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Permanent URI for this communityhttps://hdl.handle.net/20.500.14288/2
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Publication Metadata only An experimental study on predicting the mass flow rate of self-pressurizing oxidizers through injectors(American Institute of Aeronautics and Astronautics Inc, AIAA, 2021) Kara, Ozan; Department of Mechanical Engineering; N/A; Karabeyoğlu, Mustafa Arif; Karpat, Miray; Faculty Member; Master Student; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; 114595; N/ASelf-pressurizing propellants are recently gaining attention, specifically in hybrid rocket propulsion systems. Use of self-pressurizing propellants reduces system complexity and overall weight due to their high vapor pressure. N2O has been used widely as an oxidizer since it has a vapor pressure of approximately 5 MPa (730 psi) at room temperature. However, because they operate near or at saturation line, their flow exhibits two-phase behaviour. Therefore, it is difficult to model the feed system and injector flows. A method to predict the two-phase critical mass flow rate has been proposed. In addition, an experimental setup has been designed for validation of the proposed model. Multiple cold flow tests using nitrous oxide has been performed, and data obtained have been compared to that predicted by the two-phase critical flow model. Results have been showed that the proposed model estimates the actual mass flow rate within an error range of 6 to 17%.Publication Metadata only Challenges in the development of large-scale hybrid rockets(Begell House Inc, 2017) N/A; Department of Mechanical Engineering; Karabeyoğlu, Mustafa Arif; Faculty Member; Department of Mechanical Engineering; College of Engineering; 114595Advanced hybrid rockets, which combine fast burning fuels, composite motor construction, and innovative internal ballistic design, have the capability to deliver high performance while retaining the cost, environmental, and simplicity advantages of the classical hybrids. This makes hybrid rocket propulsion a tipping point technology in the sense that a small, short-term investment could have game-changing consequences in the development of green, safe, affordable, and high-performance systems needed for future space missions. In order to demonstrate the advantages of hybrids most effectively, the effort should be concentrated on improving the technology readiness level of the technology for a carefully selected class of missions. That being said, some serious challenges still exist in the development of operational motors, even for applications highly suitable for hybrid propulsion. These challenges, some perceived whereas others are very real, are carefully outlined in this paper. The real-life importance of each challenge is also discussed, along with potential methods to mitigate these issues. The ultimate strategy in the elimination of any practical challenge is that the solution should not compromise the simplicity, cost, and safety advantages of classical hybrid rockets. The solution methodology should be an iterative process that involves a well-balanced combination of theoretical modeling, numerical simulations, and actual motor testing.Publication Metadata only Control of bistable structures using a modified hybrid position feedback controller(American Institute of Aeronautics and Astronautics Inc, AIAA, 2022) Schieni, Rick; Cunis, Torbjørn; Bilgen, Onur; Burlion, Laurent; Şimşek, Mehmet Ramazan; PhD Student; Graduate School of Sciences and Engineering; N/ABistable structures show promise for morphing applications as they have the capability of obtaining two stable shapes which do not require energy to be maintained. The vibration of a bistable structure has been modelled previously as a Duffing-Holmes oscillator. To control the motion of a bistable structure from one equilibrium point to the other, a hybrid unstable-then-stable position feedback controller has been successfully employed. The hybrid controller destabilizes the structure around the initial equilibrium position then stabilizes it around the second equilibrium point. Previously, the decision to switch from destabilization mode to stabilization mode is made based upon the position of the structure. In the present research, new methods for determining when to activate and deactivate the stabilizing and destabilizing control schemes are presented. The proposed methods employ optimization techniques, model predictive control, and energy methods to determine when to activate or deactivate each scheme. Results of numerical simulations for the proposed switching methods are presented in this work.Publication Restricted Design & analysis and development of turbine system for hybrid rocket applications(Koç University, 2022) Atasoy, Mert; Karabeyoğlu, Mustafa Arif; 0000-0002-5071-6133; Koç University Graduate School of Sciences and Engineering; Mechanical Engineering; 114595Publication Metadata only Effect of pressure loss devices on the performance of hybrid rocket systems(International Astronautical Federation (IAF), 2018) N/A; Department of Mechanical Engineering; Karabeyoğlu, Mustafa Arif; Faculty Member; Department of Mechanical Engineering; College of Engineering; 114595Internal ballistic devices that are used to trip the gas flow such as blades, steps, diaphragms or screens are commonly implemented in hybrid rocket motors to improve the mixing in the system. Enhanced mixing typically leads to an improvement in the regression rates and combustion efficiencies. The major issues with the use of these elements are 1) the pressure drop associated with the gas flow over these obstacles, 2) additional weight and 3) additional system complexity and cost. Even though a total pressure drop leads to a reduction in the thrust specific fuel consumption for air breathing propulsion systems, rockets do not suffer a direct hit on their specific impulse. The objective of this paper is to outline a theoretical proof that any pressure drop encountered along the motor axis does not lead to a reduction in the thrust or specific impulse performance of the rocket system. The primary adverse effect of the pressure loss is on the structural mass fraction of the rocket system. Assuming that the pressure at the nozzle entrance does not change, pressure drop requires higher head end pressures leading to increased injector manifold and feed system pressures. Using some example cases, we have estimated the combustion efficiency improvement required to balance the structural mass fraction increase caused by the flow trip devices. Such analysis needs to be conducted to justify the use of pressure drop elements for each design. Even though these arguments were developed for hybrid rockets, the analysis and conclusions are valid for all other chemical rocket types as well (i.e. solids and liquids).Publication Metadata only Electric propulsion optimization of microsatellite moon missions preliminary design application on CubeSats and Turkish small satellite field(International Astronautical Federation (IAF), 2014) N/A; N/A; Department of Mechanical Engineering; Kara, Ozan; Karabeyoğlu, Mustafa Arif; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 114595Subsystems miniaturization of spacecraft is making scientific microsatellite missions feasible. Specifically interplanetary space exploration mission can be provided by onboard micro propulsion systems. Due to the low requirements, Moon is a feasible destination for a preliminary space mission that universities, companies and governments can perform. This paper addresses the optimization of an electric propulsion system for a potential microsatellite lunar mission. Optimization takes the thrust level as a free variable to find the minimum initial mass along with the associated total burn time. The initial thrust range is chosen between 0.5-6mN. For a given thrust value, corresponding specific impulse, thruster power and thruster mass are determined based on curve fittings. As the next step, the input thrust level is extended up to 42mN to observe optimization over a broader thruster size. A feasible low thrust continuous orbit transfer to the Moon requires a high ΔV which is over 7,000 m/s. Edelbaum's analysis with optimal control theory is utilized to estimate the ΔV value. Edelbaum presents an approach for two non-coplanar circular orbits without any perturbations and shadowing effects. Furthermore, the optimization approach is applied for the preliminary design of a CubeSat Moon Mission. The spacecraft is determined to have an initial mass of 12 kg and requires a total power up to 100W. The particular mission selected for the study starts at 700km LEO and finishes at 200 km LLO. In addition, preliminary mission design presents (1) mass and power budgets, (2) thermal analysis, (3) ADCS selection, (4) structure and array mechanisms, and (5) cost estimation. In this paper, previous and planned small satellite researches in Turkey have also been reviewed. Small satellite projects which are performed by government, universities and industries show that Turkey has a small but growing small satellite activity.Publication Metadata only Experimental study of lunar-based hybrid rocket engine(American Institute of Aeronautics and Astronautics Inc, AIAA, 2021) Yalçıntaş, Ali; Kara, Ozan; Baysal, Mustafa; Department of Mechanical Engineering; N/A; Karabeyoğlu, Mustafa Arif; Yelken, Ümit; Faculty Member; PhD Student; Department of Mechanical Engineering; College of Engineering; Graduate School of Sciences and Engineering; 114595; N/AIn this paper, it was aimed to prepare a metal-based hybrid rocket engine by using elements such as magnesium and aluminum, which are abundant in lunar soil. In thermodynamic performance calculations, a mixture ratio with high specific impulse (Isp) was determined using NASA’s Chemical Equilibrium Analysis (CEA) package program, and a rigid fuel was formed from metal powders by using sodium silicate as the binding component. While determining the mixing ratio of aluminum, magnesium, and sodium silicate, the criterion that was taken into consideration was the temperature values to prevent residue formation at the combustion chamber and nozzle throat. The temperature values above the boiling points of the combustion products were tried to be obtained both in the combustion chamber and at the nozzle throat. Thus it was aimed to make a hybrid rocket engine that could be used for extended runtimes. Experimental studies of this hybrid rocket engine fuel obtained from the elements found in the lunar soil and rocks were carried out.Publication Metadata only Findings from IAC 2013 Young Professional Workshop: tools and project organization methodologies that can be implemented into the space sector from other industries(International Astronautical Federation (IAF), 2014) Stube, Kevin; Wood, Danielle; Svoboda, Jan; Li, Rui; Fuse, Tetsuhito; Kukhta, Andrii; N/A; Kara, Ozan; PhD Student; Graduate School of Sciences and Engineering; N/AApplied technologies in space sector are performing complicated and challenging projects in comparison other industries. This complexity in the space sector requires new alternatives for business management and project development. Therefore, management strategies in an organization directly affect the project achievements. Project applications, improvement of economic earnings, relations among people in an organization, mentorships, motivation factors and international activities are other significant issues which are really crucial for space sector. To discuss these important issues, we were one of five groups at International Astronautical Congress, Young Professional Workshop in Beijing, 20th September 2013. Our relevant group topic was "What tools and project organization methodologies have been and can be implemented into the space sector from other industries and the YPs' experience (e.g. software, automotive)?". As a group we have met several times prior to the workshop. Many ideas are emerged in consequence of meetings. Pre-meeting report helped us to prepare individual materials as members thru the workshop. These different reflections were: (1) agile software and engineering issues, (2) process improvement techniques and learning from manufacturing by multiple copies of the same space platform, (3) social activities of organizations for the internal motivation, (4) TRL improvement, (5) project management and system engineering certification the examples from NASA APPEL and Aerospace Corporation, (6) technology transfer among sectors just as military-space and biology-space, (7) Experience assessment of JAXA, (8) software tools that are being used across industries. During the workshop, we simplified these findings and made the final presentation. In addition, preliminary survey questions are listed and determined after the workshop. Finally, common grounds in our final report are summarized as (1) Software development tools, (2) Process improvement techniques, (3) Project management, system engineering education and certification, (4) Company organization structures and (5) Social Activities to improve sector interest. In the final report, group recommendations are given for the each topic and presented to the IAF YP Committee.Publication Restricted In-process monitoring and qualification of SLM produced nickel based superalloys using eddy current inspection method and a novel EC array probe design(Koç University, 2022) Bektaş, Erdem; Canadinç, Demircan; 0000-0001-9961-7702; Koç University Graduate School of Sciences and Engineering; Mechanical Engineering; 23433Publication Restricted Material performance determination for nozzle erosion in hybrid rocket motors(Koç University, 2023) Kahraman, Büşra; Karabeyoğlu, Mustafa Arif; 0000-0002-5071-6133; Koç University Graduate School of Sciences and Engineering; Mechanical Engineering; 114595