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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Optimal trajectories for an aerospace plane. Part 2: Data, tables, and graphs

Data, tables, and graphs relative to the optimal trajectories for an aerospace plane are presented. A single-stage-to-orbit (SSTO) configuration is considered, and the transition from low supersonic speeds to orbital speeds is studied for a single aerodynamic model (GHAME) and three engine models. Four optimization problems are solved using the sequential gradient-restoration algorithm for optimal control problems: (1) minimization of the weight of fuel consumed; (2) minimization of the peak dynamic pressure; (3) minimization of the peak heating rate; and (4) minimization of the peak tangential acceleration. The above optimization studies are carried out for different combinations of constraints, specifically: initial path inclination that is either free or given; dynamic pressure that is either free or bounded; and tangential acceleration that is either free or bounded.

Miele, Angelo↗
NASA NTRS1992

Comment paper: Workshop on Engineering Turbulence Modeling

The speaker for this paper describes and evaluates a k-epsilon model for calculating Samuel-Joubert flow. He proceeds to present both Boeing's and his positions on the state-of-the-art in this area and future goals. Finally, presented is a one equation mathematical model for calculating Samuel-Joubert flow. All results are presented in viewgraph format.

Spalart, P. R.↗
NASA NTRS1992

Advances in engineering turbulence modeling

Some new developments in two equation models and second order closure models are presented. In this paper, modified two equation models are proposed to remove shortcomings such as computing flows over complex geometries and the ad hoc treatment near the separation and reattachment points. The calculations using various two equation models are compared with direct numerical solutions of channel flows and flat plate boundary layers. Development of second order closure models will also be discussed with emphasis on the modeling of pressure related correlation terms and dissipation rates in the second moment equations. All existing models poorly predict the normal stresses near the wall and fail to predict the three dimensional effect of mean flow on the turbulence. The newly developed second order near-wall turbulence model to be described in this paper is capable of capturing the near-wall behavior of turbulence as well as the effect of three dimension mean flow on the turbulence.

Shih, T.-H.↗
NASA NTRS2002

Application of Modern Design of Experiments to CARS Thermometry in a Model Scramjet Engine

We have applied formal experiment design and analysis to optimize the measurement of temperature in a supersonic combustor at NASA Langley Research Center. We used the coherent anti-Stokes Raman spectroscopy (CARS) technique to map the temperature distribution in the flowfield downstream of an 1160 K, Mach 2 freestream into which supersonic hydrogen fuel is injected at an angle of 30 degrees. CARS thermometry is inherently a single-point measurement technique; it was used to map thc flow by translating the measurement volume through the flowfield. The method known as "Modern Design of Experiments" (MDOE) was used to estimate the data volume required, design the test matrix, perform the experiment and analyze the resulting data. MDOE allowed us to match the volume of data acquired to the precision requirements of the customer. Furthermore, one aspect of MDOE, known as response surface methodology, allowed us to develop precise maps of the flowfield temperature, allowing interpolation between measurement points. An analytic function in two spatial variables was fit to the data from a single measurement plane. Fitting with a Cosine Series Bivariate Function allowed the mean temperature to be mapped with 95% confidence interval half-widths of +/- 30 Kelvin, comfortably meeting the confidence of +/- 50 Kelvin specified prior to performing the experiments. We estimate that applying MDOE to the present experiment saved a factor of 5 in data volume acquired, compared to experiments executed in the traditional manner. Furthermore, the precision requirements could have been met with less than half the data acquired.

Danehy, P. M.↗
NASA NTRS2005

Development of the NEXT Power Processing Unit

Boeing Electron Dynamic Devices, Inc. (EDD) has designed and fabricated a breadboard version of a 6 kW power processing unit (PPU) for gridded ion thrusters. This breadboard PPU will be integrated with an engineering model 40 cm ion engine designed and tested at NASA Glenn. The results of our tests using resistive loads are reported in this paper. The PPU demonstrated efficiencies to date are higher than 95 percent for the beam supply and higher than 92 percent for the discharge supply at full power. Overall PPU efficiency is greater than 94 percent at full throttle settings.

Phelps, Thomas K.↗
NASA NTRS2005

Scramjet Development Tests Supporting the Mach 10 Flight of the X-43

The Hyper-X Project s successful third flight of the X-43 at near Mach 10 in 2004 proved the potential for airbreathing propulsion at hypersonic speeds. The engine flowpath used in the X-43 research vehicle was developed and evaluated in a systematic series of ground tests in the NASA HyPulse Shock Tunnel at conditions duplicating Mach 10 flight using a full scale height, partial width engine model of the flight engine. Tests were conducted over a range of equivalence ratios from 0.8 to 1.6 using hydrogen and a mixture of two-percent silane in hydrogen fuels. Silane gas was used as an ignition aid during the short duration of the pulse facility tests. Variation of the engine inflow conditions, pressure, temperature, and Mach number, were parametrically varied during the test entries to broaden the database over the expected uncertainty in the flight conditions. A review of the ground test technique and comparisons of the ground test pressures along with selected flight data are presented.

Rogers, R. C.↗
NASA NTRS2005

Single-String Integration Test Measurements of the NEXT Ion Engine Plume

Measurements were made of a 40 cm ion-thruster plume as part of the single-string-integration-test (SSIT) activity of Phase I of the NASA's Evolutionary Xenon Thruster (NEXT) project. The NEXT ion engine incorporates design improvements that extend NSTAR power levels and efficiencies. During SSIT, an engineering model (EM2) 40 cm engine was operated using an advanced xenon propellant system in combination with either a GRC power console or advanced power processing unit. Integral goals of the single-string phase were to characterize engine performance over the full input power range and to detail thruster operation within the specification of the NEXT throttle table. Plume diagnostics measurements of relative Xe(+) and Xe(++) currents were made using near-field and far-field ExB probes. Planar geometry faraday probes were used to obtain beam current density profiles. This paper reports on the characterization of the EM2 plume over a range of SSIT operating conditions, first with the advanced propellant management system teamed with the GRC power console and then with the power-processing unit.

Snyder, Aaron↗
NASA NTRS2004

How to Overcome Numerical Challenges to Modeling Stirling Engines

Nuclear thermal to electric power conversion carries the promise of longer duration missions and higher scientific data transmission rates back to Earth for a range of missions, including both Mars rovers and deep space missions. A free-piston Stirling convertor is a candidate technology that is considered an efficient and reliable power conversion device for such purposes. While already very efficient, it is believed that better Stirling engines can be developed if the losses inherent in current designs could be better understood. However, they are difficult to instrument and so efforts are underway to simulate a complete Stirling engine numerically. This has only recently been attempted and a review of the methods leading up to and including such computational analysis is presented. And finally it is proposed that the quality and depth of Stirling loss understanding may be improved by utilizing the higher fidelity and efficiency of recently developed numerical methods. One such method, the Ultra HI-FI technique is presented in detail.

Dyson, Rodger W.↗
NASA NTRS2007

Progress in Technology Validation of the Next Ion Propulsion System

The NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system has been in advanced technology development under the NASA In-Space Propulsion Technology project. The highest fidelity hardware planned has now been completed by the government/industry team, including a flight prototype model (PM) thruster, an engineering model (EM) power processing unit, EM propellant management assemblies, a breadboard gimbal, and control unit simulators. Subsystem and system level technology validation testing is in progress. To achieve the objective Technology Readiness Level 6, environmental testing is being conducted to qualification levels in ground facilities simulating the space environment. Additional tests have been conducted to characterize the performance range and life capability of the NEXT thruster. This paper presents the status and results of technology validation testing accomplished to date, the validated subsystem and system capabilities, and the plans for completion of this phase of NEXT development.

Benson, Scott W.↗
NASA NTRS2008

Technology Readiness of the NEXT Ion Propulsion System

The NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system has been in advanced technology development under the NASA In-Space Propulsion Technology project. The highest fidelity hardware planned has now been completed by the government/industry team, including: a flight prototype model (PM) thruster, an engineering model (EM) power processing unit, EM propellant management assemblies, a breadboard gimbal, and control unit simulators. Subsystem and system level technology validation testing is in progress. To achieve the objective Technology Readiness Level 6, environmental testing is being conducted to qualification levels in ground facilities simulating the space environment. Additional tests have been conducted to characterize the performance range and life capability of the NEXT thruster. This paper presents the status and results of technology validation testing accomplished to date, the validated subsystem and system capabilities, and the plans for completion of this phase of NEXT development. The next round of competed planetary science mission announcements of opportunity, and directed mission decisions, are anticipated to occur in 2008 and 2009. Progress to date, and the success of on-going technology validation, indicate that the NEXT ion propulsion system will be a primary candidate for mission consideration in these upcoming opportunities.

Benson, Scott W.↗
NASA NTRS2001

The Space Debris Environment for the ISS Orbit

With thirty-five planned missions over the next five years, the International Space Station (ISS) will be the focus for manned space activity. At least 6 different vehicles will transport crew and supplies to and from the nominally 400 km, 51.6 degree orbit. When completed, the ISS will be the largest space structure ever assembled and hence the largest target for space debris. Recent work at the Johnson Space Center has focused on updating the existing space debris models. The Orbital Debris Engineering Model, has been restructured to take advantage of state of the art desktop computing capability and revised with recent measurements from Haystack and Goldstone radars, additional analysis of LDEF and STS impacts, and the most recent SSN catalog. The new model also contains the capability to extrapolate the current environment in time to the year 2030. A revised meteoroid model based on the work of Divine has also been developed, and is called the JSC Meteoroid Model. The new model defines flux on the target per unit angle per unit speed, and for Earth orbit, includes the meteor showers. This paper quantifies the space debris environment for the ISS orbit from natural and anthropogenic sources. Particle flux and velocity distributions as functions of size and angle are be given for particles 10 microns and larger for altitudes from 350 to 450 km. The environment is projected forward in time until 2030.

Theall, Jeff↗
NASA NTRS2012

A Systems-Level Perspective on Engine Ice Accretion

Talk covers: (1) Problem of Engine Power Loss;(2) Modeling Engine Icing Effects; (3) Simulation of Engine Rollback; (4) Icing/Engine Control System Interaction; (5) Detection of Ice Accretion; (6) Potential Mitigation Strategies.

May, Ryan David↗
NASA NTRS2012

AeroPropulsoServoElasticity: Dynamic Modeling of the Variable Cycle Propulsion System

This presentation was made at the 2012 Fundamental Aeronautics Program Technical Conference and it covers research work for the Dynamic Modeling of the Variable cycle Propulsion System that was done under the Supersonics Project, in the area of AeroPropulsoServoElasticity. The presentation covers the objective for the propulsion system dynamic modeling work, followed by the work that has been done so far to model the variable Cycle Engine, modeling of the inlet, the nozzle, the modeling that has been done to model the affects of flow distortion, and finally presenting some concluding remarks and future plans.

Kopasakis, George↗
NASA NTRS2017

Marshall Engineering Thermosphere Model, Version MET-2007

The region of the Earth's atmosphere between about 90 and 500 km altitude is known as the thermosphere, while the region above about 500 km is known as the exosphere. For space vehicle operations, the neutral atmosphere in these regions is significant. Even at its low density, it produces torques and drags on vehicles and affects orbital lifetimes. The thermosphere density above 100 km altitude also modulates the flux of trapped radiation and orbital debris. Atomic oxygen at orbital altitudes is important because it can erode and chemically change exposed vehicle surfaces.

Suggs, R. J.↗