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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 757 records · Page 42
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NASA NTRSDate not supplied

TriTruss Strut-to-Joint Bond Test: Analysis and Setup

The TriTruss is a novel structural module developed by researchers at NASA Langley Research Center (LaRC) that can be used in space to assemble large backing structures for a variety of applications. One such application is the metering truss or primary mirror backbone support structure of an in-space assembled telescope (iSAT). For the iSAT application, the TriTruss will be supporting mirror segments, payloads and instruments, all of which require them to have robust structural integrity. Structural proof tests are needed to ensure the integrity of the bonded interface between the joint and structural struts that make up a TriTruss module. For the first phase of the analysis and test setup effort, described in this paper, a series of analyses were performed to determine the optimal setup for applying a single set of loads to a module to verify the integrity of the bonds. This paper describes all the test setup configurations and loads considered and summarizes the final set of loading states that were selected for proof testing each module.

TriTruss↗
NASA NTRS1992

Coded 16-CPFSK for downlink applications

A bandwidth-efficient constant-envelope Proof-of-Concept (POC) modem is described. The modem was developed on an Advanced Modulation Techniques Development contract for the NASA/Lewis Research Center. The POC modem employs 16-ary Continuous Phase Frequency Shift Keying (16-CPFSK) modulation. The 16 frequencies are spaced every 1/16th baud rate which produces a compact spectrum allowing 2 bits/sec/Hz operation. The modem is designed for 200 mb/s Time Division Multiple Access (TDMA) application with 100 MHz adjacent channel spacing. Overall rate 3.4 convolutional coding is incorporated. The demodulator differs significantly from typical quadrature phase detector approaches in that phase is coherently measured by processing the baseband output of a frequency discriminator. Baud rate phase samples for the baseband processor are subsequently decoded to yield the original data stream. The method of encoding onto the 16-ary symbol-ending phase nodes, together with convolutional coding gain, results in near Quadrature Phase Shift Keying (QPSK) theoretical performance. The modulated signal is of constant envelope; thus the power amplifier can be saturated for peak performance. The spectrum is inherently bandlimited and requires no RF filter for sidelobe containment. Two novel theoretical techniques are used in this 16-CPFSK modem: (1) coherent phase measurements are obtained by processing an FM discriminator baseband output; and (2) modulation is accomplished via a closed-loop-linearized voltage controlled oscillator (VCO).

Davis, Robert↗
NASA NTRS2003

Mechanical Amplifier for a Piezoelectric Transducer

A mechanical amplifier has been devised to multiply the stroke of a piezoelectric transducer (PZT) intended for use at liquid helium temperatures. Interferometry holds the key to high angular resolution imaging and astrometry in space. Future space missions that will detect planets around other solar systems and perform detailed studies of the evolution of stars and galaxies will use new interferometers that observe at mid- and far-infrared wavelengths. Phase-measurement interferometry is key to many aspects of astronomical interferometry, and PZTs are ideal modulators for most methods of phase measurement, but primarily at visible wavelengths. At far infrared wavelengths of 150 to 300 m, background noise is a severe problem and all optics must be cooled to about 4 K. Under these conditions, piezos are ill-suited as modulators, because their throw is reduced by as much as a factor of 2, and even a wavelength or two of modulation is beyond their capability. The largest commercially available piezo stacks are about 5 in. (12.7 cm) long and have a throw of about 180 m at room temperature and only 90 m at 4 K. It would seem difficult or impossible to use PZTs for phase measurements in the far infrared were it not for the new mechanical amplifier that was designed and built.

Moore, James↗
NASA NTRS1988

Space Station thermal control during on-orbit assembly

This paper summarizes the Space Station program requirements for the Thermal Control System (TCS), and outlines the capabilities of the TCS for each assembly configuration. The TCS architecture for the completed assembly configuration is described, consisting of an active TCS (ATCS) and a passive TCS (PTCS). The four ATCS subsystems are described, including the two-phase ammonia central ATCS, photovoltaic power module, attached payload accommodation equipment and the single-phase water internal ATCS.

Bilardo, Vincent J., Jr.↗
NASA NTRS2007

NASA CEV Reference Entry GN&C System and Analysis

As part of its overall objectives, the Orion spacecraft will be required to perform entry and Earth landing functions for Low Earth Orbit (LEO) and Lunar missions. Both of these entry scenarios will begin with separation of the Service Module (SM), making them unique from other Orion mission phases in that only the Command Module (CM) portion of the Crew Exploration Vehicle (CEV) will be involved, requiring a CM specific Guidance, Navigation and Control (GN&C) system. Also common to these mission scenarios will be the need for GN&C to safely return crew (or cargo) to earth within the dynamic thermal and structural constraints of entry and within acceptable accelerations on the crew, utilizing the limited aerodynamic performance of the CM capsule. The lunar return mission could additionally require an initial atmospheric entry designed to support a precision skip and second entry, all to maximize downrange performance and ensure landing in the United States. This paper describes the Entry GN&C reference design, developed by the NASA-led team, that supports these entry scenarios and that was used to validate the Orion System requirements. Description of the reference design will include an overview of the GN&C functions, avionics, and effectors and will relate these to the specific design drivers of the entry scenarios, as well as the desire for commonality in vehicle systems to support the different missions. The discussion will also include the requirement for an Emergency Entry capability beyond that of the nominal performance of the multi-string GNC system, intended to return the crew to the earth in a survivable but unguided manner. Finally, various analyses will be discussed, including those completed to support validation efforts of the current CEV requirements, along with those on-going and planned with the intention to further refine the requirements and to support design development work in conjunction with the prime contractor. Some of these ongoing analyses will include work to size effectors (jets) and fuel budgets, to refine skip entry concepts, to characterize navigation performance and uncertainties, to provide for SM disposal offshore and to identify requirements to support target site selection.

Munday, S.↗
NASA NTRS2008

Advanced Precipitation Radar Antenna to Measure Rainfall From Space

To support NASA s planned 20-year mission to provide sustained global precipitation measurement (EOS-9 Global Precipitation Measurement (GPM)), a deployable antenna has been explored with an inflatable thin-membrane structure. This design uses a 5.3 5.3-m inflatable parabolic reflector with the electronically scanned, dual-frequency phased array feeds to provide improved rainfall measurements at 2.0-km horizontal resolution over a cross-track scan range of up to 37 , necessary for resolving intense, isolated storm cells and for reducing the beam-filling and spatial sampling errors. The two matched radar beams at the two frequencies (Ku and Ka bands) will allow unambiguous retrieval of the parameters in raindrop size distribution. The antenna is inflatable, using rigidizable booms, deployable chain-link supports with prescribed curvatures, a smooth, thin-membrane reflecting surface, and an offset feed technique to achieve the precision surface tolerance (0.2 mm RMS) for meeting the low-sidelobe requirement. The cylindrical parabolic offset-feed reflector augmented with two linear phased array feeds achieves dual-frequency shared-aperture with wide-angle beam scanning and very low sidelobe level of -30 dB. Very long Ku and Ka band microstrip feed arrays incorporating a combination of parallel and series power divider lines with cosine-over-pedestal distribution also augment the sidelobe level and beam scan. This design reduces antenna mass and launch vehicle stowage volume. The Ku and Ka band feed arrays are needed to achieve the required cross-track beam scanning. To demonstrate the inflatable cylindrical reflector with two linear polarizations (V and H), and two beam directions (0deg and 30deg), each frequency band has four individual microstrip array designs. The Ku-band array has a total of 166x2 elements and the Ka-band has 166x4 elements with both bands having element spacing about 0.65 lambda(sub 0). The cylindrical reflector with offset linear array feeds reduces the complexity from "NxN" transmit/receive (T/R) modules of a conventional planar-phased array to just "N" T/R modules. The antenna uses T/R modules with electronic phase-shifters for beam steering. The offset reflector does not provide poor cross-polarization like a double- curved offset reflector would, and it allows the wide scan angle in one plane required by the mission. Also, the cylindrical reflector with two linear array feeds provides dual-frequency performance with a single, shared aperture. The aperture comprises a reflective surface with a focal length of 1.89 m and is made from aluminized Kapton film. The reflective surface is of uniform thickness in the range of a few thousandths of an inch and is attached to the chain-link support structure via an adjustable suspension system. The film aperture rolls up, together with the chain-link structure, for launch and can be deployed in space by the deployment of the chain-link structure.

Rahmat-Samii, Yahya↗
NASA NTRS2015

Development of an Ablative 3D Quartz / Cyanate Ester Composite for the Orion Spacecraft Compression Pad

With the successful flight test of the Orion Multipurpose Crew Vehicle last December, NASA is well on its way to sending humans into deep space with the ultimate goal of putting astronauts on Mars in the 2030s. Orion will receive some upgrades for its next launch in 2018 including a newly developed 3D quartz / cyanate ester composite material for the compression pad. Multiple pad locations in the heat shield serve as a part of the mechanism for holding the Crew and Service Modules together during most mission phases prior to separation followed by Earth re-entry of the Crew Module. Thus the compression pad must survive structural and aerothermal loads, and protect the adjascent structure and heat shield materials from over-heating.This paper describes the approach used for developing the new 3D composite, including continuous 3D weaving on an automated loom followed by resin transfer molding. Mechanical, thermal, arc jet ,and stress relaxation testing of the 3D composite are also described.

Feldman, Jay D.↗
NASA NTRS2024

Extended Investigation into Fault-Tolerant Integrated Motor Drive for a Quadrotor Urban Air Mobility (UAM) Aircraft

Electric propulsor machines and their associated power electronics have been identified in past studies as low-reliability components in emerging Urban Air Mobility (UAM) Vertical Takeoff and Landing (VTOL) vehicles that raise their predicted catastrophic failure rates. This research effort extends previously presented work investigating the use of fault-tolerant (FT) motor drives in quadrotor aircraft as a promising approach to significantly increase their mean-time-to-failure (MTTF). In particular, fault-tolerant modular motor drives (FT-MMDs) are identified as strong candidates for closing the electric propulsor reliability gap. These FT-MMDs divide a machine drive into multiple redundant modules, each consisting of three phase stator windings and power electronics units, enabling continued machine operation after a module failure. Achieving the highest possible isolation between modules (physical, magnetic, thermal, electrical) is critically important in FT-MMDs to prevent the propagation of any failure between modules. Key additional requirements for achieving the highest possible reliability characteristics with FT-MMDs are high repair rates and aggressive suppression of all single-point failures.

quadrotor↗
NASA NTRS1989

Impulsive solar wind-driven emission from Uranus

Several days prior to the Voyager spacecraft encounter with Uranus, the plasma wave and radio astronomy receivers detected extraordinarily narrowband bursty signals, the first indication of any radio emission from the planet. The characteristics of these signals were so unusual that their identity as a natural planetary emission was questioned at first. Subsequent analysis has shown, however, that the n bursts are modulated at the 17.24-hour Uranus rotation period and are, therefore, planetary in origin. It is shown, in addition, that the typical bandwidth and time scale for the bursts are about 5 kHz and 250 ms, respectively. The phase of the rotation modulation suggests a probable source for these events in the vicinity of the north (weak) magnetic pole. The waves are right-hand polarized and are therefore emitted in the extraordinary magnetoionic mode if the emission in fact originates above the north magnetic pole.

Desch, M. D.↗
NASA NTRS1991

Multiple-Symbol Differential Detection Of MPSK

Multiple-symbol differential detection proposed for reception of radio-frequency signals modulated by mutliple-phase-shift keying (MPSK). Offers advantage of less complexity in not requiring equipment to acquire and track carrier signal. Performance approaches that of ideal coherent detection. Applicable to coded as well as uncoded MPSK, and to other forms of modulation.

Divsalar, Dariush↗
NASA NTRS2015

Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for ASCENDS O2 Column Measurements

Global atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity- Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These results are extended to include Richardson-Lucy deconvolution techniques to extend the resolution of the lidar beyond that implied by limit of the bandwidth of the modulation, where it is shown useful for making tree canopy measurements.

Campbell, Joel F.↗
NASA NTRS1979

Dynamic cross correlation studies of wave particle interactions in ULF phenomena

Magnetic field observations made by satellites in the earth's magnetic field reveal a wide variety of ULF waves. These waves interact with the ambient particle populations in complex ways, causing modulation of the observed particle fluxes. This modulation is found to be a function of species, pitch angle, energy and time. The characteristics of this modulation provide information concerning the wave mode and interaction process. One important characteristic of wave-particle interactions is the phase of the particle flux modulation relative to the magnetic field variations. To display this phase as a function of time a dynamic cross spectrum program has been developed. The program produces contour maps in the frequency time plane of the cross correlation coefficient between any particle flux time series and the magnetic field vector. This program has been utilized in several studies of ULF wave-particle interactions at synchronous orbit.

Mcpherron, R. L.↗
NASA NTRS1966

Some Aspects of an Air-Core Single-Coil Magnetic Suspension System

This paper presents some of the technical aspects in the development at the Langley Research Center of an air-cove, dual-wound, single-coil, magnetic-suspension system with one-dimensional control. Overall electrical system design features and techniques are discussed in addition to the problems of control and stability. Special treatment is given to the operation of a dual-wound, high-current support coil which provides the bias fields and superimposed modulated field. Other designs features include a six-phase, solid-state power stage for modulation of the relatively large magnitude control current, and an associated six-phase trigger circuit.

SUPPORT SYSTEM↗
NASA NTRS1982

Application of MMIC modules in future multiple beam satellite antenna systems

Multiple beam antenna systems for advanced communication satellites operating in the 30/20 GHz frequency bands (30 GHz uplink, 20 GHz downlink) were developed. Up to twenty 0.3 deg HPBW fixed spot beams and six 0.3 deg HPBW scanning spot beams will be required. Array-fed dual reflector antenna systems in which monolithic microwave integrated circuit (MMIC) phase shift and amplifier modules are used with each radiating element of the feed array for beam pointing and power gain were developed. The feasibility of distributed power amplification and beam pointing with MMIC modules in the elements of an array and to develop a data base for future development were demonstrated. The technical discussion centers around the potential advantages of ""monolithic'' antennas for specific applications as compared to systems using high powered TWT's. These include: reduced losses in the beam forming network; advantage of space combining and graceful degradation; dynamic control of beam pointing and illumination contour; and possibilities for cost and weight reduction.

Smetana, J.↗
DOE OSTI2026

Field-resolved observation of exciton coherence in a van der Waals magnet

The emergence of coherence among electronic quasiparticles underlies collective quantum phenomena from superconductivity to superradiance. In semiconductors, exciton coherence is generally thought to decay rapidly due to scattering and dephasing, limiting its persistence on ultrafast timescales. Here, in this work, we demonstrate a light-field-driven mechanism that creates and stabilizes exciton coherence in the layered antiferromagnet CrSBr. We directly record the coherent optical field emitted by excitons and track in real time how a deterministic phase, imprinted by the excitation laser, drives incoherent excitons to synchronize into a collective state. This ensemble remains phase coherent for more than 2 ps, whereas its resonance energy undergoes an ultrafast modulation mediated by spin and lattice interactions. The time-resolved field evolution indicates that the multiple peaks seen in conventional spectra originate from a single excitonic resonance subject to dynamic energy modulation. Our findings establish optical phase imprinting as a mechanism to control and sustain collective order in semiconducting magnets, bridging light-driven dynamics with excitonic and magnetic correlations in layered quantum materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

ALS mutations disrupt self-association between the ubiquilin STI1 hydrophobic groove and internal placeholder sequences

Ubiquilins are molecular chaperones that play multifaceted roles in proteostasis, with point mutations in UBQLN2 leading to altered phase-separation properties and amyotrophic lateral sclerosis (ALS). Our mechanistic understanding of this essential process has been hindered by a lack of structural information on the STI1 domain, which is essential for ubiquilin chaperone activity and phase separation. Here, we present the first crystal structure of a ubiquilin-family STI1 domain bound to a transmembrane domain (TMD), and show that ALS mutations disrupt the STI1-TMD interaction. We further demonstrate that ubiquilins contain multiple conserved internal sequences that bind to the STI1 domain, including the PXX-repeat region that is a hotspot for ALS mutations. We propose that these placeholder sequences prevent solvent exposure of the STI1 hydrophobic groove and contribute to the multivalency that drives ubiquilin phase-separation. Together, this work provides a new paradigm for understanding how STI1 domains modulate ubiquilin chaperone activity and phase separation, and offers insights into the molecular basis of ALS pathogenesis.

Onwunma, Joan [Univ. of Toledo, OH (United States)↗
NASA NTRS2019

Flow Boiling and Condensation Experiment Flight Hardware Development

The Flow Boiling and Condensation Experiment (FBCE) to be manifested on the International Space Station (ISS) consists of a fluid system and the associated electronics to provide for conditioning the test fluid (normal-PerFluorohexane or nPFH-C6F14) to the proper thermodynamic state prior to entering a test module, which can be interchangeable based on the science objectives. Two separate test modules have been manufactured for the FBCE, the Flow Boiling Module (FBM), which investigates flow boiling for a subcooled liquid, saturated liquid, or two phase mixture, and the Condensation Module Heat Transfer (CM-HT), which investigates condensation of a flowing saturated or superheated vapor. The test fluid heating is accomplished using the Bulk Heater Module (BHM), which heats the fluid to various states based on the demands of the currently installed test module. ISS Internal Thermal Control System (ITCS) water is utilized to cool the test fluid prior to entering the circulation pump, and is also utilized for cooling for condensation in CM-HT, for cooling of a camera in FBM. An adjustable pressure bellows-type accumulator is used to set the pressure at the inlet of the test section, but does not provide active pressure control during testing. The flow of the test fluid is achieved using a gear pump controlled by a coriolis flow meter, which also provides the flow rate measurement. Flow rates for the ITCS water loops are measured and controlled using coriolis flow meters with directly controlled proportional valves. During execution of FBCE operations, the FBM is scheduled to collect data for three months before being exchanged with CM-HT for another three month data collection run. In this work, we present the development of the flight hardware, the associated challenges experienced during the development such as packaging flight system hardware, and the lessons learned in overcoming the encountered challenges.

Guzik, Monica C.↗
NASA NTRS1981

Development of a dual-field heteropoplar power converter

The design and testing of a 400 watt, dual phase, dual rotor, field modulated inductor alternator is described. The system is designed for use as a flywheel to ac utility line or flywheel to dc bus (electric vehicle) power converter. The machine is unique in that it uses dual rotors and separately controlled fields to produce output current and voltage which are in phase with each other. Having the voltage and current in phase allows the power electronics to be made of simple low cost components. Based on analytical predictions and experimental results, development of a complete 22 kilowatt (30 Hp) power conversion system is recommended. This system would include power electronics and controls and would replace the inductor alternator with an improved electromagnetic conversion system.

Eisenhaure, D. B.↗