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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 415 records · Page 23

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NASA NTRS1973

Development costs for a nuclear electric propulsion stage.

Development costs are presented for an unmanned nuclear electric propulsion (NEP) stage based upon a liquid metal cooled, in-core thermionic reactor. A total of 120 kWe are delivered to the thrust subsystem which employs mercury ion engines for electric propulsion. This study represents the most recent cost evaluation of the development of a reactor power system for a wide range of nuclear space power applications. These include geocentric, and outer planet and other deep space missions. The development program is described for the total NEP stage, based upon specific development programs for key NEP stage components and subsystems.

Mondt, J. F.↗

NASA NTRS1974

Nuclear electric propulsion stage requirements and description

The application of a nuclear electric propulsion (NEP) stage in the exploration of near-earth, cometary, and planetary space was discussed. The NEP stage is powered by a liquid-metal-cooled, fast spectrum thermionic reactor capable of providing 120 kWe for 20,000 hours. This power is used to drive a number of mercury ion bombardment thrusters with specific impulse in the range of 4000-5000 seconds. The NEP description, characteristics, and functional requirements are discussed. These requirements are based on a set of five coordinate missions, which are described in detail. These five missions are a representative part of a larger set of missions used as a basic for an advanced propulsion comparison study. Additionally, the NEP stage development plan and test program is outlined and a schedule presented.

Mondt, J. F.↗

NASA NTRS1973

Trajectory analysis for solar electric propulsion stage /SEPS/ planetary missions

This paper summarizes a portion of the planetary mission analysis results of past and present studies conducted by Rockwell International for NASA-MSFC (Contract NAS8-27360) dealing with the feasibility of a Solar Electric Propulsion Stage (SEPS). The SEPS is envisioned as an upper stage of a transportation system capable of delivering either separable payload spacecraft or attached science packages to various planetary targets. The purpose of the paper is to demonstrate that, from a payload performance capability standpoint, a common SEP Stage can deliver various payloads to a host of planetary targets including inner and outer planets, asteroids, and comets.

Dazzo, E. J.↗

NASA NTRS1973

A nonlinear programming approach for optimizing two-stage lifting vehicle ascent to orbit

An optimal atmospheric flight branched trajectory-shaping capability is presented based on the Davidon-Fletcher-Powell variable metric parameter optimization technique. Gradient information is generated using finite difference methods. A typical atmospheric flight branched optimization problem is analyzed which requires the determination of 31 parameters. This parameter set includes the three-dimensional description of vehicle attitude control angles for three branches of flight: first-stage ascent, second-stage ascent, and first-stage flyback. The important inflight inequality contraints required to maintain the integrity of the vehicles are considered. Some of the numerical methods employed are discussed, along with several new auxiliary techniques developed to improve the compatibility of the numerical gradient and iterator.

Kamm, J. L.↗

NASA NTRS1974

Aerodynamic performance of 0.5 meter-diameter, 337 meter-per-second tip speed, 1.5 pressure-ratio, single-stage fan designed for low noise aircraft engines

Overall and blade-element aerodynamic performance of a 0.271-scale model of QF-1 are presented, examined, and then compared and evaluated with that from similar low noise fan stage designs. The tests cover a wide range of speeds and weight flows along with variations in stator setting angle and stator axial spacing from the rotor. At design speed with stator at design setting angle and a fixed distance between stage measuring stations, there were no significant effects of increasing the axial spacing between rotor stator from 1.0 to 3.5 rotor chords on stage overall pressure ratio, efficiency or stall margin.

Gelder, T. F.↗

NASA NTRS1975

Scout fourth stage attitude and velocity control (AVC) system feasibility study

The feasibility of incorporating a guidance system in the Scout fourth stage to achieve a significant improvement in expected payload delivery accuracy is studied. The technical investigations included the determination of the AVC equipment performance requirements, establishment of qualification and acceptance test levels, generation of layouts illustrating design approaches for the upper D and payload transition sections to incorporate the hardware, and the preparation of a vendor bid package. Correction concepts, utilizing inertial velocity and attitude, were identified and evaluated. Fourth stage attitude adjustments as determined from inertial velocity variation through the first three stages and a final velocity correction based upon the measured in-plane component errors at injection were employed. Results show radical reductions in apogee-perigee deviations.

Byars, L. B.↗

NASA NTRS1975

SERV - A reusable single stage to orbit space shuttle concept

Feasibility studies were made on the SERV (Single-stage Earth-orbital Reusable Vehicle), which is a single-stage, fully reusable space shuttle concept. The studies show that a reusable single-stage-to-orbit shuttle can be built using present technology. The SERV satisfies all of NASA's requirements for low earth orbital and space station resupply missions. The baseline vehicle has a modified Apollo external configuration, 90 ft in diameter and 66 ft in height, with a cargo hold 23 ft in diameter and 60 ft long. Take-off is vertical, powered by an integral aerospike rocket engine. An Apollo-type ballistic reentry profile is used, and precision vertical landing is possible with power provided by an array of turbojet engines. The key feasibility issues discussed are engine performance, aerodynamic drag, subsystem weights, method and type of thermal protection during reentry, descent aerodynamic characteristics, and landing method.

Tharratt, C. E.↗

NASA NTRS1975

An optimized output stage for MOS integrated circuits

An output device for optimizing propagation delay and minimizing chip area is described. An optimum means of tapering the output stages to minimize propagation delay is determined. The minimum delay is a function of the capacitive load to node ratio, the number of output stages, and the interstage propagation delay. The effects on area are also presented. A figure of merit which is a function of area and propagation time is defined which is of use in designing output stages. An optimum exists which can be considered the best compromise between further decreasing propagation delay and increasing chip area. Data are also presented which allow a designer to determine the minimum chip area once the capacitive load and the maximum allowable delay are known.

Lin, H. C.↗

NASA NTRS1976

Performance of inlet stage of transonic compressor

The overall and blade-element performances are presented over the stable flow operating range of the stage at the design tip speed of 426 m/sec. Stage peak efficiency of 0.83 was obtained at a weight flow of 28.8 kg/sec and a pressure ratio of 1.52. The stall margin for the stage was 8 percent based on weight flow and pressure ratio at peak efficiency and stall. The rotor appears to be stalling prematurely as evidenced by high rotor tip losses.

Urasek, D. C.↗

NASA NTRS1976

Performance of a low-pressure fan stage with reverse flow

The reverse flow aerodynamic performance of a 51-centimeter-diameter fan stage is presented. The stage was tested with the variable pitch rotor blades set through feather at -75 deg, -80 deg, and -85 deg from design setting angle. Of the three tested the stage with the rotor blades set at -75 deg exhibited the highest pressure ratio and highest flow. For all three configurations, there was little or no flow in the inner third of the exit passage due to the rotor blade being almost perpendicular to the axial direction in the hub region.

Moore, R. D.↗

NASA NTRS1976

Aerodynamic Performance of Two Variable-Pitch Fan Stages

The NASA-Lewis Research Center is investigating a variety of fan stages applicable for short haul aircraft. These low-pressure-ratio low-speed fan stages may require variable-pitch rotor blades to provide optimum performance for the varied flight demands and for thrust reversal on landing. A number of the aerodynamic and structural compromises relating to the variable-pitch rotor blades are discussed. The aerodynamic performance of two variable-pitch fan stages operated at several rotor blade setting angles for both forward and reverse flow application are presented. Detailed radial surveys are presented for both forward and reverse flow.

Moore, R. D.↗

NASA NTRS1975

Two-stage, low noise advanced technology fan. Volume 2: Aerodynamic data

Aerodynamic data from static tests of a two-stage advanced technology fan designed to minimize noise are presented. Fan design conditions include delivery of 209.1kg/sec/sq m (42.85 lbm/sec/sq ft) specific corrected flow at an overall pressure ratio of 1.9 and an adiabatic efficiency of 85.3 percent. The 0.836m (2.74ft) diameter first stage rotor has a hub/tip ratio of 0.4 and 365.8m/sec (1200ft/sec) design tip speed. In addition to the moderate tip speed and pressure rise per stage, other noise control design features involve widely spaced blade rows and proper selection of blade-vane ratios. Aerodynamic data are presented for tests with unifrom and with hub and tip radially distorted inlet flow. Aerodynamic data are also presented for tests of this fan with acoustic treatments, including acoustically treated casing walls, a flowpath exit acoustic ring, and a translating centerbody sonic inlet device. A complete tabulation of the overall performance data, the blade element data, and the power spectral density information relating to turbulence levels generated by the sonic inlet obtained during these tests is included. For vol. 1, see N74-33789.

Harley, K. G.↗

NASA NTRS1975

Two-stage, low noise advanced technology fan. 5: Acoustic final report

The NASA Q2S(quiet two-stage) fan is a 0.836m (32.9 in.) diameter model of the STF 433 engine fan, selected in a 1972 study for an Advanced Technology Transport (ATT) airplane. Noise-control features include: low tip speed, moderate stage pressure rise, large blade-vane spacings, no inlet guide vanes, and optimum blade and vane numbers. Tests were run on the baseline Q2S fan with standard inlet and discharge ducts. Further tests were made of a translating centerbody sonic inlet device and treated discharge ducts. Results were scaled to JT8D and JT3D engine fan size for comparison with current two-stage fans, and were also scaled to STF 433 fan size to compare calculated ATT flyover noise with FAR 36 limits. Baseline Q2S results scaled to JT8D and JT3D engine fan sizes showed substantial noise reductions. Calculated unsuppressed baseline ATT flyovers averaged about 2.5 EPNdB below FAR 36 limits. Using measured sonic inlet results, scaled baseline Q2S fan results, and calculated attenuations for a 1975 technology duct liner, projected flyover noise calculations for the ATT averaged about FAR 36 limits minus 10 EPNdB. Advances in suppression technology required to meet the 1985 goal of FAR 36 limits minus 20 EPNdB are discussed.

Sofrin, T. G.↗

NASA NTRS1976

Aerodynamic performance of a 1.20-pressure ratio fan stage designed for low noise

The aerodynamic design and the overall blade element performance of a 51 centimeter diameter fan stage is presented. The stage was designed to minimize the noise generated by rotor stator interactions. The design pressure ratio was 1.20 at a flow of 30.6 kilograms per second and a rotor blade tip speed of 228.6 meters per second. At design speed the rotor peak efficiency was 0.935. The peak efficiency of the stage, however, was 0.824. The radial distribution of rotor performance parameters at peak efficiency and design speed indicated excellent agreement with design values.

Lewis, G. W., Jr.↗

NASA NTRS1976

Numerical solution of periodic transonic flow through a fan stage

A numerical method of solution of the inviscid, compressible, two-dimensional unsteady flow on a blade-to-blade stream surface through a stage (rotor and stator), or a single blade row, of an axial flow compressor or fan is described. A cyclic procedure has been developed for representation of adjacent blade-to-blade passages, which asymptotically achieves the correct phase between all passages of a stage. A shock-capturing finite-difference method is employed in the interior of the passage, and a method-of-characteristics technique is used at the boundaries. The blade slipstreams form two of the passage boundaries, and are treated as moving contact surfaces capable of supporting jumps in entropy and tangential velocity. The Kutta condition is imposed by requiring the slipstreams to originate at the trailing edges, which are assumed to be sharp. Results are presented for several transonic fan rotors, and compared with available experimental data consisting of holographic observations of shock structure and pressure contour maps. A subcritical stator solution is also compared with results from a relaxation method. Finally, a periodic solution for a stage consisting of 44 rotor blades and 46 stator blades is discussed.

Erdos, J. I.↗

NASA NTRS1976

Aerodynamic performance of two variable-pitch fan stages

NASA-Lewis Research Center is investigating a variety of fan stages applicable for short-haul aircraft. These low-pressure-ratio low-speed fan stages may require variable-pitch rotor blades to provide optimum performance for the varied flight demands and for thrust reversal on landing. A number of the aerodynamic and structural compromises relating to variable-pitch rotor blades are discussed. The aerodynamic performance of two variable-pitch fan stages operated at several rotor-blade setting angles is evaluated for both forward- and reverse-flow application. Detailed radial surveys are presented for both forward and reverse flow.

Moore, R. D.↗

NASA NTRS1977

Assessment of Relative Velocity as Independent Variable for Space Shuttle First Stage Guidance Attitude Command Tables

The selection of relative velocity as the independent variable for the space shuttle first stage guidance attitude command tables was assessed to support the first stage guidance point design. The criterion for selecting the independent variable for first stage open loop guidance is to reduce or minimize performance dispersions, primarily those affecting structural loads. The products of angle of attack and angle of sideslip times dynamic pressure are used as load indicators, and minimizing their dispersions will indicate a minimum loads dispersion. Relative velocity is shown to be an acceptable steering independent variable.

Kimbrough, M.↗

NASA NTRS1977

Small-size 81- to 83.5-percent efficient 2- and 4-stage depressed collectors for octave-bandwidth high-performance TWT's

In a joint USAF-NASA Program, Lewis Research Center is carrying out an efficiency improvement program on traveling wave tubes for use in electronic counter measures by applying multistage depressed collector (MDC) and spent beam refocusing techniques. In the analytic part of the effort, three-dimensional electron trajectories are computed throughout the TWT. On the experimental side, tube performance is evaluated first without the MDC; then, the spent beam is analyzed for symmetry, circularity, and velocity spread. The three-dimensional theory predicts a MDC-efficiency, at mid-band, of 81 per cent for a 2-stage MDC with symmetric, circular, and optimally refocused beams and 85.5 per cent for a 4-stage MDC. Experimental results to date have yielded MDC efficiencies of a minimum of 81 and 83 per cent for a 2- and 4-stage MDC, respectively, across a one-octave bandwidth of a 4.8 to 9.6 GHz 330-to-550-W TWT.

Kosmahl, H. G.↗