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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Exposure of Highly Reflective Far-Ultraviolet Coatings to LEO Environment for TRL Advancement for the Habitable Worlds Observatory

Over the past several years, our team at the NASA Goddard Space Flight Center (GSFC), in collaboration with the Jet Propulsion Laboratory (JPL) and the Naval Research Laboratory (NRL), have developed several new protected Al coating technologies with improved Far-Ultraviolet (FUV) reflectance performance and more robust environmental stability. These include Al protected with lithium-based fluoride (LiF) coatings such as hot deposited LiF (eLiF), XeF 2 -passivated LiF coatings (XeLiF), Li 3 AlF 6 overcoats, AlF 3 (plasma passivated), and XeF 2 passivated MgF 2 coatings (XeMgF 2 ). However, despite these developments, relatively little experimental information exists regarding the long-term stability of these coatings after simultaneous exposure to the Low Earth Orbit (LEO) environment. To evaluate their environmental durability and advance their Technology Readiness Level (TRL), representative samples of these coating technologies, Al+XeLiF, Al+eLiF, Al+Li 3 AlF 6 , Al+AlF 3 , Al+XeMgF 2 , and bare Al as reference samples, were flown onboard the International Space Station (ISS) as part of the Materials International Space Station Experiment 20 (MISSE-20). The MISSE platform is operated by Aegis Aerospace for relatively long-duration (e.g. 6 months) external exposure experiments in a space environment. The coatings were deposited on ULE and Zerodur substrates, and witness samples deposited on the same coatings runs, but on glass slides were left on Earth as control. A subset of the flight samples were fitted with MgF 2 windows to reduce direct exposure to atomic oxygen (AO) and charged particles, and still let through UV and other types of radiation on these samples. After approximately 6 months of exposure in the forward-facing (RAM) direction, the samples were returned to Earth and characterized by performing FUV/NUV/VIS/NIR reflectance measurements to quantify degradation, spectroscopic ellipsometry to evaluate coating thickness and optical constants, atomic force microscopy (AFM) to quantify surface roughness evolution during the flight in the ISS. The MgF 2 protective windows were also analyzed through FUV transmission measurements. Comparison with the witness samples left on the ground and with the flown bare Al samples (with just the naturally occurring Al 2 O 3 layer) provided a quantitative assessment of coating thickness variations, optical performance degradation, and morphological changes induced by prolonged exposure to the LEO environment.

Far Ultraviolet (FUV)↗
DOE OSTI2022

Reconfigurable Intelligent Surfaces Empowered THz Communication in LEO Satellite Networks

Massive swarms of low Earth orbit (LEO) satellites are poising to serve for high-speed and low-latency ubiquitous connectivity with almost global coverage. Broadband inter-satellite communication is one of the key elements of satellite communication systems that orchestrate massive satellite swarms in cooperation. Thanks to technological advancements in microelectronics and micro-systems, the terahertz (THz) band has emerged as a strong candidate for inter-satellite links (ISLs) due to its promise of wideband communication. Especially, multi-antenna systems can improve the system performance along with the wideband supported by the THz band. However, multi-antenna systems should be reconsidered due to their size, weight, and price/power (SWaP) constraints. On the other hand, as a state-of-art multi-antenna technology, reconfigurable intelligent surface (RIS) is able to relax SWaP constraints because of its passive component-based structures. However, as similar reflection characteristic throughout wideband is difficult to meet, it is possible to observe beam misalignment. In this work, we first provide an assessment of the use of the THz band for ISLs and quantify the impact of misalignment fading on error performance. Then, in order to compensate for the high path loss associated with high carrier frequencies, and to further improve the signal-to-noise ratio (SNR), we propose the use of RISs mounted on neighboring satellites to enable signal propagation. Based on a mathematical analysis of the problem, we present the error rate expressions for RIS-assisted ISLs with misalignment fading. Also, numerical results show that RIS can leverage the error rate performance and achievable capacity of THz ISLs.

reconfigurable intelligent surfaces (RISs)↗
NASA NTRS2017

LEO to GEO (and Beyond) Transfers Using High Power Solar Electric Propulsion (HP-SEP)

Rideshare, or Multi-Payload launch configurations, are becoming more and more commonplace but access to space is only one part of the overall mission needs. The ability for payloads to achieve their target orbits or destinations can still be difficult and potentially not feasible with on-board propulsion limitations. The High Power Solar Electric Propulsion (HP-SEP) Orbital Maneuvering Vehicle (OMV) provides transfer capabilities for both large and small payload in excess of what is possible with chemical propulsion. Leveraging existing secondary payload adapter technology like the ESPA provides a platform to support Multi-Payload launch and missions. When coupled with HP-SEP, meaning greater than 30 kW system power, very large delta-V maneuvers can be accomplished. The HP-SEP OMV concept is designed to perform a Low Earth Orbit to Geosynchronous Orbit (LEO-GEO) transfer of up to six payloads each with 300kg mass. The OMV has enough capability to perform this 6 kms maneuver and have residual capacity to extend an additional transfer from GEO to Lunar orbit. This high deltaV capability is achieved using state of the art 12.5kW Hall Effect Thrusters (HET) coupled with high power roll up solar arrays. The HP-SEP OMV also provides a demonstration platform for other SEP technologies such as advanced Power Processing Units (PPU), Xenon Feed Systems (XFS), and other HET technologies. The HP-SEP OMV platform can be leveraged for other missions as well such as interplanetary science missions and applications for resilient space architectures.

Leo and Geo and HP-SEP↗
NASA NTRS2023

Space Biology Beyond LEO Instrumentation & Science Series Science Working Group 2022 Annual Report

Humans are poised to explore deep space: the realm of space beyond Earth's orbit. NASA will soon send humans back to the Moon with the Artemis program, and is developing programs to support crewed missions to Mars. Human exploration of such new environments demands fundamental research that can provide the knowledge necessary to ensure the safety of explorers and aid in the development of a sustainable presence in space. Accordingly, the Agency's Moon to Mars objectives1 include three goals in the area of Human Biological Sciences (HBS-1, -2, -3), with the aim to "Advance understanding of how biology responds to the environments of the Moon, Mars, and deep space to advance fundamental knowledge, support safe, productive human space missions and reduce risks for future exploration." Advancing this understanding is a task that is both complex-- comprising diverse organisms, processes, and methods-- and difficult-- because the very aspects of deep space that we strive to understand are the aspects that make it hard to conduct research in that environment. This report of the Beyond LEO Instrumentation & Science Series Science Working Group (BLISS-SWG) represents input from a group of scientists from diverse disciplines within the space biology research and engineering community on the nature of the science and technology that can be used to achieve those aims.

Space Biology↗
DOE OSTI2026

Predictive Modeling and Operational Monitoring of Starlink Leo Satellite Network Performance in Maritime Environments

This thesis investigates short-term performance prediction for maritime LEO operational planning and application performance cannot anticipate available bandwidth or communication delay, which complicates variation alter signal conditions over short time scales. As a result, maritime users often fluctuations in link quality. In addition, Frequent satellite handoffs and Doppler-induced rapid satellite movement and changing atmospheric conditions cause substantial unavailable. Despite their availability, reliable operation at sea remains difficult because broadband connectivity in maritime regions where terrestrial infrastructure in

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Integrating LEO and GEO Observations: Toward Optimal Summertime Satellite Precipitation Retrieval

Abstract Reliable quantitative precipitation estimation with a rich spatiotemporal resolution is vital for understanding the Earth’s hydrological cycle. Precipitation estimation over land and coastal regions is necessary for addressing the high degree of spatial heterogeneity of water availability and demand, and for resolving the extremes that modulate and amplify hazards such as flooding and landslides. Advancements in computation power along with unique high spatiotemporal and spectral resolution data streams from passive meteorological sensors aboard geosynchronous Earth-orbiting (GEO) and low Earth-orbiting (LEO) satellites offer exciting opportunities to retrieve information about surface precipitation phenomena using data-driven machine learning techniques. In this study, the capabilities of U-Net–like architecture are investigated to map instantaneous, summertime surface precipitation intensity at the spatial resolution of 2 km. The calibrated brightness temperature products from the Global Precipitation Measurement (GPM) Microwave Imager (GMI) radiometer are combined with multispectral images (visible, near-infrared, and infrared bands) from the Advanced Baseline Imager (ABI) aboard the GOES-R satellites as main inputs to the U-Net–like precipitation algorithm. Total precipitable water and 2-m temperature from the Global Forecast System (GFS) model are also used as auxiliary inputs to the model. The results show that the U-Net–like algorithm can capture fine-scale patterns and intensity of surface precipitation at high spatial resolution over stratiform and convective precipitation regimes. The evaluations reveal the potential of extracting relevant, high spatial features over complex surface types such as mountainous regions and coastlines. The algorithm allows users to interpret the inputs’ importance and can serve as a starting point for further exploration of precipitation systems within the field of hydrometeorology.

Meteorology & Atmospheric Sciences↗
DOE OSTI2020

Recovery and Calibration of Legacy Underground Nuclear Test Seismic Data from the Leo Brady Seismic Network

The Leo Brady Seismic Network (LBSN, originally the Sandia Seismic Network) was established in 1960 by Sandia National Laboratories to monitor underground nuclear tests (UGTs) at the Nevada National Security Site (NNSS, formerly named the Nevada Test Site). The LBSN has been in various configurations throughout its existence, but it has generally been comprised of four to six stations at regional distances (~150–400 km) from the NNSS with approximately evenly spaced azimuthal coverage. Between 1962 and the end of nuclear testing in 1992, the LBSN—and a sister network operated by Lawrence Livermore National Laboratories—was the most comprehensive United States source of regional seismic data of UGTs. Approximately 75% of all UGTs performed by the United States occurred in the predigital era. At that time, LBSN data were transmitted as frequency-modulated (FM) audio over telephone lines to a central location and recorded as analog waveforms on high-fidelity magnetic audio tapes. These tapes have been in dry temperature-stable storage for decades and contain the sole record of this irreplaceable data; full waveforms of LBSN-recorded UGTs from this era were not routinely digitized or otherwise published. We have developed a process to recover and calibrate data from these tapes. First, we play back and digitize the tapes as audio. Next, we demodulate the FM “audio” into individual waveforms. We then estimate the various instrument constants through careful measurement of “weight-lift” tests performed prior to each UGT on each instrument. Finally, these coefficients allow us to scale and shape the derived instrument response of the seismographs and compute poles and zeros. Finally, the result of this process is a digital record of the recorded seismic ground motion in a modern data format, stored in a searchable database. To date, we have digitized tapes from 592 UGTs.

58 GEOSCIENCES↗
DOE OSTI2020

BVR{sub C}I{sub C} Observations and Analysis of the UV LEO-type Binary, the Pre-WUMa, V1023 Persei

V1023 Per is a polar spotted, but well-detached dwarf binary, very likely a Pre-WUMa eclipsing binary. It was observed on 11 nights in 2015 October, November, and December at Dark Sky Observatory in North Carolina with the 0.81 m reflector of Appalachian State University. The period behavior is complex and may be increasing with a cubic or quadratic ephemeris. Its odd light curves are of high amplitude but have no totality and reach maximum light just before and following the secondary eclipse, indicating that it has polar spots similar to UV Leo. The 28 yr orbital period study calls the attention of observers to further monitor this binary to understand the complex nature of the period evolution. Its presently fixed polar spot does indicate that it must have a strong magnetic field and that it is synchronously rotating. The BVR{sub c}I{sub c} simultaneous 2016 Wilson–Devinney program (W-D) solution gives fillouts of 68% and 75% for the primary and secondary components, respectively. The polar position of the spot, its radius (24°), and T-fact (0.75) indicate that a strong magnetic field is present. The small ΔT in the components (∼289 K) show that the stars are similar in spectral type despite them being well detached. The inclination is high, ∼85.°19 ± 0.°04, but there is not a total eclipse due to the high mass ratio (∼0.739 ± 0.001). Due to the low galactic position (longitude = 150.°390, latitude = −1.°023), its reddening is addressed. The primary components temperature is estimated to be 5250 ± 250 K.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Mitigation of LEO Satellite Brightness and Trail Effects on the Rubin Observatory LSST

In this work, we report studies on the mitigation of optical effects of bright low-Earth-orbit (LEO) satellites on Vera C. Rubin Observatory and its Legacy Survey of Space and Time (LSST). These include options for pointing the telescope to avoid satellites, laboratory investigations of bright trails on the Rubin Observatory LSST camera sensors, algorithms for correcting image artifacts caused by bright trails, experiments on darkening SpaceX Starlink satellites, and ground-based follow-up observations. The original Starlink v0.9 satellites are g ~ 4.5 mag, and the initial experiment "DarkSat" is g ~ 6.1 mag. Future Starlink darkening plans may reach g ~ 7 mag, a brightness level that enables nonlinear image artifact correction to well below background noise. However, the satellite trails will still exist at a signal-to-noise ratio ~ 100, generating systematic errors that may impact data analysis and limit some science. For the Rubin Observatory 8.4 m mirror and a satellite at 550 km, the full width at half maximum of the trail is about 3'' as the result of an out-of-focus effect, which helps avoid saturation by decreasing the peak surface brightness of the trail. For 48,000 LEOsats of apparent magnitude 4.5, about 1% of pixels in LSST nautical twilight images would need to be masked.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1971

Absolute ultraviolet spectrophotometry of: alpha CMa, gamma Ori, kappa Ori, and alpha Leo; and a continuing calibration program and some preliminary results

Spectral observations of the stars alpha CMa, gamma Ori, kappa Ori, and alpha Leo have been obtained in the range 1150 to 4000 Angstroms, using rocket borne spectrometers. The payloads have a 13-inch diameter telescope, a rotatable concave diffraction grating, and three pulse counting photomultiplier photometers. The laboratory standards used as photometric references derive their primary calibration directly or indirectly from the National Bureau of Standards. An error range of up to + or - 10 percent is attributed to these laboratory standards; + or - 8 percent to the calibration procedure; and + or - 10 percent is assigned as an accidental error range.

Evans, D. C.↗
NASA NTRS1980

LEO-to-GEO low thrust chemical propulsion

One approach being considered for transporting large space structures from low Earth orbit (LEO) to geosynchronous equatorial orbit (GEO) is the use of low thrust chemical propulsion systems. A variety of chemical rocket engine cycles evaluated for this application for oxygen/hydrogen and oxygen/hydrocarbon propellants (oxygen/methane and oxygen/RF-1) are discussed. These cycles include conventional propellant turbine drives, turboalternator/electric motor pump drive, and fuel cell/electric motor pump drive as well as pressure fed engines. Thrust chamber cooling analysis results are presented for regenerative/radiation and film/radiation cooling.

Shoji, J. M.↗
NASA NTRS1984

High speed, low cost, LEO-thermal-cycling facility

The design and operations of a low cost, high rate thermal cycling facility designed for LEO conditions is described. Thermal cycling facilities were constructed with various design criteria. Some were designed to duplicate as closely as possible the conditions a cell or module would encounter while in orbit about the Earth. A typical facility to perform this type of cycling was a large vacuum system with liquid nitrogen cooled walls. The cells were heated by an AMO spectrum solar simulator, then a shutter was closed allowing the cells to give up their heat to the cold walls. This system was good at duplicating the orbital conditions but was slow and very costly to operate. Other systems used a gas atmosphere and heated the cells with radiant heat and cooled the cells by moving them into close proximity to a cold plate. The systems greatly increased the cycle times. Other systems moved the heating and cooling atmosphere into and out of the test areas and achieved reasonable cycle rates. All these systems, however, are expensive to operate.

Hart, R. E., Jr.↗
NASA NTRS1984

LEO atomic oxygen effects on spacecraft materials: STS-5 results

Effects of low Earth orbit (LEO) atomic oxygen were measured on a variety of spacecraft materials which obtained exposure on STS-5. Material degradation dependency on temperature was found in one material. Of the five paints flown, only S13GLO was unaffected. Generally, the glossy paints became Lambertian and the diffuse coatings improved. Scanning electron microscope examinations indicated removal of urethane and epoxy paint binder materials. Reaction products were evident on the surfaces of Z302 paint and Mylar. Thin films showed thickness losses ranging from negligible loss in Teflon to considerable loss in Mylar and Kapton. Glossy films such as black Kapton and white Tedlar became diffused. Kevlar 29 rope lost tensile strength and silver solar cell interconnect material oxidized. Oxidation on the backside of an elevated specimen indicated that reflections of oxygen atoms were occurring and that reflecting surfaces, probably Kapton, were not fully accommodating the incident atoms.

Whitaker, A. F.↗
NASA NTRS1984

Limits on the infrared and visual luminosity of the intergalactic H I cloud in Leo

Low surface brightness photometry of the intergalactic neutral hydrogen cloud in Leo sets upper limits on the intensity of this object of 28.0 mag/sq arcsec in the V photometric band and 22.8 mag/sq arcsec in the K band. The corresponding ratio of the H I mass to blue luminosity in the H I emission peaks of the cloud must be greater than 2.9 (solar units) depending on the star formation history of the object. The limits imposed on the star formation rate suggest a strong dependence of this rate on gas density.

Skrutskie, M. F.↗
NASA NTRS1985

Radiation exposure and performance of multiple burn LEO-GEO orbit transfer trajectories

Many potential strategies exist for the transfer of spacecraft from low Earth orbit (LEO) to geosynchronous (GEO) orbit. One strategy has generally been utilized, that being a single impulsive burn at perigee and a GEO insertion burn at apogee. Multiple burn strategies were discussed for orbit transfer vehicles (OTVs) but the transfer times and radiation exposure, particularly for potentially manned missions, were used as arguments against those options. Quantitative results concerning the trip time and radiation encountered by multiple burn orbit transfer missions in order to establish the feasibility of manned missions, the vulnerability of electronics, and the shielding requirements are presented. The performance of these multiple burn missions is quantified in terms of the payload and propellant variances from the minimum energy mission transfer. The missions analyzed varied from one to eight perigee burns and ranged from a high thrust, 1 g acceleration, cryogenic hydrogen-oxygen chemical prpulsion system to a continuous burn, 0.001 g acceleration, hydrogen fueled resistojet propulsion system with a trip time of 60 days.

Gorland, S. H.↗
NASA NTRS1985

Radiation exposure and performance of multiple burn LEO-GEO orbit transfer trajectories

Many potential strategies exist for the transfer of spacecraft from low Earth orbit (LEO) to geosynchronous (GEO) orbit. One strategy has generally been utilized, that being a single impulsive burn at perigee and a GEO insertion burn at apogee. Multiple burn strategies were discussed for orbit transfer vehicles (OTVs) but the transfer times and radiation exposure, particularly for potentially manned missions, were used as arguments against those options. Quantitative results concerning the trip time and radiation encountered by multiple burn orbit transfer missions in order to establish the feasibility of manned missions, the vulnerability of electronics, and the shielding requirements are presented. The performance of these multiple burn missions is quantified in terms of the payload and propellant variances from the minimum energy mission transfer. The missions analyzed varied from one to eight perigee burns and ranged from a high thrust, 1 g, acceleration, cryogenic hydrogen-oxygen chemical propulsion system for a continuous burn, 0.001 g acceleration, hydrogen, fueled resistojet propulsion system with a trip time of 60 days.

Gorland, S. H.↗