 3D orthogonal architecture. Applying the predictive and visualization tools toward advanced 3D orthogonal SiC/SIC composites, and combining them into a user-friendly software program.

Lang, J.↗
NASA NTRS2019

The Semiannual and 4.4-Year Modulations of Extreme High Tides

In most places extreme high tides undergo a clear seasonal variation. It is well known that semidiurnal tides tend to peak during equinox seasons, and diurnals during solstice seasons. This is a consequence of the solar and lunar declinations, which when large maximize diurnal tides at the expense of semidiurnals. The semiannual range modulation of tidal extremes for a pure semidiurnal tide is determined mainly by the amplitude of the K2 constituent; a pure diurnal is determined mainly by P1. Mixed tidal regimes tend to experience maxima very roughly around the times of solstice, but not always, with the semiannual modulation generally a complicated function of constituent amplitudes and phases. These modulations are here mapped worldwide by analyzing tidal extremes predicted with a global tide model. The known 4.4-year modulation in extreme tides is a consequence of declinational and perigean effects coming in and out of phase. The phase of the 4.4-year modulation is controlled by the phase of the semiannual modulation, irrespective of whether the tide is diurnal, semidiurnal, or mixed.

Ray, R. D.↗
NASA NTRS1995

Fluidic Control of Nozzle Flow: Some Performance Measurements

Results are presented of an experimental program that investigated the use of a secondary air stream to control the amount of flow through a convergent-divergent nozzle. These static tests utilized high pressure, ambient temperature air that was injected at the throat of the nozzle through an annular slot. Multiple injection slot sizes and injection angles were tested. The introduction of secondary flow was made in an opposing direction to the primary flow and the resulting flow field caused the primary stream to react as though the physical throat size had been reduced. The percentage reduction in primary flow rate was generally about twice the injected flow rate. The most effective throttling was achieved by injecting through the smallest slot in an orientation most nearly opposed to the approaching primary flow. Thrust edliciency, as measured by changes in nozzle thrust coefficient, was highest at high nozzle pressure ratios, NPR. The static test results agreed with predictions obtained prior from PABSD, a fully viscous computational fluid dynamics program. Since use of such an injection system on gas turbine engine exhaust nozzles would be primarily at high NPRs, it was concluded that fluidic control holds promise for reducing nozzle weight and complexity on future systems.

Federspiel, John↗
NASA NTRS1975

Prediction of unsteady aerodynamic loadings caused by leading edge and trailing edge control surface motions in subsonic compressible flow: Computer program description

A digital computer program has been developed to calculate unsteady loadings caused by motions of lifting surfaces with leading edge or trailing edge controls based on the subsonic kernel function approach. The pressure singularities at hinge line and side edges have been extracted analytically as a preliminary step to solving the integral equation by collocation. The program calculates generalized aerodynamic forces for user supplied deflection modes. Optional intermediate output includes pressure at an array of points, and sectional generalized forces. From one to six controls on the half span can be accommodated.

Redman, M. C.↗
NASA NTRS1980

An empirical propellant response function for combustion stability predictions

An empirical response function model was developed for ammonium perchlorate propellants to supplant T-burner testing at the preliminary design stage. The model was developed by fitting a limited T-burner data base, in terms of oxidizer size and concentration, to an analytical two parameter response function expression. Multiple peaks are predicted, but the primary effect is of a single peak for most formulations, with notable bulges for the various AP size fractions. The model was extended to velocity coupling with the assumption that dynamic response was controlled primarily by the solid phase described by the two parameter model. The magnitude of velocity coupling was then scaled using an erosive burning law. Routine use of the model for stability predictions on a number of propulsion units indicates that the model tends to overpredict propellant response. It is concluded that the model represents a generally conservative prediction tool, suited especially for the preliminary design stage when T-burner data may not be readily available. The model work included development of a rigorous summation technique for pseudopropellant properties and of a concept for modeling ordered packing of particulates.

Hessler, R. O.↗
NASA NTRS1981

Creep and creep rupture of laminated graphite/epoxy composites

An incremental numerical procedure based on lamination theory is developed to predict creep and creep rupture of general laminates. Existing unidirectional creep compliance and delayed failure data is used to develop analytical models for lamina response. The compliance model is based on a procedure proposed by Findley which incorporates the power law for creep into a nonlinear constitutive relationship. The matrix octahedral shear stress is assumed to control the stress interaction effect. A modified superposition principle is used to account for the varying stress level effect on the creep strain. The lamina failure model is based on a modification of the Tsai-Hill theory which includes the time dependent creep rupture strength. A linear cumulative damage law is used to monitor the remaining lifetime in each ply.

Dillard, D. A.↗
NASA NTRS1983

Stability and control over the supersonic and hypersonic speed range

The performance and aerodynamic characteristics of the Space Shuttle Columbia are analyzed over the speed range from Mach 2 to 26 using flight data taken from the first five Space Transportation System flights. These data are used to reconstruct the entry trajectory, calculate vehicle performance, and estimate lateral stability and control derivatives including those assocated with the onboard Reaction Control System. The trajectory reconstruction process is discussed in its relationship to the determination of the vehicle flight characteristics. Vehicle performance results are presented which show that lift and drag were generally overpredicted by 3 percent and that the life-to-drag ratio was underpredicted by 1 percent. Anomalies in pitching-moment trim characteristics are shown and noted to be due to real-gas and Mach-number effects. Lateral stability and control derivatives estimated using programmed test input maneuvers are corrected with preflight predictions and are usually within the uncertainties associated with the predictions. The lateral reaction-control system effectiveness is evaluated.

Compton, H. R.↗
NASA NTRS1986

Automotive Stirling engine: Mod 2 design report

The design of an automotive Stirling engine that achieves the superior fuel economy potential of the Stirling cycle is described. As the culmination of a 9-yr development program, this engine, designated the Mod 2, also nullifies arguments that Stirling engines are heavy, expensive, unreliable, demonstrating poor performance. Installed in a General Motors Chevrolet Celebrity car, this engine has a predicted combined fuel economy on unleaded gasoline of 17.5 km/l (41 mpg)- a value 50% above the current vehicle fleet average. The Mod 2 Stirling engine is a four-cylinder V-drive design with a single crankshaft. The engine is also equipped with all the controls and auxiliaries necessary for automotive operation.

Nightingale, Noel P.↗
NASA NTRS1996

Certain cardiovascular indices predict syncope in the postural tachycardia syndrome

Patients with postural tachycardia syndrome (POTS) represent a patient population with orthostatic intolerance; some are prone to syncope, others are not. The underlying neurocardiovascular mechanisms are not completely understood. The current study was undertaken to assess if certain cardiovascular indices are predictive of syncope in POTS. We compared the response to tilt-up and the Valsalva maneuver in four groups: POTS patients who fainted (POTS-f; n = 11;31 +/- 11 years): POTS patients who did not faint (POTS-nf; n = 9; 29 +/- 9 years); normal controls (NLS; n = 13; 39 +/- 11 years); patients with generalized autonomic failure with orthostatic hypotension and syncope (n = 10; 59 +/- 14 years). Beat-to-beat heart rate (HR), systolic arterial pressure, diastolic arterial pressure (DAP) and pulse pressure (PP) were monitored using Finapres. Cardiac output, stroke volume (SV) and end-diastolic volume (EDV), and calculated total peripheral resistance (TPR) were recorded using thoracic electrical bioimpedance. An autonomic reflex screen which quantitates the distribution and severity of autonomic failure was also done. With the patient supine, all POTS patients (POTS-nf; POTS-f) had increased HR (p < 0.001) and reduced SV/EDV (p < 0.001) when compared with NLS. On tilt-up, POTS-f patients were significantly different from both NLS and POTS-nf patients; the most consistent alteration was a fall instead of an increase in TPR; other changes were a greater reduction in PP, a reduction (instead of an increment) in DAP, and a different pattern of changes during the Valsalva maneuver (excessive early phase II, attenuated or absent late phase II). Our results suggest alpha-adrenergic impairment with increased pooling or hypovolemia in POTS-f patients. We conclude that it is possible to identify the mechanism of syncope in POTS patients, and perhaps other patients with orthostatic intolerance and an excessive liability to syncope.

NASA Discipline Number 14-10↗
NASA NTRS2008

Analysis of Effectiveness of Phoenix Entry Reaction Control System

Interaction between the external flowfield and the reaction control system (RCS) thruster plumes of the Phoenix capsule during entry has been investigated. The analysis covered rarefied, transitional, hypersonic and supersonic flight regimes. Performance of pitch, yaw and roll control authority channels was evaluated, with specific emphasis on the yaw channel due to its low nominal yaw control authority. Because Phoenix had already been constructed and its RCS could not be modified before flight, an assessment of RCS efficacy along the trajectory was needed to determine possible issues and to make necessary software changes. Effectiveness of the system at various regimes was evaluated using a hybrid DSMC-CFD technique, based on DSMC Analysis Code (DAC) code and General Aerodynamic Simulation Program (GASP), the LAURA (Langley Aerothermal Upwind Relaxation Algorithm) code, and the FUN3D (Fully Unstructured 3D) code. Results of the analysis at hypersonic and supersonic conditions suggest a significant aero-RCS interference which reduced the efficacy of the thrusters and could likely produce control reversal. Very little aero-RCS interference was predicted in rarefied and transitional regimes. A recommendation was made to the project to widen controller system deadbands to minimize (if not eliminate) the use of RCS thrusters through hypersonic and supersonic flight regimes, where their performance would be uncertain.

Dyakonov, Artem A.↗
NASA NTRS1978

Theory of the control of structures by low authority controllers

The novel idea presented is based on the observation that if a structure is controlled by distributed systems of sensors and actuators with limited authority, i.e., if the controller is allowed to modify only moderately the natural modes and frequencies of the structure, then it should be possible to apply root perturbation techniques to predict analytically the behavior of the total system. Attention is given to the root perturbation formula first derived by Jacobi for infinitesimal perturbations which neglect the induced eigenvector perturbation, a more general form of Jacobi's formula, first-order structural equations and modal state vectors, state-space equations for damper-augmented structures, and modal damping prediction formulas.

Aubrun, J. N.↗
NASA NTRS1981

Sources, control, and effects of noise from aircraft propellers and rotors

Source noise predictions are compared with measurements for conventional low-speed propellers, for new high speed propellers (propfans), and for a helicopter. Results from a light aircraft demonstration program are described, indicating that about 5-dB reduction of flyover noise can be obtained without significant performance penalty. Sidewall design studies are described for interior noise control in light general aviation aircraft and in large transports using propfan propulsion. The weight of the added acoustic treatment is estimated and tradeoffs between weight and noise reduction are discussed. A laboratory study of passenger response to combined broadband and tonal propeller like noise is described. Subject discomfort ratings of combined tone broadband noises are compared with ratings of broadband (boundary layer) noise alone, and the relative importance of the propeller tones is examined.

Mixson, J. S.↗
NASA NTRS1981

Sources, control, and effects of noise from aircraft propellers and rotors

Recent NASA and NASA sponsored research on the prediction and control of propeller and rotor source noise, on the analysis and design of fuselage sidewall noise control treatments, and on the measurement and quantification of the response of passengers to aircraft noise is described. Source noise predictions are compared with measurements for conventional low speed propellers, for new high speed propellers (propfans), and for a helicopter. Results from a light aircraft demonstration program are considered which indicates that about 5 dB reduction of flyover noise can be obtained without significant performance penalty. Sidewall design studies are examined for interior noise control in light general aviation aircraft and in large transports using propfan propulsion. The weight of the added acoustic treatment is estimated and tradeoffs between weight and noise reduction are discussed. A laboratory study of passenger response to combined broadband and tonal propeller-like noise is described. Subject discomfort ratings of combined tone broadband noises are compared with ratings of broadband (boundary layer) noise alone and the relative importance of the propeller tones is examined.

Mixson, J. S.↗