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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 145 records · Page 8

Microelectronics Instrument Products Shock and Vibration Electro-optics: C-Qualification Test Report

In this test report all measurements made during testing are recorded in ATP 20049 DS data sheets and are included in the log. The motor/encoder (henceforth referred to as the UUT) test sequence began with a baseline functional evaluation, which demonstrated that the motor satisfied the operating torque, cogging torque, winding resistance, and mechanical requirements of SOW. In addition, the encoder electrical requirements were verified, as well as the alignment of the encoder outputs relative tc, the motor shaft position. There were no discrepancies observed in this portion of the test. The UUT was then exposed to a number of environments, including thermal vacuum, thermal cycling, random and sine vibration, and mechanical shock. During the thermal environments, the performance of the UUT under load was verified at specified points in the cycles, as described in ATP 20049. In addition, the UUT was bench tested between the two thermal environments. No anomalies were observed during the thermal tests. The load attachment method was subsequently corrected, and vibration of S/N 0002 began while 0003 was being repaired.

Source record↗

Effects of Transverse Seat Vibration on Near-Viewing Readability of Alphanumeric Symbology

We measured the impacts on human visual function of a range of vibration levels (0.15, 0.3, 0.5, and 0.7 g) at the frequency and along the axis of the anticipated Ares thrust oscillation. We found statistically significant and equivalent decrements in performance on a reading and a numeric processing task at tested vibration levels above 0.3 g (0-to-peak), but no evidence of after-effects. At the smallest font and highest vibration level tested, the average effect was a 50 percent increase in response time and six-fold increase in errors. Our findings support a preliminary trade space in which currently planned Orion font sizes and text spacing appear to be too small to support accurate and efficient reading at the tested vibration levels above 0.3 g, but not too small to support reading at 0.3 g. This study does not address potential impacts on crew cognitive decision-making or motor control and does not test either the full induced Orion-Ares environment with its sustained Gx-loading or the full complexity of the final Orion seat-helmet-suit interface. A final determination of the Orion-Ares program limit on vibration must take these additional factors into consideration and, thus, may need to be lower than that needed to support effective reading at 1-Gx bias.

Readability↗

Annular Momentum Control Device (AMCD). Volume 1: Laboratory model development

The annular momentum control device (AMCD) a thin hoop-like wheel with neither shaft nor spokes is described. The wheel floats in a magnetic field and can be rotated by a segmented motor. Potential advantages of such a wheel are low weight, configuration flexibility, a wheel that stiffens with increased speed, vibration isolation, and increased reliability. The analysis, design, fabrication, and testing is described of the laboratory model of the AMCD.

Source record↗

A new assessment of chamber pressure oscillations in the shuttle SRB

Oscillatory data from three static firings of the shuttle SRB are analyzed. The data from these and four additional motors were pooled and predictions made for the maximum amplitude and range of frequency to be expected in future motor firings. The predictions form the basis for various studies by other groups of the shuttle's response to vibration generated by the SRB's.

Mathes, H. B.↗

A 10 deg K triple-expansion Stirling-cycle cryocooler

The design of a triple expansion closed cycle Stirling cryocooler optimized for a cooling load of 50 mW at 10 K is described. The cooler was designed with the objectives of low power, low weight, compactness, low mechanical motion, low electromagnetic noise, and low output temperature fluctuations. The design employs a direct drive linear motion piston motor and a triple expansion free displacer. Piston motion is controlled by feedback from an optical position transducer. Mechanical vibrations are attenuated with a passive resonant counterbalance. Electromagnetic noise is attenuated with layered high permeability magnetic shielding. The regenerators move with the displacer within a thin titanium cold finger. The piston and displacer oscillate at 8.33 Hz on bearings and seals of reinforced Teflon. The cooler is designed to provide the desired 50 mW of cooling at 10 K with a power input of less than 100 W. The piston can be driven at a greater stroke to produce up to 200 mW of cooling with an input power of 250 W. A lead and copper cold tip heat exchanger will limit temperature fluctuations to within 0.01 K.

Newman, W.↗

Piezoelectric Driver for Incremental Motion

Vibrating device containing two piezoelectric ceramic slabs acts as mechanical driver. Eventually substitutes for small continuous or stepping electric motors of slow to moderate speeds. Piezoelectric driver simple in construction, requires no precise dimensions, inexpensive to make, and needs no lubrication. Not damaged by stalling or overloads and safe for use in explosive atmospheres; Motion controllable in micron-size increments, and holds position when power turned off. Potential applications as positioner or mover. Used to position instrument pointers, antennas, or solar panels; to focus lenses; or operate tuners, recording instruments, or valves.

Bruman, Joseph R.↗

Sealing Nitrogen Tetroxide Leaks

Use of Furmanite FSC-N-6B sealant in clam-shell sealing device makes it possible to stop leaks of nitrogen tetroxide through defective or improperly-seated plumbing fittings. Devised to stop leaks in vent line of small rocket motor on Space Shuttle. Also used on plumbing containing hydrazine and other hazardous fluids, and repair withstands severe temperature, vibration, and shock. Leaks stopped in place, without draining or replacement of leaking parts.

Garrard, George G.↗

Effects of entrained water and strong turbulence on afterburning within solid rocket motor plumes

During the first few seconds of the space shuttle trajectory, the solid rocket boosters will be in the proximity of the launch pad. Because of the launch pad structures and the surface of the earth, the turbulent mixing experienced by the exhaust gases will be greatly increased over that for the free flight situation. In addition, a system will be present, designed to protect the lifting vehicle from launch structure vibrations, which will inject quantities of liquid water into the hot plume. The effects of these two phenomena on the temperatures, chemical composition, and flow field present in the afterburning solid rocket motor exhaust plumes of the space shuttle were studied. Results are included from both a computational model of the afterburning and supporting measurements from Titan 3 exhaust plumes taken at Kennedy Space Center with infrared scanned radiometers.

Gomberg, R. I.↗

Random Vibration Simulation and Testing of a Compact, Magnetic Bearing Supported Blower for Space Applications

NASA is developing a next-generation CO2 removal system, the Four Bed Carbon Dioxide Scrubber (4BCO2), which will use the International Space Station (ISS) as a testbed. A key component of both the existing and the new system is the blower that provides the airflow through the CO2 sorbent beds. To improve performance and reliability, magnetic bearings will be used in lieu of more conventional bearings (e.g. ball bearings or hydrodynamicbearings) to improve resistance to contaminants and enable extensibility with regards to blower speed, pressure rise and mass flow rate. The new blower features a high-efficiency permanent magnet motor, a five-axis, active magnetic bearing system, and a compact controller containing both a variable speed drive and magnetic bearing controller. The blower uses a centrifugal impeller to pull air from the inlet port and drive it through an annular space around the motor and magnetic bearing components to the exhaust port. Technical challenges of the blower and controller development include survival of the blower system under launch random vibration loads, operation in microgravity, packaging under strict size and weight requirements, and successful operation during 4BCO2 operational changeovers. Each serial build of the blower must pass a severe random vibration test to prove it will survive launch conditions. This paper discusses the vibration test requirements and provides details of a simulation performed to estimate the peak backup bearing displacements and loads. Results from the successful random vibration testing of the prototype build are discussed and compared to the simulation.

bearings↗

High temperature skin friction measurement

Skin friction measurement in the NASA Langley hypersonic propulsion facility is described. The sensor configuration utilized an existing balance, modified to provide thermal isolation and an increased standoff distance. For test run times of about 20 sec and ambient-air cooling of the test section and balance, the modified balance performed satisfactorily, even when it was subjected to acoustic and structural vibration. The balance is an inertially balanced closed-loop servo system where the current to a moving-coil motor needed to restore or null the output from the position sensor is a measure of the force or skin friction tending to displace the moving element. The accuracy of the sensor is directly affected by the position sensor in the feedback loop, in this case a linear-variable differential transformer which has proven to be influenced by temperature gradients.

Tcheng, Ping↗

Synchronous meteorological satellite system description document, volume 3

The structural design, analysis, and mechanical integration of the synchronous meteorological satellite system are presented. The subjects discussed are: (1) spacecraft configuration, (2) structural design, (3) static load tests, (4) fixed base sinusoidal vibration survey, (5) flight configuration sinusoidal vibration tests, (6) spacecraft acoustic test, and (7) separation and shock test. Descriptions of the auxiliary propulsion subsystem, the apogee boost motor, communications system, and thermal control subsystem are included.

Pipkin, F. B.↗

Application of fluidics to new control components

The inherent tolerance for nuclear radiation makes fluidic devices candidates for nuclear rocket control systems. Also, they are being considered for supersonic jet engine inlet control because of their high temperature and vibration tolerance. Three new control components being considered for these applications are described. A fluidic circuit to control a pneumatic stepping motor for nuclear rocket control drum actuation is discussed. An all-fluidic sensor being developed for determining the position of the normal shock in the inlet of a supersonic jet engine is outlined. A new vortex valve configuration is developed to prevent supersonic jet engine inlet unstarts by regulating bypass flow.

Dustin, M. O.↗

National geotechnical centrifuge

A high G-ton centrifuge, able to take a 2700 kg (6000 lb) payload up to 300 G, is described. The stability of dams and embankments, the bearing capacity of soil foundations, and the dynamic behavior of foundations due to vibration of machinery are examples of applications. A power rating of 6,000 kW (9,000 hp) was established for the motor. An acceptable maximum speed of 70 rpm was determined. A speed increase with a ratio of 1:3 is discussed. The isolated tension straps, the anti-spreader bar and the flexwall bucket, and safety precautions are also discussed.

Hallam, J. A.↗

Acoustic measurements on aerofoils moving in a circle at high speed

Features of the test apparatus, research objectives and sample test results at the Stanford University rotor aerodynamics and noise facility are described. A steel frame equipped to receive lead shot for damping vibrations supports the drive shaft for rotor blade elements. Sleeve bearings are employed to assure quietness, and a variable speed ac motor produces the rotations. The test stand can be configured for horizontal or vertical orientation of the drive shaft. The entire assembly is housed in an acoustically sealed room. Rotation conditions for hover and large angles of attack can be studied, together with rotational and blade element noises. Research is possible on broad band, discrete frequency, and high speed noise, with measurements taken 3 m from the center of the rotor. Acoustic signatures from Mach 0.3-0.93 trials with a NACA 0012 airfoil are provided.

Wright, S. E.↗

Solid Rocket Motor Case (SRMC) dynamic sensitivity to changes in composite properties

Traditional composite lamination theory was used to compute the constitutive matrices using a potential range of lamina properties. Sensitivity of vibrational frequencies was examined for variations in constituent materials and geometric properties. The material component interactions examined were the lamina longitudinal and transverse Young's modulus, the lamina Poisson's ratio, and the shear modulus. Fiber and resin properties were related to the frequency response through lamina properties. Geometric properties examined are void ratio and helical wind angle. Capabilities and applications of the SPAR and NASTRAN computer codes are examined for laminated cylindrical shells.

Tolbert, R. N.↗

Flight Balance For Skin-Friction Measurements

Skin-friction balance (flight balance) for use in flight on aircraft fuselage incorporates type-one, closed-loop control to make direct skin-friction force measurements. Curved surface element 2 in. (5.08 cm) in diameter used to sense tangential force of airstream passed over it. Linear electromagnetic force motor exerts restoring force that nulls position of sensing element. Applied skin-friction force measured by sensing amount of current through motor necessary to maintain null position. Unit is rugged, accurate, reliable, and easy to operate. Insensitivity of balance to background rectilinear vibrations and ability to sustain large transient loads during takeoffs and landings make it attractive for flight testing.

Tcheng, Ping↗

An evaluation of reaction wheel emitted vibrations for space telescope

Emitted forces and moments characteristics of the Space Telescope Reaction Wheel Assembly (ST RWA) were measured under room temperature and pressure, thermal extremes, and vibratory conditions. The RWA/Emitted Vibration Measurement Fixture was calibrated statically and dynamically, and background noise was measured with ST RWA not operating. A base line set of forces and moments of the ST RWA along and about three mutually perpendicular axes were recorded at room ambient. The temperature vibration sensitivites shown are those which were concluded to be a function of rotor unbalance changes and not associated with either spin motor nor rotor electronic changes.

Source record↗

Active balance system and vibration balanced machine

An active balance system is provided for counterbalancing vibrations of an axially reciprocating machine. The balance system includes a support member, a flexure assembly, a counterbalance mass, and a linear motor or an actuator. The support member is configured for attachment to the machine. The flexure assembly includes at least one flat spring having connections along a central portion and an outer peripheral portion. One of the central portion and the outer peripheral portion is fixedly mounted to the support member. The counterbalance mass is fixedly carried by the flexure assembly along another of the central portion and the outer peripheral portion. The linear motor has one of a stator and a mover fixedly mounted to the support member and another of the stator and the mover fixedly mounted to the counterbalance mass. The linear motor is operative to axially reciprocate the counterbalance mass.

Qiu, Songgang↗