Suitable Strategies for In-plane Orbit Acquisition using Micro-thrusters

The deviations in the injection orbital parameters, resulting from launcher dispersions, need to be corrected through a set of acquisition maneuvers to achieve the desired nominal parameters. When multiple satellites are injected into a single orbital plane, as a part of constellation establishment, they have to positioned in the plane with appropriate semi-major axis ‘a’ and mean anomaly ‘M’. In this paper, three strategies are studied for achieving orbit acquisition. The first strategy is by deriving an analogy to the Linear Quadratic Regulator (LQR). The state dynamics and the control law are of the form X&= AX + BU and U = −KX . The feedback gain K is calculated by minimizing the cost function. Under this strategy the thrust (N) and velocity increment ( ÄV ) are functions of time and only the matrix K needs to be up-linked. Any revision in the current or the target states, will then lead to a simple re-calculation of K and up-linking them. The second strategy assumes that ÄV is same for each maneuver and calculates the number of maneuvers and the ÄV required for each maneuver. If the maneuvers are stopped for reasons like orbit assessment, and thruster performance evaluation, the strategy can be restarted easily without having any penalty on the overall ÄV. Besides these two strategies, a third strategy based on the application of Fuzzy Modified Potential Function is also studied for autonomous orbit acquisition with constraints in the path. By adding Fuzzy logic to the potential function it is shown that, maneuvers can be changed gradually ahead of the constraints. Onboard implementation related aspects are also briefly addressed for all the strategies

Development of electrical power supply system for micro-satellite with maximum power point tracking

180 p.The development of intelligent power supply system for small satellite has always been a major challenge in satellite communication. Maximum Power Point Tracking approach offers numerous advantages, has become a main candidate for the power supply system for small satellite. This thesis presents the research and development work done on designing and developing a Maximum Power Point Tracking (MPPT) for microsatellite system. The MPPT techniques that are analyzed in this research are the Open circuit solar voltage, Perturbation & Observation, Incremental Conductance and Hybrid MPPT. Through the study on the hostile effects in space on the Component-Off-The-Shelves, a Buck type switch mode power supply with variable duty cycle and microcontroller were designed and built by using space qualified components for conducting experiments in this research.MASTER OF ENGINEERING (EEE

Recapitalization of Amphibious Operation and Lift

Includes supplementary material.CAPSTONE PROJECT REPORTSystem Engineering and Analysis Cohort 18A and Temasek Defense Systems InstituteThe aging Whidbey Island and Harpers Ferry class ships, LSD-41 and 49 respectively, comprise just over one third of the amphibious navy. However, a solution to the capability gap created by the loss of these ships is needed to maintain the effectiveness of the amphibious fleet across a broad spectrum of mission areas. This research effort considers future ship designs and fleet architectures to meet the capability gaps left by the decommissioning of the LSD-41 and 49 class ships. With respect to lift capacity, performance capability, cost and a risk assessment, the analysis showed the LPD-17 or a LSD(X) approximately 30% larger than the existing classes to be acceptable replacement classes. This analysis also supports further research to determine the most robust fleet architecture apart from the current eleven LHA or LHD, eleven LPD and eleven LSD paradigm.Approved for public release; distribution is unlimited