Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Jamming”

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.

447 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Stable 1.25 watts CW far infrared laser radiation at the 119 micron methanol line

Far-infrared CW radiation of 1.25 watts has been obtained at the 119 micron methanol line with a CO2 pump power of 125 watts, and the maximum frequency fluctuation of the free running laser is measured to be less than + or - 100 kHz per hour. Reflecting optics have been used, when possible, to minimize CO2 degradation, and the frequency stability is ensured by cooling the input and output couplers. The input and output assemblies within the lasing medium are enclosed to minimize the external effects on the cavity length and to eliminate the mechanical instabilities associated with the use of bellows. The vibrational bottle-neck is broken by cooling the resonator wall to 5 deg and adding He as the buffer gas.

Farhoomand, Jam↗
NASA NTRS1989

Stable 1.25-W CW Methanol Laser

Far-infrared (FIR) laser operating at 119-micrometer-wavelength transition of methanol achieves very low drift in frequency. Continuous-wave (CW) FIR output is 1.25 W when laser pumped by 125-W commercial CO2 laser. Rate of drift of output frequency less than plus or minus 100 kHz per hour because laser designed to have low thermal-expansion coefficients and because temperatures of input and output couplers held within 0.1 degree C of fixed values.

Farhoomand, Jam↗
NASA NTRS1988

A stable, high power optically pumped far infrared laser system

The generation of 1.25 watts of CW laser power at the 119-micron (2522.8 GHz) methanol line is reported. The maximum frequency fluctuation of the free running laser is less than + or - 100 kHz per hour. This laser has also been tested on numerous other lines ranging from 403.7 GHz (HCOOH) to 5260 GHz (CH3OD) with improved power and stability.

Farhoomand, Jam↗
NASA NTRS1990

Performance of multiplexed Ge:Ga detector arrays in the far infrared

The performance of two multi-element, multiplexed Ge:Ga linear arrays under low-background conditions was investigated. The on-focal switching is accomplished by MOSFET switches, and the integrated charge is made available through MOSFET source followers. The tests were conducted at 106 microns, and the radiation on the detectors was confined to a spectral window 1.25 microns wide using a stack of cold filters. At 4.2 K, the highest responsivity was 584 A/W, the noise equivalent power was 1.0 x 10(exp -16) W/square root of Hz, and the read noise was 6100 electrons/sample. A detailed description of the test setup and procedure is presented.

Farhoomand, Jam↗
NASA NTRS1991

Design parameters of a resonant infrared photoconductor with unity quantum efficiency

This paper proposes a concept of a resonant infrared photoconductor that has characteristics of 100 percent quantum efficiency, high photoconductive gain, and very low noise equivalent power. Central to this concept is an establishment of a high-finesse absorption cavity internal to the detector element. A theoretical analysis is carried out, demonstrating this concept and providing some design guidelines. A Ge:Ga FIR detector is presently being fabricated using this approach.

Farhoomand, Jam↗
NASA NTRS1990

Evaluation of a far infrared Ge:Ga multiplexed detector array

The performance of a multielement Ge:Ga linear array under low-background conditions is investigated. On-focal plane switching is accomplished by MOSFET switches and the integrated charge is made available through MOSFET source followers. The tests were conducted at 106 microns and the radiation on the detectors was confined to a spectral window 1.25 microns wide using a stack of cold filters. At 4.2 K, the responsivity was measured to be nominally 584 A/W, and the NEP was 1.0 x 10 exp -16 W/sq rt Hz. A detailed description of the test setup and the procedure is presented.

Farhoomand, Jam↗
NASA NTRS1994

Resonant infrared detector with substantially unit quantum efficiency

A resonant infrared detector includes an infrared-active layer which has first and second parallel faces and which absorbs radiation of a given wavelength. The detector also includes a first tuned reflective layer, disposed opposite the first face of the infrared-active layer, which reflects a specific portion of the radiation incident thereon and allows a specific portion of the incident radiation at the given wavelength to reach the infrared-active layer. A second reflective layer, disposed opposite the second face of the infrared-active layer, reflects back into the infrared-active layer substantially all of the radiation at the given wavelength which passes through the infrared-active layer. The reflective layers have the effect of increasing the quantum efficiency of the infrared detector relative to the quantum efficiency of the infrared-active layer alone.

Farhoomand, Jam↗
NASA NTRS2009

Lunar Regolith Figures of Merit

This viewgraph presentation reviews the lunar regolith figures of merit. The contents include: 1) A quick review of Figures-of-Merit (FoM); 2) Software Implementation of FoM Algorithms; and 3) Demonstration of the Software.

Rickman, Doug↗
NASA NTRS2010

Soyuz 22 Return Samples: Assessment of Air Quality Aboard the International Space Station

Three mini-grab sample containers (m-GSCs) were returned aboard Soyuz 22 because of concerns that new air pollutants were present in the air and these were getting into the water recovery system. The Total Organic Carbon Analyzer had been giving increasing readings of total organic carbon (TOC) in the potable water, and it was postulated that an increased load into the system was responsible. The toxicological assessment of 3 m-GSCs from the ISS is shown in Table 1. The recoveries of the 3 standards (as listed above) from the GSCs averaged 103, 95 and 76%, respectively. Recovery from formaldehyde control badges were 90 and 91%.

Jams, John T.↗
NASA NTRS2025

Rheology of Lunar Regolith Simulant Under Varying Gravitational Conditions

Understanding structure-property-process relationship aka rheology of regolith in varying gravity conditions is critical for exploration and future missions. In this work, a framework for studying rheology of lunar regolith simulant in varying gravity conditions (Terrestrial, Lunar and Martian) is described theoretically/numerically, where the driving force of flow of simulants was gravitational acceleration. In the analysis particle-particle interaction forces were included. It was found that the dynamic behavior of granular material is extremely sensitive to external conditions by virtue of the myriad of forces present between particle grains. The results obtained were validated against results obtained in earth and Lunar gravity conditions. The theoretical/numerical and experimental results showed that the complex interaction of these forces can drastically change the dynamics of the material, which is not captured by standard design rules, generally used in industry, for variable gravity applications.

Simulation↗
NASA NTRSDate not supplied

Behaviors of Lunar Regolith Simulant Under Varying Gravitational Conditions

Understanding the behavior of regolith in varying gravity conditions is critical for space exploration and future missions. In this work, the gravity-driven hopper flow of lunar regolith simulant in different gravitational accelerations (terrestrial, lunar) is first observed experimentally. Numerical simulations (DEM) are then developed to understand the role which cohesive inter-particle forces play in such gravity-driven flow, using the theoretical framework of granular Bond number. Qualitative comparison between a terrestrial experiment and numerical simulation validated this framework. Following that, we numerically studied the dynamic behavior under varying gravitational conditions (from terrestrial to lunar to asteroid gravitational accelerations). We find that this behavior is extremely sensitive to the interplay of the gravity conditions and the attractive/cohesive forces among particles. The numerical and experimental results show that the complex interaction of these forces can drastically change the dynamics of the material producing effects relevant for variable gravity applications.

Soft Matter↗
DOE OSTI2025

Simulation of a Wireless Authentication Protocol

Abstract—A wireless authentication protocol that employs timeslots and associated frequency-channels (APEC) is simulated using Python as the simulation environment and implemented into radio hardware as a proof of concept. The APEC protocol does not rely on the use of challenge-response, multifactor authentication schemes but relies instead on the physical properties of a wireless signal. The APEC protocol provides opportunities for real-time deployment in cell phone network infrastructure, as well as in adverse civil and military applications. Description of the APEC implementation and the corresponding results of the simulation study are presented.

42 - ENGINEERING↗
DOE OSTI2024

APEC Poster

A wireless authentication protocol that employs timeslots and associated frequency- channels (APEC) is simulated using Python as the simulation environment and implemented into radio hardware as a proof of concept. The APEC protocol does not rely o n the use of challenge -response, multifactor authentication schemes but relies instead on the physical properties of a wireless signal. The APEC protocol provides opportunities for real-time deployment in cell phone network infrastructure, as well as in adverse civil and military applications. Description of the APEC implementation and the corresponding results of the simulation study are presented.

42 - ENGINEERING↗