Search NASA⌕ Search

SEARCH · Search NASA

Results for “SCREEN EFFECT”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1963

Component design, construction and evaluation for satellites

Components for a high-reliability system such as the Telstar project are obtained by: (a) design of the component for the required environment, (b) careful control of manufacturing processes, (c) elimination of potential early failures by screening tests, and (d) selection of the most stable components. For passive components, these methods could be applied by using design parameters, suppliers and screening techniques established in the earlier submarine cable program, with consideration being given to the additional effects of the satellite launch and orbit environments. Semiconductor component designs were selected by qualification tests using accelerated electrical and environmental stress conditions. Screening tests were applied to eliminate early failures, and resulting components were aged from two to six months before selection for the satellite. The recognition of the effect of ionizing radiation on transistors caused the addition of a radiation qualification test, or a screening to assure selection of the least sensitive devices. Tests have shown this screening to be effective for the radiation intensity expected. Experience with the passive components, and evaluation of the accelerated test results and aging data of the semiconductor devices, indicate that the reliability objective was obtained.

TELSTAR SATELLITE↗
DOE OSTI2025

A Comprehensive Machine Learning Model for Metal–Ligand Binding Prediction: Applications in Chemistry and Biology

A machine-learning (ML) model that predicts metal–ligand binding constants was developed using the open-source Chemprop software. The model was trained on over 30,000 experimental log K 1 values, which include both protonation and metal–ligand stability constants, comprising over 3500 ligands and 10 2 metal ions from 73 total elements, thus generalizing beyond existing limited approaches, which focus only on specific metals or ligand families. The best-performing model included a combination of SMILES-based molecular representations along with descriptors for the metal ion and experimental conditions. It had an external test R 2 value of 0.942, and MAE value of 0.834. A “SMILES-only” simpler version also produced accurate predictions and preserved the binding trends, serving as a quick and easily accessible alternative for users without computational expertise. The SMILES-only model performed comparably to density functional theory (DFT) calculations but utilized a fraction of the computational resources. The model was successfully applied across diverse domains, including bioinorganic chemistry, heavy metal remediation, and sensor development and demonstrated its effectiveness as a rapid and reliable screening tool for both academic and industrial uses.

Ligands↗
DOE OSTI2024

Data for "Propagation of EMIC Waves from Shabansky Orbits in the Dayside Magnetosphere"

Full-wave simulations of electromagnetic ion cyclotron waves in a non-dipole compressed magnetic field have been conducted using the Petra-M simulation code. The manuscript investigates the effect of misalignment of the Faraday screen and electron density in the scrape-off layer on the excitation and propagation of fast helicon and slow mode waves.

Magnetosphere: outer↗
NASA NTRS1975

Fracture control method for composite tanks with load sharing liners

The experimental program was based on the premise that the plastic sizing cycle, which each pressure vessel is subjected to prior to operation, acts as an effective proof test of the liner, screening out all flaws or cracks larger than a critical size. In doing so, flaw growth potential is available for cyclic operation at pressures less than the sizing pressure. Static fracture and cyclic life tests, involving laboratory type specimens and filament overwrapped tanks, were conducted on three liner materials: (1) 2219-T62 aluminum, (2) Inconel X750 STA, and (3) cryoformed 301 stainless steel. Variables included material condition, thickness, flaw size, flaw shape, temperature, sizing stress level, operating stress level and minimum-to-maximum operating stress ratio. From the empirical data base obtained, a procedure was established by which the service life of composite tanks with load sharing liners could be guaranteed with a high degree of confidence.

Bixler, W. D.↗
NASA NTRS1978

Comparison of calculated and altitude-facility-measured thrust and airflow of two prototype F100 turbofan engines

A comparison is made of the facility performance data for the two engines with an engine performance model, and it provides corrections that can be applied to the model so that it represents the test engines accurately over the flight envelope. Test conditions ranged from Mach numbers of 0.80 to 2.00 and altitudes from 4020 meters to 15,240 meters. Two distortion screens were used to determine the effect of distortion on airflow. Reynolds number effects were also determined. Engine hysteresis is documented, as is an attempt to determine engine degradation. The calibrated engine model had a twice standard deviation accuracy of approximately 1.24 percent for corrected airflow and 2.38 percent for gross thrust.

Kurtenbach, F. J.↗
NASA NTRS1980

Study of surge current effects on solid tantalum capacitors

Results are presented of a 2,000 hour cycled life test program conducted to determine the effect of short term surge current screening on approximately 47 micron f/volt solid tantalum capacitors. The format provides average values and standard deviations of the parameters, capacitance, dissipation factor, and equivalent series resistance at 120 Hz, 1KHz, abd 40 KHz.

Source record↗
NASA NTRS1981

Lessons from NASA

Particular requirements related to the design and the operation of spacecraft have forced NASA to take a reliability approach that differs somewhat from that used in many other applications. NASA has found that some of the traditional tools of reliability engineering, such as life testing, reliability demonstration testing, maintainability analysis, and direct failure analysis, are impractical for spacecraft. In place of a statistical approach, the space agency uses an engineering approach to mission reliability. Reliability is to be obtained with the aid of three different approaches, including the application of effective design principles, the control and screening of all parts, and the testing of the entire spacecraft or its prototype for predicted capabilities. Attention is given to failure-mode analysis, the enhancement of Voyager reliability by autonomous operation, the redundancy in Shuttle design, the weeding out of bad hardware, and the preference for off-the-shelf devices.

Williams, W. C.↗
NASA NTRS1983

Motion sickness - Acquisition and retention of adaptation effects compared in three motion environments

The acquisition and retention of adaptation effects in motion sickness was invetigated using a sudden-stop vestibulovisual interaction test for measuring susceptibility to motion sickness (Graybiel and Lackner, 1980). The test procedure included four successive assessments that provide not only an index of susceptibility to motion sickness but also the rates of acquisition and decay of adaptation effects. The 14 subjects who had participated in this test had previously served as subjects in parabolic flight experiments and seven of them had also taken part in the assessment of antimotion-sickness remedies in a slow rotation room. A study was conducted to determine whether these subjects' rates of acquisition and decay of adaptation to stressful motion represent consistent general features of their response across motion environments. It is found that an individual's rates of acquiring and losing adaptation are quite consistent in very different situations. In addition, the pattern of results indicate modifications of the sudden-stop vestibulovisual test that should increase its effectiveness as a motion-sickness screening procedure, both for orbital flight and for terrestrial conditions.

Graybiel, A.↗
NASA NTRS1988

Experimental investigation of inlet flow-control cascades for the NFAC 80- by 120-foot Indraft Wind Tunnel

The present investigation of aerodynamic performance for various inlet cascade configurations of an indraft wind tunnel with a short inlet and a low contraction ratio has given attention to the effects of inlet wall shape, antiturbulence screens, and horizontal flow straighteners on test-section flow quality. It is found that an inlet cascade with a tailored vane-splay distribution, antiturbulence screen, and horizontal splitters, will both yield good test section flow quality and furnish isolation from atmospheric winds and turbulence.

Van Aken, Johannes M.↗
NASA NTRS1991

Overview of the NASA-sponsored HSCT propulsion system studies

A brief overview of the NASA-sponsored HSCT propulsion system studies is presented that includes objectives, approach, schedules, and a summary of interim results highlighting the NASA in-house studies. Seven propulsion system concepts have been considered to date and comparatively evaluated on a first-order basis using takeoff gross weight (TOGW) as the main discriminator. Only two concepts have been screened out thus far and it is apparent that TOGW is not a strong discriminator. However, the first-order screening process did not account for differences in propulsion installation effects or climb-noise suppression penalties-both of which may strongly influence the screening process.

Strack, William C.↗
NASA NTRS2003

Extended Acceleration in Slot Gaps and Pulsar High-Energy Emission

We revise the physics of primary electron acceleration in the "slot gap" (SG) above the pulsar polar caps (PCs), a regime originally proposed by Arons and Scharlemann (1979) in their electrodynamic model of pulsar PCs. We employ the standard definition of the SG as a pair-free space between the last open field lines and the boundary of the pair plasma column which is expected to develop above the bulk of the PC. The rationale for our revision is that the proper treatment of primary acceleration within the pulsar SGs should take into account the effect of the narrow geometry of the gap on the electrodynamics within the gap and also to include the effect of inertial frame dragging on the particle acceleration. We show that the accelerating electric field within the gap, being significantly boosted by the effect of frame dragging, becomes reduced because of the gap geometry by a factor proportional to the square of the SG width. The combination of the effects of frame dragging and geometrical screening in the gap region naturally gives rise to a regime of extended acceleration, that is not limited to favorably curved field lines as in earlier models, and the possibility of multiple-pair production by curvature photons at very high altitudes, up to several stellar radii. We present our estimates of the characteristic SG thickness across the PC, energetics of primaries accelerated within the gap, high-energy bolometric luminosities emitted from the high altitudes in the gaps, and maximum heating luminosities produced by positrons returning from the elevated pair fronts. The estimated theoretical high-energy luminosities are in good agreement with the corresponding empirical relationships for gamma-ray pulsars. We illustrate the results of our modeling of the pair cascades and gamma-ray emission from the high altitudes in the SG for the Crab pulsar. The combination of the frame-dragging field and high-altitude SG emission enables both acceleration at the smaller inclination angles and a larger emission beam, both necessary to produce widely-spaced double-peaked profiles.

White, Nicholas E.↗
NASA NTRS2008

Countermeasure for Radiation Protection and Repair

Exposure to ionizing radiation during long-duration space missions is expected to cause short-term illness and increase long-term risk of cancer for astronauts. Radiation-induced free radicals overload the antioxidant defense mechanisms and lead to cellular damage at the membrane, enzyme, and chromosome levels. A large number of radioprotective agents were screened, but most had significant side effects. But there is increasing evidence that significant radioprotective benefit is achieved by increasing the dietary intake of foods with high antioxidant potential. Early plant-growing systems for space missions will be limited in both size and volume to minimize power and mass requirements. These systems will be well suited to producing plants containing high concentrations of bioprotective antioxidants. This project explored whether the production of bioprotective compounds could be increased by altering the lighting system, without increasing the space or power requirements for production, and evaluated the effects of environmental conditions (light quantity, light quality, and carbon dioxide [CO2] concentration) on the production of bioprotective compounds in lettuce, which provide a biological countermeasure for radiation exposure. The specific deliverables were to develop a database of bioprotectant compounds in plants that are suitable for use on longduration space missions, develop protocols for maintaining and increasing bioprotectant production under light emitting diodes (LEDs), recommend lighting requirements to produce dietary countermeasures of radiation, and publish results in the Journal of the American Society for Horticultural Science.

Source record↗
NASA NTRS1957

Experimental evaluation of methods for improving diffuser-exit total-pressure profiles for a side-inlet model at Mach number 1.91

Distortion effects of the following model additions or changes were studied: (1) constant-area mixing lengths at the end of the subsonic diffuser, (2) screens with systematic variations in mesh and flow-area blockage, (3) bleeds slots on the inlet cowl, and (4) a simulated compressor hub. Data at a diffuser-exit Mach number of 0.36 are compared with data of a similar study at Mach 0.20. At the higher Mach number, the same length of constant-area mixing was less effective in reducing total-pressure distortions, while the use of screens was more effective.

Klann, John L↗
NASA NTRS1985

Flow through very porous inclined screens

The steady, inviscid flow through and around a screen inclined at a uniform angle to the incoming flow was investigated. For a screen placed in an infinite flow field, an asymptotic analysis for small resistance coefficients was performed, and the effects of inclination were determined. The velocity at first order in the asymptotic expansion was nonuniform along the screen. This nonuniformity caused the wake behind the screen to contain distributed vorticity at second order. These effects therefore occurred at one order lower than for normal screens.

Muramoto, K. K.↗
NASA NTRS1985

Flow through very porous inclined screens

The steady, inviscid flow through and around a screen inclined at a uniform angle to the incoming flow was investigated. For a screen placed in an infinite flow field, an asymptotic analysis for small resistance coefficients was performed, and the effects of inclination were determined. The velocity at first order in the asymptotic expansion was nonuniform along the screen. This nonuniformity caused the wake behind the screen to contain distributed vorticity at second order. These effects therefore occurred at one order lower than for normal screens.

Muramoto, K. K.↗