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NASA NTRS2013

Engineered Surfaces for Mitigation of Insect Residue Adhesion

Maintenance of laminar flow under operational flight conditions is being investigated under NASA s Environmentally Responsible Aviation (ERA) Program. Among the challenges with natural laminar flow is the accretion of residues from insect impacts incurred during takeoff or landing. Depending on air speed, temperature, and wing structure, the critical residue height for laminar flow disruption can be as low as 4 microns near the leading edge. In this study, engineered surfaces designed to minimize insect residue adhesion were examined. The coatings studied included chemical compositions containing functional groups typically associated with abhesive (non-stick) surfaces. To reduce surface contact by liquids and enhance abhesion, the engineered surfaces consisted of these coatings doped with particulate additives to generate random surface topography, as well as coatings applied to laser ablated surfaces having precision patterned topographies. Performance evaluation of these surfaces included contact angle goniometry of pristine coatings and profilometry of surfaces after insect impacts were incurred in laboratory scale tests, wind tunnel tests and flight tests. The results illustrate the complexity of designing antifouling surfaces for effective insect contamination mitigation under dynamic conditions and suggest that superhydrophobic surfaces may not be the most effective solution for preventing insect contamination on aircraft wing leading edges.

Siochi, Emilie J.↗

NASA NTRS2014

Bi-Metallic Composite Structures With Designed Internal Residual Stress Field

Shape memory alloys (SMA) have a unique ability to recover small amounts of plastic strain through a temperature induced phase change. For these materials, mechanical displacement can be accomplished by heating the structure to induce a phase change, through which some of the plastic strain previously introduced to the structure can be reversed. This paper introduces a concept whereby an SMA phase is incorporated into a conventional alloy matrix in a co-continuous reticulated arrangement forming a bi-metallic composite structure. Through memory activation of the mechanically constrained SMA phase, a controlled residual stress field is developed in the interior of the structure. The presented experimental data show that the memory activation of the SMA composite component significantly changes the residual stress distribution in the overall structure. Designing the structural arrangement of the two phases to produce a controlled residual stress field could be used to create structures that have much improved durability and damage tolerance properties.

Brice, Craig A.↗

NASA NTRS2014

Performance of Silica Gel in the Role of Residual Air Drying

Removal of carbon dioxide (CO2) is a necessary step in air revitalization and is often accomplished with sorbent materials. Since moisture competes with CO2 in sorbent materials, it is necessary to remove the water first. This is typically accomplished in two stages: bulk removal and residual drying. Silica gel is used as the bulk drying material in the Carbon Dioxide Removal Assembly (CDRA) in operation on ISS. There has been some speculation that silica gel may also be capable of serving as the residual drying material. This paper will describe test apparatus and procedures for determining the performance of silica gel in residual air drying.

air revitalization↗

NASA NTRS2016

Sugar and Sugar Derivatives in Residues Produced from the UV Irradiation of Astrophysical Ice Analogs

A large variety and number of organic compounds of prebiotic interest are known to be present in carbonaceous chondrites. Among them, one sugar (dihydroxyacetone) as well as several sugar acids, sugar alcohols, and other sugar derivatives have been reported in the Murchison and Murray meteorites. Their presence, along with amino acids, amphiphiles, and nucleobases strongly suggests that molecules essential to life can form abiotically under astrophysical conditions. This hypothesis is supported by laboratory studies on the formation of complex organic molecules from the ultraviolet (UV) irradiation of simulated astrophysical ice mixtures consisting of H2O, CO, CO2, CH3OH, CH4, NH3, etc., at low temperature. In the past 15 years, these studies have shown that the organic residues recovered at room temperature contain amino acids, amphiphiles, nucleobases, as well as other complex organics. However, no systematic search for the presence of sugars and sugar derivatives in laboratory residues have been reported to date, despite the fact that those compounds are of primary prebiotic significance. Indeed, only small (up to 3 carbon atoms) sugar derivatives including glycerol and glyceric acid have been detected in residues so far.

Ice Irradiation↗

NASA NTRS2015

A Complementary Note to 'A Lag-1 Smoother Approach to System-Error Estimation': The Intrinsic Limitations of Residual Diagnostics

Recently, this author studied an approach to the estimation of system error based on combining observation residuals derived from a sequential filter and fixed lag-1 smoother. While extending the methodology to a variational formulation, experimenting with simple models and making sure consistency was found between the sequential and variational formulations, the limitations of the residual-based approach came clearly to the surface. This note uses the sequential assimilation application to simple nonlinear dynamics to highlight the issue. Only when some of the underlying error statistics are assumed known is it possible to estimate the unknown component. In general, when considerable uncertainties exist in the underlying statistics as a whole, attempts to obtain separate estimates of the various error covariances are bound to lead to misrepresentation of errors. The conclusions are particularly relevant to present-day attempts to estimate observation-error correlations from observation residual statistics. A brief illustration of the issue is also provided by comparing estimates of error correlations derived from a quasi-operational assimilation system and a corresponding Observing System Simulation Experiments framework.

Fixed-lag smoothing↗

NASA NTRS2015

Search for Sugars and Related Compounds in Residues Produced from the UV Irradiation of Astrophysical Ice Analogs

A large variety of organics of biological and prebiotic interests have been detected in meteorites, including one sugar and several sugar acids and sugar alcohols [1]. The presence of these compounds in meteorites, along with amino acids, amphiphiles, and nucleobases [2-4], indicates that molecules essential to life can be formed abiotically under astrophysical conditions. This hypothesis is supported by extensive laboratory studies involving the formation of complex organic molecules from the ultraviolet (UV) irradiation of astrophysical ice analogs (H2O, CO, CO2, CH3OH, CH4, NH3, etc.). These studies show that the organic residues recovered at room temperature contain many of the same compounds as those found in meteorites[3,58]. However, to the best of our knowledge, no systematic search for the presence of sugars and sugar derivatives in such laboratory residues have been reported to date. Only a limited number of small (greater than 4 C atoms) sugar-related compounds such as glycerol and glyceric acid [9], and more recently small (2-4 C atoms) aldehydes [10] have been detected in residues.

Astrophysics↗

NASA NTRS2016

Retention of Compressive Residual Stresses Introduced by Shot Peening in a Powder Metal Disk Superalloy

The fatigue lives of disk superalloys can be increased by shot peening their surfaces, to induce compressive residual stresses near the surface that impede cracking there. As disk application temperatures increase for improved efficiency, the persistence of these beneficial stresses could be impaired, especially with continued fatigue cycling. The objective of this work was to study the retention of residual stresses introduced by shot peening, when subjected to fatigue and high temperatures. Fatigue specimens of powder metallurgy processed nickel-base disk superalloy ME3 were prepared with consistent processing and heat treatment. They were then shot peened using varied conditions. Strain-controlled fatigue cycles were run at room temperature and 704 C, to allow re-assessment of residual stresses.

fatigue↗

NASA NTRS2017

Method for the Collection, Gravimetric and Chemical Analysis of Nonvolatile Residue (NVR) on Surfaces

Nonvolatile residue (NVR), sometimes referred to as molecular contamination is the term used for the total composition of the inorganic and high boiling point organic components in particulates and molecular films deposited on critical surfaces surrounding space structures, with the particulate and NVR contamination originating primarily from pre-launch operations. The "nonvolatile" suggestion from the terminology NVR implies that the collected residue will not experience much loss under ambient conditions. NVR has been shown to have a dramatic impact on the ability to perform optical measurements from platforms based in space. Such contaminants can be detected early by the controlled application of various detection techniques and contamination analyses. Contamination analyses are the techniques used to determine if materials, components, and subsystems can be expected to meet the performance requirements of a system. Of particular concern is the quantity of NVR contaminants that might be deposited on critical payload surfaces from these sources. Subsequent chemical analysis of the contaminant samples by infrared spectroscopy and gas chromatography mass spectrometry identifies the components, gives semi-quantitative estimates of contaminant thickness, indicates possible sources of the NVR, and provides guidance for effective cleanup procedures. In this report, a method for the collection and determination of the mass of NVR was generated by the authors at NASA Langley Research Center. This report describes the method developed and implemented for collecting NVR contaminants, and procedures for gravimetric and chemical analysis of the residue obtained. The result of this NVR analysis collaboration will help pave the way for Langley's ability to certify flight hardware outgassing requirements in support of flight projects such as Stratospheric Aerosol and Gas Experiment III (SAGE III), Clouds and the Earth's Radiant Energy System (CERES), Materials International Space Station Experiment - X (MISSE-X), and Doppler Aerosol Wind Lidar (DAWN).

Gordon, Keith↗

NASA NTRS2019

Improving Accuracy of Structural Dynamic Modification with Augmented Residual Vectors

It is often important to perform sensitivity analysis to determine how a structural model will be impacted by design changes. Often, the structural analysts will manually make changes to the finite element model (FEM) to determine the effects. But when dealing with a large FEM with millions of degrees of freedom these manual changes can be cumbersome and calculation of the effects can computationally expensive. Therefore, it is desirable to determine the effects of model changes through approximation methods. One common technique is to determine the analytical sensitivity of the FEM model with respect to the given change. These analytical sensitivities are valid when small changes are made to the structural model, but invalid if large changes need to be assessed. Another approach is to use Structural Dynamic Modification (SDM) to create a surrogate model to analyze model changes. SDM is a widely-used sensitivity method and is used in applications of model updating, uncertainty quantification, and model design studies. SMD is valid for moderate (10-20 percent) changes in the structural model, but model approximations are often needed for large parameter changes (greater than 20 percent). Structural Dynamic Modification can be improved by using residual vectors to augment the surrogate model formulation from SDM. Adding the residual modes increases the fidelity of the surrogate model while keeping the computational cost low. This paper discusses the application and limitations of the augmented residual modes method to two structures: the Integrated Spacecraft and Payload Element (ISPE) of the Space Launch System (SLS) and the full SLS as it is configured during its Integrated Modal Test (IMT).

Stewart, Eric C.↗

NASA NTRS2019

Spacecraft Adhesive Residue On-Composite Analysis

Tapes are used on space vehicles for numerous reasons. They are used for taping close ports, labeling, and even temporarily attaching something to the spacecraft. This project stemmed from the need to determine which tapes are most effective for our customer's space vehicle during its ground processing stage. During ground processing, there are multiple stages of building where workers need to use tape to temporarily stabilize or close something for a matter of seconds, days, weeks, or even a few months. After peeling these tapes off the flight hardware, the residue left behind by the tape poses potential risks that can lead to incidents, which may not be easily noticeable to the engineers. It is important to identify these issues since nothing can be done once it is in space. The purpose of this project is to assist in research to create an accessible reference for which tapes are preferred on common flight hardware surfaces. Five different substrates and eight tapes were selected for evaluation. The selected substrates were chosen because they comprise the most surface area on the vehicle. The tapes selected were either heritage or new contenders. The adhesive studies were performed for multiple dwell times to study the tendency of different tapes to leave residue behind on various substrates and quantifying that residue. Many other tests were performed to supplement the main objective of the project. These tests included adhesive solubility, peel adhesion, and SEM analyses.

McFadden, Saleah J.↗

NASA NTRS2021

Evaluation of SWIR Crop Residue Bands for the Landsat Next Mission

This research reports the findings of a Landsat Next expert review panel that evaluated the use of narrow shortwave infrared (SWIR) reflectance bands to measure ligno-cellulose absorption features centered near 2100 and 2300 nm, with the objective of measuring and mapping non-photosynthetic vegetation (NPV), crop residue cover, and the adoption of conservation tillage practices within agricultural landscapes. Results could also apply to detection of NPV in pasture, grazing lands, and non-agricultural settings. Currently, there are no satellite data sources that provide narrowband or hyperspectral SWIR imagery at sufficient volume to map NPV at a regional scale. The Landsat Next mission, currently under design and expected to launch in the late 2020’s, provides the opportunity for achieving increased SWIR sampling and spectral resolution with the adoption of new sensor technology. This study employed hyperspectral data collected from 916 agricultural field locations with varying fractional NPV, fractional green vegetation, and surface moisture contents. These spectra were processed to generate narrow bands with centers at 2040, 2100, 2210, 2260, and 2230 nm, at various bandwidths, that were subsequently used to derive 13 NPV spectral indices from each spectrum. For crop residues with minimal green vegetation cover, two-band indices derived from 2210 and 2260 nm bands were top performers for measuring NPV (R^(2) = 0.81, RMSE = 0.13) using bandwidths of 30 to 50 nm, and the addition of a third band at 2100 nm increased resistance to atmospheric correction residuals and improved mission continuity with Landsat 8 Operational Land Imager Band 7. For prediction of NPV over a full range of green vegetation cover, the Cellulose Absorption Index, derived from 2040, 2100, and 2210 nm bands, was top performer (R^(2) = 0.77, RMSE = 0.17), but required a narrow (≤20 nm) bandwidth at 2040 nm to avoid interference from atmospheric carbon dioxide absorption. In comparison, broadband NPV indices utilizing Landsat 8 bands centered at 1610 and 2200 nm performed poorly in measuring fractional NPV (R^(2) = 0.44), with significantly increased interference from green vegetation

Wells Dean Hively↗

NASA NTRS2024

Raman spectroscopy of Ryugu particles and their extracted residues: Fluorescence background characteristics and similarities to CI chondrites

We present here an investigation of Ryugu particles recovered by the Hayabusa2 space mission and their extracted carbonaceous acid residues using Raman spectroscopy. Raman parameters of Ryugu intact grains and their acid residues are characterized by broad D (defect induced) and G (graphite) band widths, indicating the presence of polyaromatic carbonaceous matter with low thermal maturity. Raman spectra of Ryugu particles and CI (type 1) chondrites exhibit stronger laser-induced fluorescence backgrounds compared to Type 2 and Type 3 carbonaceous chondrites. The high fluorescence signatures and wide bandwidths of the D and G bands of Ryugu intact grains are similar to the Raman spectra observed in CI chondrites, reflecting the low structural order of their aromatic carbonaceous matter, and strengthening the link between Ryugu particles and CI chondrites. The high fluorescence background intensity of the Ryugu particles is due to multiple causes, but it is likely that the relative abundance of geometry-bearing macromolecular organic matter in total organic carbon contents makes a large contribution to the fluorescence intensities. Locally observed high fluorescence in the acid-extracted residues of Ryugu is due to nitrogen-bearing outlier phase. The high fluorescence signature is one consequence of the low degree of thermal maturity of the organic matter and supports evidence that the Ryugu particles have escaped significant parent body thermal metamorphism.

Ryugu particles↗

NASA NTRSDate not supplied

X-Ray Diffraction Measurements of Residual Stress in a Cold Sprayed Ni Coating

X-ray diffraction (XRD) was used to investigate the residual stress in a cold sprayed Ni coating which failed to form a bimetallic joint with NASA HR-1. The objective was to apply pure Ni by cold spray as a diffusion barrier between the Ni-based alloy NASA HR-1 and the Cu-based GRCop-42 for a thrust cell assembly. After additive manufacturing of the GRCop-42 cylinder, the commercially pure Ni coating was cold sprayed onto the cylinder. It was intended to have NASA HR-1 applied directly onto the Ni coating by Directed Energy Deposition (DED), however the bond failed during the first layer of DED. Residual stress measurements were collected via the Sin²ψ method in three equally spaced locations on the top surface of the Ni coating in both as-cold sprayed and heat-treated conditions. The results revealed both compressive and tension stresses on the as-cold sprayed sample and compressive stresses in the heat-treated sample. The results were illuminated when plotted at their respective positions and with their respective orientation angles around a circle. This showed rotational symmetry in the residual stress measurements, which correlated to the processing method used during application of the Ni coating.

Laura Wilson↗

NASA NTRS2024

Residual Thrust in a Solid Rocket Motor: A Model Applied to the Mars Ascent Vehicle

A model for solid rocket motor residual thrust is built from the concept that hot nozzle phenolic or carbon materials provide a radiating source of heat flux to the insulation, leading to continued off-gassing by pyrolysis. This model is 1. Fitted to flight datasets and scaled to the Mars Ascent Vehicle second stage motor (MAV SRM2), and 2. Derived with MAV SRM2 design and material estimates. The two methods show a potential range of modeling uncertainty for use by mission analysts. Further loss methods that could reduce the maximum residual impulse are identified but left to further work to evaluate.

Solid rocket motors↗

NASA NTRSDate not supplied

Residual Thrust in a Solid Rocket Motor: A Model Applied to the Mars Ascent Vehicle

Solid rocket motors↗

NASA NTRSDate not supplied

An Examination of Autumn Southern Polar Ozone Tendencies and the Residual Circulation in MERRA-2 Products

Changes in lower stratospheric ozone caused by dynamical transport can be difficult to characterize and thus are sometimes difficult to distinguish from chemical losses. Correlations between ozone changes and various dynamical proxies (e.g., the eddy heat flux) from year to year can be of interest, but they do little in themselves to explain the ozone transport mechanisms behind such correlations. In this study, we use products from the Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) to calculate the ozone mass flux, integrating it in space and time over the upper tropospheric/lower stratospheric Southern polar cap during periods when little chemical loss is expected. The ozone mass flux is expressed in terms of components of the residual circulation of the Transformed Eulerian Mean (TEM, i.e., 𝑣𝑣̅ ∗and 𝑤𝑤(∗) as well as eddy mixing terms. We relate these terms to the local ozone mass tendency ("#! "$ ), similarly integrated, and we find that the interannual variability of the ozone changes are strongly related to the residual meridional circulation and the meridional eddy mixing terms. These directly calculated dynamical transport terms provide clearer ozone proxies. Removing these advective terms from a long-term ozone time series can more effectively reveal ozone variations and long-term trends, specifically those caused by photochemical production and losses (e.g., human-produced ozone depletion).

Ozone↗

NASA NTRS1969

Apparatus automatically measures soluble residue content of volatile solvents

Solvent Purity Meter /SPM/ automatically measures the soluble residue in volatile solvents used in cleaning or extraction of oils, greases, and other nonvolatile materials. The SPM gives instantaneous and continuous readout of soluble contaminant residues in concentrations as low as one part per million of solution.

Oswalt, F. W.↗

NASA NTRS1971

C-130: Results of center wing residual strength and crack propagation test program

Fourteen C-130 airplane center wings which had experienced from approximately 4,000 to 13,000 hours of flight service and its associated fatigue damage were tested to destruction, seven in upbending and seven in downbending. Six wings were tested directly for static residual strength in the fatigue-damaged condition as received from field service. The other eight wings were tested in crack propagation cyclic testing at a prescribed stress level for a maximum of 10,000 cycles. Then the stress level was reduced and testing was continued up to a maximum of 20,000 total cycles. Cyclic testing was performed with constant-amplitude stresses at a stress ratio of +0.1. Maximum cyclic skin stresses were approximately 18,000 psi. At the conclusion of cyclic testing, a static test to destruction was conducted to determine the residual strength of each fatigue-damaged specimen.

Reeder, F. L.↗