Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “protective structures”

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.

At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Rapid loss of complex polymers and pyrogenic carbon in subsoils under whole-soil warming

Subsoils contain more than half of soil organic carbon (SOC) and are expected to experience rapid warming in the coming decades. Yet our understanding of the stability of this vast carbon pool under global warming is uncertain. In particular, the fate of complex molecular structures (polymers) remains debated. Here we show that 4.5 years of whole-soil warming (+4 °C) resulted in less polymeric SOC (sum of specific polymers contributing to SOC) in the warmed subsoil (20–90 cm) relative to control, with no detectable change in topsoil. Warming stimulated the subsoil loss of lignin phenols (–17 ± 0%) derived from woody plant biomass, hydrolysable lipids cutin and suberin, derived from leaf and woody plant biomass (–28 ± 3%), and pyrogenic carbon (–37 ± 8%) produced during incomplete combustion. Given that these compounds have been proposed for long-term carbon sequestration, it is notable that they were rapidly lost in warmed soils. We conclude that complex polymeric carbon in subsoil is vulnerable to decomposition and propose that molecular structure alone may not protect compounds from degradation under future warming.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Atomic-scale manipulation of buried graphene–silicon carbide interface by local electric field

Abstract Precision of scanning tunneling microscopy (STM) enables control of matter at scales of single atoms. However, transition from atomic-scale manipulation strategies to practical devices encounters fundamental problems in protection of the designer structures formed atop the surface. In this context, STM manipulation of subsurface structures on technologically relevant materials is encouraging. Here, we propose a material platform and protocols for precise manipulation of a buried graphene interface. We show that an electric field from the STM tip reversibly controls breaking and restoring of covalent bonds between the graphene buffer layer and the SiC substrate. The process involves charge redistribution at the atomically sharp interface plane under the epitaxial graphene layer(s). This buried manipulation platform is laterally defined by unit cells from the corresponding (6×6) SiC moiré lattice of the epitaxial graphene. Local and reversible electric-field-induced patterning of graphene heterostructures from the bottom interface creates an alternative architecture concept for their applications.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

A high-solid DES pretreatment using never-dried biomass as the starting material: towards high-quality lignin fractionation

This study investigated a high-solid diol deep eutectic solvent (DES) pretreatment using a wet substrate as the starting material. This pretreatment led to a remarkable glucan saccharification of 94.8% with efficient lignin and xylan removal (as high as 63.1% and 73.0%, respectively). Here the chemical structures of the substrates were analyzed comprehensively to reveal the impact of the pretreatment. In addition, over 90% of the removed lignin was recovered from the pretreated liquid, which exhibited a well-preserved β-O-4 structure (46–56/100Ar). The protection mechanism of our DES was investigated by 2D HSQC NMR, GPC, and 31 P NMR analysis. This study emphasized that diol-based DES pretreatment of undried lignocellulosic biomass at a high-solid loading can significantly utilize both carbohydrates and lignin fractions with high saccharification yields and high-quality lignin as a co-product.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Data Fusion to Enhance Quality Control and Analysis with Instruments at the Marine and Coastal Research Laboratory

Deploying environmental monitoring instruments in the marine environment can be challenging, facing challenges around device survivability, biofouling and corrosion, and consistent data collection. This project explores the use of data fusion – the process of integrating multiple data sources to produce more consistent, accurate, and useful information – to build a consistent long-term monitoring system at the Marine and Coastal Research Laboratory (MCRL) in Sequim, Washington. Unused instruments that had been acquired from past projects were inventoried and deployments planned on the MCRL pier and floating dock. A total of 8 instruments were deployed including a tide gauge, hydrophone, acoustic Doppler current profiler (ADCP), photosynthetically active radiation (PAR) sensors, meteorological station, and three water quality sensors. Deployments were planned to be well-protected around the pier structure and a maintenance schedule was created for cleaning and recalibration. An automated data pipeline was created to aggregate data on edge computers that push data to Amazon Web Services (AWS) cloud storage every 15 minutes, performing automated quality control and data transformations using the Time Series Data Analytical Toolkit (TSDAT). Continued efforts are underway to maintain this system into the future, take a data-driven approach to maintenance scheduling, improve the reliability of the system, and share the data with a variety of end-users.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1967

Lunar module alightment system

The lunar module (LM) landing phase is one of the most critical phases of the entire Apollo mission. Landing impact is of critical concern because at no other time during the LM mission is there less opportunity for vehicle control. To assure a successful landing, the alightment system must not only provide required shock attenuation for protection of crew and structure, but must also assure stability against overturning after touchdown. The paper discusses important design features of the alightment system, such as geometric arrangement, energy absorber characteristics, and deployment mechanisms. Performance characteristics of the vehicle at touchdown, as found analytically, are presented. Model and full-size testing of the landing system is briefly discussed.

LANDING SYSTEM↗
NASA NTRS1975

Study of the application of hydrogen fuel to long-range subsonic transport aircraft. Volume 1: Summary

The feasibility of using liquid hydrogen as fuel in advanced designs of long range, subsonic transport aircraft is assessed. Both passenger and cargo type aircraft are investigated. Comparisons of physical, performance, and economic parameters of the LH2 fueled designs with conventionally fueled aircraft are presented. Design studies are conducted to determine appropriate characteristics for the hydrogen related systems required on board the aircraft. These studies included consideration of material, structural, and thermodynamic requirements of the cryogenic fuel tanks and fuel systems with the structural support and thermal protection systems.

Brewer, G. D.↗
NASA NTRS1981

Common data buffer

Time-shared interface speeds data processing in distributed computer network. Two-level high-speed scanning approach routes information to buffer, portion of which is reserved for series of "first-in, first-out" memory stacks. Buffer address structure and memory are protected from noise or failed components by error correcting code. System is applicable to any computer or processing language.

Byrne, F.↗
NASA NTRS1979

Meteoroid protection for the Comet Halley probe

The high closing speed of 57km/s between the spacecraft and Halley poses special problems in the design of the required meteoroid protection. A double wall structure with a total thickness equal to 0.1 to 1 times the diameter of the largest meteoroid encountered is sufficient to stop that meteoroid. However, the unusually high number of meteoroid impacts on the Halley probe will cause significant erosion of the outer wall so that failure of the second wall is more likely to occur from a small meteoroid passing through a previously created hole in the outer wall and then penetrating the second wall. Calculations of the shielding required based on this failure mode, show that a double wall structure must actually have a total thickness 1.2 to 7.3 times the diameter of the largest meteoroid encountered, depending on the size distribution of the meteoroids.

Humes, D.↗
NASA NTRS1980

Wind-tunnel experiments on divergence of forward-swept wings

An experimental study to investigate the aeroelastic behavior of forward-swept wings was conducted in the Langley Transonic Dynamics Tunnel. Seven flat-plate models with varying aspect ratios and wing sweep angles were tested at low speeds in air. Three models having the same planform but different airfoil sections (i.e., flat-plate, conventional, and supercritical) were tested at transonic speeds in Freon 12. Linear analyses were performed to provide predictions to compare with the measured aeroelastic instabilities which include both static divergence and flutter. Six subcritical response testing techniques were formulated and evaluated at transonic speeds for accuracy in predicting static divergence. Two "divergence stoppers" were developed and evaluated for use in protecting the model from structural damage during tests.

Ricketts, R. H.↗
NASA NTRS1980

Mass reduction for advanced winged entry vehicles through integrated thermostructural-trajectory design

This study examines the impact of aerothermo-structure design integration on thermal protection system (TPS) mass for advanced winged entry vehicles. Four basic categories of TPS are considered: external insulation, metallic hot structures, metallic standoff, and hybrid systems. A variety of concepts that fit in these basic categories are examined. Entry trajectories tailored specifically to the characteristics of each TPS concept are generated. An aerodynamic heating program is used with the appropriately tailored trajectories to determine the centerline TPS requirements for each concept. Included in the investigation is the impact on the combined TPS-structure mass of structural materials which maintain their integrity to higher temperatures. Results indicate that significant mass reduction can be realized through appropriate aerothermo-structure design integration. An assessment is made of the relative merits of the TPS/structure/trajectory combinations considered in the study.

Wurster, K. E.↗
NASA NTRS1979

Mass estimating techniques for earth-to-orbit transports with various configuration factors and technologies applied

A study of an array of advanced earth-to-orbit space transportation systems with a focus on mass properties and technology requirements is presented. Methods of estimating weights of these vehicles differ from those used for commercial and military aircraft; the new techniques emphasizing winged horizontal and vertical takeoff advanced systems are described utilizing the space shuttle subsystem data base for the weight estimating equations. The weight equations require information on mission profile, the structural materials, the thermal protection system, and the ascent propulsion system, allowing for the type of construction and various propellant tank shapes. The overall system weights are calculated using this information and incorporated into the Systems Engineering Mass Properties Computer Program.

Klich, P. J.↗
NASA NTRS1980

Collision avoidance in space

Collisions in earth orbital space between operational payloads and various forms of space debris (nonoperational payloads, nonfunctional mission-related objects and fragments resulting from collisions and explosions) are discussed and possible means of avoiding them are considered. From 10,000 to 15,000 objects are estimated to be in earth orbital space, most of which represent spacecraft fragments and debris too small to be detected and tracked by earth-based sensors, and it is considered likely that some of them will be or have already been involved in direct collisions with the ever increasing number of operational satellites and space stations. Means of protecting proposed large space structures and smaller spacecraft from significant damage by larger space objects, particularly in the 400-4000 km altitude range where most debris occurs, include structural redundancy and the double shielding of sensitive components. Other means of collision avoidance are the collection or relocation of satellites, rocket bodies and other objects by the Space Shuttle, the prevention of explosions and the disposal of spent rocket parts by reentry. Finally, a management structure would be required to administer guidelines for the prevention and elimination of space debris.

Kessler, D. J.↗
NASA NTRS1983

The new space transportation begins today

It is pointed out that increasing space capabilities and the inevitable industrialization of space will place an even greater traffic demand on the Space Shuttle than first projected. The Shuttle will be upgraded by evolutionary steps, and then a new system will be developed to replace it. System-level studies aimed at post-2000 vehicles have been conducted by NASA under the name Future Space Transportation System (FSTS). FSTS began in October 1981 with the objective to define a launch-vehicle concept which improves space transportation capabilities and economics. A second aim was related to the projection of technology requirements beyond previous studies, especially in the areas of structures, propellant tankage, thermal protection, aerothermodynamics and operation. It has been estimated that a fully reusable two-stage system could deliver a payload of 150,000 lb, more than twice the payload of the Space Shuttle for only a slight increase in size and weight.

Freeman, D. C., Jr.↗