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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1939

Pressure-distribution measurements on a rectangular wing with a partial-span split flap in curved flight

Pressure-distribution tests were made on the 32-foot whirling arm of the Daniel Guggenheim Airship Institute of a rectangular wing of NACA 23012 section to determine the rolling and the yawing moment due to angular velocity in yaw. The model was tested at 0 and 5 degree pitch; 0, +/- 5, and +/- 10 degrees yaw; and with no flap and with split flaps 25, 50 and 75 percent of the wing span and deflected 60 degrees. The results are given in the form of span load distributions and as calculated moment coefficients. The experimental values of rolling- and yawing-moment coefficients were in fairly close agreement with theory.

Rokus, Frank G↗
NASA NTRS1983

Analysis of unswept and swept wing chordwise pressure data from an oscillating NACA 0012 airfoil experiment. Volume 2: Data report

The analysis of the chordwise load distribution and its sensitivity to the various system parameters represents the next phase of the overall study and is the subject of the present two volume report. The present volume is a compilation of all of the time history response data obtained during the test program previously described. The data have been tabulated in the form of Fourier coefficients for reasons of compactness and for ease by the user to reproduce the unsteady component of the individual pressures and the complete (unsteady plus steady state components) integrated load results. This data volume contains the individual pressure response time histories along the chord followed by the corresponding integrated load results. A further description of these data tables can be found in the text that follows.

St.hilaire, A. O.↗
NASA NTRS1939

Free-Spinning Wind-Tunnel Tests of a Low-Wing Monoplane with Systematic Changes in Wings and Tails IV : Effect of Center-of-Gravity Location

Eight wings and three tails, covering a wide range of aerodynamic characteristics, were independently ballasted so as to be interchangeable with no change in mass distribution. For each of the 24 resulting wing-tail combinations, observations were made of the steady spin for four control settings and of recoveries for five control manipulations. The results are presented in the form of charts comparing the spin characteristics. The tests are part of a general investigation being made in the NACA free-spinning tunnel to determine the effects of systematic changes in wing and tail arrangement upon the steady-spin and the recovery characteristics of a conventional low-wing monoplane for various load distributions.

Seidman, Oscar↗
NASA NTRS1998

Modified locking thread form for fastener

A threaded fastener has a standard part with a standard thread form characterized by thread walls with a standard included angle, and a modified part complementary to the standard part having a modified thread form characterized by thread walls which are symmetrically inclined with a modified included angle that is different from the standard included angle of the standard part's thread walls, such that the threads of one part make pre-loaded edge contact with the thread walls of the other part. The thread form of the modified part can have an included angle that is greater, less, or compound as compared to the included angle of the standard part. The standard part may be a bolt and the modified part a nut, or vice versa. The modified thread form holds securely even under large vibrational forces, it permits bi-directional use of standard mating threads, is impervious to the build up of tolerances and can be manufactured with a wider range of tolerances without loss of functionality, and distributes loading stresses (per thread) in a manner that decreases the possibility of single thread failure.

Roopnarine,↗
NASA NTRS1947

Investigation of Axial-flow Fan and Compressor Rotors Designed for Three-dimensional Flow

An investigation has been conducted to determine whether three-dimensional flows may be utilized in axial-flow fan and compressor rotors so that the spanwise load distribution may be varied to obtain high pressure rise. Two rotors, one with approximately uniform and one with solid-body downstream tangential-velocity distributions, were designed and tested at the design blade angle. Radial surveys of total pressure, static pressure, and flow angle were made upstream and downstream of the test rotors through a quantity-coefficient range. Tests of the solid-body rotor were also conducted at a large value of tip clearance. The results indicated that the three-dimensional flows may be utilized with high efficiency and that the three-dimensional theory used in conjunction with two-dimensional cascade data is sufficiently accurate for design purposes. The tests also showed that the tip-clearance losses of rotors highly loaded at the tips are not excessive. The existing three-dimensional theory in simplified for and an illustrative rotor design are presented in appendixes.

Kahane, A↗
NASA NTRS2008

Damage Tolerance Testing of a NASA TransHab Derivative Woven Inflatable Module

Current options for Lunar habitat architecture include inflatable habitats and airlocks. Inflatable structures can have mass and volume advantages over conventional structures. Inflatable structures are perceived to carry additional risk because they are at a lower Technical Readiness Level (TRL) than conventional metallic structures. One of the risks associated with inflatable structures is understanding the tolerance to component damage and the resulting behavior of the system after the damage is introduced. The Damage Tolerance Test (DTT) is designed to study the structural integrity of an expandable structure during and subsequent to induced damage. The TransHab Project developed an experimental inflatable module developed at Johnson Space Center in the 1990's. The TransHab design was originally envisioned for use in Mars Transits but was also studied as a potential habitat for the International Space Station (ISS). The design of the TransHab module was based on a woven design using an Aramid fabric. Testing of this design demonstrated a high level of predictability and repeatability and good correlation with analytical predictions of stresses and deflections. Based on JSC's experience with the design and analysis of woven inflatable structures, the Damage Tolerance Test article was designed and fabricated using a woven design. The Damage Tolerance Test Article consists of a load bearing restraint layer, a bladder or gas barrier, and a structural metallic core. The test article restraint layer is fabricated from one inch wide Kevlar webbing that is woven in a basket weave pattern. Underneath the structural restraint layer is the bladder or gas barrier. For this test the bladder was required to maintain pressure for testing only and was not representative of a flight design. The bladder and structural restraint layer attach to the structural core of the module at steel bulkheads at each end. The two bulkheads are separated by a 10 foot center tube which provides the structural support for the module when in a non-inflated state as well as resists a portion of the axial load when pressurized. The longitudinal members of the structural restraint layer are attached to the bulkheads using a series of clevises that are bolted to the bulkheads. Strain gages are placed on the clevises that can measure change in load when the structural restraint is inflated. The test module is 88 inches in diameter and 120 inches in height. The objectives of the DTT are to (1) verify the structural integrity of the assembled and pressurized structure when a section of the structural restraint layer is cut by a foreign object, and (2) verify the load distribution of the structural restraint layer during pressurization, before and after the structural restraint layer is severed. For this test, a longitudinal structural restraint strap will be severed using a linear shape charge. The linear shape charge was designed specifically for this application to cut only a single longitudinal strap, while not damaging the bladder. An array of strain gages were located at the bulkhead mounted clevises where the longitudinal restraint layer straps are attached. The DTT article was inflated to 45 psig, 25% of the ultimate design pressure, and one of the one-inch wide longitudinal structural members was severed. Strain gage measurements of loading in an array of longitudinal straps were taken throughout pressurization of the module to 45 psig, before firing of the linear shape charge, and after firing of the shape charge and separation of the strap. During testing not only were the original objectives met but better than expected results occurred. This paper will discuss space inflatable structures, damage tolerance analysis, test results, and applicability to the Lunar architecture.

Edgecombe, John↗
NASA NTRS1950

Use of source distributions for evaluating theoretical aerodynamics of thin finite wings at supersonic speeds

A series of publications on the source-distribution methods for evaluating the aerodynamics of thin wings at supersonic speeds is summarized, extended, and unified. Included in the first part are the deviations of: (a) the linearized partial-differential equation for unsteady flow at a substantially constant Mach number. b) The source-distribution solution for the perturbation-velocity potential that satisfies the boundary conditions of tangential flow at the surface and in the plane of the wing; and (c) the integral equation for determining the strength and the location of sources to describe the interaction effects (as represented by upwash) of the bottom and top wing surfaces through the region between the finite wing boundary and the foremost Mach wave. The second part deals with steady-state thin-wing problems. The third part of the report approximates the integral equation for unsteady upwash and includes a solution of approximate equation. Expressions are then derived to evaluate the load distributions for time-dependent finite-wing motions.

Evvard, John C↗
NASA NTRS2001

Active Control of the Operating Temperature in a Loop Heat Pipe with Two Evaporators and Two Condensers

The operating temperature of a loop heat pipe (LHP) with multiple evaporators is a function of the total heat load, heat load distribution among evaporators, condenser temperature and ambient temperature. Because of the many variables involved, the operating temperature also showed more hystereses than an LHP with a single evaporator. Tight temperature control can be achieved by controlling its compensation chamber (CC) temperatures at the desired set point. This paper describes a test program on active control of the operating temperature in an LHP with two evaporators and two condensers. Temperature control was achieved by heating one or both CC's. Tests performed included start-up, power cycle, sink temperature cycle, CC temperature cycle, and capillary limit. Test results show that, regardless one or two CC's were heated to the set point temperature, one of CC's was always flooded with liquid. The loop could operate successfully at the desired set point temperature under most conditions, including some fast transients. At low heat loads, however, the CC temperature could suddenly increase above the set point temperature, possibly due to a sudden change of the vapor content inside the evaporator core.

Ku, Jentung↗
NASA NTRS1938

Flight and Wind-tunnel Tests of an XBM-1 Dive Bomber

Results are given of pressure-distribution measurements made in flight over the right wing cellule and the right half of the horizontal tail surfaces of a dive-bombing biplane. Simultaneous measurements were also taken of the air speed, control-surface positions, control forces, and normal accelerations during various abrupt maneuvers in vertical plane. These maneuvers consisted of push-downs and pull-ups from level flight, dives and dive pull-ups from inverted flight. Besides the pressure measurements, flight tests were made to obtain (1) wing-fabric deflections during dives and (2) variation of the minimum drag coefficient with Reynolds Number. Supplementary tests were also done in the full-scale wind tunnel to obtain the characteristics of the airplane under various propeller conditions and with various tail settings. The results indicate that: (1) by increasing the fabric deflection between pressure ribs, the span load distribution was considerably modified near the center and the wing moment relations were changed; and (2) the minimum drag was less for the idling propeller than for the propeller locked in a vertical position. The value of C(sub D sub min) was equal to K(Reynolds Number)(exp -0.03) for a range from 2,800,000 to 13,100,000.

Donely, Philip↗
NASA NTRS1951

A Comparison of the Experimental and Theoretical Loading over Triangular Wings in Sideslip at Supersonic Speeds

The results of an experimental investigation of the load distribution over two triangular wings in sideslip at Mach numbers from 1.20 to 1.79 are presented and compared with theory. The two wings tested have identical plan form, 45 degrees sweepback of the leading edge, and an aspect ratio of 4.0. One model was composed of round-nose airfoil sections and the other of sharp-nose, biconvex sections. For both wings the maximum thickness of streamwise sections was 6 percent and was located at the 30-percent chord.

DIHEDRAL - COMPLETE WING↗
NASA NTRS1990

Buckling and postbuckling behavior of square compression-loaded graphite-epoxy plates with circular cutouts

Results are presented for unidirectional (0, 10)(sub s) and (90,10)(sub s) plates, ((0/90)(sub 5)(sub s)) plates, and for aluminum plates. Results are also presented for ((+/- theta)(sub 6)(sub s)) angle-ply plates for values of theta = 30, 45, and 60 degrees. The results indicate that the change in axial stiffness of a plate at buckling is strongly dependent upon cutout size and plate orthotropy. The presence of a cutout gives rise to an internal load distribution that changes, sometimes dramatically, as a function of cutout size coupled with the plate orthotropy. In the buckled state, the role of orthotropy becomes more significant since bending in addition to membrane orthotropy is present. Most of the plates with cutouts exhibited less postbuckling stiffness than the corresponding plate without a cutout, and the postbuckling stiffness decreased with increasing cutout size. However, some of the highly orthotropic plates with cutouts exhibited more postbuckling stiffness than the corresponding plate without a cutout. These results suggest the possibility of tailoring the cutout size and the stacking sequence of a composite plate to optimize postbuckling stiffness. It was found that plates with large radius cutouts do exhibit some postbuckling strength. The results also indicate that a cutout can influence modal interaction in a plate. Specifically, results are presented that show a plate with a relatively small cutout buckling at a higher load than the corresponding plate without a cutout, due to modal interaction. Other results are presented that indicate the presence of nonlinear prebuckling deformations, due to material nonlinearity, in the angle-ply plates with theta = 45 and 60 degrees. The nonlinear prebuckling deformations are more pronounced in the plates with theta = 45 degrees and become even more pronounced as the cutout size increases. Results are also presented that show how load-path eccentricity due to improper machining of the test specimens affects the buckling behavior. Some of the plates with cutouts and eccentricity exhibited a snap-through type of buckling behavior.

Nemeth, Michael P.↗
NASA NTRS2000

Shape Measurement of Large Aerospace Structures Using Sensitivity Electrical TDR Distributed Strain Sensor

Electrical time domain reflectometry (ETDR) sensing technique can be best described as "closed-loop radar," where the information is derived from the reflections of a voltage pulse sent through a transmission medium. The ETDR sensing technique is a well-developed method and has been widely used to locate and evaluate discontinuities in long coaxial power transmission cables. The ETDR technique provides a true distributed sensing capability which can not only sense the distributed loading condition of the structure but also can pin-point the location of disturbance, such as the locations of stress concentration and structural damages. Proof-of-concept experiments have been conducted using photoelastic specimens with embedded commercial coaxial cables, i.e., RG85/U and RG174, to demonstrate the stress/strain sensing capability of ETDR sensors for structural health monitoring application. Although the test results showed that the ETDR sensor signals capture specimen deformation pattern both in bending and tension and indicate the location and type of crack damages of the photoelastic specimen; yet, the low signal-to-noise ratio of the sensor signal smears the details of the strain measurement that the ETDR signals can convey. A high-sensitivity ETDR coaxial strain sensor prototype newly developed at Clark Atlanta University will be presented. The construction of the prototype sensing cable as well as its electrical properties relevant to distributed strain sensing application will be shown in details. Test results of the sensitivity and tension responses of the ETDR signal of the prototype sensor will be presented and compared with those of commercial coaxial cables. Promising potentials of the ETDR distributed strain sensing method for shape measurement application of large aerospace structures will also be demonstrated using long slender beam with surface-bonded ETDR distributed strain sensor.

Lin, Mark W.↗
NASA NTRS1968

Shock-absorbing caster wheel is simple and compact

Compact shock-absorbing caster wheel mitigates or absorbs shock by a compressible tire which deforms into a cavity between its inner edge and the wheel hub. A tee-shaped annular ring embedded in the tire distributes loads more uniformly throughout both wheel and tire.

Kindley, R. J.↗