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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Judgments of natural and anomalous trajectories in the presence and absence of motion

Three experiments using McCloskey's curved tube problem, in which people are asked to predict the path that a ball takes when it is shot through a tube curved in a 'C' or spiral, are reported. The first experiment compared the perceptual and representational competencies of observers in recognizing the natural trajectory of the ball, and the second examined the competencies of children on this problem. The third experiment attempted to enhance the representational competence of observers by encouraging them to use a mental imagery approach to the problem. The subjects were presented with both on-going events and with static representations of the event. Men performed better than women under both these conditions, a result not attributable to formal instruction in physics. Children showed no gender effect. The use of mental imagery did not enhance performance on the static test.

Kaiser, M. K.↗
NASA NTRS1986

Experimental verification of distributed piezoelectric actuators for use in precision space structures

An analytic model for structures with distributed piezoelectric actuators is experimentally verified for the cases of both surface-bonded and embedded actuators. A technique for the selection of such piezoelectric actuators' location has been developed, and is noted to indicate that segmented actuators are always more effective than continuous ones, since the output of each can be individually controlled. Manufacturing techniques for the bonding or embedding of segmented piezoelectric actuators are also developed which allow independent electrical contact to be made with each actuator. Static tests have been conducted to determine how the elastic properties of the composite are affected by the presence of an embedded actuator, for the case of glass/epoxy laminates.

Crawley, E. F.↗
NASA NTRS1986

Thrust imbalance of solid rocket motor pairs on Space Shuttle flights

This analysis extends the investigation presented at the 17th Joint Propulsion Conference in 1981 to include fifteen sets of Space Shuttle flight data. The previous report dealt only with static test data and the first flight pair. The objective is to compare the authors' previous theoretical analysis of thrust imbalance with actual Space Shuttle performance. The theoretical prediction method, which involves a Monte Carlo technique, is reviewed briefly as are salient features of the flight instrumentation system and the statistical analysis. A scheme for smoothing flight data is discussed. The effects of changes in design parameters are discussed with special emphasis on the filament wound motor case being developed to replace the steel case. Good agreement between the predictions and the flight data is demonstrated.

Foster, W. A., Jr.↗
NASA NTRS1984

Static internal performance of single-expansion-ramp nozzles with thrust-vectoring capability up to 60 deg

An investigation has been conducted at static conditions (wind off) in the static-test facility of the Langley 16-Foot Transonic Tunnel. The effects of geometric thrust-vector angle, sidewall containment, ramp curvature, lower-flap lip angle, and ramp length on the internal performance of nonaxisymmetric single-expansion-ramp nozzles were investigated. Geometric thrust-vector angle was varied from -20 deg. to 60 deg., and nozzle pressure ratio was varied from 1.0 (jet off) to approximately 10.0.

Berrier, B. L.↗
NASA NTRS1986

Effect of port corner geometry on the internal performance of a rotating-vane-type thrust reverser

An investigation has been conducted in the static-test facility of the Langley 16-Foot Transonic Tunnel to determine the effects of reverser port geometry on the internal performance of a nonaxisymmetric rotating-vane-type thrust reverser. Thrust reverser vane positions representing a spoiled-trust (partially deployed) position and a full-reverse-thrust (fully deployed) position were tested with each port geometry variable. The effects of upstream port corner radius and wall angle on internal performance were determined. In addition, the effect of the length of a simulated cooling liner (blunt-base step) near the reverser port entrance was investigated; five different lengths were tested. All tests were conducted with no external flows, and nozzle pressure ratio was varied from 1.2 to 5.0.

Berrier, B. L.↗
NASA NTRS1987

Elastic-plastic stress concentrations around crack-like notches in continuous fiber reinforced metal matrix composites

Continuous fiber silicon-carbide/aluminum composite laminates with slits were tested statically to failure. Five different layups were examined: (0) sub 8, (0 sub 2/ + or - 45) sub s, (0/90) sub 2s), (0/ + or - 45/90 sub s), and (+ or - 45) sub 2s. Either a 9.5 or a 19 mm slit was machined in the center of each specimen. The strain distribution ahead of the slit tip was found experimentally with a series of strain gages bonded ahead of the slit tip. A three-dimensional finite element program (PAFAC) was used to predict the strain distribution ahead of the slit tip for several layups. For all layups, except the (0) sub 8, the yielding of the metal matrix caused the fiber stress concentration factor to increase with increasing load. This is contrary to the behavior seen in homogeneous materials where yielding causes the stress concentration to drop. For the (0) sub 8 laminate, yielding of the matrix caused a decrease in the fiber stress concentration. The finite element analysis predicted these trends correctly.

Johnson, W. S.↗
NASA NTRS1987

Static internal performance of a two-dimensional convergent-divergent nozzle with thrust vectoring

A parametric investigation of the static internal performance of multifunction two-dimensional convergent-divergent nozzles has been made in the static test facility of the Langley 16-Foot Transonic Tunnel. All nozzles had a constant throat area and aspect ratio. The effects of upper and lower flap angles, divergent flap length, throat approach angle, sidewall containment, and throat geometry were determined. All nozzles were tested at a thrust vector angle that varied from 5.60 tp 23.00 deg. The nozzle pressure ratio was varied up to 10 for all configurations.

Bare, E. Ann↗
NASA NTRS1987

Aircraft turbofan noise

Turbofan noise generation and suppression in aircraft engines are reviewed. The chain of physical processes which connect unsteady flow interactions with fan blades to far field noise is addressed. Mechanism identification and description, duct propagation, radiation, and acoustic suppression are discussed. The experimental techniques of fan inflow static tests are discussed. Rotor blade surface pressure and wake velocity measurements aid in the determination of the types and strengths of the generation mechanisms. Approaches to predicting or measuring acoustic mode content, optimizing treatment impedance to maximize attenuation, translating impedance into porous wall structure, and interpreting far field directivity patterns are illustrated by comparisons of analytical and experimental results. The interdependence of source and acoustic treatment design to minimize far field noise is emphasized. Areas requiring further research are discussed, and the relevance of aircraft turbofan results to quieting other turbomachinery installation is addressed.

Groeneweg, J. F.↗
NASA NTRS1987

Sound radiation from single and annular stream nozzles, with modal decomposition of in-duct acoustic power

An experimental program was carried out to study the acoustic characteristics of single and annular stream duct-nozzle systems at various flow conditions by using a refined acoustic impulse technique. In this technique, signal synthesis and signal averaging processes are incorporated to generate a desired impulsive signal from acoustic driver(s) and to eliminate background noise (flow noise) from in-duct and far field signals, respectively. The contribution of higher order modes to incident reflected and transmitted acoustic powers is accounted for by using a modal decomposition process. The annular stream terminations were tested statically at various annular stream flow velocities with no inner stream flow. The results derived from the experiments include in-duct acoustic powers, termination reflection coefficients, transmission coefficients, far field power, and acoustic dissipation.

Salikuddin, M.↗
NASA NTRS1988

Static performance of an axisymmetric nozzle with post-exit vanes for multiaxis thrust vectoring

An investigation was conducted in the static test facility of the Langley 16-Foot Transonic Tunnel to determine the flow-turning capability and the nozzle internal performance of an axisymmetric convergent-divergent nozzle with post-exit vanes installed for multiaxis thrust vectoring. The effects of vane curvature, vane location relative to the nozzle exit, number of vanes, and vane deflection angle were determined. A comparison of the post-exit-vane thrust-vectoring concept with other thrust-vectoring concepts is provided. All tests were conducted with no external flow, and nozzle pressure ratio was varied from 1.6 to 6.0.

Berrier, Bobby L.↗
NASA NTRS1985

Critical joints in large composite primary aircraft structures. Volume 2: Technology demonstration test report

A program was conducted to develop the technology for critical structural joints in composite wing structure that meets all the design requirements of a 1990 commercial transport aircraft. The results of four large composite multirow bolted joint tests are presented. The tests were conducted to demonstrate the technology for critical joints in highly loaded composite structure and to verify the analytical methods that were developed throughout the program. The test consisted of a wing skin-stringer transition specimen representing a stringer runout and skin splice on the wing lower surface at the side of the fuselage attachment. All tests were static tension tests. The composite material was Toray T-300 fiber with Ciba-Geigy 914 resin in 10 mil tape form. The splice members were metallic, using combinations of aluminum and titanium. Discussions are given of the test article, instrumentation, test setup, test procedures, and test results for each of the four specimens. Some of the analytical predictions are also included.

Bunin, Bruce L.↗
NASA NTRS1988

A static investigation of a simultaneous pitch and yaw thrust vectoring 2-D C-D nozzle

An investigation has been conducted in the static test facility of the Langley 16-Foot Transonic Tunnel to determine the internal performance and flow-turning capability of a two-dimensional convergent-divergent nozzle. Thrust vectoring in the pitch plane was provided by rotation of the divergent flaps. The exhaust stream was turned in the yaw direction by deflection of yaw flaps hinged at the end of the nozzle sidewalls. The yaw flap hinge location was varied along the divergent region of the nozzle at four locations including the exit plane and the throat plane. The three hinge locations upstream of the nozzle exit plane required the downstream corners of both upper and lower divergent flaps to be cut off to eliminate interference when the yaw flaps were deflected. Three different lengths of yaw flaps were tested at several angles of deflection. The nozzle simulated a dry power setting with an expansion ratio typical of subsonic cruise and was tested at nozzle pressure ratios from 2.0 to 7.0.

Taylor, John G.↗
NASA NTRS1988

Validating the airborne and ground based components of a differential GPS system

A differential GPS mechanization of an external data link concept under development at NASA Ames Research Center is discussed. The system is intended to evaluate the use of differential GPS to support helicopter approach operation. Analytical techniques for static testing and evaluation of the system hardware and software performance in real time are described. Several techniques that have been used to detect and rectify a specific problem encountered during the tests are dicussed. An example of flight test results using the validated system is provided.

Edwards, F. G.↗
NASA NTRS1989

Qualification Motor no. 8 (QM-8), volume 1

All inspection and instrumentation data indicate that the QM-8 static test firing conducted 20 January 1989 was successful. Ambient temperature at T-0 was 28 F. With two flights successfully accomplished, this final test in the redesigned solid rocket motor (RSRM) program certified that the design meets motor performance requirements under extreme cold conditions. This test was a prerequisite to the third flight. The entire test article was cold conditioned at 20 to 25 F for approximately 31 days to assure a maximum propellant mean bulk temperature (PMBT) of 40 F, making it the lowest PMBT in the history of the program. This extreme condition also presented the opportunity to certify critical components at low temperatures. Certification of field joint and igniter heaters, adhesive bondline integrity, flex bearing performance, flight instrumentation performance, RSRM seal performance, and LSC and nozzle plug performance was accomplished. Prior to motor ignition, the field joints were maintained between 75 to 130 F, the igniter-to-case joint was maintained between 75 to 123 F, and the case-to-nozzle joint was maintained between 75 to 120 F. QM-8 was tested with induced side loads to simulate the strut loads experienced during ignition and maximum aerodynamic loading conditions. The ability of the safe and arm device to change position from safe-to-arm and arm-to-safe was certified. Ballistics performance was certified at the lower limits. Values were within specification requirements. Nozzle performance was nominal with typical erosion. The use of Fiberite carbon-cloth phenolic was certified. The water deluge system, CO2 quench, and other test equipment performed as planned during all required test operations.

Garecht, D. M.↗
NASA NTRS1989

Static internal performance of a nonaxisymmetric vaned thrust reverser with flow splay capability

An investigation was conducted in the Static Test Facility of the Langley 16-Foot Transonic Tunnel on a dual-port, nonaxisymmetric, block-and-turn type thrust reverser model with vane cascades in the reverser ports which turned the flow in the splay direction and aided in turning the flow in the reverse direction. Splaying reverser flow is a method of delaying to lower landing ground roll speeds the reingestion of hot exhaust flow into the inlets. Exhaust flow splay can also help prevent the impingement of hot exhaust gases on the empennage surfaces when the reverser is integrated into an actual airframe. The vane cascades consisted of two sets of perpendicular vanes with a variable number of turning and splay vanes. A skewed vane box was also tested which had only one set of vanes angled to provide both turning and splay. Vane cascades were designed to provide different amounts of flow splay in the top and bottom ports. Inner doors, trim tabs, and an orifice plate all provided means of varying the port area for reverser flow modulation. The outer door position was varied as a means of influencing the flow reverse angle. Nozzle pressure ratio was varied from 1.75 to approximately 6.00.

Bangert, Linda S.↗
NASA NTRS1989

Technical Evaluation Motor 3 (TEM-3)

A primary objective of the technical evaluation motor program is to recover the case, igniter and nozzle hardware for use on the redesigned solid rocket motor flight program. Two qualification objectives were addressed and met on TEM-3. The Nylok thread locking device of the 1U100269-03 leak check port plug and the 1U52295-04 safe and arm utilizing Krytox grease on the barrier-booster shaft O-rings were both certified. All inspection and instrumentation data indicate that the TEM-3 static test firing conducted 23 May 1989 was successful. The test was conducted at ambient conditions with the exception of the field joints (set point of 121 F, with a minimum of 87 F at the sensors), igniter joint (set point at 122 F with a minimum of 87 F at sensors) and case-to-nozzle joint (set point at 114 F with a minimum of 87 F at sensors). Ballistics performance values were within specification requirements. Nozzle performance was nominal with typical erosion. The nozzle and the case joint temperatures were maintained at the heaters controlling set points while electrical power was supplied. The water and the CO2 quench systems prevented damage to the metal hardware. All other test equipment performed as planned, contributing to a successful motor firing. All indications are that the test was a success, and all expected hardware will be refurbished for the RSRM program.

Garecht, Diane↗
NASA NTRS1989

Nonlinear and snap-through responses of curved panels to intense acoustic excitation

Assuming a single-mode transverse displacement, a simple formula is derived for the transverse load-displacement relationship of a plate under in-plane compression. The formula is used to derive a simple analytical expression for the nonlinear dynamic response of postbuckled plates under sinusoidal or random excitation. The highly nonlinear motion of snap-through can be easily interpreted using the single-mode formula. Experimental results are obtained with buckled and cylindrical aluminum panels using discrete frequency and broadband excitation of mechanical and acoustic forces. Some important effects of the snap-through motion on the dynamic response of the postbuckled plates are described. Static tests were used to identify the deformation shape during snap-through.

Ng, C. F.↗