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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Maternal provisioning gives young-of-the-year Hammerheads a head start in early life

For species that do not provide parental care after birth, excess maternal provisioning during development, beyond what is required for embryogenesis, provides offspring with resources to increase their chances of survival. Maternally derived resources are expected to be important for buffering offspring against limited food resources at birth or time needed to learn how to properly feed. Young-of-the-year (YOY) cryptic Scalloped Hammerheads (Sphyrna lewini) and Carolina Hammerheads (Sphyrna gilberti) were sampled from nurseries along the US Atlantic Coast and compared for a number of biological condition metrics across three developmental stages. Large declines in liver lipid content and hepatosomatic indices were found in neonatal sharks, using umbilical scar healing as a proxy for time since birth. Feeding commenced quickly as 96% of sharks had prey remnants in their stomachs. The combination of rapid exhaustion of maternally provided resources and high occurrence of stomachs with prey contents indicate that nursery quality, with respect to prey availability, may be important for YOY hammerhead survivorship. While externally the two species are morphologically similar, longer length-at-birth in S. lewini and higher hepatic condition in neonatal S. gilberti suggest that aspects of reproductive biology, including physiology, may differ between species. While more information is needed to distinguish life history differences between these two species, data collected from YOY may serve as a useful proxy to inform management when adult samples of cryptic species are difficult to collect.

none↗
NASA NTRSDate not supplied

Exploring Endothelial Function Risk Factors and Optic Disc Edema Changes During Strict 6º Head-Down Tilt Bed Rest

Approximately 20% of astronauts on International Space Station missions experience ophthalmic pathologies including optic disc edema, part of what is characterized as Spaceflight Associated Neuro-ocular Syndrome (SANS). While the cause of SANS is unknown, there are likely multiple contributing factors, including genetics, that may affect the response to spaceflight in affected individuals. B-vitamin status and the presence of specific one-carbon pathway single nucleotide polymorphism (SNP) alleles predicted the incidence of SANS pathologies in astronauts and in bed rest subjects. There are several hypotheses for how genetic variants could lead to SANS, specifically related to endothelial function. The biochemical pathway to which these genes are associated is intimately involved in maintaining endothelial function via nitric oxide synthase (eNOS) coupling and nitric oxide (NO) production. Furthermore, eNOS uncoupling can impair the functional status of the endothelial glycocalyx, which lines the entirety of the vascular lumen and affects endothelial function. Vascular distension, stasis and altered shear forces, which are associated with headward fluid shifts, may also contribute to glycocalyx dysfunction and shedding, resulting in endothelial dysfunction and increased vascular permeability and tissue edema, potentially contributing to optic nerve and optic disc edema in affected individuals. Given the findings relating genetics and the risk of optic disc edema in astronauts during flight and subjects during bed rest, further investigation is warranted. In this study, we will assess the same genetic variants in another bed rest study: AGBRESA. Some of the AGBRESA subjects developed optic disc edema, but their genetics have not been studied. Furthermore, we will test available urine samples from prior bed rest studies (VaPER and AGBRESA) for markers of glycocalyx degradation to expand our understanding of factors contributing to SANS.

S R Zwart↗
NASA NTRSDate not supplied

Recent Results from Dragonfly Testing/Analysis as we head to PDR

Dragonfly is a relocatable lander mission to Saturn's moon Titan4, which as well as being a target of out-standing astrobiological interest as an organic-rich Ocean World, has the combination of low gravity (1/7 that of Earth) and a thick atmosphere (4x the density of Earth), making it an environment uniquely suitable for flight. Thus, the Dragonfly lander (similar in size to the Curiosity Mars rover) can take off using lift from a set of eight rotors and fly to a new landing site several kilometers away. The ability to perform such flights, lasting approximately 30 minutes, every month or so on Titan brings unprecedented mobility to planetary exploration, on a world known to have a diverse land-scape of dunes, craters and other features. Dragonfly is planned to launch in 2027, and following a nearly seven year interplanetary cruise would arrive at Titan by 2034. Due to the large scale height of the Titan atmosphere, Entry, Descent, and Landing (EDL) will be prolonged affair, taking nearly two hours to reach the surface. The ballistic entry environments that Dragonfly will be subjected to are fairly similar to that experienced by recent Mars missions; peak heating on the aeroshell will be about 300 W/sq.cm and peak deceleration is about 10g’s. Following the five minute entry segment, much of the remaining time is spent descending on the drogue and main para-chutes, which carry the dual role of decelerating the spacecraft and stabilizing the system during the long descent. While on one hand, this leisurely EDL sequence affords a relaxed timeline and plenty of time for event staging, it also provides ample opportunity for small disturbances to grow into potential flight safety risks, adding emphasis to the need for careful modeling, simulation and testing of key dynamic events. About two hours after entering the atmosphere, the nearly one metric ton rotocraft will be lowered approximately one meter out of the backshell (the ‘pose’ maneuver) to expose all eight rotors. The rotors will then be used to arrest any residual spin rate and prepare the system for transition to powered flight. Once despin is complete and the lander reaches a target altitude of 1.2 km above the surface (as verified by on-board lidar), the lander will be released and free fall for approximately one second before beginning controlled free flight. This entire “preparation for powered flight” process takes place over several minutes while the system is subject to the dynamic environment produced by so-called “wrist-mode” oscillations as the lander and backshell swing on the main parachute. Once in free flight, the lander will engage on-board terrain relative navigation to locate and navigate to a safe landing zone in the Shangri-La dune field south of Selk crater. Communication during this sequence will be limited to a series of direct-to-Earth X-band tones signalling key events and providing forensic information. Once on the ground, the lander will begin to send additional information, including data collected during this EDL sequence by the on-board Dragonfly Entry Aerosciences Measurements (DrEAM) instrumentation suite. This presentation will walk through the entry to first landing timeline in more detail, with a focus on recent analysis and testing results that inform system performance, margins and residual risk estimation.

Dragonfly↗
NASA NTRS2022

Optimizing Screening for Preventable Blindness With Head-Mounted Visual Assessment Technology

Age-related macular degeneration (AMD) is a leading cause of blindness and is diagnosed as early-stage or late-stage. Early-stage AMD is usually asymptomatic and entails pigmentary changes of the retina (Ayoub & Patel, 2009). As the disorder progresses, there are atrophic or neovascular changes that distort vision, especially the central visual field (Ayoub & Patel, 2009). There are several genetic and non-genetic risk factors for AMD and no proven therapy to slow or reverse late-stage atrophic AMD, while anti-VEGF has effectively treated late-stage neovascular AMD. Several genes of interest have also been investigated thoroughly thus far in their connection to AMD and the CFH and ARMS2 genes have shown promise in understanding the genetic basis of the disorder (Awh et al., 2013). There are other epigenetic and environmental factors as well including smoking and low antioxidant levels (Cano et al., 2010). Ongoing investigations include antioxidant supplementation and a smoking cessation regimen to reverse early-stage AMD (Cano et al., 2010). Progress in treating AMD as a disorder across its varied stages requires newer therapeutics along with a more detailed understanding of the genetic and cellular pathways of pathophysiology is needed to better counter this prevalent disorder of the eye.

age-related macular degeneration↗
NASA NTRS2023

Radiation Shielding Plasma Sprayed Coatings Heads to International Space Station for MISSE-17 Experiments

NASA's Artemis program aims to return to the moon in search of scientific discoveries and establish a habitat using in-situ resource utilization. However, the past lunar explorations presented challenges, such as thermal cycles, solar and intergalactic cosmic radiation, and severe abrasive interaction of sharp lunar regolith particles[1]–[4].Dust mitigation and radiation shielding have become the most important concerns for lunar structural components and rovers which can fail abruptly without a protective solution. To counter these threats, Plasma Forming Laboratory(PFL) at Florida International University (FIU), in collaboration with NASA, has developed a novel multi-functional coating to protect the components synergistically against abrasion, erosion ,and radiation. The titanium-boron nitride composite coatings were prepared using the atmospheric plasma spray technique from engineered composite powders [5], [6].The coatings were subjected to extensive characterization and tribological study with lunar mare simulant JSC-1A, which shows tremendous improvement in the wear performance. The coatings subjected to neutron radiation shielding experiments at NASA Langley Research Center exhibited significantly improved neutron attenuation capacity compared to the substrate. The coating is selected to undergo radiation exposure on the International Space Station as a part of MISSE-17 (Materials International Space Station Experiment).

Thermal Spray↗
NASA NTRSDate not supplied

Cardiovascular Responses to Daily Use of Lower Body Negative Pressure During 30 Days of Strict Head-Down Tilt Bedrest

The purpose of this study was to (1) measure the heart rate (HR) and mean arterial pressure (MAP) response and subject tolerance before and during twice daily use of 3 hours of 25 mmHg LBNP during 30 days of HDTBR and (2) determine if this level of LBNP during HDTBR would reverse the headward fluid shift to a similar degree as upright posture.

Jason R. Lytle↗