The 2016 Wisconsin Space Grant Consortium Elijah High Altitude Balloon Launch Team was comprised of students from the Milwaukee School of Engineering, UW-Fox Valley, and Carthage College. This year, a majority of the students involved were discovering the balloon launch experience for the first time. The 2016 Elijah Balloon Launch Team held a meeting for the new members to learn how all of the equipment worked through a practice run using the tools in a trial. The flight location was based on launch predictions ran in the week leading up to the launch. The balloon was launched from Clinton, Wisconsin, and landed near Darien, WI. This launch did not follow the launch prediction as accurately as expected, but the payload was recovered in safely and in good condition and launch reached a peak altitude of 31,021m, which was above our goal of 30,480m. Therefore, the launch was deemed successful.

The 2015 Wisconsin Space Grant Consortium Elijah High Altitude Balloon Launch Team was comprised of three students from Milwaukee School of Engineering and one student from Ripon College. This year, all members of the team had experience with high altitude balloon launches due to previous participation on either the Elijah Payload or Launch Team, or both. A training session was hosted by the 2014 Elijah Launch Team to familiarize the new team with the physical set up of a launch train as well as how to run track predictions and how to read the jet stream charts. Launches were planned for both Carthage College and the Elijah High Altitude Balloon Payload Team, but only the launch for the Payload Team came to fruition. This launch was successful, reaching a peak altitude of 31,021m. IntroductionThe purpose of the 2015 Wisconsin Space Grant Consortium (WSGC) Elijah Balloon Launch program was to provide four students from WSGC affiliate universities with the opportunity to organize and launch high altitude weather balloons in order to fly science experiments in nearspace environments. The team was responsible for coordinating with the WSGC Elijah Balloon Payload design team in order to create and execute a flight plan in order to carry the payload constructed by the design team to an altitude of approximately 31,000m in elevation.

Acoustic levitation is an advantageous particle positioning mechanism currently employed for applications of x-ray spectroscopy and micro-material manufacturing[1], [2]. By levitating a particle using only acoustic pressure waves, one eliminates the need for a container or other physical structure which may contaminate the specimen. Unfortunately, the pressure field generated by a standing acoustic wave is susceptible to periodic instabilities, and a particle that is levitated in this field tends to vibrate. The amplitude of the vibration is largest in the directions that are orthogonal to the axis in which the acoustic wave is generated. Therefore, by generating additional acoustic waves in each orthogonal axis, the vibration amplitude of the levitated particle is significantly reduced. The authors have shown this phenomenon to be true in a previous study[3]. In this paper, the authors explore the details of the pressure field that is generated with the device. A single degree-of-freedom relationship is developed between the acoustic field pressure, the location of the levitated particle, and the mechanical vibration needed to produce levitation. In order to levitate a 100 micrometer diameter water droplet at 55 kilohertz, the calculations suggest that the transducer must achieve an average surface vibration amplitude of at least 6.43 micrometers. This mechanical vibration must produce a root means-squared pressure amplitude of 933 Pascal. Under these conditions, the particle will levitate approximately 0.4 millimeters below a zero pressure node. To validate the use of the single degree of freedom relationships and to explore the acoustic field for one, two, and three-axis levitation, the authors designed and prototyped an acoustic levitator capable of generating standing waves in three orthogonal directions. Using a simple electrical control circuit, the acoustic wave transducers of each axis can be turned on individually or simultaneously. An experiment was developed to measure the pressure of the acoustic field using a microphone. Preliminary pressure magnitude results were measured for one-axis levitation along the center of the vertical axis of the levitator. The measurements suggest that the theoretical development provides a valid first approximation for the pressure magnitude and required mechanical vibration amplitude.