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All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Apparatus and Method for Elimination of Polarization-Induced Fading in Fiber-optic Sensor System

The invention is an apparatus and method of eliminating polarization-induced fading in interferometric fiber-optic sensor system having a wavelength-swept laser optical signal. The interferometric return signal from the sensor arms are combined and provided to a multi-optical path detector assembly and ultimately to a data acquisition and processing unit by way of a switch that is time synchronized with the laser scan sweep cycle.

Chan, Hon Man↗
NASA NTRS2016

Quantification of ln-Flight Physical Changes: Anthropometry and Neutral Body Posture

Currently, NASA does not have sufficient in-flight anthropometric data to assess the impact of changes in body shape and size. For developing future planetary and reduced-gravity suits, NASA needs to quantify the impacts of microgravity on anthropometry and body posture to ensure optimal crew performance, fit, and comfort. To obtain data on these changes, circumference, length, height, breadth, and depth for body segments (chest, waist, bicep, thigh, calf) from astronauts for preflight, in-flight, and post-flight conditions needs to be collected. Once these data have been collected, pre-flight, in-flight, and post-flight anthropometric values will be compared, yielding microgravity factors. The neutral body posture (NBP) will also be measured, to determine body posture (joint angle) changes between subjects throughout the duration of a mission. Data collection, starting with Increments 37/38, is still in progress but has been completed for 6 out of 9 subjects. NASA suit engineers and NASA's Extravehicular Activity (EVA) Project Office have identified that suit fit in microgravity could become an issue. It has been noted that crewmembers often need to adjust their suit sizing once they are in orbit. This adjustment could be due to microgravity effects on anthropometry and postural changes, and is necessary to ensure optimal crew performance, fit, and comfort in space. To date, the only data collected to determine the effects of microgravity on physical human changes were collected during Skylab 4, the Apollo-Soyuz Test Project (ASTP), Space Shuttle mission STS-57, and a recent HRP study on seated height changes due to spinal elongation (Spinal Elongation, Master Task List [MTL] #221). The Skylab 4, ASTP, and the STS-57 studies found that, according to photographs, a distinct NBP exists. The still photographs showed a distinguishable posture with the arms raised and the shoulders abducted; in addition, the knees are flexed, with noticeable hip flexion, and the foot is plantar flexed [1,2]. This combination is considered to be the standard set of body joint angles for an NBP in microgravity. A recent simulated microgravity NBP study [3] showed individual variability and inconsistencies in defining NBP. This variation may be influenced by spinal growth, and other potential anthropometry factors such as spinal curvature, age, and gender. Data on the variation of this posture data is required for all kinds of space device designs (such as suits, habitat, and mobility aids). The method proposed in this study considers the dynamic nature of body movement and will use a measurement technique to continually monitor posture and develop a probability likelihood of the neutral posture and how the NBP postures are affected by anthropometry. Additionally, Skylab studies found that crewmembers experienced a stature growth of up to 3 percent. The data included 3 crewmembers and showed that a biphasic stature growth occurs once the crewmember enters into weightlessness. However, the HRP Spinal Elongation study showed that crewmembers could experience about a 6 percent growth in seated height and a 3 percent stature growth, when exposed to microgravity. The results of that study prove that not all anthropometric measurements have the same microgravity percent growth factor. For EVA and suit engineers to properly update the sizing protocol for microgravity, they need additional anthropometric data from space missions. Hence, this study is aimed at gathering additional in-flight anthropometric measurements, such as length, depth, breadth, and circumference, to determine the changes to body shape and size caused by microgravity effects. It is anticipated that by recording the potential changes to body shape and size, NASA will develop a better suit sizing protocol for the International Space Station and other space missions. In essence, this study will help NASA quantify the impacts of microgravity on anthropometry to ensure optimal crew performance, fit, and comfort. This study will use standard anthropometry data collection techniques, 3D laser scanning, digital still photography, and video data, and perform photogrammetric analyses to determine the changes that occur to the body shape and size, and to NBP, when the human body is exposed to a microgravity environment.

Young, K. S.↗
NASA NTRS2015

Interphase Chromosome Conformation and Chromatin-Chromatin Interactions in Human Epithelial Cells Cultured Under Different Gravity Conditions

Microgravity has been shown to alter global gene expression patterns and protein levels both in cultured cells and animal models. It has been suggested that the packaging of chromatin fibers in the interphase nucleus is closely related to genome function, and the changes in transcriptional activity are tightly correlated with changes in chromatin folding. This study explores the changes of chromatin conformation and chromatin-chromatin interactions in the simulated microgravity environment, and investigates their correlation to the expression of genes located at different regions of the chromosome. To investigate the folding of chromatin in interphase under various culture conditions, human epithelial cells, fibroblasts, and lymphocytes were fixed in the G1 phase. Interphase chromosomes were hybridized with a multicolor banding in situ hybridization (mBAND) probe for chromosome 3 which distinguishes six regions of the chromosome as separate colors. After images were captured with a laser scanning confocal microscope, the 3-dimensional structure of interphase chromosome 3 was reconstructed at multi-mega base pair scale. In order to determine the effects of microgravity on chromosome conformation and orientation, measures such as distance between homologous pairs, relative orientation of chromosome arms about a shared midpoint, and orientation of arms within individual chromosomes were all considered as potentially impacted by simulated microgravity conditions. The studies revealed non-random folding of chromatin in interphase, and suggested an association of interphase chromatin folding with radiation-induced chromosome aberration hotspots. Interestingly, the distributions of genes with expression changes over chromosome 3 in cells cultured under microgravity environment are apparently clustered on specific loci and chromosomes. This data provides important insights into how mammalian cells respond to microgravity at molecular level.

International Space Station↗
NASA NTRS2015

Multipurpose Pressure Vessel Scanner and Photon Doppler Velocimetry

Critical flight hardware typically undergoes a series of nondestructive evaluation methods to screen for defects before it is integrated into the flight system. Conventionally, pressure vessels have been inspected for flaws using a technique known as fluorescent dye penetrant, which is biased to inspector interpretation. An alternate method known as eddy current is automated and can detect small cracks better than dye penetrant. A new multipurpose pressure vessel scanner has been developed to perform internal and external eddy current scanning, laser profilometry, and thickness mapping on pressure vessels. Before this system can be implemented throughout industry, a probability of detection (POD) study needs to be performed to validate the system's eddy current crack/flaw capabilities. The POD sample set will consist of 6 flight-like metal pressure vessel liners with defects of known size. Preparation for the POD includes sample set fabrication, system operation, procedure development, and eddy current settings optimization. For this, collaborating with subject matter experts was required. This technical paper details the preparation activities leading up to the POD study currently scheduled for winter 2015/2016. Once validated, this system will be a proven innovation for increasing the safety and reliability of necessary flight hardware. Additionally, testing of frangible joint requires Photon Doppler Velocimetry (PDV) and Digital Image Correlation instrumentation. There is often noise associated with PDV data, which necessitates a frequency modulation (FM) signal-to-noise pre-test. Generally, FM radio works by varying the carrier frequency and mixing it with a fixed frequency source, creating a beat frequency which is represented by audio frequency that can be heard between about 20 to 20,000 Hz. Similarly, PDV reflects a shifted frequency (a phenomenon known as the Doppler Effect) from a moving source and mixes it with a fixed source frequency, which results in a beat frequency. However, for PDV, discerning the signal from the noise is difficult without a moving source to induce the modulation. A rotating wheel is currently being used as the moving source but its configuration is impractical and has cumbersome placement inside the current frangible joint test cell. As a way to combat this problem and verify a satisfactory signal-to-noise ratio, a reflective moving crystal piezo will be used to modulate a beat frequency, and an absorptive target will be used to block the signal in order to determine any back reflection coming from the probe and discern the true signal-to-noise ratio. The piezo will be mounted and inserted onto the test table on an extendable telescopic antenna grounded by a magnetic base in the test zone. This piezo configuration will be more compatible within the test zone and allow for easy removal of the disk following acceptable signal verification and prior to frangible joint tests.

Ellis, Tayera↗
NASA NTRS2015

Multipurpose Pressure Vessel Scanner and Photon Doppler Velocimetry

Critical flight hardware typically undergoes a series of nondestructive evaluation methods to screen for defects before it is integrated into the flight system. Conventionally, pressure vessels have been inspected for flaws using a technique known as fluorescent dye penetrant, which is biased to inspector interpretation. An alternate method known as eddy current is automated and can detect small cracks better than dye penetrant. A new multipurpose pressure vessel scanner has been developed to perform internal and external eddy current scanning, laser profilometry, and thickness mapping on pressure vessels. Before this system can be implemented throughout industry, a probability of detection (POD) study needs to be performed to validate the system’s eddy current crack/flaw capabilities. The POD sample set will consist of 6 flight-like metal pressure vessel liners with defects of known size. Preparation for the POD includes sample set fabrication, system operation, procedure development, and eddy current settings optimization. For this, collaborating with subject matter experts was required. This technical paper details the preparation activities leading up to the POD study currently scheduled for winter 2015/2016. Once validated, this system will be a proven innovation for increasing the safety and reliability of necessary flight hardware.Additionally, testing of frangible joint requires Photon Doppler Velocimetry (PDV) and Digital Image Correlation instrumentation. There is often noise associated with PDV data, which necessitates a frequency modulation (FM) signal-to-noise pre-test. Generally, FM radio works by varying the carrier frequency and mixing it with a fixed frequency source, creating a beat frequency which is represented by audio frequency that can be heard between about 20 to 20,000 Hz. Similarly, PDV reflects a shifted frequency (a phenomenon known as the Doppler Effect) from a moving source and mixes it with a fixed source frequency, which results in a beat frequency. However, for PDV, discerning the signal from the noise is difficult without a moving source to induce the modulation. A rotating wheel is currently being used as the moving source but its configuration is impractical and has cumbersome placement inside the current frangible joint test cell. As a way to combat this problem and verify a satisfactory signal-to-noise ratio, a reflective moving crystal piezo will be used to modulate a beat frequency, and an absorptive target will be used to block the signal in order to determine any back reflection coming from the probe and discern the true signal-to noise ratio. The piezo will be mounted and inserted onto the test table on an extendable telescopic antenna grounded by a magnetic base in the test zone. This piezo configuration will be more compatible within the test zone and allow for easy removal of the disk following acceptable signal verification and prior to frangible joint tests.Additionally, topics of what was learned and smaller tasks given at White Sands Test Facility (WSTF) will be discussed. All statements in this paper are newly gained knowledge of what I have learned, observed, and have done while at WSTF.

Ellis, Tayera↗
NASA NTRS2016

Launch Pad in a Box

NASA Kennedy Space Center (KSC) is developing a new deployable launch system capability to support a small class of launch vehicles for NASA and commercial space companies to test and launch their vehicles. The deployable launch pad concept was first demonstrated on a smaller scale at KSC in 2012 in support of NASA Johnson Space Center's Morpheus Lander Project. The main objective of the Morpheus Project was to test a prototype planetary lander as a vertical takeoff and landing test-bed for advanced spacecraft technologies using a hazard field that KSC had constructed at the Shuttle Landing Facility (SLF). A steel pad for launch or landing was constructed using a modular design that allowed it to be reconfigurable and expandable. A steel flame trench was designed as an optional module that could be easily inserted in place of any modular steel plate component. The concept of a transportable modular launch and landing pad may also be applicable to planetary surfaces where the effects of rocket exhaust plume on surface regolith is problematic for hardware on the surface that may either be damaged by direct impact of high speed dust particles, or impaired by the accumulation of dust (e.g., solar array panels and thermal radiators). During the Morpheus free flight campaign in 2013-14, KSC performed two studies related to rocket plume effects. One study compared four different thermal ablatives that were applied to the interior of a steel flame trench that KSC had designed and built. The second study monitored the erosion of a concrete landing pad following each landing of the Morpheus vehicle on the same pad located in the hazard field. All surfaces of a portable flame trench that could be directly exposed to hot gas during launch of the Morpheus vehicle were coated with four types of ablatives. All ablative products had been tested by NASA KSC and/or the manufacturer. The ablative thicknesses were measured periodically following the twelve Morpheus free flight tests. The thermal energy from the Morpheus rocket exhaust plume was only found to be sufficient to cause appreciable ablation of one of the four ablatives that were tested. The rocket exhaust plume did cause spalling of concrete during each descent and landing on a landing pad in the hazard field. The Extended Abstract ASE Earth and Space Conference April, 2016 - Orlando, FL concrete surface was laser scanned following each Morpheus landing, and the total volume of spalled concrete that eroded between the first and final landings of the Morpheus Project's test campaign was estimated. This paper will also describe a new deployable launch system (DLS) capability that is being developed at KSC and was publicly announced in May 2015 (KSC Partnerships, 2015). The DLS is a set of multi-user Ground Support Equipment that will be used to test and launch small class launch vehicles. The system is comprised of four main elements: the Launch Stand, the Flame Deflector, the Pad Apron and the KAMAG transporter. The system elements are designed to be deployed at launch or test sites within the KSC/CCAFS boundaries. The DLS is intended to be used together with the Fluid and Electrical System of the Universal Propellant Servicing Systems and Mobile Power Data and Communications Unit.

Ablatives Testing↗
NASA NTRS2016

Flux Recovery of a Forward Osmosis Membrane After a Fouling Process

Wastewater treatment through Forward Osmosis (FO) membranes is a process that has been evaluated in the past years as an innovative technology for the Next Generation Life Support Systems. FO technologies are cost effective, and require very low energy consumption, but are subject to membrane fouling. Membrane fouling occurs when unwanted materials accumulate on the active side of the membrane during the wastewater treatment process, which leads to a decrease in membrane flow rates. Membrane fouling can be reversed with the use of antifoulant solutions. The aim of this study is to identify the materials that cause flow rate reduction due to membrane fouling, as well as to evaluate the flux recovery after membrane treatment using commercially available antifoulants. 3D Laser Scanning Microscope images were taken to observe the surface of the membrane. Fourier Transform Infrared (FTIR) spectrometry results identified possible compounds that cause membrane fouling and FO testing results demonstrated flow rate recovery after membrane treatment using antifoulants.

Forward osmosis↗
NASA NTRS2016

Launch Pad in a Box

NASA Kennedy Space Center (KSC) is developing a new deployable launch system capability to support a small class of launch vehicles for NASA and commercial space companies to test and launch their vehicles. The deployable launch pad concept was first demonstrated on a smaller scale at KSC in 2012 in support of NASA Johnson Space Center's Morpheus Lander Project. The main objective of the Morpheus Project was to test a prototype planetary lander as a vertical takeoff and landing test-bed for advanced spacecraft technologies using a hazard field that KSC had constructed at the Shuttle Landing Facility (SLF). A steel pad for launch or landing was constructed using a modular design that allowed it to be reconfigurable and expandable. A steel flame trench was designed as an optional module that could be easily inserted in place of any modular steel plate component. The concept of a transportable modular launch and landing pad may also be applicable to planetary surfaces where the effects of rocket exhaust plume on surface regolith is problematic for hardware on the surface that may either be damaged by direct impact of high speed dust particles, or impaired by the accumulation of dust (e.g., solar array panels and thermal radiators). During the Morpheus free flight campaign in 2013-14, KSC performed two studies related to rocket plume effects. One study compared four different thermal ablatives that were applied to the interior of a steel flame trench that KSC had designed and built. The second study monitored the erosion of a concrete landing pad following each landing of the Morpheus vehicle on the same pad located in the hazard field. All surfaces of a portable flame trench that could be directly exposed to hot gas during launch of the Morpheus vehicle were coated with four types of ablatives. All ablative products had been tested by NASA KSC and/or the manufacturer. The ablative thicknesses were measured periodically following the twelve Morpheus free flight tests. The thermal energy from the Morpheus rocket exhaust plume was only found to be sufficient to cause appreciable ablation of one of the four ablatives that were tested. The rocket exhaust plume did cause spalling of concrete during each descent and landing on a landing pad in the hazard field. The Extended Abstract ASE Earth and Space Conference April, 2016 - Orlando, FL concrete surface was laser scanned following each Morpheus landing, and the total volume of spalled concrete that eroded between the first and final landings of the Morpheus Project's test campaign was estimated. This paper will also describe a new deployable launch system (DLS) capability that is being developed at KSC and was publicly announced in May 2015 (KSC Partnerships, 2015). The DLS is a set of multi-user Ground Support Equipment that will be used to test and launch small class launch vehicles. The system is comprised of four main elements: the Launch Stand, the Flame Deflector, the Pad Apron and the KAMAG transporter. The system elements are designed to be deployed at launch or test sites within the KSC/CCAFS boundaries. The DLS is intended to be used together with the Fluid and Electrical System of the Universal Propellant Servicing Systems and Mobile Power Data and Communications Unit

Mobile Launch Pad Development↗
NASA NTRS2016

A Parametric Model of Shoulder Articulation for Virtual Assessment of Space Suit Fit

Shoulder injury is one of the most severe risks that have the potential to impair crewmembers' performance and health in long duration space flight. Overall, 64% of crewmembers experience shoulder pain after extra-vehicular training in a space suit, and 14% of symptomatic crewmembers require surgical repair (Williams & Johnson, 2003). Suboptimal suit fit, in particular at the shoulder region, has been identified as one of the predominant risk factors. However, traditional suit fit assessments and laser scans represent only a single person's data, and thus may not be generalized across wide variations of body shapes and poses. The aim of this work is to develop a software tool based on a statistical analysis of a large dataset of crewmember body shapes. This tool can accurately predict the skin deformation and shape variations for any body size and shoulder pose for a target population, from which the geometry can be exported and evaluated against suit models in commercial CAD software. A preliminary software tool was developed by statistically analyzing 150 body shapes matched with body dimension ranges specified in the Human-Systems Integration Requirements of NASA ("baseline model"). Further, the baseline model was incorporated with shoulder joint articulation ("articulation model"), using additional subjects scanned in a variety of shoulder poses across a pre-specified range of motion. Scan data was cleaned and aligned using body landmarks. The skin deformation patterns were dimensionally reduced and the co-variation with shoulder angles was analyzed. A software tool is currently in development and will be presented in the final proceeding. This tool would allow suit engineers to parametrically generate body shapes in strategically targeted anthropometry dimensions and shoulder poses. This would also enable virtual fit assessments, with which the contact volume and clearance between the suit and body surface can be predictively quantified at reduced time and cost.

Kim, K. Han↗
NASA NTRS2016

Delamination Detection Using Guided Wave Phased Arrays

This paper presents a method for detecting multiple delaminations in composite laminates using non-contact phased arrays. The phased arrays are implemented with a non-contact scanning laser Doppler vibrometer (SLDV). The array imaging algorithm is performed in the frequency domain where both the guided wave dispersion effect and direction dependent wave properties are considered. By using the non-contact SLDV array with a frequency domain imaging algorithm, an intensity image of the composite plate can be generated for delamination detection. For the proof of concept, a laboratory test is performed using a non-contact phased array to detect two delaminations (created through quasi-static impact test) at different locations in a composite plate. Using the non-contact phased array and frequency domain imaging, the two impact-induced delaminations are successfully detected. This study shows that the non-contact phased array method is a potentially effective method for rapid delamination inspection in large composite structures.

Tian, Zhenhua↗
NASA NTRS2016

Generation of Fullspan Leading-Edge 3D Ice Shapes for Swept-Wing Aerodynamic Testing

The deleterious effect of ice accretion on aircraft is often assessed through dry-air flight and wind tunnel testing with artificial ice shapes. This paper describes a method to create fullspan swept-wing artificial ice shapes from partial span ice segments acquired in the NASA Glenn Icing Reserch Tunnel for aerodynamic wind-tunnel testing. Full-scale ice accretion segments were laser scanned from the Inboard, Midspan, and Outboard wing station models of the 65% scale Common Research Model (CRM65) aircraft configuration. These were interpolated and extrapolated using a weighted averaging method to generate fullspan ice shapes from the root to the tip of the CRM65 wing. The results showed that this interpolation method was able to preserve many of the highly three dimensional features typically found on swept-wing ice accretions. The interpolated fullspan ice shapes were then scaled to fit the leading edge of a 8.9% scale version of the CRM65 wing for aerodynamic wind-tunnel testing. Reduced fidelity versions of the fullspan ice shapes were also created where most of the local three-dimensional features were removed. The fullspan artificial ice shapes and the reduced fidelity versions were manufactured using stereolithography.

Icing↗
NASA NTRS2016

Convection from Hemispherical and Conical Model Ice Roughness Elements in Stagnation Region Flows

To improve ice accretion prediction codes, more data regarding ice roughness and its effects on convective heat transfer are required. The Vertical Icing Studies Tunnel (VIST) at NASA Glenn Research was used to model realistic ice roughness in the stagnation region of a NACA 0012 airfoil. In the VIST, a test plate representing the leading 2% chord of the airfoil was subjected to flows of 7.62 m/s (25 ft/s), 12.19 m/s (40 ft/s), and 16.76 m/s (55 ft/s). The test plate was fitted with multiple surfaces or sets of roughness panels, each with a different representation of ice roughness. The sets of roughness panels were constructed using two element distribution patterns that were created based on a laser scan of an iced airfoil acquired in the Icing Research Tunnel at NASA Glenn. For both roughness patterns, surfaces were constructed using plastic hemispherical elements, plastic conical elements, and aluminum conical elements. Infrared surface thermometry data from tests run in the VIST were used to calculate area averaged heat transfer coefficient values. The values from the roughness surfaces were compared to the smooth control surface, showing convective enhancement as high as 400% in some cases. The data gathered during this study will ultimately be used to improve the physical modeling in LEWICE or other ice accretion codes and produce predictions of in-flight ice accretion on aircraft surfaces with greater confidence.

Icing Physics↗
NASA NTRS2016

Bimodal SLD Ice Accretion on a NACA 0012 Airfoil Model

This presentation describes the results of ice accretion measurements on a NACA 0012 airfoil model, from the NASA Icing Research Tunnel, using an icing cloud composed of a bimodal distribution of Supercooled Large Droplets. The data consists of photographs, laser scans of the ice surface, and measurements of the mass of ice for each icing condition. The results of ice shapes accumulated as a result of exposure to an icing cloud with a bimodal droplet distribution were compared to the ice shapes resulting from an equivalent cloud composed of a droplet distribution with a standard bell curve shape.

aircraft icing↗
NASA NTRS2017

Ice Accretion Roughness Measurements and Modeling

Roughness on aircraft ice accretions is very important to the overall ice accretion process and to the resulting degradation in aircraft aerodynamic performance. Roughness enhances the local convection leading to more rapid ice accumulation rates, and roughness generates local flow perturbations that lead to higher skin friction. This paper presents 1) a review of the developments in ice shape three-dimensional laser scanning developed at NASA Glenn, 2) a review of the approach of McClain and Kreeger employed to characterize ice roughness evolution on an airfoil surface, and 3) a review of the experimental efforts that have been performed over the last five years to characterize, scale, and model ice roughness evolution physics.

SLD↗
NASA NTRS2018

Further Examinations of Bimodal SLD Ice Accretion in the NASA Icing Research Tunnel

An ice shape database has been created to document ice accretions on a 72-inch chord NACA 23012 airfoil model resulting from an exposure to a Supercooled Large Drop (SLD) icing cloud with a bimodal drop size distribution. The ice shapes created were documented with photographs, laser scanned surface measurements over a section of the model span, and measurement of the ice mass over the same section of each accretion. The icing conditions used in the test matrix were based upon previously measured ice shapes on the same model to connect the current database to previously measured information. Ice shapes resulting from the bimodal distribution as well as from equivalent mono-modal drop size distributions were obtained and compared. Results indicate that the ice shapes resulting from the bimodal drop size distributions had higher mass and volume values than their mono-modal distribution equivalents as well as having icing limits that extended further back on the chord of the model.

Aircraft↗
NASA NTRS2019

Long-Term Impacts of Selective Logging on Amazon Forest Dynamics from Multi-Temporal Airborne LiDAR

Forest degradation is common in tropical landscapes, but estimates of the extent and duration of degradation impacts are highly uncertain. In particular, selective logging is a form of forest degradation that alters canopy structure and function, with persistent ecological impacts following forest harvest. In this study, we employed airborne laser scanning in 2012 and 2014 to estimate three-dimensional changes in the forest canopy and understory structure and aboveground biomass following reduced-impact selective logging in a site in Eastern Amazon. Also, we developed a binary classification model to distinguish intact versus logged forests. We found that canopy gap frequency was significantly higher in logged versus intact forests even after 8 years (the time span of our study). In contrast, the understory of logged areas could not be distinguished from the understory of intact forests after 6–7 years of logging activities. Measuring new gap formation between LiDAR acquisitions in 2012 and 2014, we showed rates 2 to 7 times higher in logged areas compared to intact forests. New gaps were spatially clumped with 76 to 89% of new gaps within 5 m of prior logging damage. The biomass dynamics in areas logged between the two LiDAR acquisitions was clearly detected with an average estimated loss of -4.14 +/- 0.76 MgC/hay. In areas recovering from logging prior to the first acquisition, we estimated biomass gains close to zero. Together, our findings unravel the magnitude and duration of delayed impacts of selective logging in forest structural attributes, confirm the high potential of airborne LiDAR multitemporal data to characterize forest degradation in the tropics, and present a novel approach to forest classification using LiDAR data.

Pinage, Ekena Rangel↗
NASA NTRS2017

Bimodal SLD Ice Accretion on a NACA 0012 Airfoil Model

An initial ice shape database has been created to document ice accretions on a 21-inch chord NACA 0012 airfoil model resulting from an exposure to a Supercooled Large Droplet (SLD) icing cloud with a bimodal droplet distribution. The ice shapes created were documented with photographs, laser scanned surface measurements over a section of the model span, and measurement of the ice mass over the same section of each accretion. The icing conditions used in the test matrix were based upon previously measured ice shapes on the same model to connect the current database to previously measured information. Ice shapes resulting from the bimodal distribution as well as from equivalent standard droplet distributions were obtained and compared. Results indicate that the ice shapes resulting from the bimodal droplet distributions had higher mass and volume values than their standard distribution equivalents as well as having icing limits that extended further back on the chord of the model.

aircraft icing↗
NASA NTRS2019

Frostwing Co-Operation in Aircraft Icing Research

e aerodynamic effects of Cold Soaked Fuel Frost have become increasingly significant as airworthiness authorities have been asked to allow it during aircraft take-off. The Federal Aviation Administration and the Finnish Transport Safety Agency signed a Research Agreement in aircraft icing research in 2015 and started a research co-operation in frost formation studies, computational fluid dynamics for ground de/anti-icing fluids, and de/anti-icing fluids aerodynamic characteristics. The main effort has been so far on the formation and aerodynamic effects of CSFF. To investigate the effects, a generic high-lift common research wind tunnel model and DLR-F15 airfoil, representing the wing of a modern jet aircraft, was built including a wing tank cooling system. Real frost was generated on the wing in a wind tunnel test section and the frost thickness was measured with an Elcometer gauge. Frost surface geometry was measured with laser scanning and photogrammetry. The aerodynamic effect of the frost was studied in a simulated aircraft take-off sequence, in which the speed was accelerated to a typical rotation speed and the wing model was then rotated to an angle of attack used at initial climb. Time histories of the lift coefficient were measured with a force balance. The experiments showed that depending on the ambient temperature the frost may evaporate/melt during the take-off sequence. Lift losses after rotation with CSFF contamination at ambient temperatures of 4˚ to 7˚C above freezing point were measured to be 4 to 5 % for roughness values, k/c, below 10(exp -3). For comparison, lift loss tests with typical anti-icing fluids were to roughly equal lift losses. This paper gives an overview of the performed activities.

Koivisto, Pekka↗