Steve R. Best

Design of a surface-scanning coil detector for direct bacteria detection on food surfaces using a magnetoelastic biosensor

The real-time, in-situ bacteria detection on food surfaces was achieved by using a magnetoelastic biosensor combined with a surface-scanning coil detector. This paper focuses on the coil design for signal optimization. The coil was used to excite the sensors vibration and detect its resonant frequency signal. The vibrating sensor creates a magnetic flux change around the coil, which then produces a mutual inductance. In order to enhance the signal amplitude, a theory of the sensors mutual inductance with the measurement coil is proposed. Both theoretical calculations and experimental data showed that the working length of the coil has a significant effect on the signal amplitude. For a 1 mm-long sensor, a coil with a working length of 1.3 mm showed the best signal amplitude. The real-time detection of Salmonella bacteria on a fresh food surface was demonstrated using this new technology.

Design of a Low-Energy FARAD Thruster

The design of an electrodeless thruster that relies on a pulsed, rf-assisted discharge and electromagnetic acceleration using an inductive coil is presented. The thruster design is optimized using known performance scaling parameters and experimentally-determined design rules, with design targets for discharge energy, plasma exhaust velocity, and thrust efficiency of 100 J/pulse, 25 km/s, and 50%, respectively. Propellant is injected using a high-speed gas valve and preionized by a pulsed-RF signal supplied by a vector inversion generator, allowing for current sheet formation at lower discharge voltages and energies relative to pulsed inductive accelerators that do not employ preionization. The acceleration coil is designed to possess an inductance of at least 700 nH while the target stray (noncoil) inductance in the circuit is 70 nH. A Bernardes and Merryman pulsed power train or a pulse compression power train provide current to the acceleration coil and solid-state components are used to switch both powertrains.

Direct-Drive Performance of a T-100 HET Powered by Triple Junction, High-Voltage Concentrator PV Array

Auburn University’s Space Research Institute working with Entech Solar, Inc. has been conducting a “direct drive” experiment using a high-voltage (600 Voc), III-V multijunction Entech Solar SunLine concentrator array coupled to a Russian T-100 Hall Effect Thruster. This possibly is the first time III-V-based multi-junction solar cells have been used to run a Hall thruster powered directly at high voltage. This paper will discuss the set-up and testing results. Testing included the addition of Entech Solar’s Stretched Lens Array hardware in a vacuum chamber to measure plume impingement effects at various positions relative to the exhaust axis of the thruster.

A plasma drag hypervelocity particle accelerator (HYPER)

Abstract Current debris models are able to predict the growth of the space debris problem and suggest that spacecraft must employ armor or bumper shields for some orbital altitudes now and that the problem will become worse as a function of time. The practical upper limit to the velocity distribution is on the order of 40 km/s and is associated with the natural environment. The velocity distribution of the man-made component peaks at 9–10 km/s with maximum velocity in the 14–16 km/s range. Experience in space has verified that the “high probability of impact” particles are in the microgram to milligram range. These particles can have very significant effects on coatings, insulators, and thin metallic layers. The surface of thick materials becomes pitted and the local debris component is enhanced by ejecta from the impact events. In this paper, the HYPER facility is described which produces a reasonable simulation of the man-made space debris spectrum in a controlled environment. The facility capability is discussed in terms of drive geometry, energetics, velocity distribution, diagnostics, and projectile/debris loading. The facility has been used to study impact phenomena on Space Station Freedoms solar array structure, the calibration of space debris collectors, other solar array materials, potential structural materials for use in the space, electrical breakdown in the space environment, and as a means of clarifying or duplicating the impact phenomena on surfaces which have been exposed in space.

Comparison of solar modeling data to actual PV installations: Power predictions and optimal tilt angles

Solar tracking mechanisms were developed to maximize the energy yield of solar cells. Software models can help predict the optimum tilt angle to point the single axis tracker for maximum energy output for the entire year. We used modeling programs to predict the optimal angle and for this region they do not agree. In 2009 Auburn University designed and built a test structure that allowed us to conduct comparison of these models. There are six test panels, five panels are rotated in a single axis azimuthally at the tilt angles of 20°, 25°, 32° (latitude), 40°, and 50°. Another panel is a fixed control panel facing south at latitude tilt. The system has collected data for over one year. Also data collected at the Lee Countys T.K. Davis Justice Centers 16.6 kW grid-connected solar array system is compared to the performance data to the results of three photovoltaic modeling programs used before and during installation of the system. This research will shed light on the accuracy of modeling programs and discuss reasons behind program results variations.

Accomplishments and objectives of the Stretched Lens Array Technology Experiment (SLATE)

This study presents the design and fabrication of the Stretched Lens Array Technology Experiment (SLATE). SLATE is a radiation-hardened solar array flight experiment to be flown in the Van Allen radiation belts and provide flight validation for the Stretched Lens Array (SLA). TacSat 4 is due to be launched in September, 2009 into a high radiation orbit (700 km × 12,050 km, 63.4°). This orbit will provide valuable solar cell degradation information along with proving flight validation for the Stretched Lens Array. In addition, a photovoltaic curve tracer Data Acquisition System (DAS) prototype was designed and built using a new flexible architecture. This project is part of Phase II of a MDA STTR project entitled, “Radiation-Hardened Stretched Lens Array,” with Entech Solar, Inc.

Analysis and Simulations of Low Power Plasma Blasting for processing Lunar Materials

A prototype blasting power system suitable for excavation on the moon’s surface was constructed and tested in the Space Research Institute (SRI) facilities. Such a system incorporates the use of electrically powered plasma blasting via a blasting probe and comprises a capacitor bank which is charged with a power supply at a relatively low rate (e.g. a few seconds) and then discharged at a very high rate (power pulse of tens of microseconds), generating a shock wave on a sample solid substance causing its fracture. After successfully testing the blasting power system and blasting probes, breaking specimens with masses of up to 850kg, 2-D and 3-D numerical simulations were carried out in order to correlate the experimental data of several samples of concrete cylinders. It is possible with a non-linear hydro-code numerical approach to simulate the rapid discharge into high peak power transient loads which eventually break the specimens.

A Low Power Approach for Processing Lunar Materials

An attractive alternative method of surface blasting for excavation on the moon’s surface could incorporate the use of electrically powered plasma blasting. Such a technique also allows easily adjusted explosive yield control for additional safety. This paper discusses the design, construction, and performance of a prototype plasma blasting power system and blasting probes. Electrical storage devices such as capacitors are charged slowly, and then rapidly discharged into high peak power transient loads. A Bernardes-Merryman (BM) capacitor bank configuration was used as a voltage reversal protection scheme. Tests on concrete and granite rock samples are reported. Blasting probe design effects to deliverable energy is also discussed.

Comparison of Photovoltaic Modeling Analysis and Actual Performance Data of Lee County Justice Center Solar Power Installation Project

This paper will discuss the installation of photovoltaic panels to Lee County’s TK Davis Justice Center (LCJC) in Lee County, Alabama in the city of Opelika. This project consists of installing a 16.6 kW grid-connected solar-powered system that will be used to offset the energy costs of electricity used by the LCJC. The project monitors the performance of the system along with weather and environmental factors. Information gathered through the system’s design, installation, and monitoring provides valuable information concerning photovoltaic alternative energy systems on public facilities. By using different mounting options and tilt angles the project is a learning tool and showcase for potential solar array installations at other facilities. This paper will take the data collected at the Lee County’s T.K. Davis Justice Center 16.6 kW grid-connected solar-powered system and analyze it to find trends and anomalies. The analyses will include performance with insolation, especially early and late in the day, average overall operating efficiency and AC performance. Most importantly it compares the performance data to the results of photovoltaic modeling programs that were used before and during installation of the system. We wish to determine how accurate these modeling programs are and to determine the reasons behind variations between program results. We are also documenting the success story of Alabama’s first State Government sponsored PV energy project. It serves as a model of how local governments can be a leading example of how to increase energy-efficiency, be environmentally friendly, and reduce operational costs over the long-term.

Pulsed powered plasma blasting for lunar materials processing

This paper discusses the design, construction, and performance of a prototype plasma blasting power system and blasting probes. In this system, a capacitor is charged over a long period of time at low current (power), then discharged in a very short pulse at very high current to break blocks of concrete or large rocks. Scalable prototypes of the plasma blasting probes for electrically powered pulsed plasma rock blasting were also designed and constructed. The blasting system is able to provide pressures well above the tensile strengths comparable to those of common rocks, i.e. granite (10-20 MPa), tuff (1-4 MPa) and concrete (7 MPa). The system was successfully tested by reducing concrete specimens into small rubble with blasting probe delivered net energy levels starting at 9 kJ and greater. Tests on concrete and granite rock test samples are reported.