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NASA NTRS2011

Development of Position-Sensitive Magnetic Calorimeters for X-Ray Astronomy

Metallic magnetic calorimeters (MMC) are one of the most promising devices to provide very high energy resolution needed for future astronomical x-ray spectroscopy. MMC detectors can be built to large detector arrays having thousands of pixels. Position-sensitive magnetic (PoSM) microcalorimeters consist of multiple absorbers thermally coupled to one magnetic micro calorimeter. Each absorber element has a different thermal coupling to the MMC, resulting in a distribution of different pulse shapes and enabling position discrimination between the absorber elements. PoSMs therefore achieve the large focal plane area with fewer number of readout channels without compromising spatial sampling. Excellent performance of PoSMs was achieved by optimizing the designs of key parameters such as the thermal conductance among the absorbers, magnetic sensor, and heat sink, as well as the absorber heat capacities. Micro fab ri - cation techniques were developed to construct four-absorber PoSMs, in which each absorber consists of a two-layer composite of bismuth and gold. The energy resolution (FWHM full width at half maximum) was measured to be better than 5 eV at 6 keV x-rays for all four absorbers. Position determination was demonstrated with pulse-shape discrimination, as well as with pulse rise time. X-ray microcalorimeters are usually designed to thermalize as quickly as possible to avoid degradation in energy resolution from position dependence to the pulse shapes. Each pixel consists of an absorber and a temperature sensor, both decoupled from the cold bath through a weak thermal link. Each pixel requires a separate readout channel; for instance, with a SQUID (superconducting quantum interference device). For future astronomy missions where thousands to millions of resolution elements are required, having an individual SQUID readout channel for each pixel becomes difficult. One route to attaining these goals is a position-sensitive detector in which a large continuous or pixilated array of x-ray absorbers shares fewer numbers of temperature sensors. A means of discriminating the signals from different absorber positions, however, needs to be built into the device for each sensor. The design concept for the device is such that the shape of the temperature pulse with time depends on the location of the absorber. This inherent position sensitivity of the signal is then analyzed to determine the location of the event precisely, effectively yielding one device with many sub-pixels. With such devices, the total number of electronic channels required to read out a given number of pixels is significantly reduced. PoSMs were developed that consist of four discrete absorbers connected to a single magnetic sensor. The design concept can be extended to more than four absorbers per sensor. The thermal conductance between the sensor and each absorber is different by design and consequently, the pulse shapes are different depending upon which absorber the xrays are received, allowing position discrimination. A magnetic sensor was used in which a paramagnetic Au:Er temperature-sensitive material is located in a weak magnetic field. Deposition of energy from an x-ray photon causes an increase in temperature, which leads to a change of magnetization of the paramagnetic sensor, which is subsequently read out using a low noise dc-SQUID. The PoSM microcalorimeters are fully microfabricated: the Au:Er sensor is located above the meander, with a thin insulation gap in between. For this position-sensitive device, four electroplated absorbers are thermally linked to the sensor via heat links of different thermal conductance. One pixel is identical to that of a single-pixel design, consisting of an overhanging absorber fabricated directly on top of the sensor. It is therefore very strongly thermally coupled to it. The three other absorbers are supported directly on a silicon-nitride membrane. These absorbers are thermally coupled to the sensor via Ti (5 nm)/Au250 nm) metal links. The strength of the links is parameterized by the number of gold squares making up the link. For detector performance, experimentally different pulse-shapes were demonstrated with 6 keV x-rays, which clearly show different rise times for different absorber positions. For energy resolution measurement, the PoSM was operated at 32 mK with an applied field that was generated using a persistent current of 50 mA. Over the four pixels, energy resolution ranges from 4.4 to 4.7 eV were demonstrated.

Bandler, SImon↗

NASA NTRS1956

Turbojet-engine Starting and Acceleration

From considerations of safety and reliability in performance of gas-turbine aircraft, it is clear that engine starting and acceleration are of utmost importance. For this reason extensive efforts have been devoted to the investigation of the factors involved in the starting and acceleration of engines. In chapter III it is shown that certain basic combustion requirements must be met before ignition can occur; consequently, the design and operation of an engine must be tailored to provide these basic requirements in the combustion zone of the engine, particularly in the vicinity of the ignition source. It is pointed out in chapter III that ignition by electrical discharges is aided by high pressure, high temperature, low gas velocity and turbulence, gaseous fuel-air mixture, proper mixture strength, and-an optimum spark. duration. The simultaneous achievement of all these requirements in an actual turbojet-engine combustor is obviously impossible, yet any attempt to satisfy as many requirements as possible will result in lower ignition energies, lower-weight ignition systems, and greater reliability. These factors together with size and cost considerations determine the acceptability of the final ignition system. It is further shown in chapter III that the problem of wall quenching affects engine starting. For example, the dimensions of the volume to be burned must be larger than the quenching distance at the lowest pressure and the most adverse fuel-air ratio encountered. This fact affects the design of cross-fire tubes between adjacent combustion chambers in a tubular-combustor turbojet engine. Only two chambers in these engines contain spark plugs; therefore, the flame must propagate through small connecting tubes between the chambers. The quenching studies indicate that if the cross-fire tubes are too narrow the flame will not propagate from one chamber to another. In order to better understand the role of the basic factors in actual engine operation, many investigations have been conducted in single combustors from gas-turbine engines and in full-scale engines in altitude tanks and in flight. The purpose of the present chapter is to discuss the results of such studies and, where possible, to interpret these results qualitatively in terms of the basic requirements reported in chapter III. The discussion parallels the three phases of turbojet engine starting: (1) Ignition of the fuel-air mixture (2) Propagation of flame throughout the combustion zone (3) Acceleration of the engine to operating speed.

Mc Cafferty, R. J.↗

NASA NTRS1971

Arterial and grooved cryogenic heat pipes.

Tests were conducted on two cryogenic heat pipes using nitrogen as the working fluid. Both pipes are 1.27 cm in diameter. The first pipe is 141 cm long and uses longitudinal grooves in the aluminum wall as the wick structure. The second pipe is 91 cm long and has an arterial wick adjacent to the wall. In addition, circumferential screw threads are machined along the entire length of the inside pipe wall. Both heat pipes primed with no difficulty in the horizontal position. Start-up after burn-out was obtained repeatedly. However, more testing is required to determine whether the artery pipe is as reliable as the grooved pipe with respect to priming. Once primed, the artery heat pipe is much less sensitive to elevation than the grooved design and, consequently, offers a significant advantage with respect to ground testing. Heat-transfer characteristics of the two pipes were comparable, with both pipes achieving the initial goal of 1000 watt-cm of heat-transport capability.

Brennan, P.↗

NASA NTRS1977

Modeling error analysis of stationary linear discrete-time filters

The performance of Kalman-type, linear, discrete-time filters in the presence of modeling errors is considered. The discussion is limited to stationary performance, and bounds are obtained for the performance index, the mean-squared error of estimates for suboptimal and optimal (Kalman) filters. The computation of these bounds requires information on only the model matrices and the range of errors for these matrices. Consequently, a design can easily compare the performance of a suboptimal filter with that of the optimal filter, when only the range of errors in the elements of the model matrices is available.

Patel, R.↗

NASA NTRS1980

High-power microwave optics for flexible power transmission systems

A large concave microwave mirror near the transmitter can magnify the apparent size of the Earth as seen from a phased array, and vice versa, permitting a small phased array to be coupled to a small rectenna while preserving the transmission efficiency (the reflection loss is slight) and peak power densities characteristic of the reference system. This augmentation of the phased array aperture with a large mirror gives the system greater resolution (in the optical sense), and opens new degrees of freedom in SPS design. The consequences of such an approach for a prototype satellite were explored. Its consequences for a mature SPS are discussed.

Drexler, K. E.↗

NASA NTRS1989

Electrical, Electronic, and Electromechanical (EEE) parts management and control requirements for NASA space flight programs

This document establishes electrical, electronic, and electromechanical (EEE) parts management and control requirements for contractors providing and maintaining space flight and mission-essential or critical ground support equipment for NASA space flight programs. Although the text is worded 'the contractor shall,' the requirements are also to be used by NASA Headquarters and field installations for developing program/project parts management and control requirements for in-house and contracted efforts. This document places increased emphasis on parts programs to ensure that reliability and quality are considered through adequate consideration of the selection, control, and application of parts. It is the intent of this document to identify disciplines that can be implemented to obtain reliable parts which meet mission needs. The parts management and control requirements described in this document are to be selectively applied, based on equipment class and mission needs. Individual equipment needs should be evaluated to determine the extent to which each requirement should be implemented on a procurement. Utilization of this document does not preclude the usage of other documents. The entire process of developing and implementing requirements is referred to as 'tailoring' the program for a specific project. Some factors that should be considered in this tailoring process include program phase, equipment category and criticality, equipment complexity, and mission requirements. Parts management and control requirements advocated by this document directly support the concept of 'reliability by design' and are an integral part of system reliability and maintainability. Achieving the required availability and mission success objectives during operation depends on the attention given reliability and maintainability in the design phase. Consequently, it is intended that the requirements described in this document are consistent with those of NASA publications, 'Reliability Program Requirements for Aeronautical and Space System Contractors,' NHB 5300.4(1A-l); 'Maintainability Program Requirements for Space Systems,' NHB 5300.4(1E); and 'Quality Program Provisions for Aeronautical and Space System Contractors,' NHB 5300.4(1B).

Source record↗

NASA NTRS1992

Dynamic Forms and Their Application to Control

The rigid body model plays a basic role in both mod- and control of many systems, including aircraft flight control. The distinctive feature of the rigid body is that its motion evolves on a curved space, Consequently, the designer must take into account the deterioration of chosen coordinations near their singularities. In these regions the control actions and the sensitivity to modeling and sensor errors become unacceptable. Thus, coordinate patches and patching logic should be a part of the overall control law design and implementation. The various dynamic forms, such as scalar forms, vector forms, matrix forms, rotational forms, Euler angle forms, and Euler parameter forms, described in the paper provide an effective means for coordinate patching and control law implementation. The utility of these forms is illustrated by means of several applications to flight control.

Meyer, George↗

NASA NTRS2000

The Electric Power System of the International Space Station: A Platform for Power Technology Development

The electrical power system developed for the International Space Station represents the largest space-based power system ever designed and, consequently, has driven some key technology aspects and operational challenges. The full U.S.-built system consists of a 160-Volt dc primary network, and a more tightly regulated 120-Volt dc secondary network. Additionally, the U.S. system interfaces with the 28-Volt system in the Russian segment. The international nature of the Station has resulted in modular converters, switchgear, outlet panels, and other components being built by different countries, with the associated interface challenges. This paper provides details of the architecture and unique hardware developed for the Space Station, and examines the opportunities it provides for further long-term space power technology development, such as concentrating solar arrays and flywheel energy storage systems.

Gietl, Eric B.↗

NASA NTRS2005

Trajectory Reconstruction for the Genesis Entry

An overview of the reconstruction analyses performed for the Genesis capsule entry is described. The results indicate that the actual entry prior to the drogue deployment failure was very close to the pre-entry predictions. The capsule landed 8.3 km south of the desired target at Utah Test and Training Range. Analysis on infrared video footage (obtained from the tracking stations) during the descent estimated the onset of the capsule tumble at Mach 0.9. Frequency analysis on the infrared video data indicates that the aerodynamics generated for the Genesis capsule reasonably predicted the drag and static stability. Observations of the heatshield support the pre-entry simulation estimates of a small hypersonic angles-of-attack, since there is very little, if any, charring of the shoulder region or the afterbody. Through this investigation, an overall assertion can be made that all the data gathered from the Genesis entry is consistent with flight performance close to the nominal pre-entry prediction. Consequently, the design principles and methodologies utilized for the flight dynamics, aerodynamics, and aerothermodynamics analyses have been corroborated.

Desai, Prasun N.↗

NASA NTRS2008

Stardust Entry Reconstruction

An overview of the reconstruction analyses performed for the Stardust capsule entry is described. The results indicate that the actual entry was very close to the pre-entry predictions. The capsule landed 8.1 km north-northwest of the desired target at Utah Test and Training Range. Analyses of infrared video footage and radar range data (obtained from tracking stations) during the descent show that drogue parachute deployment was 4.8 s later than the pre-entry prediction, while main parachute deployment was 19.3 s earlier than the pre-set timer indicating that main deployment was actually triggered by the backup baroswitch. Reconstruction of a best estimated trajectory revealed that the aerodynamic drag experienced by the capsule during hypersonic flight was within 1% of pre-entry predications. Observations of the heatshield support the pre-entry estimates of small hypersonic angles of attack, since there was very little, if any, charring of the shoulder region or the aftbody. Through this investigation, an overall assertion can be made that all the data gathered from the Stardust capsule entry were consistent with flight performance close to nominal pre-entry predictions. Consequently, the design principles and methodologies utilized for the flight dynamics, aerodynamics, and aerothermodynamics analyses have been corroborated.

Desai, Prasun N.↗

NASA NTRS2007

Reconstruction of the Stardust Entry

An overview of the reconstruction analyses performed for the Stardust capsule entry is described. The results indicate that the actual entry was very close to the pre-entry predictions. The capsule landed 8.1 km northwest of the desired target at Utah Test and Training Range. Frequency analysis on the infrared video data indicates that the aerodynamics generated for the Stardust capsule reasonably predicted the drag and static stability. Observations of the heatshield support the pre-entry simulation estimates of a small hypersonic angles-of-attack, since there is very little, if any, charring of the shoulder region or the aftbody. Through this investigation, an overall assertion can be made that all the data gathered from the Stardust entry is consistent with flight performance close to the nominal pre-entry prediction. Consequently, the design principles and methodologies utilized for the flight dynamics, aerodynamics, and aerothermodynamics analyses have been corroborated.

Desai, Prasun N.↗

NASA NTRS2007

Reconstruction of the Genesis Entry

An overview of the reconstruction analyses performed for the Genesis capsule entry is described. The results indicate that the actual entry prior to the drogue deployment failure was very close to the pre-entry predictions. The capsule landed 8.3 km south of the desired target at Utah Test and Training Range. Analysis on infrared video footage (obtained from the tracking stations) during the descent estimated the onset of the capsule tumble at Mach 0.9. Frequency analysis on the infrared video data indicates that the aerodynamics generated for the Genesis capsule reasonably predicted the drag and static stability. Observations of the heatshield support the pre-entry simulation estimates of a small hypersonic angles-of-attack, since there is very little, if any, charring of the shoulder region or the aftbody. Through this investigation, an overall assertion can be made that all the data gathered from the Genesis entry is consistent with flight performance that was close to the nominal preentry prediction. Consequently, the design principles and methodologies utilized for the flight dynamics, aerodynamics, and aerothermodynamics analyses have been corroborated.

Desai, Prasun N.↗

NASA NTRS2015

Multidisciplinary Simulation of Graphite-Composite and Cermet Fuel Elements for NTP Point of Departure Designs

This paper compares the expected performance of two Nuclear Thermal Propulsion fuel types. High fidelity, fluid/thermal/structural + neutronic simulations help predict the performance of graphite-composite and cermet fuel types from point of departure engine designs from the Nuclear Thermal Propulsion project. Materials and nuclear reactivity issues are reviewed for each fuel type. Thermal/structural simulations predict thermal stresses in the fuel and thermal expansion mis-match stresses in the coatings. Fluid/thermal/structural/neutronic simulations provide predictions for full fuel elements. Although NTP engines will utilize many existing chemical engine components and technologies, nuclear fuel elements are a less developed engine component and introduce design uncertainty. Consequently, these fuel element simulations provide important insights into NTP engine performance.

Cermets↗

NASA NTRS2017

Field Programmable Gate Array Reliability Analysis Guidelines for Launch Vehicle Reliability Block Diagrams

Field Programmable Gate Arrays (FPGAs) integrated circuits (IC) are one of the key electronic components in today's sophisticated launch and space vehicle complex avionic systems, largely due to their superb reprogrammable and reconfigurable capabilities combined with relatively low non-recurring engineering costs (NRE) and short design cycle. Consequently, FPGAs are prevalent ICs in communication protocols and control signal commands. This paper will identify reliability concerns and high level guidelines to estimate FPGA total failure rates in a launch vehicle application. The paper will discuss hardware, hardware description language, and radiation induced failures. The hardware contribution of the approach accounts for physical failures of the IC. The hardware description language portion will discuss the high level FPGA programming languages and software/code reliability growth. The radiation portion will discuss FPGA susceptibility to space environment radiation.

Al Hassan, Mohammad↗

NASA NTRS2018

FPGA Reliability and Failure Rate Analysis for Launch and Space Vehicles Environments

Field Programmable Gate Arrays (FPGAs) integrated circuits (IC) are one of the key electronic components in today's sophisticated launch and space vehicle complex avionic systems, largely due to their superb reprogrammable and reconfigurable capabilities combined with relatively low non-recurring engineering costs (NRE) and short design cycle. Consequently, FPGAs are prevalent ICs in communication protocols and control signal commands. This paper will demonstrate guidelines to estimate FPGA failure rates for ascent and in space operations. The guidelines will account for hardware and radiation-induced failures, as well as Bayesian updates to failure rates. The hardware contribution of the approach accounts for physical failures of the FPGA IC. The radiation portion will expand on FPGA susceptibility to different space radiation environments.

Al Hassan, Mohammad↗

NASA NTRSDate not supplied

Material Compatibility Study of Coated Metals to Maintain Biocidal Silver in a Spacecraft Potable Water System

Ionic silver-based biocide is an option of strong interest for future exploration and has been baselined for several emerging spacecraft potable water systems. A challenge for the use of silver biocide remains the depletion of ionic silver on wetted materials of construction. Consequently, the design and/or selection of materials that can be used as the wetted system components need specific consideration. As part of the strategy to address this issue, a multitiered approach is being investigated that looks at combinations of conventional and non-conventional spacecraft treatment processes and materials. In this study, eleven chemically-resistant polymer coatings were applied as surface treatments onto coupons that were cut out from three types of conventional spacecraft-grade metals (Titanium Grade 2, Inconel 718, and 316L Stainless Steel). The coated metals were immersed in a static 400 parts per billion silver biocide solution at a surface-area-to-volume ratio of 2.0 cm^-1 and left to soak for predefined periods of time. The concentration of the solution in contact with the coated samples were then analyzed via inductively coupled plasma mass spectrometry, and the data used to determine the extent to which the coatings provided a barrier to silver loss. This paper summarizes the coating selection process, the configuration of the test, and the performance of each coating-metal combination as a mitigation to silver depletion. The preliminary results demonstrate that select coatings are proving effective at maintaining biocidal silver concentrations. The knowledge acquired through this investigation will be used to assess the feasibility of using these coatings as a robust strategy for maintaining biocidal silver in the water systems. Future studies are planned to assess the specific use of these coatings and to better understand the implications of utilizing this material approach in the future spacecraft potable water system designs.

coatings↗

NASA NTRSDate not supplied

Material Compatibility Study of Coated Metals to Maintain Biocidal Silver in a Spacecraft Potable Water System

coatings↗

NASA NTRS1989

Investigations into a new algorithm for calculating H infinity optimal controllers

A new algorithm for calculating H (sup infinity) optimal controllers is investigated. The algorithm is significantly simpler than existing approaches and yields much simpler controllers. The design equations are first presented. Special system transformations required to apply the algorithm are then presented. The use of the algorithm with sampled-data systems is outlined in detail. Several constraints on the characteristics of the problem formulation are required for the application of the design equations. The consequences of these constraints are investigated by applying the algorithm to a simplified design for a subsystem of a large space structure ground test facility. The investigation of these constraints is continued by application of the design equations and constraints to an extremely simple tracking problem. The result of these investigations is the development of a frequency dependent weighting strategy that allows realistic control problems to be cast in a form compatible with the new algorithm. Further work is indicated in the area of developing strategies for choosing frequency-dependent weights to achieve specific design goals. The use of the freedom in problem formulation to achieve robustness/performance tradeoffs should also be investigated. It is not clear that the algorithm always leads to simpler controllers. The more restrictive formulation may dictate that frequency-dependent weighting adds to the controller order disproportionately. This effect must also be investigated.

Irwin, R. Dennis↗