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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Advanced general aviation propeller study

Methods for predicting the performance, noise, weight, and cost of propellers for advanced general aviation aircraft of the 1980 time period were developed and computerized. This basic program was refined to incorporate a method of including the blade shape parameter, integrated design lift coefficient. This method and a reverse thrust computational procedure were included in the computer program. The weight equation was refined and also incorporated in the computer program. A User's Manual which includes a complete listing of this computer program with detailed instructions on its use has been written.

Worobel, R.↗
NASA NTRS2000

An Enhanced Multi-Objective Optimization Technique for Comprehensive Aerospace Design

An enhanced multiobjective formulation technique, capable of emphasizing specific objective functions during the optimization process, has been demonstrated on a complex multidisciplinary design application. The Kreisselmeier-Steinhauser (K-S) function approach, which has been used successfully in a variety of multiobjective optimization problems, has been modified using weight factors which enables the designer to emphasize specific design objectives during the optimization process. The technique has been implemented in two distinctively different problems. The first is a classical three bar truss problem and the second is a high-speed aircraft (a doubly swept wing-body configuration) application in which the multiobjective optimization procedure simultaneously minimizes the sonic boom and the drag-to-lift ratio (C(sub D)/C(sub L)) of the aircraft while maintaining the lift coefficient within prescribed limits. The results are compared with those of an equally weighted K-S multiobjective optimization. Results demonstrate the effectiveness of the enhanced multiobjective optimization procedure.

Chattopadhyay, Aditi↗
NASA NTRS2023

Exploration of Design Drivers for the RVLT Lift+Cruise Reference Aircraft

A trade study was performed on an all-electric version of the Lift+Cruise urban air mobility reference aircraft developed under the Revolutionary Vertical Lift Technology Project. The trade study varied the input parameters of mission range, takeoff altitude, mission reserve time, cell specific energy, disk loading, and payload weight. A step-by-step incremental change in the input parameters was also examined. Analyses were performed using the NASA Design and Analysis of Rotorcraft tool and a Rapid Sizing Tool for electric vertical takeoff and landing aircraft. A comparison of the analysis results between the two tools shows good agreement in trends with differences in slope. Overall, the analysis shows that the Lift+Cruise configuration performs poorly on a NASA-defined, energy-dominated mission due to poor aerodynamic efficiency in forward flight. This poor cruise-flight efficiency results in a large energy requirement, which increases the required battery sizing and corresponding aircraft gross weight. As such, continued conceptual design and refinement of the Lift+Cruise reference aircraft by the RVLT Concepts Team will likely be limited.

UAM↗
NASA NTRS1975

A semibuoyant vehicle for general transportation missions

The concept of a small, semibuoyant, lifting-body airship with either a disposable or nondisposable buoyant fluid is discussed. Estimations of fuel consumption, payload capability, power requirements and productivity are made and compared to other flight systems. Comparisons are made on the basis of equal cost vehicles. The assumption is made that, to a first-order approximation, the costs of developing, procuring, and operating a commercial air transport vehicle are proportional to vehicle empty weight. It must be noted that no historical cost data exist for the lifting-body airship and therefore these comparisons must be considered preliminary.

Havill, C. D.↗
NASA NTRS1976

A hybrid airship concept for Naval missions

A preliminary analysis of a hybrid semibuoyant delta-planform airship was performed using a computer synthesis program. The delta-planform hull shape was studied parametrically to determine the effects on vehicle performance for two Navy antisubmarine missions. The effects of buoyancy ratio, design speed, and altitude were also studied. The results suggest that long-range mission vehicles require a near buoyant or fully buoyant design and that there is no special advantage to the use of a lifting-body hull shape. For shorter-range missions, hybrid vehicles may have merit, and optimum vehicle buoyancy varies depending on whether a minimum-weight or minimum-fuel-consumption design is desired. As compared with conventionally shaped airships, the benefits, if any, from a lifting-body configuration will be limited to missions requiring relatively higher flight speeds.

Harper, M.↗
NASA NTRS2010

ACT Payload Shroud Structural Concept Analysis and Optimization

Aerospace structural applications demand a weight efficient design to perform in a cost effective manner. This is particularly true for launch vehicle structures, where weight is the dominant design driver. The design process typically requires many iterations to ensure that a satisfactory minimum weight has been obtained. Although metallic structures can be weight efficient, composite structures can provide additional weight savings due to their lower density and additional design flexibility. This work presents structural analysis and weight optimization of a composite payload shroud for NASA s Ares V heavy lift vehicle. Two concepts, which were previously determined to be efficient for such a structure are evaluated: a hat stiffened/corrugated panel and a fiber reinforced foam sandwich panel. A composite structural optimization code, HyperSizer, is used to optimize the panel geometry, composite material ply orientations, and sandwich core material. HyperSizer enables an efficient evaluation of thousands of potential designs versus multiple strength and stability-based failure criteria across multiple load cases. HyperSizer sizing process uses a global finite element model to obtain element forces, which are statistically processed to arrive at panel-level design-to loads. These loads are then used to analyze each candidate panel design. A near optimum design is selected as the one with the lowest weight that also provides all positive margins of safety. The stiffness of each newly sized panel or beam component is taken into account in the subsequent finite element analysis. Iteration of analysis/optimization is performed to ensure a converged design. Sizing results for the hat stiffened panel concept and the fiber reinforced foam sandwich concept are presented.

Zalewski, Bart B.↗
NASA NTRS1955

Full-scale-wind-tunnel Tests of a 35 Degree Sweptback Wing Airplane with High-velocity Blowing over the Training-edge Flaps

A wind-tunnel investigation was made to determine the effects of ejecting high-velocity air near the leading edge of plain trailing-edge flaps on a 35 degree sweptback wing. The tests were made with flap deflections from 45 degrees to 85 degrees and with pressure ratios across the flap nozzles from sub-critical up to 2.9. A limited study of the effects of nozzle location and configuration on the efficiency of the flap was made. Measurements of the lift, drag, and pitching moment were made for Reynolds numbers from 5.8 to 10.1x10(6). Measurements were also made of the weight rate of flow, pressure, and temperature of the air supplied to the flap nozzles.The results show that blowing on the deflected flap produced large flap lift increments. The amount of air required to prevent flow separation on the flap was significantly less than that estimated from published two-dimensional data. When the amount of air ejected over the flap was just sufficient to prevent flow separation, the lift increment obtained agreed well with linear inviscid fluid theory up to flap deflections of 60 degrees. The flap lift increment at 85 degrees flap deflection was about 80 percent of that predicted theoretically.With larger amounts of air blown over the flap, these lift increments could be significantly increased. It was found that the performance of the flap was relatively insensitive to the location of the flap nozzle, to spacers in the nozzle, and to flow disturbances such as those caused by leading-edge slats or discontinuities on the wing or flap surfaces. Analysis of the results indicated that installation of this system on an F-86 airplane is feasible.

Kelley, Mark W↗
NASA NTRS2013

Initial Assessment of a Variable-Camber Continuous Trailing-Edge Flap System on a Rigid Wing for Drag Reduction in Subsonic Cruise

In this paper, we describe an initial optimization study of a Variable-Camber Continuous Trailing-Edge Flap (VCCTEF) system. The VCCTEF provides a light-weight control system for aircraft with long flexible wings, providing efficient high-lift capability for takeoff and landing, and greater efficiency with reduced drag at cruising flight by considering the effects of aeroelastic wing deformations in the control law. The VCCTEF system is comprised of a large number of distributed and individually-actuatable control surfaces that are constrained in movement relative to neighboring surfaces, and are non-trivially coupled through structural aeroelastic dynamics. Minimzation of drag results in a constrained, coupled, non-linear optimization over a high-dimension search space. In this paper, we describe the modeling, analysis, and optimization of the VCCTEF system control inputs for minimum drag in cruise. The purpose of this initial study is to quantify the expected benefits of the system concept. The scope of this analysis is limited to consideration of a rigid wing without structural flexibility in a steady-state cruise condition at various fuel weights. For analysis, we developed an optimization engine that couples geometric synthesis with vortex-lattice analysis to automate the optimization procedure. In this paper, we present and describe the VCCTEF system concept, optimization approach and tools, run-time performance, and results of the optimization at 20%, 50%, and 80% fuel load. This initial limited-scope study finds the VCCTEF system can potentially gain nearly 10% reduction in cruise drag, provides greater drag savings at lower operating weight, and efficiency is negatively impacted by the severity of relative constraints between control surfaces.

trailing edge flaps↗
NASA NTRS1980

Preliminary study of VTO thrust requirements for a V/STOL aircraft with lift plus lift/cruise propulsion

A preliminary assessment was made of the VTO thrust requirements for a supersonic (Type B) aircraft with a Lift plus Lift/Cruise propulsion system. A baseline aircraft with a takeoff gross weight (TOGW) of 13 608 kg (30,000 lb) was assumed. Pitch, roll, and yaw control thrusts (i.e., the thrusts needed for aircraft attitude control in the flight hover mode) were estimated based on a specified set of maneuver acceleration requirements for V/STOL aircraft. Other effects (such as installation losses, suckdown, reingestion, etc.), which add to the thrust requirements for VTO were also estimated. For the baseline aircraft, the excess thrust required for attitude control of the aircraft during VTO and flight hover was estimated to range from 36.9 to 50.9 percent of the TOGW. It was concluded that the total thrust requirements for the aircraft/propulsion system are large and significant. In order to achieve the performance expected of this aircraft/propulsion system, reductions must be made in the excess thrust requirements.

Turney, G. E.↗
NASA NTRS1982

A remote augmentor lift system with a turbine bypass engine

Two supersonic vertical takeoff or landing (VTOL) aircraft engine types, a conventional medium bypass ratio turbofan, and a turbine bypass turbojet were studied. The aircraft assumed was a clipped delta wing with canard configuration. A VTOL deck launched intercept, DLI, mission with Mach 1.6 dash and cruise segments was used as the design mission. Several alternate missions requiring extended subsonic capabilities were analyzed. Comparisons were made between the turbofan (TF) and the turbine bypass turbojet (TBE) engines in airplane types using a Remote Augmented Lift Systems, RALS and a Lift plus Lift Cruise system (L+LC). The figure of merit was takeoff gross weight for the VTOL DLI mission. The results of the study show that the turbine bypass turbojet and the conventional turbofan are competitive engines for both type of aircraft in terms of takeoff gross weight and range. However, the turbine bypass turbojet would be a simpler engine and may result in more attractive life cycle costs and reduced maintenance. The RALS and L+LC airplane types with either TBE or TF engines have approximately the same aircraft takeoff gross weight.

Fishbach, L. H.↗
NASA NTRS1984

Joined-wing research airplane feasibility study

The joined wing is a new type of aircraft configuration which employs tandem wings arranged to form diamond shapes in plan view and front view. Wind-tunnel tests and finite-element structural analyses have shown that the joined wing provides the following advantages over a comparable wing-plus-tail system; lighter weight and higher stiffness, higher span-efficiency factor, higher trimmed maximum lift coefficient, lower wave drag, plus built-in direct lift and direct sideforce control capability. To verify these advantages at full scale a manned research airplane is required. A study has therefore been performed of the feasibility of constructing such an airplane, using the fuselage and engines of the existing NAA AD-1 oblique-wing airplane. Cost and schedule constraints favored converting the AD-1 rather than constructing a totally new airframe. By removing the outboard wing panels the configuration can simulate wings joined at 60, 80, or 100 percent of span. For maximum versatility the aircraft has alternative control surfaces (such as ailerons and elevators on the front and/or rear wings), and a removeable canard to explore canard/joined-wing interactions at high-lift conditions. Design, performance, and flying qualities are discussed.

Wolkovitch, J.↗
NASA NTRS1990

Performance Data from a Wind-Tunnel Test of Two Main-rotor Blade Designs for a Utility-Class Helicopter

An investigation was conducted in the NASA Langley Transonic Dynamics Tunnel to evaluate an advanced main rotor designed for use on a utility class helicopter, specifically the U.S. Army UH-60A Blackhawk. This rotor design incorporated advanced twist, airfoil cross sections, and geometric planform. For evaluation purposes, the current UH-60A main rotor was also tested and is referred to as the baseline blade set. A total of four blade sets were tested. One set of both the baseline and the advanced rotors were dynamically scaled to represent a full scale helicopter rotor blade design. The remaining advanced and baseline blade sets were not dynamically scaled so as to isolate the effects of structural elasticity. The investigation was conducted in hover and at rotor advance ratios ranging from 0.15 to 0.4 at a range of nominal test medium densities from 0.00238 to 0.009 slugs/cu ft. This range of densities, coupled with varying rotor lift and propulsive force, allowed for the simulation of several vehicle gross weight and density altitude combinations. Performance data are presented for all blade sets without analysis; however, cross referencing of data with flight condition may be useful to the analyst for validating aeroelastic theories and design methodologies as well as for evaluating advanced design parameters.

Singleton, Jeffrey D.↗
NASA NTRS1995

Noise impact of advanced high lift systems

The impact of advanced high lift systems on aircraft size, performance, direct operating cost and noise were evaluated for short-to-medium and medium-to-long range aircraft with high bypass ratio and very high bypass ratio engines. The benefit of advanced high lift systems in reducing noise was found to be less than 1 effective-perceived-noise decibel level (EPNdB) when the aircraft were sized to minimize takeoff gross weight. These aircraft did, however, have smaller wings and lower engine thrusts for the same mission than aircraft with conventional high lift systems. When the advanced high lift system was implemented without reducing wing size and simultaneously using lower flap angles that provide higher L/D at approach a cumulative noise reduction of as much as 4 EPNdB was obtained. Comparison of aircraft configurations that have similar approach speeds showed cumulative noise reduction of 2.6 EPNdB that is purely the result of incorporating advanced high lift system in the aircraft design.

Elmer, Kevin R.↗
NASA NTRS1961

Subsonic Longitudinal Aerodynamic Characteristics of Disks with Elliptic Cross Sections and Thickness-Diameter Ratios from 0.225 to 0.425

General interest in manned space flight has provided a stimulus for the investigation of shapes which appear to be attractive for application to re-entry vehicles. Such vehicles can be classed as either nonlifting or lifting. Nonlifting types, such as used in Project Mercury, have certain advantages which include structural simplicity, no requirement for an elaborate flight-control system, ease of mating with the booster, and short exposure times to high heating rates during entry. Advantages of lifting types, by comparison, include lower peak heating rates and decelerations, the possibility for a conventional horizontal landing, and the ability to maneuver, thus providing control over longitudinal and lateral range and a wider entry corridor on return from planetary or lunar missions. A lifting shape which appears attractive in terms of the considerations is a thick disk. At high attitudes, the weight to drag ratio is low and the radius of curvature of the surface exposed to the airstream is large, a combination of parameters which results in reduced convective heating rates. The low-speed lift-drag ratios associated with this type of shape appear sufficiently high to permit a conventional horizontal landing. The investigation reported herein was undertaken to assess the effects of thickness on the aerodynamic characteristics of disk shapes suitable for lifting re-entry into the earth's atmosphere and potentially capable of conventional horizontal landing. The models had elliptic cross sections which varied in thickness from 0.225 to 0.425 diameter. The tests were conducted in the Ames 12-Foot Pressure Wind Tunnel over a Mach number range from 0.25 to 0.90 at a Reynolds number of 3.3x10 (exp 6) and at Reynolds numbers to 16x10 (exp 6) at a Mach number of 0.25. Tests on similar shapes have been conducted at subsonic, transonic, and supersonic speeds and the results have been presented.

Demele, Fred A.↗
NASA NTRS1997

Super-Low-Mass Spaceborne SAR Array Concepts

For Earth remote sensing applications, a synthetic aperture radar (SAR) typically employs an antenna with a fairly long along-track aperture in order to achieve the desired performance. At orbital velocities, the antenna along-track dimension is driven by a careful trade off between resolution, swath width, and available data rate and is independent of wavelength. 10 to 20 m long antennas have been flown or proposed in previous spaceborne SAR designs. To maintain an acceptable electrical flatness across this long aperture, very massive antenna support structures, weighing several hundred kilograms or more, have been used to date. For example, the fixed-beam L-band SeaSat antenna, which used a microstrip array with honeycomb substrate, had a mass of 250 Kg (including deployment mechanism). The beam-scanning L/C/X-band shuttle-based SIR-C antenna has a mass of l,800 Kg. These massive antenna systems generally require a launch vehicle with large stowage volume and heavy-payload-lift capability. To achieve good launch volume efficiency and to reduce payload weight, three super-low-mass array concepts are proposed and described here. With these new concepts, the mass of the future Earth remote sensing SAR antennas is expected to be less than 100 Kg.

Huang, J.↗
NASA NTRS1961

A Flight Examination of Operating Problems of V/STOL Aircraft in STOL-Type Landing and Approach

A flight investigation has been conducted using a large twin-engine cargo aircraft to isolate the problems associated with operating propeller-driven aircraft in the STOL speed range where appreciable engine power is used to augment aerodynamic lift. The problems considered would also be representative of those of a large overloaded VTOL aircraft operating in an STOL manner with comparable thrust-to-weight ratios. The study showed that operation at low approach speeds was compromised by the necessity of maintaining high thrust to generate high lift and yet achieving the low lift-drag ratios needed for steep descents. The useable range of airspeed and flight path angle was limited by the pilot's demand for a positive climb margin at the approach speed, a suitable stall margin, and a control and/or performance margin for one engine inoperative. The optimum approach angle over an obstacle was found to be a compromise between obtaining the shortest air distance and the lowest touchdown velocity. In order to realize the greatest low-speed potential from STOL designs, the stability and control characteristics must be satisfactory.

Innis, Robert C.↗
NASA NTRS2006

Performance, Loads and Stability of Heavy Lift Tiltrotors

Summaries of rotor performance are presented for a 124,000-lb Large Civil Tilt Rotor (LCTR) design, along with isolated-rotor and fully-coupled wing/rotor aeroelastic stability. A major motivation of the present research is the effect of size on rotor dynamics. Simply scaling up existing rotor designs to the vehicle size under study would result in unacceptable rotor weight. The LCTR was the most promising of several large rotorcraft concepts produced by the NASA Heavy Lift Rotorcraft Systems Investigation. It was designed to carry 120 passengers for 1200 nm, with performance of 350 knots at 30,000 ft altitude. Design features included a low-mounted wing and hingeless rotors, with a very low cruise tip speed of 350 ft/sec. The LCTR was sized by the'RC code developed by the U. S. Army Aeroflightdynamics Directorate. The rotor was then optimized using the CAMRAD II comprehensive analysis code. The blade and wing structures were designed by Pennsylvania State University to meet the rotor loads calculated by CAMRAD II and wing loads required for certification. Aeroelastic stability was confirmed by further CAMRAD II analysis, based on the optimized rotor and wing designs.

Acree, Cecil W., Jr.↗