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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 NTRS2021

Demonstration of a 1-D Submillimeter-Wave Phased Array with MEMS Phase Shifters

At submillimeter-wave frequencies, due to the nonavailability of low-loss phase shifters, electronic antenna beam scanning is difficult to realize. Traditionally, power-hungry and bulky motors are used to mechanically scan the antenna beam. At lower-frequencies, phased array antennas are most commonly used where low-loss phase shifters are used with the array elements to accomplish beam steering. However, development of similar phased array antennas at submillimeter-waves has been challenging. Recently, we have developed a low-loss microelectromechanical systems (MEMS) based phased shifter in the 500-750 GHz band. In this work, we present a submillimeter-wave phased array antenna system with a cavity-backed double slot antenna architecture using the MEMS-based phase shifters. To demonstrate the concept, we developed two arrays: first one is a 8×1 linear antenna array with a fixed waveguide feeding network that achieved ±20◦ beam scanning, 18 dB directivity, and less than 1 dB scan loss over the design frequency of 500–570 GHz. The second one is a 4 × 1 linear antenna array with integrated MEMS-based phase shifters on each array element, achieving 15 dB directivity and capable of dynamic beam scanning over a range of ±9 ◦ . All the plots presented are simulated results since the parts are currently being fabricated. We hope to have access to our assembly and measurement facilities over the next few months and present measured performances at the conference.

Chattopadhyay, G.↗
NASA NTRS2025

Temperature Variation Analysis of the STIM300 Inertial Measurement Unit

A key navigation instrument found on most autonomous and semi-autonomous platforms is the inertial measurement unit (IMU). This type of sensor is a combination of microelectromechanical systems (MEMS) that provide inertial information to the navigation system. Typical MEMS hardware include a gyroscope and an accelerometer (for rates and accelerations, respectively) within a single platform. The Near Earth Asteroid (NEA) Scout mission, slated to launch in October of 2018 (Author’s note: NEA Scout ultimately launch on November 16, 2022), carries an on-board IMU from Sensonor. This particular model has yet to see spaceflight, and questions about its on-orbit reliability remain. Dynamic tests were produced in the summer of 2016 by a visiting faculty member from Arkansas Tech University, Daniel Bullock. During these experiments, concerns about the noise characteristics of the sensor were raised, specifically relating to how temperature fluctuations affected the unit. It was found that the IMU took an extended period of time before reaching an internal steady state temperature. These tests often displayed large temperature variations, making the calculation of noise characteristics, such as bias drift, difficult to attribute entirely to noise. Static and dynamic tests were re-performed under more stringent constraints on temperature. Tests reported herein conclude that the IMU is adequately capable of providing inertial information for the NEA Scout mission.

Ivan Rodrigues Bertaska↗
NASA NTRS1999

Fabrication system, method and apparatus for microelectromechanical devices

A fabrication system and method of fabrication for producing microelectromechanical devices such as field-effect displays using thin-film technology. A spacer is carried at its proximal end on the surface of a substrate having field-effect emitters with the spacer being enabled for tilting movement from a nested position to a deployed position which is orthogonal to the plane of the substrate. An actuator is formed with one end connected with the substrate and another end connected with spacer. The actuator is made of a shape memory alloy material which contracts when heated through the material's phase-change transition temperature. Contraction of the actuator exerts a pulling force on the spacer which is tilted to the deployed position. A plurality of the spacers are distributed over the area of the display. A glass plate having a phosphor-coated surface is fitted over the distal ends of the deployed spacer.

Johnson, A. David↗
NASA NTRS1991

Advances in microsensor development for gas and flow measurement in space power and propulsion systems

Emerging microelectromechanical sculpturing technology is presently extended, in conjunction with the use of deep semiconductor impurities having extreme flow sensitivities, small masses for shortest time response, and unconventional electrode schemes for elevated-temperature operation, for rocket-engine fuel flow sensing tasks. The radiation component of heat transfer is negligible, so that the device operates on the basis of conduction and convection loss.

Henderson, H. T.↗
NASA NTRS2002

A Piezoelectric Unimorph Deformable Mirror Concept by Wafer Transfer for Ultra Large Space Telescopes

Future concepts of ultra large space telescopes include segmented silicon mirrors and inflatable polymer mirrors. Primary mirrors for these systems cannot meet optical surface figure requirements and are likely to generate over several microns of wavefront errors. In order to correct for these large wavefront errors, high stroke optical quality deformable mirrors are required. JPL has recently developed a new technology for transferring an entire wafer-level mirror membrane from one substrate to another. A thin membrane, 100 mm in diameter, has been successfully transferred without using adhesives or polymers. The measured peak-to-valley surface error of a transferred and patterned membrane (1 mm x 1 mm x 0.016 mm) is only 9 nm. The mirror element actuation principle is based on a piezoelectric unimorph. A voltage applied to the piezoelectric layer induces stress in the longitudinal direction causing the film to deform and pull on the mirror connected to it. The advantage of this approach is that the small longitudinal strains obtainable from a piezoelectric material at modest voltages are thus translated into large vertical displacements. Modeling is performed for a unimorph membrane consisting of clamped rectangular membrane with a PZT layer with variable dimensions. The membrane transfer technology is combined with the piezoelectric bimorph actuator concept to constitute a compact deformable mirror device with a large stroke actuation of a continuous mirror membrane, resulting in a compact A0 systems for use in ultra large space telescopes.

continuous mirror↗
NASA NTRS2015

Evaluation of MEMS-Based Wireless Accelerometer Sensors in Detecting Gear Tooth Faults in Helicopter Transmissions

The diagnostics capability of micro-electro-mechanical systems (MEMS) based rotating accelerometer sensors in detecting gear tooth crack failures in helicopter main-rotor transmissions was evaluated. MEMS sensors were installed on a pre-notched OH-58C spiral-bevel pinion gear. Endurance tests were performed and the gear was run to tooth fracture failure. Results from the MEMS sensor were compared to conventional accelerometers mounted on the transmission housing. Most of the four stationary accelerometers mounted on the gear box housing and most of the CI's used gave indications of failure at the end of the test. The MEMS system performed well and lasted the entire test. All MEMS accelerometers gave an indication of failure at the end of the test. The MEMS systems performed as well, if not better, than the stationary accelerometers mounted on the gear box housing with regards to gear tooth fault detection. For both the MEMS sensors and stationary sensors, the fault detection time was not much sooner than the actual tooth fracture time. The MEMS sensor spectrum data showed large first order shaft frequency sidebands due to the measurement rotating frame of reference. The method of constructing a pseudo tach signal from periodic characteristics of the vibration data was successful in deriving a TSA signal without an actual tach and proved as an effective way to improve fault detection for the MEMS.

gears↗
NASA NTRS2002

MEMS adaptive optics

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stroke actuator membrane transfer segmented space ↗
NASA NTRS2000

COTS MEMS

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MicroElectroMechanical Systems MEMS COTS technolog↗
NASA NTRS2000

Comparison of IC and MEMS packaging reliability approaches

This paper reviews the current status of IC and MEMS packaging technology with emphasis on reliability, compares the norm for IC packaging reliability evaluation and identifies challenges for development of reliability methodologies for MEMS, and finally, proposes the use of COTS MEMS in order to start generating statistically meaningful reliability data as a vehicle for future standardization of reliability test methodology for MEMS packaging.

microelectromechanical systems (MEMS) chip scale p↗
NASA NTRS1999

NEPP Cots Mems Programs

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COTS Microelectromechanical Systems MEMS reliabili↗
NASA NTRS2004

Isolated post resonator mesogyroscope

A new symmetric vibratory gyroscope principle has been devised in which a central post proof mass is counter-rocked against an outer sensing plate such that the motion is isolated from the gyroscope case. Prototype gyroscopes have been designed and fabricated with micromachined silicon at mesoscale (20-cm resonator width), vs. microscale (e.g., 2-mm resonator width) to achieve higher sensitivity and machined precision. This novel mesogyro design arose out of an ongoing technical cooperation between JPL and Boeing begun in 1997 to advance the design of micro-inertial sensors for low-cost space applications. This paper describes the theory of operation of the mesogyro and relationships with other vibratory gyroscopes, the mechanical design, closed loop electronics design, bulk silicon fabrication and packaged gyroscope assembly and test methods. The initial packaged prototype test results are reported for what is believed to be the first silicon mesogyroscope.

mesogyroscope↗