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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 1,585 records · Page 88
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Fatigue Crack Growth Threshold Testing of Metallic Rotorcraft Materials

Results are presented for a program to determine the near-threshold fatigue crack growth behavior appropriate for metallic rotorcraft alloys. Four alloys, all commonly used in the manufacture of rotorcraft, were selected for study: Aluminum alloy 7050, 4340 steel, AZ91E Magnesium, and Titanium alloy Ti-6Al-4V (beta-STOA). The Federal Aviation Administration (FAA) sponsored this research to advance efforts to incorporate damage tolerance design and analysis as requirements for rotorcraft certification. Rotorcraft components are subjected to high cycle fatigue and are typically subjected to higher stresses and more stress cycles per flight hour than fixed-wing aircraft components. Fatigue lives of rotorcraft components are generally spent initiating small fatigue cracks that propagate slowly under near-threshold cracktip loading conditions. For these components, the fatigue life is very sensitive to the near-threshold characteristics of the material.

Newman, John A.↗
NASA NTRS2014

Elastomeric Structural Attachment Concepts for Aircraft Flap Noise Reduction - Challenges and Approaches to Hyperelastic Structural Modeling and Analysis

Airframe noise is a significant part of the overall noise of transport aircraft during the approach and landing phases of flight. Airframe noise reduction is currently emphasized under the Environmentally Responsible Aviation (ERA) and Fixed Wing (FW) Project goals of NASA. A promising concept for trailing-edge-flap noise reduction is a flexible structural element or link that connects the side edges of the deployable flap to the adjacent main-wing structure. The proposed solution is distinguished by minimization of the span-wise extent of the structural link, thereby minimizing the aerodynamic load on the link structure at the expense of increased deformation requirement. Development of such a flexible structural link necessitated application of hyperelastic materials, atypical structural configurations and novel interface hardware. The resulting highly-deformable structural concept was termed the FLEXible Side Edge Link (FLEXSEL) concept. Prediction of atypical elastomeric deformation responses from detailed structural analysis was essential for evaluating feasible concepts that met the design constraints. The focus of this paper is to describe the many challenges encountered with hyperelastic finite element modeling and the nonlinear structural analysis of evolving FLEXSEL concepts. Detailed herein is the nonlinear analysis of FLEXSEL concepts that emerged during the project which include solid-section, foamcore, hollow, extended-span and pre-stressed concepts. Coupon-level analysis performed on elastomeric interface joints, which form a part of the FLEXSEL topology development, are also presented.

Sreekantamurthy, Thammaiah↗
NASA NTRSDate not supplied

Structural Sizing of a Composite Transonic Truss-Braced Wing

Accurate finite element modeling (FEM) is a vital part of the modern aircraft design process. As aircraft become increasingly complex, the time-consuming nature of detailed FEM approaches comes at a significant cost to program timeline and budget. In an effort produce modeling efforts that are sufficiently accurate and minimally costly, a proposed FEM approach and optimization scheme for a composite aircraft is explored, including a discussion of the manufacturing constraints of a highly tailored composite panel design. A high-fidelity structural model of a transonic truss-braced wing (TTBW) is generated, and the components are sized by structural optimization to satisfy buckling and strength constraints while subjected to critical maneuver loads. The structural modeling approaches and sizing of a TTBW are discussed, including details for FEM approaches, verification of an approximated FEM approach, a sizing optimization using the optimization software LS-OPT, and a manufacturing trial of integrally stiffened composite panels conducted to explore the validity of highly tailored composites as a design consideration. The results of study discussed herein indicate that the proposed FEM approach is suitable for modeling composite-construction aircraft and for use in sizing optimization. Further efforts regarding integrally stiffened composite panels will indicate the suitability of this method for the integration of highly tailored composite panels into the design and optimization process, given the manufacturability of such panels as shown here.

Finite Element↗
NASA NTRSDate not supplied

Structural Sizing of a Transonic Truss-Braced Wing

Accurate finite element modeling (FEM) is a vital part of the modern aircraft design process. As aircraft become increasingly complex, the time-consuming nature of detailed FEM approaches comes at a significant cost to program timeline and budget. In an effort produce modeling efforts that are sufficiently accurate and minimally costly, a proposed FEM approach and optimization scheme for a composite aircraft is explored, including a discussion of the manufacturing constraints of a highly tailored composite panel design. A high-fidelity structural model of a transonic truss-braced wing (TTBW) is generated, and the components are sized by structural optimization to satisfy buckling and strength constraints while subjected to critical maneuver loads. The structural modeling approaches and sizing of a TTBW are discussed, including details for FEM approaches, verification of an approximated FEM approach, a sizing optimization using the optimization software LS-OPT, and a manufacturing trial of integrally stiffened composite panels conducted to explore the validity of highly tailored composites as a design consideration. The results of study discussed herein indicate that the proposed FEM approach is suitable for modeling composite-construction aircraft and for use in sizing optimization. Further efforts regarding integrally stiffened composite panels will indicate the suitability of this method for the integration of highly tailored composite panels into the design and optimization process, given the manufacturability of such panels as shown here.

Finite Element↗
NASA NTRS2001

Computation of External Aerodynamics for a Canard Rotor/Wing Aircraft

The aerodynamic loads on a Canard Rotor/Wing vehicle are investigated using inviscid numerical simulations in order to understand the flight characteristics of the vehicle during conversion from rotor craft to fixed-wing flight. A series of numerical simulations at seven azimuthal rotor indices are presented covering a quarter turn of the rotor With symmetry arguments, these simulations produce 25 data points for a complete rotation. A Cartesian mesh approach is used to compute the flow field about a configuration with faired-over engine inlet and exhaust that matches the wind tunnel geometry. These simulations were performed using meshes with approximately nine Million Cartesian cells. To better understand the aerodynamic effects of the rotor hub on the configuration, the same set of simulations were repeated for a hub-less geometry. Overall loads for both configurations are similar but are due to somewhat different aerodynamic mechanisms.

Pandya, S. A.↗
NASA NTRS2017

Feasibility of Passive Cryogenic Cooling for Solar Powered Outer Planetary Missions

Spacescience instruments with cooled detectors require innovative thermal cooling solutions to meet science objectives. Detector sensitivity increases with decreasing temperature and low optics temperatures are often needed to reduce background photon noise. As the detector spectral range coverage increases from the visible to far infrared also requires lower detector temperatures. Increasing demands on detector performance lead to larger format detectors and higher refresh rates resulting in significant increases in power dissipation. Passive coolers rely on emissive power of radiating surfaces to reject heat to space. As the operating temperature requirements of detectors and optics decreases, the ability to reject heat to space becomes increasingly more difficult. Reducing both cooler internal parasitic and external environmental heat loads and maximizing the passive cooler field of view to space will enhance performance. While instrument heat loads and passive cooler parasitic heat loads are controlled by instrument designers, the external environmental heat loads and cooler views to space are governed by spacecraft and mission designers. Solar powered planetary missions require large arrays to generate sufficient power for spacecraft subsystems and payloads. Two or more solar array wings with cell coverage of the order of 40-80 m2 are often needed to generate sufficient power at 3-6 AU. These large arrays are typically symmetrically configured and can extend tens of meters. The arrays along with spacecraft attitude requirements near the target planetary bodies pose significant challenges for passive cooling at large AU. It is very difficult to provide a clear field of view to space for the cooler with large articulating arrays while keeping solar loads from impinging the cooler and meeting the spacecraft attitude science pointing requirements. This is counter intuitive because of the decreasing solar flux and colder planetary body temperatures at large AU. This paper presents the challenges and opportunities of passive cryogenic cooling versus active cooling for solar powered planetary missions.

Rodriguez, Jose I.↗
NASA NTRS1979

Effect of time dependent flight loads on JT9D-7 performance deterioration

The results of a modal transient analysis of the engine/aircraft system are presented. The response of the JT9D to analytically simulated vertical gusts and landings was predicted using a NASTRAN finite element mathematical model of the JT9D/747 propulsion system. The NASTRAN finite element model of the propulsion system included engine structural models of the fan, low/high pressure compressors, diffuser/turbine cases, and high/low pressure rotors, as well as nacelle models of the inlet cowl, tailcone, and wing pylon. The analysis conducted predicts that an insignificant level of JT9D-7 performance deterioration would occur due to a typical vertical gust encounter or a typical revenue service landing. Analysis of a high sink rate landing with a heavy fuel load indicates the possibility of local wear, however, the lack of an accurate dynamic rotor/seal interference model precludes an accurate quantitative evaluation of performance change for this once-per-airframe-life event.

Jay, A.↗
NASA NTRS1988

Analysis of the Space Shuttle Orbiter skin panels under simulated hydrodynamic loads

The Space Shuttle orbiter skin panels were analyzed under pressure loads simulating hydrodynamic loads to determine their capability to sustain a potential ditching and to determine pressures that typically would produce failures. Two Dynamic Crash Analysis of Structures (DYCAST) finite element models were used. One model was used to represent skin panels (bays) in the center body, while a second model was used to analyze a fuselage bay in the wing region of the orbiter. From an assessment of the DYCAST nonlinear computer results, it is concluded that the probability is extremely high that most, if not all, of the lower skin panels would rupture under ditching conditions. Extremely high pressure loads which are produced under hydrodynamic planning conditions far exceed the very low predicted failure pressures for the skin panels. Consequently, a ditching of the orbiter is not considered to have a high probability of success and should not be considered a means of emergency landing unless no other option exists.

Carden, Huey D.↗
NASA NTRS1948

Free-Spinning-Tunnel Tests of a 1/24-Scale Model of the Grumman XF9F-2 Airplane with Wing-Tip Tanks Installed

An investigation of the spin and recovery characteristics of a 1/24-scale model of the Grumman XF9F-2 airplane with wing-tip tanks installed has been conducted-in the Langley 20-foot free-spinning tunnel. The effects of control settings and movements on the erect spin and recovery characteristics of the model for a range of possible loadings of the tip tanks were determined. Spin and recovery characteristics without tanks were determined in a previous investigation. The model results indicated that the airplane spins will generally be oscillatory and that recoveries will be satisfactory for all loadings by normal recovery technique (full rudder reversal followed approximately one-half turn later by moving the elevator down). The rudder force necessary for recovery should be within the physical capability of the pilot but the elevator force may be excessive so that some type of balance or booster might be necessary, or it might be necessary to jettison the wing-tip tanks.

Berman, Theodore↗
NASA NTRS2019

Load Flow Analysis with Analytic Derivatives for Electric Aircraft Design Optimization

Many of the aircraft concepts of the future are exploring the use of hybrid-, turbo- or all-electric propulsion systems to improve performance and decrease environmental impacts. These aircraft concepts range from small rotorcraft for urban air mobility to conventional commercial transports to large blended wing body designs. Developing the conceptual design for these vehicles presents a challenge, however, as traditional aircraft design tools often were not developed to handle these unique propulsion system architectures. Previous studies on these vehicles have therefore relied on relatively simple models of the electrical transmission and distribution system. This paper presents the development of a hybrid AC-DC load flow (or power flow) analysis capability to enhance the conceptual design of these concept vehicles. Specifically, the desire was to create a load flow analysis capability within the OpenMDAO framework that is also being used to develop a set of compatible tools for rapid optimization of conceptual designs. This load flow analysis capability is unique in its flexible object-oriented structure and implementation of analytic derivatives to facilitate the use of solvers and gradient based optimization in the design process. The developed hybrid load flow analysis capability is first verified against a published 13-bus example then used to model the electrical distribution system for a turbo-electric tiltwing aircraft.

Load flow↗
DOE OSTI2016

Effect of Form of Chromium on Spinel Formation

A number of Hanford high level waste (HLW) streams contain sufficiently high concentrations of chromium for it to become the waste loading limiting component in the waste. Chromium has relatively low solubility in borosilicate glasses and leads to the formation of various crystal phases including spinels. The extent of crystal formation must be managed during melter processing to prevent operational issues and potential premature melter failure that can result from excessive accumulation of crystals in the melter. In previous work for the Department of Energy (DOE) Office of River Protection (ORP), high-waste loading glass formulations were developed for representative HLW streams that are high in chromium. Results from those studies suggested that there may be differences in the crystallization behavior between glasses prepared in crucible melts and those prepared in DuraMelter 100 (DM100) joule heated melter runs. Understanding the cause of those differences has the potential to lead to the development of methods to further increase waste loadings for high chromium HLW streams through control of the formation of chromium-bearing crystals. As noted previously, the potential causes include differences in the form of components in the batch, including the form of chromium, as well as redox effects. This report describes the results from work to elucidate the origins of the observed differences and to identify melter feed composition modifications to control the formation of chromium-bearing crystal phases. The work focused on determining the effects of the form of chromium and the concentrations of oxidants in feed batches on spinel crystallization. Also evaluated was the use of potential melter feed additives to influence the redox state of chromium in the melt and its effect on spinel crystallization. As described in the Test Plan for this work, the objectives were accomplished through a combination of crucible-scale tests, small-scale tests with additives to influence redox state, and melter tests. This work builds on previous work performed at the Vitreous State Laboratory (VSL) of The Catholic University of America (CUA) for ORP to increase the waste loadings and processing rates of HLW glass formulations.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1979

Investigation of surface fluctuating pressures on a 1/4 scale YC-14 upper surface blown flap model

Fluctuating pressures were measured at 30 positions on the surface of a 1/4-scale YC-14 wing and fuselage model during an outdoor static testing program. These data were obtained as part of a NASA program to study the fluctuating loads imposed on STOL aircraft configurations and to further the understanding of the scaling laws of unsteady surface pressure fields. Fluctuating pressure data were recorded at several discrete engine thrust settings for each of 16 configurations of the model. These data were reduced using the technique of random data analysis to obtain auto-and cross-spectral density functions and coherence functions for frequencies from 0 to 10 kHz, and cross-correlation functions for time delays from 0 to 10.24 ms. Results of this program provide the following items of particular interest: (1) Good collapse of normalized PSD functions on the USB flap was found using a technique applied by Lilley and Hodgson to data from a laboratory wall-jet apparatus. (2) Results indicate that the fluctuating pressure loading on surfaces washed by the jet exhaust flow was dominated by hydrodynamic pressure variations, loading on surface well outside the flow region dominated by acoustic pressure variations, and loading near the flow boundaries from a mixture of the two.

Pappa, R. S.↗
NASA NTRS1941

Hydrodynamic Tests of a 1/10-size Model of the Hull of the Latecoere 521 Flying Boat : NACA Model 83

A 1/10-size model of the hull of the French flying boat Latecoere 521 was tested in the NACA tank. This model is one of a series of models of the hulls of actual flying boats of both foreign and domestic type that are being tested in the NACA tank to provide information regarding the water characteristics of a variety of forms of hull and to illustrate the development of present-day types of flying boat. The lines and the offsets of the hull were obtained from the manufacturer through the Paris office of the NACA. The form of the stub-wing stabilizers was not furnished and, therefore, the model was tested without them. The model was tested free to trim at the design initial load (initial load coefficient of 0.428) and by the general method at load coefficients from 0.025 to 0.6. The spray characteristics of the model are good. The form of the bow would be particularly desirable for rough water use. The interference of the afterbody and the tail extension is excessive, causing very high resistance at high speeds. A violent vertical instability is present at trims of 4 degrees and 6 degrees with light loads and high speeds.

Olson, Roland E↗
NASA NTRS1921

Angles of Attack and Air Speeds During Maneuvers

In seeking further information as to the nature of maneuvers and as to the maneuverability characteristics of airplanes, continuous measurements of the angles of attack and air speeds at several points along the wings have been made during spins and loops. Very striking results have been obtained with reference to the rolling velocity and the distribution of load in spins and the variation of the angle of attack in loops, a surprisingly large range of angle being experienced during slow loops. The flight tests and results are fully described in this report.

Warner, E P↗
NASA NTRS2004

Crash Testing of Helicopter Airframe Fittings

As part of the Rotary Wing Structures Technology Demonstration (RWSTD) program, a surrogate RAH-66 seat attachment fitting was dynamically tested to assess its response to transient, crash impact loads. The dynamic response of this composite material fitting was compared to the performance of an identical fitting subjected to quasi-static loads of similar magnitude. Static and dynamic tests were conducted of both smaller bench level and larger full-scale test articles. At the bench level, the seat fitting was supported in a steel fixture, and in the full-scale tests, the fitting was integrated into a surrogate RAH-66 forward fuselage. Based upon the lessons learned, an improved method to design, analyze, and test similar composite material fittings is proposed.

Clarke, Charles W.↗
NASA NTRS2017

A Rigid Mid-Lift-to-Drag Ratio Approach to Human Mars Entry, Descent, and Landing

Current NASA Human Mars architectures require delivery of approximately 20 metric tons of cargo to the surface in a single landing. A proposed vehicle type for performing the entry, descent, and landing at Mars associated with this architecture is a rigid, enclosed, elongated lifting body shape that provides a higher lift-to-drag ratio (L/D) than a typical entry capsule, but lower than a typical winged entry vehicle (such as the Space Shuttle Orbiter). A rigid Mid-L/D shape has advantages for large mass Mars EDL, including loads management, range capability during entry, and human spaceflight heritage. Previous large mass Mars studies have focused more on symmetric and/or circular cross-section Mid-L/D shapes such as the ellipsled. More recent work has shown performance advantages for non-circular cross section shapes. This paper will describe efforts to design a rigid Mid-L/D entry vehicle for Mars which shows mass and performance improvements over previous Mid-L/D studies. The proposed concept, work to date and evolution, forward path, and suggested future strategy are described.

Cerimele, Christopher J.↗