@article{yoder_gemmer_mazzoleni_2019, title={Modelling and performance analysis of a tether and sail-based trajectory control system for extra-terrestrial scientific balloon missions}, volume={160}, ISSN={["1879-2030"]}, DOI={10.1016/j.actaastro.2018.12.030}, abstractNote={Balloon systems show great promise for exploring the atmospheres of extra-terrestrial bodies in the solar system. The balloon system concept was demonstrated by the aerostats aboard the Vega 1 and 2 missions sent to Venus. Such systems glean propulsion from atmospheric winds, and at present are unable to travel in a direction perpendicular to the direction of the wind, limiting their exploration potential. A control system capable of modifying the system trajectory by traveling in a direction perpendicular to the direction of the wind is desired to increase exploration potential as well as to perform tasks such as maintaining latitude. A balloon and sail system which can use wind velocity and density gradients to produce a guiding force perpendicular to the velocity of the wind is discussed here. Such a guidance system is passive in nature and requires little power for actuation and control. It was previously demonstrated that such a control system is capable of generating guiding velocities of several meters per second within the Venusian atmosphere. Furthermore, this control system was shown to be capable of achieving sufficient control for the majority of the latitudes on Venus. This work builds on previous results and demonstrates the benefits of being able to generate guiding velocities via a sail system by viewing the trajectories taken by planetary balloon systems employing such a system. First, a description of the system model is given. Next, for the atmospheres of Venus and Titan, trajectory control is demonstrated for various sail parameters, such as sail size and mass. The benefit of such control is shown by the ability to achieve various latitudes of interest for a given flight duration. These latitudes are chosen based on geographic features, such as lakes on Titan. Finally, a PI controller is added to the model to demonstrate rudimentary control of the balloon system for maintaining and changing latitudes. A brief discussion regarding the control law of the system is also provided.}, journal={ACTA ASTRONAUTICA}, author={Yoder, Christopher D. and Gemmer, Thomas R. and Mazzoleni, Andre P.}, year={2019}, month={Jul}, pages={527–537} }
 @article{gemmer_yoder_reedy_mazzoleni_2017, title={Tether enabled spacecraft systems for ultra long wavelength radio astronomy}, volume={138}, ISSN={["1879-2030"]}, DOI={10.1016/j.actaastro.2016.11.009}, abstractNote={This paper describes a proposed CubeSat mission to perform unique experiments involving interferometry and tether dynamics. A 3U CubeSat is to be placed in orbit where it will separate into three 1U CubeSats connected by a total of 100 m of tether. The separation between the three units will allow for the demonstration of high resolution radio interferometry. The increased resolution will provide access to the Ultra-Long Wavelength (ULW) scale of the electromagnetic spectrum, which is largely unexplored. During and after completion of the primary experiment, the CubeSat will be able to gather data on tethered dynamics of a space vehicle. Maneuvers to be performed and studied include direct testing of tether deployment and tethered formation flying. Tether deployment is a vital area where more data is needed as this is the phase where many tethered missions have experienced complications and failures. There are a large number of complex dynamical responses predicted by the theory associated with the deployment of an orbiting tethered system. Therefore, it is imperative to conduct an experiment that provides data on what dynamic responses actually occur.}, journal={ACTA ASTRONAUTICA}, author={Gemmer, Thomas and Yoder, Christopher D. and Reedy, Jacob and Mazzoleni, Andre P.}, year={2017}, month={Sep}, pages={530–535} }
 @inproceedings{denhart_gemmer_ferguson_mazzoleni_2014, title={A concept selection framework for early sorting of reconfigurable system designs}, DOI={10.1115/detc2013-13222}, abstractNote={A seven-step framework for sorting proposed concepts of system changes / reconfigurations is presented that seeks to characterize the overall ramifications on system architecture. This framework is intended for use immediately following a concept generation phase. The framework uses three simple questions: “What level of the system design does this concept apply to?” “What levels of the system design does the concept impact?” and “What is the severity of this impact?” A flowchart leads the designer through these questions and assigns each concept a classification from one to five based on the answers. Class one concepts have little to no impact on the rest of the system architecture. They can be included with little fear of massive change propagation and system redesign. Class five concepts carry large changes to system architecture and therefore should be included only if they can be shown to be highly beneficial, or if there remains enough design freedom such that the cost of changing the system architecture is minimal. Meanwhile, class five concepts are likely to have much higher potential to create revolutionary design. A case study is used to demonstrate the application of the sorting framework in the context of a Mars rover mission. Several example concepts are provided to illustrate key insights from the case study. Convergence of the framework is explored by comparing the authors’ results to a second test done by a new design team.}, booktitle={Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 2013, vol 3B}, author={Denhart, J. and Gemmer, T. and Ferguson, S. and Mazzoleni, A.}, year={2014} }