Development of a Modeling Capability for Energy Harvesting Modules in Electrodynamic Tether Systems

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90615/1/AIAA-2011-7323-271.pd

Investigating Miniaturized Electrodynamic Tethers for Picosatellites and Femtosatellites

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143110/1/1.A33629.pd

High Aspect Ratio Carbon Nanotube Membranes Decorated with Pt Nanoparticle Urchins for Micro Underwater Vehicle Propulsion via H2O2 Decomposition

The utility of unmanned micro underwater vehicles (MUVs) is paramount for exploring confined spaces, but their spatial agility is often impaired when maneuvers require burst-propulsion. Herein we develop high-aspect ratio (150:1), multiwalled carbon nanotube microarray membranes (CNT-MMs) for propulsive, MUV thrust generation by the decomposition of hydrogen peroxide (H2O2). The CNT-MMs are grown via chemical vapor deposition with diamond shaped pores (nominal diagonal dimensions of 4.5 × 9.0 μm) and subsequently decorated with urchin-like, platinum (Pt) nanoparticles via a facile, electroless, chemical deposition process. The Pt-CNT-MMs display robust, high catalytic ability with an effective activation energy of 26.96 kJ mol–1 capable of producing a thrust of 0.209 ± 0.049 N from 50% [w/w] H2O2 decomposition within a compact reaction chamber of eight Pt-CNT-MMs in series

Enabling Ultra-small Sensor Spacecraft for the Space Environment using Small-Scale Electrodynamic Tethers

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90614/1/AIAA-2011-7322-799.pd

Coupling between a glacier and a soft bed: I. A relation between effective pressure and local shear stress determined from till elasticity

To predict the distribution of motion beneath glaciers on soft beds, the strength of the coupling between the ice and the bed and its variation with effective pressure must be known. A record of shear strain, acquired with a tiltmeter emplaced in till beneath Storglaciären, Sweden, indicates that fluctuations in water pressure cause variations in the local shear stress on the bed and that the bed deforms elastically in response to these variations. To estimate the shear stress from the elastic component of the total shear strain, the shear modulus of the till was measured in relaxation tests conducted in the laboratory with a ring-shear device. After accounting for the elastic compliance of the device, these tests yielded shear moduli of about 1000 and 1800 kPa at confining pressures of 85 and 280 kPa, respectively. These values are comparable to those of other granular materials undergoing recoverable shear strains of the same magnitude. The local shear stress on the till, calculated by applying the measured shear moduli to the tilt record, scales with ? e 1.7, where P e is the effective pressure. This relation implies that as P e decreases at the ice/till interface, shear stresses on the till are reduced and concentrated elsewhere on the bed, perhaps where the till is absent or the glacier is frozen to the bed. When compared with the strength of the till determined from ring-shear tests, this relation also accounts for the lack of permanent deformation at depth in the bed during periods of low P e and indicates that most basal motion was by sliding or ploughing

Note: Thermal analog to atomic force microscopy force-displacement measurements for nanoscale interfacial contact resistance

Thermal diffusion measurements on polymethylmethacrylate-coated Si substrates using heated atomic force microscopy tips were performed to determine the contact resistance between an organic thin film and Si. The measurement methodology presented demonstrates how the thermal contrast signal obtained during a force-displacement ramp is used to quantify the resistance to heat transfer through an internal interface. The results also delineate the interrogation thickness beyond which thermal diffusion in the organic thin film is not affected appreciably by the underlying substrate

Current Collection to and Plasma Interaction with Femtosatellite- and CubeSat-Scale Electrodynamic Tether Subsystems

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97119/1/AIAA2012-5295.pd

Origami: Numerical Solutions of Apparent Absorptivity in Origami Folds

There are three major types of heat transfer: conduction, convection, and radiation. In many cases, radiation is ignored due to the fact that the amount of heat transferred by this method tend to be small compared to conduction and convection. However, in space and in some settings on earth, radiation is dominant and important. Absorptivity is a measure of an object’s ability to absorb radiation, and apparent absorptivity is a measure of how the shape of an object affects the amount of radiation that it absorbs. For example, if you were to shine a flashlight on a mirror, the light will hit the mirror once and bounce off. The tiny fraction of the light that the mirror absorbed would be the absorptivity. Now imagine that you had two parallel mirrors such as the mirrors that are located in the sealing room of an LDS temple. If you then were to shine a flashlight at these mirrors, it is possible that the light would bounce back and forth many times, with the mirrors absorbing a little bit of light each time. This greater fraction of light absorbed because of how the mirrors are arranged would be the apparent absorptivity. In the past, researchers have come up with ways to calculate the apparent absorptivity of very simple shapes, like the V-groove shown in Figure 1. However, with more complicated shapes like the origami fold called the Miura fold, coming up with an exact equation would be impossible. However, computer programs can help solve for the apparent absorptivity of surfaces using mathematical techniques called numerical methods, which can help scientists and engineers design satellites that will not overheat or freeze in space

Passive CubeSat Probes for Affordable, Low-Risk Inspection of Space Vehicles

Effective fault detection is vital for safe and reliable spacecraft performance. Traditionally, developers have relied almost exclusively on on-board instrumentation to detect faults in spacecraft performance. Remote inspection can provide a holistic complement to on-board instrumentation, but it is seldom incorporated into spacecraft missions due to its cost and risk. As a result, multiple spacecraft have been lost due to unchecked faults in areas without instrumentation