Robert Haehnel

Comparison of Finite Element Model (FEM) Data and Single Point Layered Elastic Model (SPLEM) Data of a C130 Operating on a Frozen Runway Structure

A 3-D Finite Element Model (FEM) was constructed of a loaded C130 tire rolling over a frozen unpaved runway. The runway was constructed of two layers, one frozen and one unfrozen, each of varying thickness, but the combined thickness was fixed. The material model used in the dynamic FEM simulation represents a frostsusceptible soil, which was used in full scale unpaved road tests at CRREL’s Frost Effects Research Facility (FERF), and was calibrated with triaxial tests and validated against direct shear test data. The area of interest in both models is the interaction between the frozen (top) layer and the unfrozen (bottom) layer. Stress and strain data collected from the dynamic FEM simulation and a prior single point layered elastic (SPLEM) simulation were compared, along with the capabilities of each model. Initial findings show that the single point layered elastic model is much faster at obtaining results for a single point, but it can only solve problems with pure elastic material. The FE model can solve problems with any material and the results can be viewed at any location or point in time during the run. The FEM visually represents what is happening in the soil around the tire as it rolls along the surface, while the static SPLE model only predicts what is occurring directly below the tire.

Feasibility of using alternate fuels in the U.S. Antarctic Program : initial assessment

Currently, the U.S. Antarctic Program (USAP) has standardized using AN8 fuel for all air operations and the majority of its ground based operations. The freeze-point (FP) specification for AN8 is −58°C. The U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) conducted an analysis of the air temperature history at McMurdo, South Pole, and the WAIS (West Antarctic Ice Sheet) Divide camp to determine if USAP could feasibly use alternate, less expensive aircraft fuels. Also, to provide context, this report details the USAP fuel purchasing methodology and price calculation. JP-8 (and Jet A-1) has an FP specification of −47°C, which is well below the minimum average daily air temperature at McMurdo (−40°C) and is also below the storage temperature of the fuel at South Pole (−45°C). The estimated fuel temperature at the WAIS Divide camp is above the FP of JP-8 during the operational season. Based on these findings, it may be possible to use JP-8 to replace ground-based applications where AN8 is currently used. Evidence suggests that JP-8 can replace the AN8 used for all flight operations, also. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/CRREL TR-17-15 iii

Changes in the albedo of the Pegasus and Phoenix Runways, 2000–2017

Albedo is the ratio of total hemispherical reflected (upwelling) to incoming (downwelling) radiative flux (or irradiance) at a surface. For operations on the McMurdo Ice Shelf, Antarctica, albedo is a controlling factor. Impurities such as dust, soot, mineral, and other organic deposits on a snow or ice surface can dramatically lower albedo, increase solar energy absorption in the ice shelf, and significantly alter the energy balance, resulting in increased melting, snow density variations, and compromised structural integrity of the snow and ice matrix. The occurrence of such impurities at Pegasus Runway may have been a factor in its decline and replacement with the Phoenix Runway in the 2016–2017 field season. Therefore, the National Science Foundation (NSF) requested that the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) establish a longterm record of surface albedo at the Pegasus and Phoenix Runway sites. To accomplish this, data from the National Aeronautics and Space Administration (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) satellite was used. MODIS satellite data has a daily temporal resolution and a significant period of record (2000–present). Additionally, its narrowband surface reflectance may be used as a proxy for albedo. This report documents the results of these analyses. ERDC/CRREL TR-17-10 iii