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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Passive Orbital Disconnect Strut (PODS 3) structural test program

A passive orbital disconnect strut (PODS-3) was analyzed structurally and thermally. Development tests on a graphite/epoxy orbit tube and S glass epoxy launch tube provided the needed data to finalize the design. A detailed assembly procedure was prepared. One strut was fabricated. Shorting loads in both the axial and lateral direction (vs. load angle and location) were measured. The strut was taken to design limit loads at both ambient and 78 K (cold end only). One million fatigue cycles were performed at predicted STS loads (half in tension, half in compression) with the cold end at 78 K. The fatigue test was repeated at design limit loads. Six struts were then fabricated and tested as a system. Axial loads, side loads, and simulated asymmetric loads due to temperature gradients around the vacuum shell were applied. Shorting loads were measured for all tests.

Parmley, R. T.↗
NASA NTRS1986

Development of Space Station strut design

Candidate Space Station struts exhibiting high stiffness (38-40 msi modulus of elasticity) were manufactured and experimentally evaluated. One and two inch diameter aluminum-clad evaluation specimens were manufactured using a unique dry fiber resin injection process. Preliminary tests were performed on strut elements having 80 percent high-modulus graphite epoxy and 20 percent aluminum. Performed tests included modulus of elasticity, thermal cycling, and coefficient of thermal expansion. The paper describes the design approach, including an analytical assessment of strut thermal deformation behavior. The major thrust of this paper is the manufacturing process which produces aluminum-clad struts with precisely controlled properties which can be fine-tuned after fabrication. An impact test and evaluation procedure for evaluating toughness is described.

Johnson, R. R.↗
NASA NTRS1990

Experimental investigation of flow about a strut-endwall configuration

An experimental study was conducted to investigate incompressible flow about a strut-endwall configuration positioned within a constant area duct. The endwal boundary layer was tripped, but natural transition occurred on the strut surface. The results indicate that spanwise varying transition on this surface leads to the formation of a secondary vortex which coexists with the horseshoe vortex generated by endwall flow separation upstream of the strut leading edge. Both vortices are similar in strength downstream of the strut trailing edge, and both distort the primary flow and local turbulence structure in the wake-endwall region. The level of distortion is demonstrated by means of axial mean velocity contours, turbulence kinetic energy contours, and Reynolds shear stress contours measured in the cross plane at two streamwise locations. Analysis of the results shows that conventional eddy viscosity and k-epsilon transport equation models are not wholly adequate for predicting this flow situation.

Chang, P. S.↗
NASA NTRS1992

Design of a D-Strut and its application results in the JPL, MIT, and LaRC test beds

High damping at very low magnitudes of vibration is provided by an 'Arched Flexure' D-Strut. Five of these devices have been incorporated in JPL's CSI truss structure, and five more in MIT's interferometer test bed. Two were also temporarily installed in the LaRC CSI test structure. Damping factors in the 50 percent category are being provided at vibration motions as small as 50 nm. The 'Arched Flexure' used in the D-Strut maximizes the volumetric stiffness parameter relative to its axial stiffness. In turn, this enables high damping factors, even in a very rigid truss structure. This paper includes a presentation and discussion of both element and system test data taken at JPL, LaRC, and MIT. Also provided is a detailed description of the D-Strut, the dynamic model, and several graphs showing design parameter variations that will make it possible to evaluate the D-Strut for other applications.

Davis, L. P.↗
NASA NTRS1992

A variable stiffness strut using strain induced bending for vibration suppression in the evolutionary model

A new piezoceramic strut has been developed. This strut utilizes strain induced bending as a means of actuation. The significance of this design is that the displacement of the strut's motion arm is independent of the expansion of the piezoceramic material. Design criteria was developed using continuous and finite element modeling techniques. Experimental and analytical results were compared. Finally, a numerical analysis was conducted that demonstrated the benefits of the piezoceramic strut configuration.

Pokines, Brett↗
NASA NTRS1993

Composite passive damping struts for large precision structures

In the field of viscoelastic dampers, a new strut design comprises a viscoelastic material sandwiched between multiple layers, some of which layers bear and dampen load force. In one embodiment, the layers are composite plies of opposing orientation. In another embodiment, the strut utilizes a viscoelastic layer sandwiched between V-shaped composite plies. In a third embodiment, a viscoelastic layer is sandwiched between sine-shaped plies. Strut strength is equal to or greater than conventional aluminum struts due to the unique high interlaminar shear ply design.

Dolgin, Benjamin P.↗
NASA NTRS1923

Wind tunnel tests of five strut sections in yaw

In the first series of wind tunnel tests, the drag and cross wing force of all the struts were measured at a wind speed of 30 mph and at angles of yaw from 0 degrees to 20 degrees. To determine the magnitude of the VL effect, each strut was tested at zero yaw and at a series of speeds ranging from 15 to 38 mph. Although designed as fairings for cables, part of these sections gave such high crosswind forces that they seemed to have possibilities as airfoils. Therefore, the lift (identical with the crosswind force) and drag coefficients were recalculated for four sections on the basis of broadside area to make them comparable with wing coefficients. The general conclusion that the best fineness ratio for a strut is a function of the Reynolds number, decreasing steadily as that quality increases, has of course been reached many times, both by theory and experiment. It was confirmed here once more, and the effect of form on sensitiveness to VL is also strikingly shown. It seems probable that this effect of form is largely due to interaction between the nose and tail, and to the influence which the form of the nose exerts over the whole flow around the strut.

PROPELLERS, METAL↗
NASA NTRS1931

Interference Effects and Drag of Struts on a Monoplane Wing

Tests were conducted in the Variable Density Wind Tunnel of the NACA to determine the importance of the interference effects and drag of struts on a monoplane. Inclined struts were placed upon a Gottingen 387 airfoil in the lower surface positions and in two upper surface positions. Tests were made at values of Reynolds Number comparable with those obtained in flight. It was found that the interference drag of struts may be as great as the drag of the struts alone.

Ward, Kenneth E↗
NASA NTRS1930

Aerodynamic Theory and Tests of Strut Forms-II

This report presents the second of two studies under the same title. In this part five theoretical struts are developed from distributed sources and sinks and constructed for pressure and resistance tests in a wind tunnel. The surface pressures for symmetrical inviscid flow are computed for each strut from theory and compared with those found by experiment. The theoretical and experimental pressures are found to agree quantitatively near the bow, only qualitatively over the suction range, the experimental suctions being uniformly a little low, and not at all near the stern. This study is the strut sequel to Fuhrmann's research on airship forms, the one being a study in two dimensions, the other in three. A comparison of results indicates that the agreement between theory and experiment is somewhat better for bodies of revolution than for cylinders when both are shaped for slight resistance. The consistent deficiency of the experimental suctions which is found in the case of struts was not found in the case of airships, for which the experimental suctions were sometimes above sometimes below their theoretical values.

Smith, R H↗
NASA NTRS1994

The reduction of takeoff ground roll by the application of a nose gear jump strut

A series of flight tests were conducted to evaluate the reduction of takeoff ground roll distance obtainable from a rapid extension of the nose gear strut. The NASA Quiet Short-haul Research Aircraft (QSRA) used for this investigation is a transport-size short take off and landing (STOL) research vehicle with a slightly swept wing that employs the upper surface blowing (USB) concept to attain the high lift levels required for its low-speed, short-field performance. Minor modifications to the conventional nose gear assembly and the addition of a high-pressure pneumatic system and a control system provided the extendable nose gear, or jump strut, capability. The limited flight test program explored the effects of thrust-to-weight ratio, wing loading, storage tank initial pressure, and control valve open time duration on the ground roll distance. The data show that a reduction of takeoff ground roll on the order of 10 percent was achieved with the use of the jump strut, as predicted. Takeoff performance with the jump strut was also found to be essentially independent of the pneumatic supply pressure and was only slightly affected by control valve open time within the range of the parameters examined.

Eppel, Joseph C.↗
NASA NTRS1994

Flight investigation of the use of a nose gear jump strut to reduce takeoff ground roll distance of STOL aircraft

A series of flight tests was conducted to evaluate the reduction of takeoff ground roll distance obtainable from a rapid extension of the nose gear strut. The NASA Quiet Short-haul Research Aircraft (QSRA) used for this investigation is a transport-size short takeoff and landing (STOL) research vehicle with a slightly swept wing that employs the upper surface blowing (USB) concept to attain the high lift levels required for its low speed, short-field performance. Minor modifications to the conventional nose gear assembly and the addition of a high pressure pneumatic system and a control system provided the extendible nose gear, or 'jump strut,' capability. The limited flight test program explored the effects of thrust-to-weight ratio, storage tank initial pressure, and control valve open time duration on the ground roll distance. The data show that the predicted reduction of takeoff ground roll on the order of 10 percent was achieved with the use of the jump strut. Takeoff performance with the jump strut was also found to be essentially independent of the pneumatic supply pressure and was only slightly affected by control valve open time within the range of the parameters examined.

Eppel, Joseph C.↗
NASA NTRS2002

Finite Element Modeling of Deployment, and Foam Rigidization of Struts and Quarter Scale Shooting Star Experiment

Inflated cylindrical struts constructed of kapton polyimide film and rigidized with foam have considerable practical application and potential for use as components of inflatable concentrator assemblies, antenna structures and space power systems, Because of their importance, it is of great interest to characterize the dynamic behavior of these components and structures both experimentally and analytically. It is very helpful to take a building-block approach to modeling and understanding inflatable assemblies by first investigating in detail the behavior of the components such as the struts. The foam material used for rigidization of such cylinders has varying modulus, which is a function of different factors, such as density of the foam. Thus, the primary motivation of the tests and analytical modeling efforts was to determine and understand the response of foam-rigidized cylinders for different densities, sizes, and construction methods. In recent years, inflatable structures have been the subject of renewed interest for space applications such as communications antennae, solar thermal propulsion, and space solar power. A major advantage of using inflatable structures in space is that they are extremely lightweight. This makes inflatables a perfect match for solar thermal propulsion because of the low thrust levels available. An obvious second advantage is on-orbit deployability and subsequent space savings in launch configuration. It can be seen that inflatable cylindrical struts and torus are critical components of structural assemblies. In view of this importance, structural dynamic and static behaviors of typical rigidized polyimide struts are investigated in this paper. The paper will focus on the finite element models that were used to model the behavior of the complete solar collector structure, and the results that they provided, as compared to test data.

Larry Leigh, Jr.↗
NASA NTRS1997

MEASUREMENT OF THE NOISE IMPROVEMENT OF A 34-METER CASSEGRAIN ANTENNA RETROFITTED WITH A LOW-BACKSCATTERING STRUT

Large axially-symmetric ground-based dual-reflector antennas are used in a variety of applications simultaneously requiring very high gain and very low noise (e.g., satellite communications, radio astronomy, deep-space communications, and radar). In these systems, reducing the noise by 10 % is equivalent to increasing the antenna gain by roughly 0.5 dB. Since the early days of radio-astronomy this fact has continuously driven efforts to reduce the noise of front-end low-noise amplifiers--a major noise contributor. As the performance of the front-end amplifiers improved, the relative importance of the noise generated by the surrounding warm ground increased, causing the antenna noise to become a major factor in the overall system sensitivity. Since large ground-based reflectors have been around for several decades, the various electrical and mechanical parameters affecting their performance have received considerable attention and are generally well understood. However, the impact of the subreflector supporting struts on the antenna noise performance remains a source of uncertainty. The reason for this stems from the usually large electrical dimensions involved, which precludes the accurate modeling of the various strut-scattering mechanisms. For the particular antennas used on NASA's Deep Space Network, which have been designed to minimize all noise sources, several studies have typically reported measured noise temperatures between 2 and 3 K (at approx. 8.45 GHz, antenna pointing at zenith), attributed to the struts and other unknown effects (see for example [1] and [2]). With this in mind, an effort has recently been conducted to determine optimal strut shapes to reduce the associated noise contribution [3].

Prata, A., Jr.↗
NASA NTRS2008

Gas Strut Separation Alternative for Ares I

This paper presents a design alternative and the rationale for a stage separation system based on Metering Adiabatic Gas Struts (MAG Struts) for the Ares 1 launch vehicle. The MAG Strut separation system was proposed as an alternative to the current Ares 1 separation system, which relies on small solid rocket motors to provide the main separation force. This paper will describe technical issues that were addressed during the trade study and present a conceptual design of the strut system that best resolved the issues. Needed development testing and programmatic considerations will be addressed as part of the paper.

Floyd, Brian↗
NASA NTRS2009

Designing Struts for the Low-Fidelity Orion Cockpit Mockup

The objective of the project was to design and construct nine struts to be installed in the low-fidelity Orion cockpit mockup (Rev F; located at NASA s Johnson Space Center in Houston, TX) as simplified representations of the existing flight designed struts designed by engineers at Lockheed Martin (the primary contractor of the Orion). The project design included: researching the existing flight designs, brainstorming design upgrades, developing three unrelated three-dimensional (3D) strut designs using Pro/Engineer Wildfire 3.0, choosing the best fit design, locating materials and their sources, implementing the chosen design, and making design modifications. The project resulted in making simple modifications to the existing struts used in the last Orion cockpit mockup. The project is relevant to NASA, because upgrades to the low-fidelity Orion cockpit mockup progresses NASA s goals of developing and testing a new spacecraft, conducting the spacecraft's first crewed mission by 2015, returning to the moon by 2020, and exploring Mars and other planets in the future.

Lucienne, Runa A.↗
NASA NTRS2011

Highly Loaded Composite Strut Test Results

Highly loaded composite struts from a proposed truss-based Altair lunar lander descent stage concept were selected for development under NASA's Advanced Composites Technology program. Predicted compressive member forces during launch and ascent of over -100,000 lbs were much greater than the tensile loads. Therefore, compressive failure modes, including structural stability, were primary design considerations. NASA's industry partner designed and built highly loaded struts that were delivered to NASA for testing. Their design, fabricated on a washout mandrel, had a uniform-diameter composite tube with composite tapered ends. Each tapered end contained a titanium end fitting with facing conical ramps that are overlaid and overwrapped with composite materials. The highly loaded struts were loaded in both tension and compression, with ultimate failure produced in compression. Results for the two struts tested are presented and discussed, along with measured deflections, strains and observed failure mechanisms.

Wu, K. C.↗
NASA NTRS2023

Elastic Modulus Testing for TriTruss Struts

The TriTruss is a novel structural module developed by researchers at NASA Langley Research Center (LaRC) that can be used in space to assemble large backing structures for a variety of applications. One such application is the metering truss and primary mirror backbone support structure of an in-space assembled telescope(iSAT). For the iSAT application, the TriTruss will be supporting mirror segments, payloads, and instruments, all of which require the TriTruss to have robust structural integrity. An accurate elastic modulus value is crucial to the finite element analysis(FEA) of the structure. Initial testing indicated that the equivalent elastic modulus provided by the manufacturer and used in the analyses did not accurately predict the behavior of the structure. In this paper, the in-house testing method developed at LaRC to accurately measure the equivalent elastic modulus of the composite struts for use in the analyses is described. A tensile and compressive equivalent elastic modulus was computed from the data obtained in this test. The testing resulted in a tensile equivalent elastic modulus of 24.6 Msi (standard deviation of 0.888 Msi) or 169 GPa (standard deviation of 6.20 GPa) and a compressive equivalent elastic modulus of 22.8 Msi (standard deviation of 0.780 Msi) or 157 GPa(standard deviation of 5.38 GPa) for the single wall thickness struts. For double wall thickness struts, the testing resulted in a tensile equivalent elastic modulus of32.1 Msi (standard deviation of 1.003 Msi) or 221 GPa (standard deviation of 6.91GPa) and a compressive equivalent elastic modulus of 31.9 Msi (standard deviation of 1.123) or 220 GPa (standard deviation of 7.74 GPa).1

TriTruss↗
NASA NTRS1974

Bonded composite to metal scarf joint performance in an aircraft landing gear drag strut

The structural performance of a boron-epoxy reinforced titanium drag strut, which contains a bonded scarf joint and was designed to the criteria of the Boeing 747 transport, was evaluated. An experimental and analytical investigation was conducted. The strut was exposed to two lifetimes of spectrum loading and was statically loaded to the tensile and compressive design ultimate loads. Throughout the test program no evidence of any damage in the drag strut was detected by strain gage measurements, ultrasonic inspection, or visual observation. An analytical study of the bonded joint was made using the NASA structural analysis computer program NASTRAN. A comparison of the strains predicted by the NASTRAN computer program with the experimentally determined values shows excellent agreement. The NASTRAN computer program is a viable tool for studying, in detail, the stresses and strains induced in a bonded joint.

Howell, W. E.↗