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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 217 records · Page 12

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NASA NTRS1991

Lag compensation of optical fibers or thermocouples to achieve waveform fidelity in dynamic gas pyrometry

Fidelity of waveform reproduction requires constant amplitude ratio and constant time lag of a temperature sensor's indication, at all frequencies of interest. However, heat-transfer type sensors usually cannot satisfy these requirements. Equations for the actual indication of a thermocouple and an optical-fiber pyrometer are given explicitly, in terms of sensor and flowing-gas properties. A practical, realistic design of each type of sensor behaves like a first-order system with amplitude-ratio attenuation inversely proportional to frequency when the frequency exceeds the corner frequency. Only at much higher frequencies does the amplitude-ratio attenuation for the optical fiber sensor become inversely proportional to the square root of the frequency. Design options for improving the frequency response are discussed. On-line electrical lag compensation, using a linear amplifier and a passive compensation network, can extend the corner frequency of the thermocouple 100-fold or more; a similar passive network can be used for the optical-fiber sensor. Design details for these networks are presented.

Warshawsky, I.↗

NASA NTRS2001

A Fiber-Optic Probe Design for Combustion Chamber Flame Detection Applications-Design Criteria, Performance Specifications, and Fabrication Technique

This paper documents the design and development of the fiber-optic probes utilized in the flame detection systems used in NASA Langley Research Center's 8-Foot High Temperature Tunnel (8-ft HTT). Two independent flame detection systems are utilized to monitor the presence and stability of the main-burner and pilot-level flames during facility operation. Due to the harsh environment within the combustor, the successful development of a rugged and efficient fiber-optic probe was a critical milestone in the development of these flame detection systems. The final optical probe design for the two flame detection systems resulted from research that was conducted in Langley's 7-in High Temperature Pilot Tunnel (7-in HTT). A detailed description of the manufacturing process behind the optical probes used in the 8-ft HTT is provided in Appendix A of this report.

Borg, Stephen E.↗

NASA NTRS1994

High Temperature Calibration Furnace System user's guide

The High Temperature Calibration Furnace System (HTCFS) was developed by Summitec Corporation. It is a high precision instrument providing a constant temperature which can be used to calibrate high temperature thermocouples. Incorporating the many recent technological advances from the fields of optical fiber thermometry, material science, computer systems interfacing, and process control, the engineers at Summitec Corporation have been able to create a system that can reach a steady operating temperature of 1700 C. The precision for the system requires the measurement of temperature to be within 1 C in two hours and within 2 C in 24 hours. As documented, the experimental result shows that this system has been able to stay within .5 C in 5 hours. No other systems commercially available have been able to achieve such high temperature precision. This manual provides an overview of the system design, instructions for instrument setup, and operation procedures. Also included are a vendor list and the source codes for the custom-designed software.

Source record↗

NASA NTRSDate not supplied

Emitter Surface Temperature Measurements of a 25-A Class Hollow Cathode

The axial emitter surface temperature profile is experimentally characterized for a 25-A class hollow cathode operating across a range of operating conditions. Profiles were measured using aratio pyrometry diagnostic featuring a fiber optic inserted into the emitter region using a fast motion stage. Emitter temperature is found to increase with increasing discharge current, decreasing flow rate, and increasing magnetic field strength. Across a range of 10 –29 A, the maximum emitter temperature increased 176 ºC, an order of magnitude more than the changes measured for flow rate or magnetic fields strength. Profiles were generally self-similar across all operating conditions, and the difference between maximum and minimum emitter temperature never surpassed 10%, indicating that this cathode design results in satisfactory emitter utilization across its operating envelope

space propulsion↗

NASA NTRS1991

Annealing of linear birefringence in single-mode fiber coils - Application to optical fiber current sensors

Annealing procedures that greatly reduce linear birefringence in single-mode fiber coils are described. These procedures have been successfully applied to coils ranging from 5 mm to 10 cm in diameter and up to 200 or more turns. They involve temperature cycles that last 3-4 days and reach maximum temperatures of about 850 C. The residual birefringence and induced loss are minimized by proper selection of fiber. The primary application of these coils is optical fiber current sensors, where they yield small sensors that are more stable than those achieved by other techniques. A current sensor with a temperature stability of 8.4 x 10 to the -5th/K over the range from -75 to 145 C has been demonstrated. This is approximately 20 percent greater than the temperature dependence of the Verdet constant. Packaging degrades the stability, but a packaged sensor coil with a temperature stability of about 1.6 + 10 to the -4th/K over the range from -20 to 120 C has also been demonstrated.

Tang, Dingding↗

NASA NTRS2004

Distributed Sensing of Composite Over-wrapped Pressure Vessel Using Fiber-Bragg Gratings at Ambient and Cryogenic Temperatures

Fiber Bragg gratings are use to monitor the structural properties of composite pressure vessels. These gratings optically inscribed into the core of a single mode fiber are used as a tool to monitor the stress strain relation in laminate structure. The fiber Bragg sensors are both embedded within the composite laminates and bonded to the surface of the vessel with varying orientations with respect to the carbon fiber in the epoxy matrix. The response of these fiber-optic sensors is investigated by pressurizing the cylinder up to its burst pressure of around 2800 psi. This is done at both ambient and cryogenic temperatures using water and liquid nitrogen. The recorded response is compared with the response from conventional strain gauge also present on the vessel. Additionally, several vessels were tested that had been damaged to simulate different type of events, such as cut tow, delimitation and impact damage.

Grant, Joseph↗

NASA NTRS2005

Distributed sensing of Composite Over-wrapped Pressure Vessel using Fiber-Bragg Gratings at Ambient and Cryogenic Temperatures

Grant, Joseph↗

NASA NTRS1998

Reusable Cryogenic Tank VHM Using Fiber Optic Distributed Sensing Technology

The reusable oxygen and hydrogen tanks are key systems for both the X-33 (sub-scale, sub-orbital technology demonstrator) and the commercial Reusable Launch Vehicle (RLV). The backbone of the X-33 Reusable Cryogenic Tank Vehicle Health Management (VHM) system lies in the optical network of distributed strain temperature and hydrogen sensors. This network of fiber sensors will create a global strain and temperature map for monitoring the health of the tank structure, cryogenic insulation, and Thermal Protection System. Lockheed Martin (Sanders and LMMSS) and NASA Langley have developed this sensor technology for the X-33 and have addressed several technical issues such as fiber bonding and laser performance in this harsh environment.

Bodan-Sanders, Patricia↗

NASA NTRS1988

Fiber optic sensor technology - An opportunity for smart aerospace structures

Fiber optic sensors provide the opportunity for fabricating materials with internal sensors which can serve as lifetime health monitors, analogous to a central nervous system. The embedded fiber optic sensors can be interrogated by various techniques to measure internal strain, temperature, pressure, acoustic waves and other parameters indicative of structural integrity. Experiments have been conducted with composite samples with embedded sensors to measure strain using optical time domain reflectometry, modal interference and an optical phase locked loop. Fiber optic sensors have been developed to detect acoustic emission and impact damage and have been demonstrated for cure monitoring. These sensors have the potential for lifetime monitoring of structural properties, providing real time nondestructive evaluation.

Heyman, J. S.↗

NASA NTRS1992

Advanced one-dimensional optical strain measurement system, phase 4

An improved version of the speckle-shift strain measurement system was developed. The system uses a two-dimensional sensor array to maintain speckle correlation in the presence of large off-axis rigid body motions. A digital signal processor (DSP) is used to calculate strains at a rate near the RS-170 camera frame rate. Strain measurements were demonstrated on small diameter wires and fibers used in composite materials research. Accurate values of Young's modulus were measured on tungsten wires, and silicon carbide and sapphire fibers. This optical technique has measured surface strains at specimen temperatures above 750 C and has shown the potential for measurements at much higher temperatures.

Lant, Christian T.↗

NASA NTRS1991

Small Business Innovations (Photodetector)

Epitaxx, Inc. of Princeton, NJ, developed the Epitaxx Near Infrared Room Temperature Indium-Gallium-Arsenide (InGaAs) Photodetector based on their Goddard Space Flight Center Small Business Innovation Research (SBIR) contract work to develop a linear detector array for satellite imaging applications using InGaAs alloys that didn't need to be cooled to (difficult and expensive) cryogenic temperatures. The photodetectors can be used for remote sensing, fiber optic and laser position-sensing applications.

Source record↗

NASA NTRS2008

Fiber Optic Cable Thermal Preparation to Ensure Stable Operation

Fiber optic cables are widely used in modern systems that must provide stable operation during exposure to changing environmental conditions. For example, a fiber optic cable on a satellite may have to reliably function over a temperature range of -50 C up to 125 C. While the system requirements for a particular application will dictate the exact method by which the fibers should be prepared, this work will examine multiple ruggedized fibers prepared in different fashions and subjected to thermal qualification testing. The data show that if properly conditioned the fiber cables can provide stable operation, but if done incorrectly, they will have large fluctuations in transmission.

Thoames Jr, William J.↗

NASA NTRS2017

Development and Testing of a Friction-Based Post-Installable Fiber-Optic Monitoring System for Subsea Applications

This paper presents the design and development of a friction-based coupling device for a fiber-optic monitoring system capable of measuring pressure, strain, and temperature that can be deployed on existing subsea structures. A summary is provided of the design concept, prototype development, prototype performance testing, and subsequent design refinements of the device. The results of laboratory testing of the first prototype performed at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) are also included. Limitations of the initial concept were identified during testing and future design improvements were proposed and later implemented. These new features enhance the coupling of the sensor device and improve the monitoring system measurement capabilities. A major challenge of a post-installed instrumentation monitoring system is to ensure adequate coupling between the instruments and the structure of interest for reliable measurements. Friction-based devices have the potential to overcome coupling limitations caused by marine growth and soil contamination on flowlines, risers, and other subsea structures. The work described in this paper investigates the design and test of a friction-based coupling device (herein referred to as a friction clamp) which is suitable for pipelines and structures that are suspended in the water column as well as for those that are resting on the seabed. The monitoring elements consist of fiberoptic sensors that are bonded to a stainless steel clamshell assembly with a high-friction surface coating. The friction clamp incorporates a single hinge design to facilitate installation of the clamp and dual rows of opposing fasteners to distribute the clamping force along the structure. The friction clamp can be modified to be installed by commercial divers in shallow depths or by remotely operated vehicles in deep-water applications. NASA-JSC was involved in the selection and testing of the friction coating, and in the design and testing of the prototype clamp device. Four-inch diameter and eight-inch diameter sub-scale friction clamp prototypes were built and tested to evaluate the strain measuring capabilities of the design under different loading scenarios. The testing revealed some limitations of the initial design concept, and subsequent refinements were explored to improve the measurement performance of the system. This study was part of a collaboration between NASA-JSC and Astro Technology Inc. within a study called Clear Gulf. The primary objective of the Clear Gulf study is to develop advanced instrumentation technologies that will improve operational safety and reduce the risk of hydrocarbon spillage. NASA provided unique insights, expansive test facilities, and technical expertise to advance technologies that will benefit the environment, the public, and commercial industries.

Bentley, Nicole L.↗

NASA NTRS2018

The HIAD Orbital Flight Demonstration Instrumentation Suite

NASA's Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology has been selected for a Technology Demonstration Mission under the Science and Technology Mission Directorate. HIADs are an enabling technology that can facilitate atmospheric entry of heavy payloads to planets such as Earth and Mars using a deployable aeroshell. The deployable nature of the HIAD technology allows it to overcome the size constraints imposed on current rigid aeroshell entry systems. This permits use of larger aeroshells resulting in increased entry system performance (e.g. higher payload mass and/or volume, higher landing altitude at Mars). The Low Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) is currently scheduled for mid-2021. LOFTID will be launched out of Vandenberg Air Force Base as a secondary payload on an expendable launch vehicle. The flight test will employ a 6m diameter, 70 degree sphere-cone aeroshell and will provide invaluable high-energy orbital re-entry flight data. This data will be essential in supporting the HIAD team to mature the technology to diameters of 10m and greater. Aeroshells of this scale will address near-term commercial applications and potential future NASA missions. LOFTID will incorporate an extensive instrumentation suite totaling over 150 science measurements. This will include thermocouples, heat flux sensors, IR cameras, and a radiometer to characterize the aeroheating environment and aeroshell thermal response. An inertial measurement unit (IMU), GPS, and flush air data system will be included in order to reconstruct the flown trajectory and aerodynamic characteristics. Loadcells will be used to measure the HIAD structural loading, and HD cameras will be mounted on the aft segment looking at the aeroshell to monitor structural response. In addition to the primary instrumentation suite, a new fiber optic sensing system will be used to measure nose temperatures as a technology demonstration. The LOFTID instrumentation suites leverages Agency-wide expertise, with hardware development occurring at Ames Research Center, Langley Research Center, Marshall Space Flight Center and Armstrong Flight Research Center. This presentation will discuss the measurement objectives for the LOFTID mission, and the extensive instrumentation suite that has been selected to capture the HIAD's performance during the high-energy orbital re-entry flight test.

Swanson, G. T.↗

NASA NTRS2018

The HIAD Orbital Flight Demonstration Instrumentation Suite

NASA's Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology has been selected for a Technology Demonstration Mission under the Science and Technology Mission Directorate. HIADs are an enabling technology that can facilitate atmospheric entry of heavy payloads to planets such as Earth and Mars using a deployable aeroshell. The deployable nature of the HIAD technology allows it to overcome the size constraints imposed on current rigid aeroshell entry systems. This permits use of larger aeroshells resulting in increased entry system performance (e.g. higher payload mass and/or volume, higher landing altitude at Mars). The Low Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) is currently scheduled for mid-2021. LOFTID will be launched out of Vandenberg Air Force Base as a secondary payload on an expendable launch vehicle. The flight test will employ a 6m diameter, 70-deg sphere-cone aeroshell and will provide invaluable high-energy orbital re-entry flight data. This data will be essential in supporting the HIAD team to mature the technology to diameters of 10m and greater. Aeroshells of this scale will address near-term commercial applications and potential future NASA missions.LOFTID will incorporate an extensive instrumentation suite totaling over 150 science measurements. This will include thermocouples, heat flux sensors, IR cameras, and a radiometer to characterize the aeroheating environment and aeroshell thermal response. An inertial measurement unit (IMU), GPS, and flush air data system will be included in order to reconstruct the flown trajectory and aerodynamic characteristics. Loadcells will be used to measure the HIAD structural loading, and HD cameras will be mounted on the aft segment looking at the aeroshell to monitor structural response. In addition to the primary instrumentation suite, a new fiber optic sensing system will be used to measure nose temperatures as a technology demonstration. The LOFTID instrumentation suites leverages Agency-wide expertise, with hardware development occurring at Ames Research Center, Langley Research Center, Marshall Space Flight Center and Armstrong Flight Research Center.This presentation will discuss the measurement objectives for the LOFTID mission, and the extensive instrumentation suite that has been selected to capture the HIAD's performance during the high-energy orbital re-entry flight test.

Swanson, Greg↗

NASA NTRS1993

Performance of low-cost commercial fiber-optic transceivers for reference frequency distribution

Precision time and frequency reference signals were effectively disseminated using high-quality intricate fiber-optic distribution systems. The quality of signals distributed by such systems is excellent, but the cost of these systems makes them unavailable to many potential users. A study of signal quality maintained using inexpensive commercial transmitter/receiver pairs is undertaken. Seven different transmitter/receiver pairs obtained from four different manufacturers were thoroughly tested using a 5 MHz sinusoid derived from a precision, temperature controlled, crystal-controlled oscillator. The electrical signal output from each fiber-optic receiver was tested for spectral purity, single-sideband phase noise, and AM noise, and the results are tabulated and discussed without identification of the manufacturer or the equipment model number.

Dragonette, Richard↗

NASA NTRS1982

Method and apparatus for a Fabry-Perot multiple beam fringe sensor

A method and the resulting apparatus for implementing a unique multiple beam fringe sensor that is adapted to be interfaced with a low cost, compact fiber optic transmission system in order to provide an accurate digital representation of a physical parameter (e.g. temperature) of a remote sample. The sensor is fabricated so as to include a Fabry-Perot gap formed between the ends of two mated optical fibers. By examining the optical characteristics of light that is transmitted through the Fabry-Perot sensor gap, an indication of gap width can be ascertained. Accordingly, a change in Fabry-Perot sensor gap width is related to a change in the particular physical parameter to be measured.

James, Kenneth A.↗

NASA NTRS1992

Fiberoptic characteristics for extreme operating environments

Fiberoptics could offer several major benefits for cryogenic liquid-fueled rocket engines, including lightning immunity, weight reduction, and the possibility of implementing a number of new measurements for engine condition monitoring. The technical feasibility of using fiberoptics in the severe environments posed by cryogenic liquid-fueled rocket engines was determined. The issues of importance and subsequent requirements for this use of fiberoptics were compiled. These included temperature ranges, moisture embrittlement succeptability, and the ability to withstand extreme shock and vibration levels. Different types of optical fibers were evaluated and several types of optical fibers' ability to withstand use in cryogenic liquid-fueled rocket engines was demonstrated through environmental testing of samples. This testing included: cold-bend testing, moisture embrittlement testing, temperature cycling, temperature extremes testing, vibration testing, and shock testing. Three of five fiber samples withstood the tests to a level proving feasibility, and two of these remained intact in all six of the tests. A fiberoptic bundle was also tested, and completed testing without breakage. Preliminary cabling and harnessing for fiber protection was also demonstrated. According to cable manufacturers, the successful -300 F cold bend, vibration, and shock tests are the first instance of any major fiberoptic cable testing below roughly -55 F. This program has demonstrated the basic technical feasibility of implementing optical fibers on cryogenic liquid-fueled rocket engines, and a development plan is included highlighting requirements and issues for such an implementation.

Delcher, R. C.↗