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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Observations of MMOD Impact Damage to the ISS

This paper describes meteoroid and orbital debris (MMOD) damage observations on the International Space Station (ISS). Several hundred MMOD damage sites on ISS have been documented using imagery taken from ISS windows. MMOD damage sites visible from ISS windows are typically larger – approximately 5mm diameter and greater – due to the larger viewer-to-surface distance. Closer inspection of these surfaces by astronauts during spacewalks reveals many smaller features that are typically less distinct. Characterization of these features as MMOD or non- MMOD is difficult, but can be partially accomplished by matching physical characteristics of the damage against typical MMOD impact damage observed on ground-based impact tests. Numerous pieces of space-exposed ISS hardware were returned during space shuttle missions. Subsequent ground inspection of this hardware has also contributed to the database of ISS MMOD impact damage. A handful of orbital replacement units (ORUs) from the ISS active thermal control and electrical power subsystems were swapped out and returned during the Space Shuttle program. In addition, a reusable logistics module was deployed on ISS for a total 59.4 days on 11 shuttle missions between 2001 and 2011 and then brought back in the shuttle payload bay. All of this returned hardware was subjected to detailed post-flight inspections for MMOD damage, and a database with over 1,400 impact records has been collected. A description of the largest observed damage features is provided in the paper. In addition, a discussion of significant MMOD impact sites with operational or design aspects is presented. MMOD impact damage to the following ISS modules/subsystems is described: (1) Solar Arrays, (2) US and Russian windows, (3) Extravehicular Activity (EVA) handrails, (4) Radiators, and (5) Russian Functional Cargo Block (FGB) module.

Hyde, James L.↗
NASA NTRS2003

Modeling Charge Collection in Detector Arrays

A detector array charge collection model has been developed for use as an engineering tool to aid in the design of optical sensor missions for operation in the space radiation environment. This model is an enhancement of the prototype array charge collection model that was developed for the Next Generation Space Telescope (NGST) program. The primary enhancements were accounting for drift-assisted diffusion by Monte Carlo modeling techniques and implementing the modeling approaches in a windows-based code. The modeling is concerned with integrated charge collection within discrete pixels in the focal plane array (FPA), with high fidelity spatial resolution. It is applicable to all detector geometries including monolithc charge coupled devices (CCDs), Active Pixel Sensors (APS) and hybrid FPA geometries based on a detector array bump-bonded to a readout integrated circuit (ROIC).

Hardage, Donna↗
NASA NTRS2013

Thermal Control Using Liquid-Metal Bridge Switches

A short term effort (3-months) was undertaken to demonstrate the feasibility of a novel method to locally control the heat transfer rate and demonstrate the potential to achieve a turndown ratio of approximately 10:1. The technology had to be demonstrated to be at a TRL of 2-3, with a plan to advance it to a TRL 5-6. Here, we show that the concept recently developed in our laboratory, namely the pinned-contact, double droplet switch made by overfilling a hole drilled in a suitable substrate can be implemented with a low-melting temperature metal. When toggled near a second substrate, a liquid bridge can be reversibly connected or disconnected, on demand. We have shown experimentally that liquid-metal bridge switches can be made from gallium with a suitable choice of substrate materials, activation strategies, and control techniques. Individual as well as arrays of gallium bridge switches were shown to be feasible and can be robustly controlled. The very short response time of the bridge connection and disconnection (on the order of 1 millisecond) provides for utility in a wide range of applications. The liquid bridge switches may be controlled actively or passively. We have shown through computations and analysis that liquid bridge switches provide locally large turndown ratios (on the order of 103:1), so a relatively sparse packing of them would be needed to obtain the desired turndown ratio of 10:1. For the laboratory demonstrations, pressure activation was utilized. Simple designs for a passive control strategy are presented which are highly attractive for several reasons, including i) large turndown ratio, ii) no solid-moving parts, and iii) stable operation. Finally, we note that passive systems do not require any electronics for their control. This along with the relatively small molecular weight of candidate materials for the system, makes for a robust design outside of Earth?s magnetic field, where spacecraft are subject to significant radiation bombardment.

Hirsa, Amir H.↗
NASA NTRS2009

Silicon Wafer-Scale Substrate for Microshutters and Detector Arrays

The silicon substrate carrier was created so that a large-area array (in this case 62,000+ elements of a microshutter array) and a variety of discrete passive and active devices could be mounted on a single board, similar to a printed circuit board. However, the density and number of interconnects far exceeds the capabilities of printed circuit board technology. To overcome this hurdle, a method was developed to fabricate this carrier out of silicon and implement silicon integrated circuit (IC) technology. This method achieves a large number of high-density metal interconnects; a 100-percent yield over a 6-in. (approximately equal to 15-cm) diameter wafer (one unit per wafer); a rigid, thermally compatible structure (all components and operating conditions) to cryogenic temperatures; re-workability and component replaceability, if required; and the ability to precisely cut large-area holes through the substrate. A method that would employ indium bump technology along with wafer-scale integration onto a silicon carrier was also developed. By establishing a silicon-based version of a printed circuit board, the objectives could be met with one solution. The silicon substrate would be 2 mm thick to survive the environmental loads of a launch. More than 2,300 metal traces and over 1,500 individual wire bonds are required. To mate the microshutter array to the silicon substrate, more than 10,000 indium bumps are required. A window was cut in the substrate to allow the light signal to pass through the substrate and reach the microshutter array. The substrate was also the receptacle for multiple unpackaged IC die wire-bonded directly to the substrate (thus conserving space over conventionally packaged die). Unique features of this technology include the implementation of a 2-mmthick silicon wafer to withstand extreme mechanical loads (from a rocket launch); integrated polysilicon resistor heaters directly on the substrate; the precise formation of an open aperture (approximately equal to 3x3cm) without any crack propagation; implementation of IR transmission blocking techniques; and compatibility with indium bump bonding. Although designed for the microshutter arrays for the NIRSpec instrument on the James Webb Space Telescope, these substrates can be linked to microshutter applications in the photomask generation and stepper equipment used to make ICs and microelectromechanical system (MEMS) devices.

Jhabvala, Murzy↗
NASA NTRS2013

PV Reliability Development Lessons from JPL's Flat Plate Solar Array Project

Key reliability and engineering lessons learned from the 20-year history of the Jet Propulsion Laboratory's Flat-Plate Solar Array Project and thin film module reliability research activities are presented and analyzed. Particular emphasis is placed on lessons applicable to evolving new module technologies and the organizations involved with these technologies. The user-specific demand for reliability is a strong function of the application, its location, and its expected duration. Lessons relative to effective means of specifying reliability are described, and commonly used test requirements are assessed from the standpoint of which are the most troublesome to pass, and which correlate best with field experience. Module design lessons are also summarized, including the significance of the most frequently encountered failure mechanisms and the role of encapsulate and cell reliability in determining module reliability. Lessons pertaining to research, design, and test approaches include the historical role and usefulness of qualification tests and field tests.

photovoltaics↗
NASA NTRS1984

High-efficiency module and array research

An outline is presented giving module high efficiency research activities and module technologies contributing to high efficiency. Some factors given on high efficiency are high cell packing factors, low optical losses, low electrical mismatch losses and low operating temperatures. Factors given which are associated with reliability of modules are high efficiency cells, narrow module borders, antisoiling coatings, and antireflection coatings on glass-air interfaces.

Ross, R. G., Jr.↗
NASA NTRS1989

Comparison of the measured and predicted response of the Earth Radiation Budget Experiment active cavity radiometer during solar observations

The Earth Radiation Budget Experiment consists of an array of radiometric instruments placed in earth orbit by the National Aeronautics and Space Administration to monitor the longwave and visible components of the earth's radiation budget. Presented is a dynamic electrothermal model of the active cavity radiometer used to measure the earth's total radiative exitance. Radiative exchange is modeled using the Monte Carlo method and transient conduction is treated using the finite element method. Also included is the feedback circuit which controls electrical substitution heating of the cavity. The model is shown to accurately predict the dynamic response of the instrument during solar calibration.

Mahan, J. R.↗
NASA NTRS1984

MOSAIC

The Mosaicked Optical Self-scanned Array Imaging Camera (MOSAIC), is a 50 sq cm active area detector system encompassing 5.76 million picture elements. This camera is being developed for use in astronomical instrumentation requiring the use of large area imaging detectors with high resolution photon counting capability in the space ultraviolet. This paper gives a descriptive outline of the MOSAIC camera system including: the 100 mm diameter microchannel plate intensifier, the 3 x 3 array of 800 x 800 pixel charge coupled devices, the signal processing and buffer storage subsystem, the electronic support and control subsystem, and the data processing subsystem. Performance characteristics of the camera and its subsystems are presented, based on system analysis.

Williams, J. T.↗
NASA NTRS2007

Active-Adaptive Control of Inlet Separation Using Supersonic Microjets

Flow separation in internal and external flows generally results in a significant degradation in aircraft performance. For internal flows, such as inlets and transmission ducts in aircraft propulsion systems, separation is undesirable as it reduces the overall system performance. The aim of this research has been to understand the nature of separation and more importantly, to explore techniques to actively control it. In this research, we extended our investigation of active separation control (under a previous NASA grant) where we explored the use of microjets for the control of boundary layer separation. The geometry used for the initial study was a simple diverging Stratford ramp, equipped with arrays of microjets. These early results clearly show that the activation of microjets eliminated flow separation. Furthermore, the velocity-field measurements, using PIV, also demonstrate that the gain in momentum due to the elimination of separation is at least an order of magnitude larger (two orders of magnitude larger in most cases) than the momentum injected by the microjets and is accomplished with very little mass flow through the microjets. Based on our initial promising results this research was continued under the present grant, using a more flexible model. This model allows for the magnitude and extent of separation as well as the microjet parameters to be independently varied. The results, using this model were even more encouraging and demonstrated that microjet control completely eliminated significant regions of flow separation over a wide range of conditions with almost negligible mass flow. Detailed studies of the flowfield and its response to microjets were further examined using 3-component PIV and unsteady pressure measurements, among others. As the results presented this report will show, microjets were successfully used to control the separation of a much larger extent and magnitude than demonstrated in our earlier experiments. In fact, using the appropriate combination of control parameters (microjet, location, angle and pressure) separation was completely eliminated for the largest separated flowfield we could generate with the present model. Separation control also resulted in a significant reduction in the unsteady pressures in the flow where the unsteady pressure field was found to be directly responsive to the state of the flow above the surface. Hence, our study indicates that the unsteady pressure signature is a strong candidate for a flow state sensor , which can be used to estimate the location, magnitude and other properties of the separated flowfield. Once better understood and properly utilized, this behavior can be of significant practical importance for developing and implementing online control.

Alvi, Farrukh S.↗
NASA NTRS2004

Micro Sun Sensor for Spacecraft

A report describes the development of a compact micro Sun sensor for use as a part of the attitude determination subsystem aboard future miniature spacecraft and planetary robotic vehicles. The prototype unit has a mass of only 9 g, a volume of only 4.2 cm(sup 3), a power consumption of only 30 mW, and a 120 degree field of view. The unit has demonstrated an accuracy of 1 arcminute. The unit consists of a multiple pinhole camera: A micromachined mask containing a rectangular array of microscopic pinholes, machined utilizing the microectromechanical systems (MEMS), is mounted in front of an active-pixel sensor (APS) image detector. The APS consists of a 512 x 512-pixel array, on-chip 10-bit analog to digital converter (ADC), on-chip bias generation, and on-chip timing control for self-sequencing and easy programmability. The digitized output of the APS is processed to compute the centroids of the pinhole Sun images on the APS. The Sun angle, relative to a coordinate system fixed to the sensor unit, is then computed from the positions of the centroids.

Mobasser, Sohrab↗
NASA NTRS1975

A 10.6 micron ladar for space rendezvous and docking

The paper describes a 10.6 micron ladar (a laser detection and ranging device) which is considered as a baseline sensor for space rendezvous and docking applications. The sensor uses a passively Q-switched CO2 laser as the transmitter active element, and a four-quadrant photodiode array, operated as a coherent receiver element in the heterodyne mode. The aperture will be about 3 inches, and the telescope will be able to steer the beam in a 40 by 40 degree window. Various aspects of the ladar system are examined in detail, including the laser control loop, the transmitter, the local oscillator, the telescope, and the output beam scanning.

Lowrey, D. O.↗
NASA NTRS1978

Method for minimizing the cost/Watt of complete photovoltaic systems and applications

The paper describes an optimization method and some applications in which the design criterion for every part of a photovoltaic system is the minimum power cost for the complete system. The various parts of a photovoltaic system are grouped so that all costs fall into four classes: fabrication steps of the active solar cells; steps associated with the collector array and its complete structure; power-handling elements such as switchgear, storage, etc.; and fixed costs that do not vary directly with any of the system parts, such as factory-level overhead. It is assumed that the total collector area is independent of any of the optimization processes. A general equation is found to be capable of optimizing all parts of a system, although the cell and array steps are basically different from the power-handling elements. It is shown that the optimization of any step in the system requires inclusion of the properties of the other parts of the system.

Redfield, D.↗
NASA NTRS1983

Detecting Solar-Cell Failures

Circuit identified malfunctioning photovoltaic array. Cell-failure detection circuit compares output of photovoltaic array to control cell. If any module fails, activates light-emitting diode. Circuit could also sound alarm.

Maloney, T. J.↗
NASA NTRS1985

Multiwavelength observations of a preflare solar active region using the VLA

A preflare active region was studied using the Very Large Array at 2, 6, and 20 cm. At 2 cm the region is composed of two components located in regions of opposite polarity. Both components are preheated prior to the impulsive onset of a flare. However, one component develops new structures during preburst phase, and the burst occurs in this location. It is believed that the new structures represent emerging flux regions which interact with an overlying loop to produce a neutral sheet, which ultimately is responsible for triggering the flare.

Kundu, M. R.↗
NASA NTRS1994

A novel computational method to simulate non-enzymatic self-replication

Non-enzymatic, template-directed synthesis of oligonucleotides has been extensively studied in the laboratory as a model to understand the kind of chemical processes that might have contributed to the origin of life on Earth. Several oligonucleotides have been shown to catalyze the synthesis of their complements from activated mononucleotides; however, a restricted number of them have been found to self-replicate. Recently we developed an efficient modified cellular automata method that supports the study of self-replicating oligonucleotides. With this method the oligonucleotide molecules are represented as active cells imbedded in a two-dimensional array of inactive cells symbolizing the environment. Random movements and probability-governed chemical reactions occurring in a cellular space can effectively simulate the experimental behavior observed in self-directed replication of oligonucleotides.

Navarro-Gonzalez, Rafael↗
NASA NTRS1971

A New All Solid State Approach to Gaseous Pollutant Detection

Recent efforts in our laboratories have concentrated on the development of an all solid state gas sensor, by combining solid electrolyte (ion exchange membrane) technology with advanced thin film deposition processes. With the proper bias magnitude and polarity these miniature electro-chemical,cells show remarkable current responses for many common pollution gases. Current activity is now focused on complementing a multiple array (matrix) of these solid state sensors, with a digital electronic scanner device possessing "scan-compare-identify-alarm: capability. This innovative approach to multi-component pollutant gas analysis may indeed be the advanced prototype for the "third generation" class of pollution analysis instrumentation so urgently needed in the decade ahead.

Brown, V.↗
NASA NTRS1995

ACTS Aeronautical Terminal Experiment (AERO-X)

During the summer of 1994, the performance of an experimental mobile satellite communication system was demonstrated. Using the Advanced Communications Technology Satellite (ACTS) and the ACTS Mobile Terminal (AMT), the system demonstrated an active Monolithic Microwave Integrated Circuit (MMIC) phased-array antenna system. The antenna system was installed onboard one of NASA Lewis Research Center's research aircraft, a Learjet Model 25. It proved the viability of in-flight satellite communications services via small, flush, mountable electronic phased-array antennas. The overall system setup for the ACTS Aeronautical Terminal Experiment (AERO-X) is illustrated. The Link Evaluation Terminal (LET) at Lewis in Cleveland, Ohio, interfaced with fixed-AMT equipment, providing a seamless connection with the Public Service Telephone Network. As the Learjet was flown over several major cities across the U.S., this demonstration system allowed passengers onboard to make telephone calls as if they were using a cellular system. ACTS was operated in its microwave switch matrix mode with a spot beam for the Learjet and another spot beam dedicated to the LET.

Source record↗
NASA NTRS2018

Exploring the Effects of Installation Geometry in High-Lift Propeller Systems

A high-lift propeller system is a distributed electric propulsion technology which dedicates an array of wing-mounted tractor propellers to actively augment wing lift during takeoff and landing. This paper describes the results of a wind tunnel experiment dedicated to investigating the effects of high-lift propeller installation geometry on lift generation. Variables investigated include propeller height, offset, and inclination. Results show that propeller height is the most critical variable and that the height for maximum lift depends highly on the angle of attack and flap deflection. In addition, a relationship between optimal propeller height and the wing’s unblown lift coefficient is discovered.

Fei, Xiaofan↗