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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Image Tiling for Profiling Large Objects

Three dimensional surface measurements of large objects arc required in a variety of industrial processes. The nature of these measurements is changing as optical instruments arc beginning to replace conventional contact probes scanned over the objects. A common characteristic of the optical surface profilers is the trade off between measurement accuracy and field of view. In order to measure a large object with high accuracy, multiple views arc required. An accurate transformation between the different views is needed to bring about their registration. In this paper, we demonstrate how the transformation parameters can be obtained precisely by choosing control points which lie in the overlapping regions of the images. A good starting point for the transformation parameters is obtained by having a knowledge of the scanner position. The selection of the control points arc independent of the object geometry. By successively recording multiple views and obtaining transformation with respect to a single coordinate system, a complete physical model of an object can be obtained. Since all data arc in the same coordinate system, it can thus be used for building automatic models for free form surfaces.

Venkataraman, Ajit↗
NASA NTRS2001

Alleviation of Facility/Engine Interactions in an Open-Jet Scramjet Test Facility

Results of a series of shakedown tests to eliminate facility/engine interactions in an open-jet scramjet test facility are presented. The tests were conducted with the NASA DFX (Dual-Fuel eXperimental scramjet) engine in the NASA Langley Combustion Heated Scramjet Test Facility (CHSTF) in support of the Hyper-X program, The majority of the tests were conducted at a total enthalpy and pressure corresponding to Mach 5 flight at a dynamic pressure of 734 psf. The DFX is the largest engine ever tested in the CHSTF. Blockage, in terms of the projected engine area relative to the nozzle exit area, is 81% with the engine forebody leading edge aligned with the upper edge of the facility nozzle such that it ingests the nozzle boundary layer. The blockage increases to 95% with the engine forebody leading edge positioned 2 in. down in the core flow. Previous engines successfully tested in the CHSTF have had blockages of no more than 51%. Oil flow studies along with facility and engine pressure measurements were used to define flow behavior. These results guided modifications to existing aeroappliances and the design of new aeroappliances. These changes allowed fueled tests to be conducted without facility interaction effects in the data with the engine forebody leading edge positioned to ingest the facility nozzle boundary layer. Interaction effects were also reduced for tests with the engine forebody leading edge positioned 2 in. into the core flow, however some interaction effects were still evident in the engine data. A new shroud and diffuser have been designed with the goal of allowing fueled tests to be conducted with the engine forebody leading edge positioned in the core without facility interaction effects in the data. Evaluation tests of the new shroud and diffuser will be conducted once ongoing fueled engine tests have been completed.

Albertson, Cindy W.↗
NASA NTRS1961

Analog Simulation of a Pilot-Controlled Rendezvous

The rendezvous of a pilot-controlled space ferry vehicle with an orbiting space station was simulated in six degrees of freedom. A fixed-base simulator and an analog computer were used. The ferry vehicle was assumed to have a single main thrusting rocket and to be provided with attitude control. Control of the thrust was provided by a rocket throttle quadrant which could provide either proportional or on-off control. The attitude of the vehicle was controlled during the rendezvous with a two-axis, pencil-type side-arm controller and rudder pedals. For the most part rendezvous maneuvers were made with the target satellite in a circular orbit. In addition, an elliptical station orbit was investigated. Tolerable initial conditions, as well as adequate data presentations, were determined. Results of the investigation indicate that a human pilot can rendezvous successfully with the vehicle and instrumentation considered over a wide band of initial conditions. Coplanar conditions are not necessary. Retro-rocket fuel used is not greatly increased by imposing perturbing influences such as rocket-misalignment torques on the rendezvous vehicle. When excessive attitude-control torques are required to maintain the necessary trim attitudes under misalignment influences, the reaction fuel used for this control increases. The time required for a specific rendezvous varies somewhat between pilots. If control of the time for completing the rendezvous is desired, requirements for retrorocket fuel are affected, and an energy-management schedule is required. Continuous variation of the thrust is not necessary. The pilot positions the throttle to obtain a desired level of thrust, and applies bursts of thrust as required. All data were presented on dialed instruments. The quantities required are range and range rate and line-of-sight rates between the vehicle and the station, vehicle attitudes and angular rates, and the angles subtended by the line of sight. For the equipment assumed herein, satellite rendezvous presented no great problem to the pilot.

Brissenden, Roy F.↗
NASA NTRS1992

Mechanisms of nascent fiber formation during avian skeletal muscle hypertrophy

This study examined two putative mechanisms of new fiber formation in postnatal skeletal muscle, namely longitudinal fragmentation of existing fibers and de novo formation. The relative contributions of these two mechanisms to fiber formation in hypertrophying anterior latissimus dorsi (ALD) muscle were assessed by quantitative analysis of their nuclear populations. Muscle hypertrophy was induced by wing-weighting for 1 week. All nuclei formed during the weighting period were labeled by continuous infusion of 5-bromo-2'-deoxyuridine (BrdU), a thymidine analog, and embryonic-like fibers were identified using an antibody to ventricular-like embryonic (V-EMB) myosin. The number of BrdU-labeled and unlabeled nuclei in V-EMB-positive fibers were counted. Wing-weighting resulted in significant muscle enlargement and the appearance of many V-EMB+ fibers. The majority of V-EMB+ fibers were completely independent of mature fibers and had a nuclear density characteristics of developing fibers. Furthermore, nearly 100% of the nuclei in independent V-EMB+ fibers were labeled. These findings strongly suggest that most V-EMB+ fibers were nascent fibers formed de novo during the weighting period by satellite cell activation and fusion. Nascent fibers were found primarily in the space between fascicles where they formed a complex anastomosing network of fibers running at angles to one another. Although wing-weighting induced an increase in the number of branched fibers, there was no evidence that V-EMB+ fibers were formed by longitudinal fragmentation. The location of newly formed fibers in wing-weighted and regenerating ALD muscle was compared to determine whether satellite cells in the ALD muscle were unusual in that, if stimulated to divide, they would form fibers in the inter- and intrafascicular space. In contrast to wing-weighted muscle, nascent fibers were always found closely associated with necrotic fibers. These results suggest that wing-weighting is not simply another model of regeneration, but rather produces a unique environment which induces satellite cell migration and subsequent fiber formation in the interfascicular space. De novo fiber formation is apparently the principal mechanism for the hyperplasia reported to occur in the ALD muscle undergoing hypertrophy induced by wing-weighting.

Non-NASA Center↗
NASA NTRS1996

Power-by-Wire Development and Demonstration for Subsonic Civil Transport

During the last decade, three significant studies by the Lockheed Martin Corporation, the NASA Lewis Research Center, and McDonnell Douglas Corporation have clearly shown operational, weight, and cost advantages for commercial subsonic transport aircraft that use all-electric or more-electric technologies in the secondary electric power systems. Even though these studies were completed on different aircraft, used different criteria, and applied a variety of technologies, all three have shown large benefits to the aircraft industry and to the nation's competitive position. The Power-by-Wire (PBW) program is part of the highly reliable Fly-By-Light/Power-By-Wire (FBL/PBW) Technology Program, whose goal is to develop the technology base for confident application of integrated FBL/PBW systems for transport aircraft. This program is part of the NASA aeronautics strategic thrust in subsonic aircraft/national airspace (Thrust 1) to "develop selected high-leverage technologies and explore new means to ensure the competitiveness of U.S. subsonic aircraft and to enhance the safety and productivity of the national aviation system" (The Aeronautics Strategic Plan). Specifically, this program is an initiative under Thrust 1, Key Objective 2, to "develop, in cooperation with U.S. industry, selected high-payoff technologies that can enable significant improvements in aircraft efficiency and cost."

Source record↗
NASA NTRS2004

Improved Nutation Damper for a Spin-Stabilized Spacecraft

A document proposes an improved liquid- ring nutation damper for a spin-stabilized spacecraft. The improvement addresses the problem of accommodating thermal expansion of the damping liquid. Heretofore, the problem has been solved by either (1) filling the ring completely with liquid and accommodating expansion by attaching a bellows or (2) partially filling the ring and accepting the formation of bubbles. The disadvantage of (1) is that a bellows is expensive and may not be reliable; the disadvantage of (2) is that bubbles can cause fluid lockup and consequent loss of damping. In the improved damper, the ring would be nearly completely filled with liquid, and expansion would be accommodated, but not by a bellows. Instead, an escape tube would be attached to the ring. The escape tube would be positioned and oriented so that the artificial gravitation and the associated buoyant force generated by the spin of the spacecraft would cause the bubbles to migrate toward the tip of the tube. In addition, when the spacecraft was on the launch pad, the escape tube would be at the top of the ring, so that bubbles would rise into the tube.

Woodard, Mark A.↗
NASA NTRS2010

Ensuring Safe Exploration: Ares Launch Vehicle Integrated Vehicle Ground Vibration Testing

Integrated vehicle ground vibration testing (IVGVT) will be a vital component for ensuring the safety of NASA's next generation of exploration vehicles to send human beings to the Moon and beyond. A ground vibration test (GVT) measures the fundamental dynamic characteristics of launch vehicles during various phases of flight. The Ares Flight & Integrated Test Office (FITO) will be leading the IVGVT for the Ares I crew launch vehicle at Marshall Space Flight Center (MSFC) from 2012 to 2014 using Test Stand (TS) 4550. MSFC conducted similar GVT for the Saturn V and Space Shuttle vehicles. FITO is responsible for performing the IVGVT on the Ares I crew launch vehicle, which will lift the Orion crew exploration vehicle to low Earth orbit, and the Ares V cargo launch vehicle, which can launch the lunar lander into orbit and send the combined Orionilander vehicles toward the Moon. Ares V consists of a six-engine core stage with two solid rocket boosters and an Earth departure stage (EDS). The same engine will power the EDS and the Ares I second stage. For the Ares IVGVT, the current plan is to test six configurations in three unique test positions inside TS 4550. Position 1 represents the entire launch stack at liftoff (using inert first stage segments). Position 2 consists of the entire launch stack at first stage burn-out (using empty first stage segments). Four Ares I second stage test configurations will be tested in Position 3, consisting of the Upper Stage and Orion crew module in four nominal conditions: J-2X engine ignition, post Launch Abort System (LAS) jettison, critical slosh mass, and J-2X burn-out. Because of long disuse, TS 4550 is being repaired and reactivated to conduct the Ares I IVGVT. The Shuttle-era platforms have been removed and are being replaced with mast climbers that provide ready access to the test articles and can be moved easily to support different positions within the test stand. The electrical power distribution system for TS 4550 was upgraded. Two new cranes will help move test articles at the test stand and at the Redstone Arsenal railhead where first stage segments will be received in 2011. The Hydrodynamic Support systems (HDSs) used for Saturn and Shuttle have been disassembled and evaluated for use during IVGVT. Analyses indicate that the 45-year-old HDSs can be refurbished to support the Ares I IVGVT. An alternate concept for a pneumatic suspension system is also being explored. A decision on which suspension system configuration to use for IVGVT will be made in 2010. In the next three years, the team will complete the updates to TS 4550, upgrade the test and data collection equipment, and finalize the configurations of the test articles to be used in the IVGVT. With NASA's GVT capabilities reestablished, the FITO team will be well positioned to perform similar work on Ares V, the largest exploration launch vehicle NASA has ever built. The GVT effort continues NASA's 50-year commitment to using testing and data analysis for safer, more reliable launch vehicles.

Tuma, M. L.↗
NASA NTRS1997

Global Mapping of the Interstellar Medium in the Far Ultraviolet

In early 1993, funding for the NUVIEWS experiment was initiated. The experiment was completed and delivered to Wallops Flight Facility in March 1996, where it has completed flight integration and testing successfully. We feel that the three year development time was too long by a year, and that the history deserves some explanation. The construction of four complete four-mirror telescope systems with unique multilayer coatings, superpolished aspheres, and four large-format, high-resolution microchannel-plate detectors required a substantial effort. Our original design included only three telescopes, but we added a fourth 18 months ago to ensure rejection of all potential contaminating line features. A six-month SMEX Definition study in 1994 required substantial efforts by key personnel. There was great synergy here: the four NUVIEWS detectors are prototypes for the SMEX UV-survey mission (JUNO). In 1993, the Principal Investigator C. Martin took a position at Caltech. The transition of the laboratory from Columbia to Caltech was unfortunately timed and led to more delays, including an additional laboratory move and calibration tank/clean room reconstruction. Following the May NUVIEWS launch, the laboratory move to Caltech will be complete.

Martin, Christopher↗
DOE OSTI2020

Dissertation Proposal: Innovations in Pulsed Power and Plasma Science Theory Simulation and Experiment

Pulsed power and plasma physics are topics of great study at both Sandia National Laboratories (SNL or Sandia) and the University of New Mexico (UNM). The goal of this research is to further knowledge and understanding of these fields using the resources of both SNL and UNM in three ways. The first way is through the comprehension, application, and testing of theory. Reading and analytically deriving theoretical solutions of problems both real-world and simplified will allow for a fresh perspective and the furthering of the theory. One such theory is Ottinger's generalized theory for voltage measurement in magnetically insulated transmission lines (MITLs). By working through the math, a deeper understanding of the theory is gained from which one may add more physically accurate and/or more detailed physics into the theory. Additionally, understanding the theory lays a good foundation from which one can analyze, test, and compare results to the theory in the following two ways that will advance the fields of pulsed power and plasma physics. The second way is through the modeling and simulation of real-world and simplified problems that utilize and test the afore mentioned theories. Theory can be applied to a simulation domain by using the unstructured time-domain electromagnetic (UTDEM) codes EMPHASIS and EMPIRE as well as the physical modeling software CUBIT, all of which were developed at SNL. Problems such as the modeling and design of the extended MITL on HERMES III, the understanding of space-charge-limited emission from vacuum cathodes, and the interaction between a relativistic electron beam and an ideal gas can all be modeled, simulated, and analyzed with this set of codes. Here the advantage is three-fold. Firstly, theory that describes our understanding of these problems can be put to the test and advanced through iterative simulation and analysis. Secondly, the understanding of these problems will have a positive impact on national security through the advancement of the technological capability of the United States of America. Thirdly, and not unrelated to the prior advantage, is the validation and verification of EMPIRE and EMPHASIS. This segues into the third way, which is through experiment and the comparison of experiment to simulated and theoretical results. Performing experimental comparisons completes the scientific method and grounds all of the work in reality. Being able to physically test theory and simulation is necessary for any real conclusions to be drawn. Another advantage for carrying out experimental work is to advance the physical testing capabilities of SNL. Several systems will be developed and tested through the course of this work that positively impact technological advancement of Sandia National Labs. Lastly, all of the above work will converge to yield a well-rounded perspective that ties the three categories of research together.

42 ENGINEERING↗
NASA NTRS2004

Resolving the Issues with Flywheel Position Sensors

For the past few years, the Advanced Electrical Systems Branch here at NASA Glenn has been pursuing research in the area of flywheels. The purpose of these pursuits has been t o explore the potential for flywheels to replace current battery-powered systems in space. So far it has been learned that flywheels offer large momentum storage capacity, comparatively small volume, high durability, and near- complete discharge capabilities, all of which are advancements over the existing nickel hydrogen and nickel cadmium batteries. Another significant advantage of flywheels is the potential they offer for combining the function of attitude control with energy storage. During the summer of 2004, I worked with Dr. Barbara Kenny in the Advanced Electrical Systems Branch, supporting the work she is doing by analyzing and testing some new components for the new Generation-2 flywheel. To monitor the speed and angular position of the flywheel rotor, a once-around (OAR) signal along with a sensorless algorithm is used. The OAR signal is used for the magnetic bearings that keep the flywheel suspended for frictionless operation. The sensorless algorithm is used for the flywheel motor/generator control. The OAR is generated from position sensors that monitor a circular plate. The plate has a cut down the middle such that one half of the circle is on a slightly lower level than the other. Every half-turn, or 180, the sensors detect the "cut" on the plate, and trigger the OAR, telling the computer that the rotor has made half a revolution. This, however, doesn't provide needed detailed information about the angular position of the rotor, since it only provides a signal alert every half- revolution. This is enough information for the magnetic bearing control but is insufficient for the motor/generator control. A new resolver was designed such that it would give continuous angle information rather than the 180 degree information of the OAR. The new resolver has two separate observable pieces: a flat middle section to monitor vertical motion, and an angled section around the circumference, which, when observed from above, produces a sine-wave displacement through the entire 360" revolution. My first job when I arrived this summer was to calibrate the sensors that would be mounted on the inside of the flywheel casing to monitor the position (angular and vertical) of the shaft. After calibration, I used the sensors to evaluate voltage outputs created by position differences between two pairs of sensors on the angled portion of the resolver for eight different angular positions, moving the resolver vertically and laterally through its entire potential range of motion. The results of these tests will be used to determine the rotor angular (and axial) position from the sensor readings once the new flywheel unit is assembled. The sensorless algorighm mentioned above consists of two operations: the signal injection method and the back electro-motive force (EMF). The signal injection is meant to work at low speeds, while the back EMF algorithm is meant to work at higher speeds. Both work together to determine the correct estimate of rotor position and speed based on the measured motor/generator current. It was determined that we wanted to know exactly how accurate our estimation methods were, and so a resolver (a commercially available mechanical sensor mounted to the motor/generator shaft to measure rotor position and speed) and a "Resolver to Digital" (R2D) circuit board was purchased to make the comparison to the existing estimation. My work related to the R2D board has included the following: creating two connector cables (one to power the circuit and one to get readable output off the board), writing Simulink code to process the board's output, and building a dSpace panel to control and monitor the circuit. The next step in the process will be to perform tests to compare the estimated rotor position and speed from the sensorless algorithm to the actual rotor and speed from the resolver signal.

Fehrmann, Elizabeth A.↗
DOE OSTI2024

Proximal Galerkin: A Structure-Preserving Finite Element Method for Pointwise Bound Constraints

The proximal Galerkin finite element method is a high-order, low iteration complexity, nonlinear numerical method that preserves the geometric and algebraic structure of pointwise bound constraints in infinite-dimensional function spaces. This paper introduces the proximal Galerkin method and applies it to solve free boundary problems, enforce discrete maximum principles, and develop a scalable, mesh-independent algorithm for optimal design with pointwise bound constraints. This paper also introduces the latent variable proximal point (LVPP) algorithm, from which the proximal Galerkin method derives. When analyzing the classical obstacle problem, we discover that the underlying variational inequality can be replaced by a sequence of second-order partial differential equations (PDEs) that are readily discretized and solved with, e.g., the proximal Galerkin method. Throughout this work, we arrive at several contributions that may be of independent interest. These include (1) a semilinear PDE we refer to as the entropic Poisson equation; (2) an algebraic/geometric connection between high-order positivity-preserving discretizations and certain infinite-dimensional Lie groups; and (3) a gradient-based, bound-preserving algorithm for two-field, density-based topology optimization. The complete proximal Galerkin methodology combines ideas from nonlinear programming, functional analysis, tropical algebra, and differential geometry and can potentially lead to new synergies among these areas as well as within variational and numerical analysis. Open-source implementations of our methods accompany this work to facilitate reproduction and broader adoption.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

A standard capsule design for structural material testing in the Advanced Test Reactor

Nuclear materials testing is commonly completed in various material test and research reactors throughout the world, including the Advanced Test Reactor (ATR), but the current capsule design, analysis, and fabrication process can take years to complete. To decrease the costs and time associated with materials testing, a standard capsule has been designed which houses various specimen geometries and allows irradiation in virtually any ATR test position. The standard capsule features locking end caps which connect and lock together to form the capsule stack, eliminating the need for a basket and maximizing the quantity of specimens which are contained within the capsule. A customizable internal gas gap provides thermal resistance between the specimens and reactor coolant, making specimen temperatures from approximately 370 to 1000 K achievable. The flexibility of the capsule design allows experimenters to choose irradiation positions based off desired neutron flux, with typical fluences per cycle ranging from 8.8x10 19 to 2.3x10 21 n/cm 2 , depending on experiment position. Here this paper presents and discusses the standard capsule design and analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2021

New Fracture Diagnostic Tool for Unconventionals: High-Resolution Distributed Strain Sensing via Rayleigh Frequency Shift during Production in Hydraulic Fracture Test 2

Fiber Optic monitoring in unconventional reservoirs has proven to be an invaluable diagnostic tool for assessing both near-wellbore stimulation effectiveness and to help describe the far-field frac geometries created by hydraulic fracture stimulation. Unfortunately, gaining any detailed qualitative and quantitative understanding of the near-wellbore frac geometry or cluster/stage productivity during production via Fiber Optic (FO) has proven to be more difficult, particularly in wells producing liquids. A new FO diagnostic method, Distributed Strain Sensing based on Rayleigh Frequency Shift (DSS-RFS), first demonstrated for oil and gas applications in the Hydraulic Test Site 2 (HFTS2) provides new insights about the characteristics of near-wellbore-region (NWR) during production. DSS-RFS is different from other FO strain measurements because it relies on accurate measurement of frequency shifts of Rayleigh backscattered spectrum obtained by scanning the fiber with a coherent optical time-domain reflectometer with a range of laser frequencies using a tunable-wavelength laser system. Changes in strain are measured with an extremely high spatial resolution of 20 cm and with high signal-to-noise ratios over long distances. In HFTS2, strain changes for the entire wellbore have been measured twice during scheduled shut-in and reopening operations (February 2020 and September 2020). After removing temperature effects, consistent strain changes have been observed at the location of most perforation clusters. These are caused by near wellbore fracture aperture changes due to pressure increases during shut-in within the near-wellbore fracture network. The strain-change patterns from the DSS-RFS during shut-in correlate very well with the location of clusters and allow for the definition of extending intervals with positive strain signals at each cluster and slightly compressing intervals with negative strain signals between the clusters and in the non stimulated intervals. The locations of the measured positive strain peaks also show good correspondence to DAS acoustic intensity measurements acquired during the stimulation. The geometry and magnitude of the strain changes differ significantly between the two tested completion designs in the same well. During shut in and reopening each cluster exhibit its own strain-change / pressure path. In addition, the September 2020 dataset also revealed the existence of small but measurable strain changes as consequence of pressure decline during production. These strain changes also correlate well with the presence of producing clusters, but the strain-rate signals are opposite to that obtained during shut-in and reopening operations. Although Downloaded from http://onepetro.org/URTECONF/proceedings-pdf/21URTC/2-21URTC/D021S031R002/2477551/urtec-2021-5408-ms.pdf/1 by Carol Worster on 28 February 2022 URTeC 5408 2 we are still in the early stages of exploring the potential of this novel FO technique, we believe that the highly detailed information contained in the measurement of strain changes using DSS-RFS during production can significantly improve our understanding of near-wellbore hydraulic fracture characteristics and the relationships between stimulation and production from unconventional oil and gas wells.

04 OIL SHALES AND TAR SANDS↗
NASA NTRS1972

Accretion process of the moon

Recent geochemical and geophysical data suggest that the initial temperature of the moon was strongly peaked toward the lunar surface. To explain such an initial temperature distribution, a simple model of accretion process of the moon is presented. The model assumes that the moon was formed from the accumulation of the solid particles or gases in the isolated, closed cloud. Two equations are derived to calculate the accretion rate and surface temperature of the accreting moon. Numerical calculations are made for a wide range of the parameters particle concentration and particle velocity in the cloud. A limited set of the parameters gives the initial temperature profiles as required by geochemical and geophysical data. These models of the proto-moon cloud indicate that the lunar outermost shell, about 400 km thick, was partially or completely molten just after the accretion of the moon and that the moon should have been formed in a period shorter than 1000 years. If the moon formed at a position nearer to the earth than its present one, the moon might have been formed in a period of less than one year.

Mizutani, H.↗
NASA NTRS1972

Accretion process of the moon.

Development of a simple model of the accretion process of the moon to explain its initial temperature distribution. The model assumes that the moon was formed from the accumulation of the solid particles or gases in the isolated, closed cloud. Two equations are derived to calculate the accretion rate and surface temperature of the accreting moon. Numerical calculations are made for a wide range of the particle concentrations and particle velocities in the cloud. A limited set of parameters gives the initial temperature profiles as required by geochemical and geophysical data. These models of the protomoon cloud indicate that the lunar outershell, about 400 km thick, was partially or completely molten just after the accretion of the moon and that the moon should have been formed in a period shorter than 1000 yr. If the moon formed at a position nearer to the earth than its present one, the moon might have been formed in a period of less than one year.

Mizutani, H.↗
NASA NTRS1972

Characteristics of the unsteady shock-induced laminar boundary layer on a flat plate.

The unsteady shock-induced laminar boundary layer on a flat plate is theoretically studied for shock speeds ranging from 1.12 to 9 km/sec. Boundary layer flows for real air, assumed to be in thermochemical equilibrium, are analyzed by extending Lam's work on shock-induced laminar boundary layers to equilibrium dissociated and ionized flows. A complete description of the unsteady nature of the boundary layer is presented in terms of heat transfer and several boundary layer thickness quantities as functions of a single time-position variable. Boundary layer development is considered for two points of view. Time-dependent boundary layer development and approach to steady state for any fixed position on the plate is described, as is the configuration of the boundary layer with position on the plate at any point in time.

Cook, W. J.↗
NASA NTRS1975

Leak detector

A detector for sensing a leaking of fluid pressures is reported. The detector is characterized by an hermetically sealed housing confining therewithin a first normalized pressure, a connector for coupling the housing in direct communication with a suspected leak established within a substantially sealed body, an electrical circuit having a first or normalized configuration and including a pair of circuit completing electrical contacts and means mounting at least one contact of said pair of contacts on a flexible wall of the housing supporting the contact for movement from a first position along a linear path to a second position in response to an altering of the pressure confined within the housing for thereby altering the configuration of the circuit.

Sawyer, J. T.↗
NASA NTRS1984

Noise generated by a propeller in a wake

Propeller performance and noise were measured on two model scale propellers operating in an anechoic flow environment with and without a wake. Wake thickness of one and three propeller chords were generated by an airfoil which spanned the full diameter of the propeller. Noise measurements were made in the relative near field of the propeller at three streamwise and three azimuthal positions. The data show that as much as 10 dB increase in the OASPL results when a wake is introduced into an operating propeller. Performance data are also presented for completeness.

Block, P. J. W.↗