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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Evaluation of a Low-Noise Formate Spiral-Bevel Gear Set

Studies to evaluate low-noise Formate spiral-bevel gears were performed. Experimental tests were performed on the OH-58D helicopter main-rotor transmission in the NASA Glenn 500-hp Helicopter Transmission Test Stand. Low-noise Formate spiral-bevel gears were compared to the baseline OH-58D spiral-bevel gear design, a high-strength design, and previously tested low-noise designs (including an original low-noise design and an improved-bearing-contact low-noise design). Noise, vibration, and tooth strain tests were performed. The Formate design showed a decrease in noise and vibration compared to the baseline OH-58D design, and was similar to that of the previously tested improved-bearing contact low-noise design. The pinion tooth stresses for the Formate design significantly decreased in comparison to the baseline OH-58D design. Also similar to that of the improved bearing-contact low-noise design, the maximum stresses of the Formate design shifted toward the heel, compared to the center of the face width for the baseline, high-strength, and previously tested low-noise designs.

Lewicki, David g.↗
NASA NTRS1983

The 30 GHz communications satellite low noise receiver

A Ka-band low noise front end in proof of concept (POC) model form for ultimate spaceborne communications receiver deployment was developed. The low noise receiver consists of a 27.5 to 30.0 GHz image enhanced mixer integrated with a 3.7 to 6.2 GHz FET low noise IF amplifier and driven by a self contained 23.8 GHz phase locked local oscillator source. The measured level of receiver performance over the 27.3 to 30.0 GHz RF/3.7 to 6.2 GHz IF band includes 5.5 to 6.5 dB (typ) SSB noise figure, 20.5 + or - 1.5 dB conversion gain and +23 dBm minimum third order two tone intermodulation output intercept point.

Steffek, L. J.↗
NASA NTRS1994

Low-Noise Spiral Bevel Gears

Modified spiral bevel gears that generate relatively little noise and vibration designed and fabricated for use in U.S. Army OH-58D helicopter. Noise reduced by 12 to 19 dB. Similar low-noise, low-vibration spiral bevel gears used in other helicopters, with consequent benefits in comfort and health of pilots and passengers, enhancement of pilots' performance and safety through reduction of audible distraction, and reduction in cost and weight of helicopters through reduction in amount of sound-proofing material. Low-noise, low-vibration spiral bevel gears also used in drive axles of cars and trucks for smoother, quieter rides.

Lewicki, David G.↗
NASA NTRS2009

Nonlinearly stacked low noise turbofan stator

A nonlinearly stacked low noise turbofan stator vane having a characteristic curve that is characterized by a nonlinear sweep and a nonlinear lean is provided. The stator is in an axial fan or compressor turbomachinery stage that is comprised of a collection of vanes whose highly three-dimensional shape is selected to reduce rotor-stator and rotor-strut interaction noise while maintaining the aerodynamic and mechanical performance of the vane. The nonlinearly stacked low noise turbofan stator vane reduces noise associated with the fan stage of turbomachinery to improve environmental compatibility.

Schuster, William B.↗
NASA NTRS1976

Ku band low noise parametric amplifier

A low noise, K sub u-band, parametric amplifier (paramp) was developed. The unit is a spacecraft-qualifiable, prototype, parametric amplifier for eventual application in the shuttle orbiter. The amplifier was required to have a noise temperature of less than 150 K. A noise temperature of less than 120 K at a gain level of 17 db was achieved. A 3-db bandwidth in excess of 350 MHz was attained, while deviation from phase linearity of about + or - 1 degree over 50 MHz was achieved. The paramp operates within specification over an ambient temperature range of -5 C to +50 C. The performance requirements and the operation of the K sub u-band parametric amplifier system are described. The final test results are also given.

Source record↗
NASA NTRS2019

Dynamic Replanning of Low Noise Rotorcraft Operations

A new method for rapidly planning and dynamically replanning low noise rotorcraft flight operations is developed. A large database of rotorcraft maneuver segments is generated, and an acoustic cost is assigned to each segment by using a computationally efficient semiempirical rotorcraft noise modeling method that accurately models the changes in rotor noise caused by maneuvering flight. Combinatoric optimization techniques are then employed to combine these maneuver segments into a low noise optimal flight path. A simple heuristic for estimating the total acoustic cost required to reach the target location is developed and incorporated into the search algorithm, allowing the computation of low noise paths in seconds. A procedure for implementing an “anytime” version of the method is described, enabling feasible solutions to be dynamically replanned “on the fly”—i.e., in fractions of a second—and refined over time to a low noise optimal solution.

Greenwood, Eric↗
NASA NTRS1992

NASA HSR phase 1 low noise nozzle technology program overview

The topics covered include the following: supersonic cruise, the High Speed Research (HSR) Program, the High Speed Civil Transport (HSCT) noise challenge, low-noise nozzle technology elements, the HSR Source Noise Reduction Program, and NASA HSR plan propulsion elements.

Blaha, Bernard J.↗
NASA NTRS1992

Cooled Low-Noise HEMT Microwave Amplifiers

Prototype cooled low-noise microwave amplifiers based on high-electron-mobility transistors (HEMT's) considered as replacements for cooled ruby masers used as low-noise receiver-front-end amplifiers in communications, radio science, radar systems, radio astronomy, and telemetry. HEMT amplifier operates at 12 K, requires less cooling power and operates at lower cost with simpler, more-reliable cooling system.

Bautista, J. Javier↗
NASA NTRS2020

Noise Evaluation of Various High-gain, Very-low-noise Current Sense Amplifier Circuits

We report an evaluation of three different electronic topologies for a high-gain, very-low-noise current sense amplifier (CSA) for use in remote sensing applications. The circuits in question were built from commercially available parts and were evaluated for their performance in an interface to a photodetector used in NASA’s Lunar Flashlight infrared spectrometer spacecraft. Through constraints on the test environment, we were able to reduce the impact of systematic noise sources by making them common mode to the measurement. The parts compared were based on the ADA4530-1, the LTC6240, and the LSK389A. We determined which of the three different versions of the CSA had superior noise performance for selection for use on the instrument. Two tests and simulations of each board compare and contrast functionality and performance, both qualitatively and quantitatively, and based on those results, we show that the ADA4350-1 out-performed the opposing components.

Foor, David↗
NASA NTRS1984

Low-Noise Submillimeter-Wave Diode

Low noise achieved without usual high resistance. Barrier of p-type material placed between metal anode and heavily-doped gallium arsenide. Ntype epitaxial layer eliminated. Barrier prevents quantum tunneling of electrons between semiconductor and metal. Higher breakdown structure provided.

Mattauch, R. J.↗
NASA NTRS1984

A low noise infrared spot scanner for testing detector arrays

A low noise spot scanner has been built for use in testing the performance of infrared detector arrays for NASA's IR detector technology development program and the University of California's MICRO program. The scanner provides a convenient low noise detector test environment and a wide range of test conditions including versatile temperature control of the detector, ambient background, and blackbody source temperature and control of spot size, color, and brightness.

Puetter, R. C.↗
NASA NTRS1988

A 2.3-GHz low-noise cryo-FET amplifier

A cryogenic cooled, low-noise Field Effect Transistor (FET) amplifier assembly for use at 2.2 to 2.3 GHz was developed for the DSN to meet the requirements of a Very Long Baseline Interferometry (VLBI) upgrade. An amplifier assembly was developed at JPL that uses a commercial closed-cycle helium refrigerator (CCR) to cool a FET amplifier to an operating temperature of 15 K. A cooled probe waveguide-to-coaxial transition similar to that used in the research and development Ultra-Low-Noise S-band Traveling Wave Maser (TWM) is used to minimize input line losses. Typical performance includes an input flange equivalent noise contribution of 14.5 K, a gain slope of less than 0.05 dB/MHz across a bandwidth of 2.2 to 2.3 GHz, an input VSWR of 1.5:1 at 2.25 GHz, and an insertion gain of 45 + or - 1 dB across the bandwidth of 2.2 to 2.3 GHz. Three 2.3 GHz FET/CCR assemblies were delivered to the DSN in the spring of 1987.

Loreman, J.↗
NASA NTRS1983

V-band low-noise integrated circuit receiver

A compact low-noise V-band integrated circuit receiver has been developed for space communication systems. The receiver accepts an RF input of 60-63 GHz and generates an IF output of 3-6 GHz. A Gunn oscillator at 57 GHz is phaselocked to a low-frequency reference source to achieve high stability and low FM noise. The receiver has an overall single sideband noise figure of less than 10.5 dB and an RF to IF gain of 40 dB over a 3-GHz RF bandwidth. All RF circuits are fabricated in integrated circuits on a Duroid substrate.

Chang, K.↗