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At least 865 records · Page 48

Fluidic Actuation for Aeropropulsive Acoustic Improvements

Experiments were performed in NASAs SW-2 cascade facility to compare three trailing edge actuation concepts to a 3D airfoil section with no trailing edge treatment. At a Reynolds number of 105, trailing edge pulsed ejection using fluidic oscillator devices was shown to fill the momentum deficit in the wake more uniformly than other actuators tested, with expected benefits for tonal noise in engine fans. Furthermore, pulsed ejection was found to alter the acoustic signature of the wake to reduce broadband noise. In some locations in the wake, spectral components of velocity were found to be reduced by 2 to 5 dB across nearly all frequencies. Trailing edge pulsed ejection is established as a feasible concept to reduce both tonal and broadband noise emissions from aircraft engines.

Stone, Mark↗

EdgeCortix SAKURA-I Machine-Learning, PCIe Accelerator SEE Heavy Ion Test Report

To enable autonomy in space, machine-learning and computer vision applications become invaluable for sensor processing. However, these algorithms are computationally complex and unfeasible for many embedded central processing units (CPUs) and usually require external coprocessors, such as graphics processing units (GPUs) or accelerators specific to the application, including application specific integrated circuits (ASICs). In power-constrained systems, GPUs tend to consume more power than is acceptable (>40W), so lower-power accelerators have shown promise to provide the performance needed under spacecraft constraints. For radiation engineers, developing methodologies that can properly test CPUs, GPUs, and accelerators, and enable comparisons between them remains a necessary complication to solve as the devices become more complex. The methodology in this test aims to be a start in developing a baseline single-event effect (SEE) test for client-device machine learning accelerators. This category of devices do not host their own operating system. This testing campaign is a continuation of a previous 200 MeV proton test performed in January 2024. This report covers two heavy ion tests of the SAKURA-I card: one in April 2024, and one in June 2024. Additional data was needed after the April test due to ion-range issues experienced at higher linear-energy transfers (LETs). These range issues are described in more detail in Section 8. This experiment characterizes SEEs and data error susceptibility of the EdgeCortix SAKURA-I machine-learning accelerator under heavy ions. The device was monitored for single event upsets (SEUs) and single event functional interrupts (SEFIs) at the Lawrence Berkeley National Laboratory’s 88-inch cyclotron. The SAKURA-I board accelerates machine-learning inference applications on a host computer through a PCIex16 connection. For the purposes of devising an end to end automated analysis workflow for this experiment, the YOLO-V5 and SSD300 objection-detection models, and the ResNet-50, EfficientNet, and MobileNetV2 image classification models were used as a representative suite of analytical machine-learning models.

Seth S Roffe↗

Development of an electrostatic propulsion engine using sub-micron powders as the reaction mass

Asteroid sample return missions would benefit from development of an improved rocket engine. Chemical rockets achieve their large thrust with high mass consumption rate (dm/dt) but low exhaust velocity; therefore, a large fraction of their total mass is fuel. Present day ion thrusters are characterized by high exhaust velocity, but low dm/dt; thus, they are inherently low thrust devices. However, their high exhausy velocity is poorly matched to typical mission requirements and therefore, wastes energy. A better match would be intermediate between the two forms of propulsion. This could be achieved by electrostatically accelerating solid powder grains, raising the possibility that interplanetary material could be processed to use as reaction mass. An experiment to study the charging properties of sub-micron sized powder grains is described. If a suitable material can be identified, then it could be used as the reaction mass in an electrostatic propulsion engine. The experiment employs a time of flight measurement to determine the exhaust velocity (v) of various negatively charged powder grains that were charged and accelerated in a simple device. The purpose is to determine the charge to mass ratio that can be sustained for various substances. In order to be competitive with present day ion thrusters, a specific impulse (v/g) of 3000 to 5000 seconds is required. Preliminary results are presented. More speculatively, there are some mission profiles that would benefit from collection of reaction mass at the remote asteroid site. Experiments that examine the generation of sub-micron clusters by electrostatic self-disruption of geologically derived material are planned.

Herbert, F.↗

Detection of bearing failure in mechanical devices using neural networks

We present a novel time-domain method for the detection of faulty bearings that has direct applicability to monitoring the health of the turbo pumps on the Space Shuttle Main Engine. A feed-forward neural network was trained to detect modelled roller bearing faults on the basis of the periodicity of impact pulse trains. The network's performance was dependent upon the number of pulses in the network's input window and the signal-to-noise ratio of the input signal. To test the model's validity, we fit the model's parameters to an actual vibration signal generated by a faulty roller element bearing and applied the network trained on this model to detect faults in actual vibration data. When this network was tested on the actual vibration data, it correctly identified the vibration signal as a fault condition 76 percent of the time.

Burne, Richard A.↗

Transition Models for Engineering Calculations

While future theoretical and conceptual developments may promote a better understanding of the physical processes involved in the latter stages of boundary layer transition, the designers of rotodynamic machinery and other fluid dynamic devices need effective transition models now. This presentation will therefore center around the development of of some transition models which have been developed as design aids to improve the prediction codes used in the performance evaluation of gas turbine blading. All models are based on Narasimba's concentrated breakdown and spot growth.

Fraser, C. J.↗

Concept of planetary gear system to control fluid mixture ratio

Mechanical device senses and corrects for fluid flow departures from the selected flow ratio of two fluids. This system has been considered for control of rocket engine propellant mixture control but could find use wherever control of the flow ratio of any two fluids is desired.

Mc~groarty, J. D.↗

A case study of technology transfer: Rehabilitative engineering at Rancho Los Amigos Hospital

The transfer of NASA technolgy to rehabilitative applications of artificial limbs is studied. Human factors engineering activities range from orthotic manipulators to tiny dc motors and transducers to detect and transmit voluntary control signals. It is found that bicarbon implant devices are suitable for medical equipment and artificial limbs because of their biological compatibility with human body fluids and tissues.

Hildred, W.↗

Semiconductor step-stress testing

Report documents behavior of discrete diodes and transistors in extensive power and temperature overstress tests. Thirty nine devices were tested in groups designated: (1) power overstress, and (2) and (3) temperature overstress. Results are of interest to users of tested components and engineers in conduction of similar tests.

Meeks, H. B.↗

A 20-GHz IMPATT transmitter

The engineering development of a solid state transmitter amplifier operating in the 20 GHz frequency band. The development effort involved a variety of disciplines including IMPATT device development, circulator design, simple and multiple diode circuits designs, and amplifier integration and test.

Chan, J. L.↗

Manned space nuclear systems design guidelines

The philosophy utilized on space nuclear system design and safety has evolved gradually over the last 30 years in the United States. Past programs have primarily been concerned with unmanned systems, except for the ROVER/NERVA engine development program which was in support of a manned mission to Mars. This papear proposes top level design guidelines for the use of nuclear devices for manned space applications. The guidelines presented cover failure and redundancy criteria, payload and flight vehicle specifications, environmental compatibility, mission operational constraints, construction and servicing, and radiation constraints. This paper also raises design and operational concerns requiring further examination. The purpose of this paper is to provide direction for the development of manned space nuclear systems currently envisioned for the Space Exploration Initiative.

Sanders, Jerry B.↗

A Review of the Suppression of Secondary Electron Emission from the Electrodes of Multistage Collectors

A review is presented of more than 20 years of research conducted at NASA Lewis Research Center on the suppression of secondary electron emission (SEE) for the enhancement of the efficiency of vacuum electron devices with multistage depressed collectors. This paper will include a description of measurement techniques, data from measurements of SEE on a variety of materials of engineering interest and methods of surface treatment for the suppression of SEE. In the course of this work the lowest secondary electron yield ever reported was achieved for ion textured graphite, and, in a parallel line of research, the highest yield was obtained for chemical vapor deposited thin diamond films.

Dayton, James A., Jr.↗

Wind Monitor

NASA needed a way to make high-resolution measurements of the wind profile before launching Saturn vehicles. The standard smooth-surface weather balloons zigzagged or spiraled as they ascended due to air vortices that shed off the surface at various positions, which made accurate radar-tracking measurement impossible. A Marshall Space Flight Center engineer modified the surface of the balloons with conical dixie cups, which stabilized them. Now produced by Orbital Sciences Corporation, the Jimsphere is the standard device at all U.S. missile/launch vehicle ranges.

Source record↗

Toward an Improved Hypersonic Engine Seal

High temperature, dynamic seals are required in advanced engines to seal the perimeters of movable engine ramps for efficient, safe operation in high heat flux environments at temperatures from 2000 to 2500 F. Current seal designs do not meet the demanding requirements for future engines, so NASA s Glenn Research Center (GRC) is developing advanced seals to overcome these shortfalls. Two seal designs and two types of seal preloading devices were evaluated in a series of compression tests at room temperature and 2000 F and flow tests at room temperature. Both seals lost resiliency with repeated load cycling at room temperature and 2000 F, but seals with braided cores were significantly more flexible than those with cores composed of uniaxial ceramic fibers. Flow rates for the seals with cores of uniaxial fibers were lower than those for the seals with braided cores. Canted coil springs and silicon nitride compression springs showed promise conceptually as potential seal preloading devices to help maintain seal resiliency.

Dunlap, Patrick H., Jr.↗

A Gas-Actuated Projectile Launcher for High-Energy Impact Testing of Structures

A gas-act,uated penetration device has been developed for high-energy impact testing of structures. The high-energy impact. t,estiiig is for experimental simulation of uncontained engine failures. The non-linear transient finite element, code LS-DYNA3D has been used in the numerical simula.tions of a titanium rectangular blade with a.n aluminum target, plate. Threshold velocities for different combinations of pitch and yaw angles of the impactor were obtained for the impactor-target, t8est configuration in the numerica.1 simulations. Complet,e penet,ration of the target plate was also simulat,ed numerically. Finally, limited comparison of analytical and experimental results is presented for complete penetration of the target by the impactor.

Ambur, Damodar R.↗

Thermal Load Considerations for Detonative Combustion-Based Gas Turbine Engines

An analysis was conducted to assess methods for, and performance implications of, cooling the passages (tubes) of a pulse detonation-based combustor conceptually installed in the core of a gas turbine engine typical of regional aircraft. Temperature-limited material stress criteria were developed from common-sense engineering practice, and available material properties. Validated, one-dimensional, numerical simulations were then used to explore a variety of cooling methods and establish whether or not they met the established criteria. Simulation output data from successful schemes were averaged and used in a cycle-deck engine simulation in order to assess the impact of the cooling method on overall performance. Results were compared to both a baseline engine equipped with a constant-pressure combustor and to one equipped with an idealized detonative combustor. Major findings indicate that thermal loads in these devices are large, but potentially manageable. However, the impact on performance can be substantial. Nearly one half of the ideally possible specific fuel consumption (SFC) reduction is lost due to cooling of the tubes. Details of the analysis are described, limitations are presented, and implications are discussed.

Paxson, Daniel E.↗

Guidelines of the Design of Electropyrotechnic Firing Circuit for Unmanned Flight and Ground Test Projects

The NASA Langley Research Center, Engineering Directorate, Electronic System Branch, is responsible for providing pyrotechnic support capabilities to Langley Research Center unmanned flight and ground test projects. These capabilities include device selection, procurement, testing, problem solving, firing system design, fabrication and testing; ground support equipment design, fabrication and testing; checkout procedures and procedure?s training to pyro technicians. This technical memorandum will serve as a guideline for the design, fabrication and testing of electropyrotechnic firing systems. The guidelines will discuss the entire process beginning with requirements definition and ending with development and execution.

Gonzalez, Guillermo A.↗

HRP's Healthcare Spin-Offs Through Computational Modeling and Simulation Practice Methodologies

Spaceflight missions expose astronauts to novel operational and environmental conditions that pose health risks that are currently not well understood, and perhaps unanticipated. Furthermore, given the limited number of humans that have flown in long duration missions and beyond low Earth-orbit, the amount of research and clinical data necessary to predict and mitigate these health and performance risks are limited. Consequently, NASA's Human Research Program (HRP) conducts research and develops advanced methods and tools to predict, assess, and mitigate potential hazards to the health of astronauts. In this light, NASA has explored the possibility of leveraging computational modeling since the 1970s as a means to elucidate the physiologic risks of spaceflight and develop countermeasures. Since that time, substantial progress has been realized in this arena through a number of HRP funded activates such as the Digital Astronaut Project (DAP) and the Integrated Medical Model (IMM). Much of this success can be attributed to HRP's endeavor to establish rigorous verification, validation, and credibility (VV&C) processes that ensure computational models and simulations (M&S) are sufficiently credible to address issues within their intended scope. This presentation summarizes HRP's activities in credibility of modeling and simulation, in particular through its outreach to the community of modeling and simulation practitioners. METHODS: The HRP requires all M&S that can have moderate to high impact on crew health or mission success must be vetted in accordance to NASA Standard for Models and Simulations, NASA-STD-7009 (7009) [5]. As this standard mostly focuses on engineering systems, the IMM and DAP have invested substantial efforts to adapt the processes established in this standard for their application to biological M&S, which is more prevalent in human health and performance (HHP) and space biomedical research and operations [6,7]. These methods have also generated substantial interest by the broader medical community though institutions like the National Institutes of Health (NIH) and the Food and Drug Administration (FDA) to develop similar standards and guidelines applicable to the larger medical operations and research community. DISCUSSION: Similar to NASA, many leading government agencies, health institutions and medical product developers around the world are recognizing the potential of computational M&S to support clinical research and decision making. In this light, substantial investments are being made in computational medicine and notable discoveries are being realized [8]. However, there is a lack of broadly applicable practice guidance for the development and implementation of M&S in clinical care and research in a manner that instills confidence among medical practitioners and biological researchers [9,10]. In this presentation, we will give an overview on how HRP is working with the NIH's Interagency Modeling and Analysis Group (IMAG), the FDA and the American Society of Mechanical Engineers (ASME) to leverage NASA's biomedical VV&C processes to establish a new regulatory standard for Verification and Validation in Computational Modeling of Medical Devices, and Guidelines for Credible Practice of Computational Modeling and Simulation in Healthcare.

Mulugeta, Lealem↗

The Evolution of Exercise Hardware on ISS: Past, Present, and Future

During 16 years in low-Earth orbit, the suite of exercise hardware aboard the International Space Station (ISS) has matured significantly. Today, the countermeasure system supports an array of physical-training protocols and serves as an extensive research platform. Future hardware designs are required to have smaller operational envelopes and must also mitigate known physiologic issues observed in long-duration spaceflight. Taking lessons learned from the long history of space exercise will be important to successful development and implementation of future, compact exercise hardware. The evolution of exercise hardware as deployed on the ISS has implications for future exercise hardware and operations. Key lessons learned from the early days of ISS have helped to: 1. Enhance hardware performance (increased speed and loads). 2. Mature software interfaces. 3. Compare inflight exercise workloads to pre-, in-, and post-flight musculoskeletal and aerobic conditions. 4. Improve exercise comfort. 5. Develop complimentary hardware for research and operations. Current ISS exercise hardware includes both custom and commercial-off-the-shelf (COTS) hardware. Benefits and challenges to this approach have prepared engineering teams to take a hybrid approach when designing and implementing future exercise hardware. Significant effort has gone into consideration of hardware instrumentation and wearable devices that provide important data to monitor crew health and performance.

Buxton, R. E.↗