Comparison of Guidance Modes for the AUV “Slocum Glider ” in Time-Varying Ocean Flows

Abstract — This paper presents possibilities for the reliable guidance of an AUV “Slocum Glider ” in a time-varying oceans flows. The presented guidance modes consider the restricted information during a real mission about the actual position and ocean current conditions as well as the available control modes of a glider. A faster-than-real-time, full software stack simulator for the Slocum glider will be described in order to test the developed guidance modes under real mission conditions. Keywords—component; AUV “Slocum Glider”; Path Planning; Glider Simulator; Time-Varying Ocean Flows; Dead Reckonin

Utilizing Additive Manufacturing of Semi-Crystalline Thermoplastics and Topology Optimized Generative Designs for Complex Small Satellite Bus Geometries

Small satellite buses have traditionally been manufactured through subtractive means and ultimately limiting capability in feature, form, and an inability to alter the volumetric density of the material. However, emergent additive manufacturing methods that utilize Fused Deposition Modeling (FDM) integrated with soluble support material allow us to print synthetic thermoplastics, such as Polyetheretherketone (PEEK). Consequently, the number of structural parts and hardware components is reduced, along with the cost. Structural strength and dimensional stability of PEEK are comparable to traditional aluminum alloys in the construction of most satellite components. Additive manufacturing further allows the implementation of topology optimization algorithms to develop and produce complex geometries with resolutions up to 5μm in x/y movements and 1μm in z movements. Thermoplastics possess ideal strength to weight ratios and thermal expansion coefficients that can be exploited to design more desirable components of small satellite buses. We believe that topology-optimized, 3D-printed small satellite frames made from PEEK can offer a lighter alternative to their metal alloy counterparts. To show this, we will demonstrate the generative optimization of the SPectral Ocean Color (SPOC) satellite’s 3U frame and compare its structural, thermal, and modal analysis simulations to those of an optimized design

Decay of oil residues in the soil is enhanced by the presence of Spartina alterniflora, with no additional effect from microbiome manipulation

Recent work has suggested that the phytoremediation potential of S. alterniflora may be linked to a selection by the plant for oil-degrading microbial communities in the soil, in combination with enhanced delivery of oxygen and plant enzymes to the soil. In salt marshes, where the soil is saline and hypoxic, this relationship may be enhanced as plants in extreme environments have been found to be especially dependent on their microbiome for resilience to stress and to respond to toxins in the soil. Optimizing methods for restoration of oiled salt marshes would be especially meaningful in the Gulf of Mexico, where there is a persistently high threat of petroleum contamination. One favorable strategy for restoration of oiled sites might include planting S. alterniflora with a microbiome that has been pre-selected for an oiled environment. We examined this strategy with a two-year greenhouse experiment and found that planting S. alterniflora in an oiled environment enhances decomposition of oil residues without a clear negative impact on plant growth. Manipulation of the S. alterniflora microbiome through soil inoculation and through exposure to oil residues, elicited a detectable response of soil prokaryote communities to the presence of oil, while only demonstrating an analogous response in fungal communities in the plant roots and leaves. Yet, manipulation of the plant microbiome did not change plant morphology or relative decomposition of polycyclic aromatic hydrocarbons (PAHs) in the soil. Therefore, despite evident relationships between the plant, microbes, and oil, manipulation of the microbiome may not be a worthwhile addition to S. alterniflora phytoremediation strategies. Nevertheless, our work adds support for replanting S. alterniflora in oiled salt marshes as an effective strategy for reducing oil residues in salt marshes, in addition to the re-vegetation and erosion reduction benefits demonstrated by others