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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Results from the Radio Frequency Mass Gauge Technology Demonstration on the Intuitive Machines Nova-C Lunar Lander

A cryogenic propellant mass gauge known as the Radio Frequency Mass Gauge (RFMG) was integrated into the Intuitive Machines (IM) Nova-C lunar lander and provided an estimate of the liquid oxygen and liquid methane mass in the lander propellant tanks throughout the IM-1 mission, including during microgravity coast phases. An RFMG electronics controller was used to measure and record the spectrum of the RF signal reflected from an antenna sensor in each tank over the frequency range 100 to 1,300 MHz. The RF spectrum of each of the tanks is unique and is sensitive to the index of refraction of the propellants and the spatial distribution of the liquid within the tanks. Electromagnetic simulation software was used to simulate the antenna response spectra for a given tank geometry, fluid properties, and liquid–vapor configurations within the tank. Over 10,000 antenna response simulations were completed for each propellant tank prior to the IM-1 mission and represented various volumetric fill levels and fluid configurations. The simulated spectra served as a database against which measured tank spectra were compared. For analysis, a spectral matching algorithm was used to find the best match between measured and simulated spectra, and the gauged mass was calculated from the most highly correlated fluid mass simulations. RFMG measurements were recorded during tank loading on the launch pad and during translunar coast, lunar orbit insertion, low lunar orbit, powered descent to the lunar surface, and postlanding on the Moon. This paper describes the RF and fluid simulations, the RFMG measurements and analysis of spectral data, the RFMG instrument, and the gauged results throughout all phases of the IM-1 mission.

lunar lander↗
NASA NTRSDate not supplied

Results from the Radio Frequency Mass Gauge Technology Demonstration on the Intuitive Machines Nova-C Lunar Lander

A cryogenic propellant mass gauge known as the Radio Frequency Mass Gauge (RFMG) was integrated into the Intuitive Machines (IM) Nova-C lunar lander and provided an estimate of the liquid oxygen and liquid methane mass in the lander propellant tanks throughout the IM-1 mission, including during microgravity coast phases. An RFMG electronics controller was used to measure and record the spectrum of the RF signal reflected from an antenna sensor in each tank over the frequency range 100 to 1,300 MHz. The RF spectrum of each of the tanks is unique and is sensitive to the index of refraction of the propellants and the spatial distribution of the liquid within the tanks. Electromagnetic simulation software was used to simulate the antenna response spectra for a given tank geometry, fluid properties, and liquid–vapor configurations within the tank. Over 10,000 antenna response simulations were completed for each propellant tank prior to the IM-1 mission and represented various volumetric fill levels and fluid configurations. The simulated spectra served as a database against which measured tank spectra were compared. For analysis, a spectral matching algorithm was used to find the best match between measured and simulated spectra, and the gauged mass was calculated from the most highly correlated fluid mass simulations. RFMG measurements were recorded during tank loading on the launch pad and during translunar coast, lunar orbit insertion, low lunar orbit, powered descent to the lunar surface, and postlanding on the Moon. This paper describes the RF and fluid simulations, the RFMG measurements and analysis of spectral data, the RFMG instrument, and the gauged results throughout all phases of the IM-1 mission.

lunar lander↗
NASA NTRS1979

Sources of the strongest RF radiation from lightning

Experiments performed at the Kennedy Space Center, Florida during TRIP-78 identified sources of the strongest RF radiation from lightning in the HF-VHF frequency range. Measurements were made of electric field changes associated with RF radiation using a field change system triggered on the output of an RF detector. The field changes associated with the strongest RF radiation are very fast (10 - 20 microseconds), bipolar pulses having an initial negative going half-cycle followed by a positive overshoot. These fast pulses consistently produced more RF radiation than was associated with return strokes, and their shape was remarkably consistent, independent of frequency.

Levine, D. M.↗
NASA NTRS1964

Improved insertion-loss tester

An improved test method accurately measures the insertion loss of RF components while avoiding amplifier drift. Currents are balanced across a bridge transformer with shorted probes and then with each component to be tested. Differences in adjustments indicate the loss.

Finnie, C. J.↗
NASA NTRS2003

Radio Frequency Telemetry System for Sensors and Actuators

The present invention discloses and teaches apparatus for combining Radio Frequency (RF) technology with novel micro-inductor antennas and signal processing circuits for RF telemetry of real time, measured data, from microelectromechanical system (MEMS) sensors, through electromagnetic coupling with a remote poweringheceiving device. Such technology has many applications, but is especially useful in the biomedical area.

Rainee N Simons↗
NASA NTRS2003

Radio frequency telemetry system for sensors and actuators

The present invention discloses and teaches apparatus for combining Radio Frequency (RF) technology with novel micro-inductor antennas and signal processing circuits for RF telemetry of real time, measured data, from microelectromechanical system (MEMS) sensors, through electromagnetic coupling with a remote powering/receiving device. Such technology has many applications, but is especially useful in the biomedical area.

Simons, Rainee N.↗
NASA NTRS2007

Potential Fluctuations and Energetic Ion Production in Hollow Cathode Discharges

Ions with energies significantly in excess of the applied discharge voltage have been reported for many years in hollow cathode discharges. Models of dc potential hills downstream of the cathode and instabilities in postulated double layers in the cathode orifice have been proposed to explain this, but have not been substantiated. Measurements of the dc and rf plasma density and potential profiles near the exit of hollow cathodes by miniature fast-scanning probes suggests that turbulent ion acoustic fluctuations and ionization instabilities in the cathode plume significantly increase the energy of the ions that flow from this region. Increases in the discharge current and/or decreases in the cathode gas flow enhance the amplitude of the fluctuations and increase the number and energy of the energetic ions, which increases the erosion rate of the cathode electrodes. The transition from the quiescent 'spot mode' to the noisy 'plume mode' characteristic of these discharges is found to be a gradual transition of increasing fluctuation amplitudes.

keeper↗
NASA NTRS1988

An optical heterodyne densitometer

Researchers are developing an optical heterodyne densitometer with the potential to measure optical density over an unprecedented dynamic range with high accuracy and sensitivity. This device uses a Mach-Zender interferometer configuration with heterodyne detection to make direct comparisons between optical and RF attenuators. Researchers expect to attain measurements of filter transmittance down to 10 to the minus 12th power with better than 1 percent uncertainty. In addition, they intend to extend the technique to the problem of measuring low levels of light scattering from reflective and transmissive optics.

Migdall, A. L.↗
NASA NTRS1999

Radio Frequencies Emitted by Mobile Granular Materials: A Basis for Remote Sensing of Sand and Dust Activity on Mars and Earth

In recent laboratory experiments, measurements were made of microsecond radio-wave (RF) bursts emitted by grains of sand as they energetically circulated in a closed, electrically ungrounded chamber. The bursts appeared to result from nanoscale electrical discharging from grain surfaces. Both the magnitude and wave form of the RF pulses varied with the type of material undergoing motion. The release of RF from electrical discharging is a well-known phenomenon, but it is generally measured on much larger energy scales (e.g., in association with lightning or electrical motors). This phenomenon might be used to detect, on planetary surfaces, the motion and composition of sand moving over dunes, the turbulent motion of fine particles in dust storms, highly-energetic grain and rock collisions in volcanic eruptions, and frictional grinding of granular materials in dry debris flows, landslides, and avalanches. The occurrence of these discharges has been predicted from theoretical considerations Additional information is contained in the original.

Marshall, J.↗
NASA NTRS1993

Results of multiband (L, S, Ku band) propagation measurements and model for high elevation angle land mobile satellite channel

Signal propagation in the land mobile satellite (LMS) service is an important consideration due to its critical impact on the overall economic and commercial viability of the system. At frequencies allocated for LMS systems, shadowing of the line-of-sight (LOS) signal as well as multipath propagation phenomena can severely impair the link availability. In particular, as most of the studies have shown, the shadowing of LOS signal causes long and deep fades in a variety of mobile environments due to the inherent nature of the channel between the satellite and a mobile. Roadside obstacles, such as buildings, trees, utility poles etc., in the immediate vicinity of a mobile and the surrounding terrain are major sources of signal shadowing in LMS links. Therefore, a proper knowledge of link degradation is essential for cost-effective planning of a satellite based mobile communication system. The results of a propagation campaign undertaken to characterize the fading nature of LMS channel at high elevation angles is presented. It was envisaged that one of the most important physical variables contributing to the amount of LOS signal shadowing is the elevation angle of the satellite. At higher elevation angles to the satellite, less obstructions in the direct satellite-to-mobile path would therefore amount to statistically better link availability. Narrowband channel measurements were carried out at three RF frequencies corresponding to L (1.3 GHz), S (2.32/2.45 GHz), and Ku (10.4 GHz) bands. The campaign itself was divided into two phases to observe the effects of seasonal variation of foliage on the roadside trees. Phase measurements were carried out in September 1991 and in April 1992. Some important aspects from the statistical analysis of the propagation data are presented.

Parks, M. A. N.↗
NASA NTRS1995

Prospects for high accuracy time dissemination and synchronization using coded radar pulses from a low-earth orbiting spacecraft

The radar (an acronym for radio detection and ranging) is an instrument developed just before the WW-II to precisely measure the position of an object (target) in space. This is done by emitting a narrow pulse of electromagnetic energy in the RF spectrum, receiving the return echo and measuring the time of flight in the two-way path from the emitter to the target. The propagation delay provides a measure of the range to the target, which is not in itself sufficient to uniquely locate the position of the same in space. However, if a directional antenna is used, the direction of the echo can be assessed by the antenna pointing angles. In this way the position of the target can be uniquely determined in space. How well this can be done is a function of the resolution of the measurements performed (range and direction, i.e.: angles); in turn, the resolution will dictate the time and frequency requirements of the reference oscillator.

Detoma, Edoardo V.↗
NASA NTRS2013

Demonstration of Space Optical Transmitter Development for Multiple High Frequency Bands

As the demand for multiple radio frequency carrier bands continues to grow in space communication systems, the design of a cost-effective compact optical transmitter that is capable of transmitting selective multiple RF bands is of great interest, particularly for NASA Space Communications Network Programs. This paper presents experimental results that demonstrate the feasibility of a concept based on an optical wavelength division multiplexing (WDM) technique that enables multiple microwave bands with different modulation formats and bandwidths to be combined and transmitted all in one unit, resulting in many benefits to space communication systems including reduced size, weight and complexity with corresponding savings in cost. Experimental results will be presented including the individual received RF signal power spectra for the L, C, X, Ku, Ka, and Q frequency bands, and measurements of the phase noise associated with each RF frequency. Also to be presented is a swept RF frequency power spectrum showing simultaneous multiple RF frequency bands transmission. The RF frequency bands in this experiment are among those most commonly used in NASA space environment communications.

Nguyen, Hung↗
NASA NTRS1973

Dynamics of midlatitude light ion trough and plasmatails

Light ion trough measurements near midnight made by the RF ion mass spectrometer on OGO-4 operating in the high resolution mode in Feb. 1968 reveal the existence of irregular structure on the low latitude side of the midlatitude trough. Using two different relations between the equatorial convection electric field, assumed spatially invariant and directed from dawn to dusk, and Kp (one based on plasmapause measurements, the other on polar cap E field measurements) a model development was made of the outer plasmasphere. The model calculations produced multiple plasmatail extensions of the plasmasphere which compare favorably with the observed irregularities. Due to magnetic local time differences between the Northern and Southern Hemisphere along OGO's orbit, the time dependent irregularity structure observed is not symmetrical about the equator. The model development produces an outer plasmasphere boundary location which varies similarly to the observed minimum density point of the light ion trough. However the measurements are not extensive enough to yield conclusive proof that one of the electric field models is better than the other.

Chen, A. J.↗
NASA NTRS2001

Exploration of Anomalous Gravity Effects by rf-Pumped Magnetized High-T(c) Superconducting Oxides

A number of anomalous gravitational effects have been reported in the scientific literature during recent years, but there has been no independent confirmation with regard to any of these claims. Therefore, the NASA Marshall Space Flight Center, in response to the propulsion challenges specified by NASA's Breakthrough Propulsion Physics (BPP) program, proposed to explore the possibility of observing anomalous gravitation behavior through the manipulation of Josephson junction effects in magnetized high-Tc superconducting oxides. The technical goal was to critically test this revolutionary physical claim and provide a rigorous, independent, empirical confirmation (or refutation) of anomalous effects related to the manipulation of gravity by radio frequency (rf)-pumped magnetized type-2 superconductors. Because the current empirical evidence for gravity modification is anecdotal, our objective was to design, construct, and meticulously implement a discriminating experiment, which would put these observations on a more firm footing within the scientific community. Our approach is unique in that we advocate the construction of an extremely sensitive torsion balance with which to measure gravity modification effects by rf-pumped type-2 superconductor test masses. This paper reviews the anecdotal evidence for anomalous gravity effects, describes the design and development of a simplified torsion balance experiment for empirically investigating these claims, and presents the results of preliminary experiments.

Robertson, Tony↗
NASA NTRS2021

Simulated Versus Measured UHF Radiated Power at LaRC Street Level

The Airspace Operations and Safety Program, System-Wide Safety Project /Technical Challenge 2 – Emerging Operations at NASA Langley aims to increase the flight safety of unmanned aerial vehicles (UAV’s) by informing UAV operators of regions of airspace where the radio frequency (RF) power at designated frequencies exceeds threshold values, indicating possible damage or interference with on-board systems. WinProp electromagnetic simulation software, a commercially available ray tracing program, has been implemented to predict radiated power from known RF sources. As a test case, the NextNav geolocation system, with nine transmitters operating at 926.227 MHz, was selected and modeled together with other existing structures at Langley. The radiated power at street level was calculated and compared with measurements taken at street level by a Signal Hound receiver and an Electro-Metrics antenna mounted on a van. The two sets of results generally agreed to within about 5 dB.

electromagnetic simulation↗
NASA NTRS1990

Olympus receiver evaluation and phase noise measurements

A set of measurements performed by the Michigan Tech Sensing and Signal Processing Group on the analog receiver built by the Virginia Polytechnic Institute (VPI) and the Jet Propulsion Laboratory (JPL) for propagation measurements using the Olympus Satellite is described. Measurements of local oscillator (LO) phase noise were performed for all of the LOs supplied by JPL. In order to obtain the most useful set of measurements, LO phase noise measurements were made using the complete VPI receiver front end. This set of measurements demonstrates the performance of the receiver from the Radio Frequency (RF) input through the high Intermediate Frequency (IF) output. Three different measurements were made: LO phase noise with DC on the voltage controlled crystal oscillator (VCXO) port; LO phase noise with the 11.381 GHz LO locked to the reference signal generator; and a reference measurement with the JPL LOs out of the system.

Campbell, Richard L.↗