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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1946

Langley Full-Scale Tunnel Investigation of a 1/3-Scale Model of the Chance Vought XF5U-1 Airplane

The results of an investigation of a 1/3-scale model of the Chance Vought XF5U-1 airplane in the Langley full-scale tunnel are presented in this report. The maximum lift and stalling characteristics of several model configurations, the longitudinal stability characteristics of the model, and the effectiveness of the control surfaces were determined with the propellers removed. The propulsive characteristics, the effect of propeller operation on the lift, and the static thrust of the model propellers were determined at several propeller-blade angles. The results with the propellers removed showed that the maximum lift coefficient of the complete model configuration was only 0.97 was compared with the value of 1.31 for the model configuration in which the engine-air ducts and canopy are removed. The model with the propellers removed (normal center-of-gravity position) has a positive static margin, stick fixed, varying from 5 to 13 percent of the mean aerodynamic chord throughout the unstalled range of lift coefficients. The unit horizontal tail is sufficiently powerful to trim the airplane with the propellers removed throughout the unstalled range of lift coefficients. The peak propulsive efficiencies for beta = 20 degrees and beta = 30 degrees were increased 7 percent at C(sub L) congruent to 0.67 and 20 percent at C(sub L) congruent to 0.74, respectively, with the propellers rotating upward in the center than with the propellers rotating downward in the center. Indications are that the minimum forward-flight speed of the airplane for full-power operation at sea level will be about 90 miles per hour. Decreasing the weight and increasing the power reduced this value of minimum speed and there were no indications from the results of a lower limit to the minimum speed.

Lange, Roy H.↗
NASA NTRS1980

Some calculated effects of non-uniform inflow on the radiated noise of a large wind turbine

Far field computations were performed for a large wind turbine to evaluate the effects of non-uniform aerodynamic loading over the rotor disk. A modified version of the Farassat/Nystrom propeller noise prediction program was applied to account for the variations in loading due to inflow interruption by the upstream support tower. The computations indicate that for the uniform inflow case, relatively low noise levels are generated and the first rotational harmonic dominated the spectrum. For cases representing wake flow deficiences due to the tower structure, subtantially increased noise levels for all harmonics are indicated, the greatest increases being associated with the higher order harmonics.

Greene, G. C.↗
NASA NTRS1978

Potential acoustic benefits of circulation control rotors

The fundamental aeroacoustic mechanisms responsible for noise generation on a rotating blade are theoretically examined. Their contribution to the overall rotor sound pressure level is predicted. Results from a theory for airfoil trailing edge noise are presented. Modifications and extensions to other source theories are described where it is necessary to account for unique aspects of circulation control (CC) aerodynamics. The circulation control rotor (CCR), as embodied on an X-wing vertical takeoff and landing (VTOL) aircraft, is used as an example for computational purposes, although many of the theoretical results presented are generally applicable to other CC applications (such as low speed rotors, propellers, compressors, and fixed wing aircraft). Using the analytical models, it is shown that the utilization CC aerodynamics theoretically makes possible unprecedented advances in rotor noise reduction. For the X-wing VTOL these reductions appear to be feasible without incurring significant attendant performance and weight penalties.

Williams, R. M.↗
NASA NTRSDate not supplied

Wind Tunnel Testing of Static Aerodynamic and Power Consumption Characteristics of an Octocopter

The introduction of multirotor unmanned aircraft systems (UAS) in low-altitude airspace poses significant safety challenges. Further development of advanced aviation systems is needed to realize the full potential of UAS applications, particularly for urban and beyond visual line-of-sight (BVLOS) operations. The NASA System Wide Safety (SWS) project is developing key technologies to mitigate future airspace safety risks involving autonomous aircraft operation in densely populated areas. An important part of these technologies requires flight dynamics and performance models to assess feasible trajectories, power consumption requirements, and operational envelope limitations. To support these efforts, this research seeks to improve the accuracy of multirotor aerodynamic models and investigate stability characteristics relevant to flight safety. This paper presents a recent study of an octocopter vehicle using the NASA Langley 12-Foot Low-Speed Tunnel (LST). Results from isolated-airframe (no propellers) and powered-airframe tests are presented. A one-factor-at-a-time (OFAT) approach was used to explore the effect of propeller advance ratio and vehicle angle of attack on vehicle forces, moments, and power consumption. The results show nonlinear aerodynamic behavior and indicate regions where aerodynamic interaction effects may be significant.

George V. Altamirano↗
NASA NTRS2010

Implications of Wind-Assisted Aerial Navigation for Titan Mission Planning and Science Exploration

The recent Titan Saturn System Mission (TSSM) proposal incorporates a montgolfiere (hot air balloon) as part of its architecture. Standard montgolfiere balloons generate lift through heating of the atmospheric gases inside the envelope, and use a vent valve for altitude control. A Titan aerobot (robotic aerial vehicle) would have to use radioisotope thermoelectric generators (RTGs) for electric power, and the excess heat generated can be used to provide thermal lift for a montgolfiere. A hybrid montgolfiere design could have propellers mounted on the gondola to generate horizontal thrust; in spite of the unfavorable aerodynamic drag caused by the shape of the balloon, a limited amount of lateral controllability could be achieved. In planning an aerial mission at Titan, it is extremely important to assess how the moon-wide wind field can be used to extend the navigation capabilities of an aerobot and thereby enhance the scientific return of the mission. In this paper we explore what guidance, navigation and control capabilities can be achieved by a vehicle that uses the Titan wind field. The control planning approach is based on passive wind field riding. The aerobot would use vertical control to select wind layers that would lead it towards a predefined science target, adding horizontal propulsion if available. The work presented in this paper is based on aerodynamic models that characterize balloon performance at Titan, and on TitanWRF (Weather Research and Forecasting), a model that incorporates heat convection, circulation, radiation, Titan haze properties, Saturn's tidal forcing, and other planetary phenomena. Our results show that a simple unpropelled montgolfiere without horizontal actuation will be able to reach a broad array of science targets within the constraints of the wind field. The study also indicates that even a small amount of horizontal thrust allows the balloon to reach any area of interest on Titan, and to do so in a fraction of the time needed by the unpropelled balloon. The results show that using the Titan wind field allows an aerobot to significantly extend its scientific reach, and that a montgolfiere (unpropelled or propelled) is a highly desirable architecture that can very significantly enhance the scientific return of a future Titan mission.

aerobot↗
NASA NTRS1984

Aeroelastic formulations for turbomachines and propellers

The task of the aeroelastic analysis is to combine the formulations of the structural dynamic and unsteady aerodynamic models in a consistent manner, to solve the resulting aeroelastic model to determine the dynamic behavior (e.g., stability, forced vibration), and to interpret those results for both qualitative trends, and quantitative detail. A review of the various formulations of the aeroelastic problem and a comparison of their relative advantages will be the subject of this paper. Specifically, the topics to be addressed are: the formulation of the aeroelastic problem, including a summary of the relations necessary to transform various diverse structural and aerodynamic models to a consistent notation for oscillatory motion; an approximate transformation for arbitrary temporal behavior; and a brief review of the applicable solution techniques.

Crawley, E. F.↗
NASA NTRS1996

User's Guide for MSAP2D: A Program for Unsteady Aerodynamic and Aeroelastic (Flutter and Forced Response) Analysis of Multistage Compressors and Turbines

This guide describes the input data required for using MSAP2D (Multi Stage Aeroelastic analysis Program - Two Dimensional) computer code. MSAP2D can be used for steady, unsteady aerodynamic, and aeroelastic (flutter and forced response) analysis of bladed disks arranged in multiple blade rows such as those found in compressors, turbines, counter rotating propellers or propfans. The code can also be run for single blade row. MSAP2D code is an extension of the original NPHASE code for multiblade row aerodynamic and aeroelastic analysis. Euler equations are used to obtain aerodynamic forces. The structural dynamic equations are written for a rigid typical section undergoing pitching (torsion) and plunging (bending) motion. The aeroelastic equations are solved in time domain. For single blade row analysis, frequency domain analysis is also provided to obtain unsteady aerodynamic coefficients required in an eigen analysis for flutter. In this manual, sample input and output are provided for a single blade row example, two blade row example with equal and unequal number of blades in the blade rows.

Reddy, T. S. R.↗
NASA NTRS1989

High speed turboprop aeroacoustic study (single rotation). Volume 1: Model development

A frequency-domain noncompact-source theory for the steady loading and volume-displacement (thickness) noise of high speed propellers has been developed and programmed. Both near field and far field effects have been considered. The code utilizes blade surface pressure distributions obtained from three-dimensional nonlinear aerodynamic flow field analysis programs as input for evaluating the steady loading noise. Simplified mathematical models of the velocity fields induced at the propeller disk by nearby wing and fuselage surfaces and by angle-of-attack operation have been developed to provide estimates of the unsteady loading imposed on the propeller by these potential field type interactions. These unsteady blade loadings have been coupled to a chordwise compact propeller unsteady loading noise model to provide predictions of unsteady loading noise caused by these installation effects. Finally, an analysis to estimate the corrections to be applied to the free-field noise predictions in order to arrive at the measurable fuselage sound pressure levels has been formulated and programmed. This analysis considers the effects of fuselage surface reflection and diffraction together with surface boundary layer refraction. The steady loading and thickness model and the unsteady loading model have been verified using NASA-supplied data for the SR-2 and SR-3 model propfans. In addition, the steady loading and thickness model has been compared with data from the SR-6 model propfan. These theoretical models have been employed in the evaluation of the SR-7 powered Gulfstream aircraft in terms of noise characteristics at representative takeoff, cruise, and approach operating conditions. In all cases, agreement between theory and experiment is encouraging.

Whitfield, C. E.↗
NASA NTRSDate not supplied

Aerodynamic Implications of Aerocapture Systems for Uranus Orbiters

Exploration of the Ice Giants, Uranus in particular, has been indicated as the highest priority new flagship-class mission by the 2022 Planetary Science Decadal Survey. However, due to it’s location in the solar system, extensive travel time and resources are required for a mission to reach Uranus. Aerocapture offers shorter interplanetary transit times and reduced propellant requirements for such a mission when compared to a traditional propulsive-capture orbiter. Considerations for the aerodynamics of an aerocapture system enabling flagship-class science mission to Uranus are presented. The applicability of a low lift-to-drag entry vehicle aeroshell with flight heritage to a new planet and atmosphere is evaluated. A preliminary aerodatabase is formulated from low-fidelity methods and heritage flight mission data to provide initial estimates of trajectory space to be considered for inserting a spacecraft into orbit at Uranus using aerocapture. Computational fluid dynamics calculations in the free molecular, transitional, and continuum regimes using Direct Simulation Monte Carlo and Navier-Stokes solutions are used to assess the validity of this preliminary aerodatabase. The considered entry vehicle is found to varying levels of agreement with work done by previous flight missions when evaluated for flight in Uranus’ atmosphere. Implications for the aerodynamics of this vehicle as applied in an aerocapture system in flight at Uranus as found by the current work are discussed.

Eli R. Shellabarger↗
NASA NTRSDate not supplied

Aerodynamic Implications of Aerocapture Systems for Uranus Orbiters

Exploration of the Ice Giants, Uranus in particular, has been indicated as the highest priority new flagship-class mission by the 2022 Planetary Science Decadal Survey. However, due to it's location in the solar system, extensive travel time and resources are required for a mission to reach Uranus. Aerocapture offers shorter interplanetary transit times and reduced propellant requirements for such a mission when compared to a traditional propulsive-capture orbiter. Considerations for the aerodynamics of an aerocapture system enabling flagship-class science mission to Uranus are presented. The applicability of a low lift-to-drag entry vehicle aeroshell with flight heritage to a new planet and atmosphere is evaluated. A preliminary aerodatabase is formulated from low-fidelity methods and heritage flight mission data to provide initial estimates of trajectory space to be considered for inserting a spacecraft into orbit at Uranus using aerocapture. Computational fluid dynamics calculations in the free molecular, transitional, and continuum regimes using Direct Simulation Monte Carlo and Navier-Stokes solutions are used to assess the validity of this preliminary aerodatabase. The considered entry vehicle is found to varying levels of agreement with work done by previous flight missions when evaluated for flight in Uranus' atmosphere. Implications for the aerodynamics of this vehicle as applied in an aerocapture system in flight at Uranus as found by the current work are discussed.

Uranus↗
NASA NTRS1979

Liquid hydrogen/oxygen external tank development for the Space Shuttle

The evolution of the Space Shuttle System using an expendable External Tank was discussed. The reasoning for the cryogenic propellant selection for the Space Shuttle Main Engine was addressed. The unique problems, solutions, and design features imposed on the External Tank by the cryogenic propellants was discussed with special emphasis on the use of cryogenic insulation for aerodynamic heating protection. Manufacturing techniques for high production rate cryogenic tankage concluded the report.

Odom, J. B.↗
NASA NTRS1983

Aeroacoustic research facilities at NASA Langley Research Center: Description and operational characteristics

A number of facilities were developed which provide unique test capabilities for aeroacoustic research. Information regarding physical layouts, dimensions, construction features, and operating capabilities of these facilities is compiled. Possible research applications include the behavior of such noise sources as jets, rotors, and propellers in simulated forward motion; studies of noise due to the interactions of aerodynamic flows with solid surfaces and bodies; sound propagation in ducts with airflow; and the evaluation of acoustical materials.

Hubbard, H. H.↗
NASA NTRS1986

Aerodynamic Characteristics of NACA 16-Series Airfoils

Standard data from literature incorporated into program. Comprehensive and easily-accessible data bank of aerodynamic characteristics of NACA 16series airfoils incorporated into AIRFOIL program for use in propeller performance research. Low-drag, high-critical-speed airfoils effective in advanced turbo-prop designs currently under investigation. AIRFOIL written in FORTRAN IV for batch execution.

Maksymiuk, C. M.↗
NASA NTRS2014

A Modular Aerospike Engine Design Using Additive Manufacturing

A modular aerospike engine concept has been developed with the objective of demonstrating the viability of the aerospike design using additive manufacturing techniques. The aerospike system is a self-compensating design that allows for optimal performance over the entire flight regime and allows for the lowest possible mass vehicle designs. At low altitudes, improvements in Isp can be traded against chamber pressure, staging, and payload. In upper stage applications, expansion ratio and engine envelope can be traded against nozzle efficiency. These features provide flexibility to the System Designer optimizing a complete vehicle stage. The aerospike concept is a good example of a component that has demonstrated improved performance capability, but traditionally has manufacturing requirements that are too expensive and complex to use in a production vehicle. In recent years, additive manufacturing has emerged as a potential method for improving the speed and cost of building geometrically complex components in rocket engines. It offers a reduction in tooling overhead and significant improvements in the integration of the designer and manufacturing method. In addition, the modularity of the engine design provides the ability to perform full scale testing on the combustion devices outside of the full engine configuration. The proposed design uses a hydrocarbon based gas-generator cycle, with plans to take advantage of existing powerhead hardware while focusing DDT&E resources on manufacturing and sub-system testing of the combustion devices. The major risks for the modular aerospike concept lie in the performance of the propellant feed system, the structural integrity of the additive manufactured components, and the aerodynamic efficiency of the exhaust flow.

Peugeot, John↗
NASA NTRSDate not supplied

Thermal Protection System Design of Aerocapture Systems for Uranus Orbiters

The National Academies Planetary Science and Astrobiology Decadal Survey recently identified Uranus and Neptune - the Ice Giants - as the priority destinations for science. A mission to Uranus, the highest priority destination due to proximity to Earth, is viable with existing launch vehicle providers during launch windows starting in 2031. However, a nominal interplanetary trajectory (between 12 and 15 years) would still necessitate more than half the initial launch mass in propellant to achieve orbital insertion. Aerocapture, a method of orbital control that directs aerodynamic forces generated on a vehicle by the planet's atmosphere, allows mission designers to achieve the desired orbital state while saving time to the final destination and increasing the available mass for the science payload. Achieving orbital insertion via aerocapture requires novel algorithms for Guidance, Navigation and Control, and mass-efficient Thermal Protection Systems (TPS) performing in an atmosphere unlike any other NASA has flown through. Multiple TPS in NASA's repertoire are suitable for the unique aerothermal environment on the forebody, and the results of predicted sizing and challenges in implementation are discussed below. Results for aftbody TPS made by NASA as well as commercial vendors are discussed, along with the discussion of alternative solutions that may save time, reduce complexity, and increase mass-efficiency for the recommended Uranus Orbiter and Probe mission.

Uranus↗
NASA NTRSDate not supplied

Thermal Protection System Design of Aerocapture Systems for Uranus Orbiters

The National Academies Planetary Science and Astrobiology Decadal Survey recently identified Uranus and Neptune - the Ice Giants - as the priority destinations for science. A mission to Uranus, the highest priority destination due to proximity to Earth, is viable with existing launch vehicle providers during launch windows starting in 2031. However, a nominal interplanetary trajectory (between 12 and 15 years) would still necessitate more than half the initial launch mass in propellant to achieve orbital insertion. Aerocapture, a method of orbital control that directs aerodynamic forces generated on a vehicle by the planet's atmosphere, allows mission designers to achieve the desired orbital state while saving time to the final destination and increasing the available mass for the science payload. Achieving orbital insertion via aerocapture requires novel algorithms for Guidance, Navigation and Control, and mass-efficient Thermal Protection Systems (TPS) performing in an atmosphere unlike any other NASA has flown through. Multiple TPS in NASA's repertoire are suitable for the unique aerothermal environment on the forebody, and the results of predicted sizing and challenges in implementation are discussed below. Results for aftbody TPS made by NASA as well as commercial vendors are discussed, along with the discussion of alternative solutions that may save time, reduce complexity, and increase mass-efficiency for the recommended Uranus Orbiter and Probe mission.

Uranus↗
NASA NTRSDate not supplied

Improvements to Thermal Protection System Design of Aerocapture Systems for Uranus Orbiters

The National Academies Planetary Science and Astrobiology Decadal Survey identified Uranus and Neptune - called Ice Giants - as the priority destinations for science. The survey assessed both a mission to Uranus through the Uranus Orbiter and Probe (UOP) concept, and Neptune through the Neptune-Triton Odyssey concept and determined that Uranus is the highest priority for a Flagship class mission. The UOP mission concept planned to deliver an in situ probe and conduct a multi-year orbital tour of the system to meet the science objectives. While the Uranus mission is currently viable with launch windows starting in 2031 using existing launch vehicles, the mission has a cruise phase of at least 12 years and would require more than half of its weight in fuel propellant to achieve the change in velocity necessary for orbital insertion. Aerocapture uses aerodynamic forces generated on a vehicle by the planet's atmosphere to modulate a spacecraft's trajectory, decreasing spacecraft velocity, and allowing mission designers to target the final orbital state. Aerocapture reduces the time-of-flight from Earth to Uranus over a fully propulsive solution, opening up more launch opportunities to arrive in the 2040's to the mission's science objectives. Aerocapture also allows a payload mass increase by mitigating the need for fuel to retropropulsively insert the payload into orbit, thereby increase the science that can be performed. For an aerocapture mission structure using a traditional aeroshell to deliver the UOP scientific payload to Uranus, Conformal Phenolic Impregnated Carbon Ablator (C-PICA) was determined to be the best-performing forebody thermal protection system (TPS) and other candidate aftbody TPS options were presented as feasible. This paper focuses on A) evaluating C-PICA as a forebody TPS using stressing entry conditions associated with a large range of potential Uranus flagship launch vehicles and interplanetary trajectories, B) widening the aftbody TPS candidates for new mass-efficient and cost-efficient solutions, and C) a summary list of actions remaining to provide a technically feasible and supply-robust set of TPS for an aerocapture vehicle to the Ice Giants is presented.

C-PICA↗