Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2003. / Includes bibliographical references (p. 175-176). / The demonstration micro turbopump was designed to prove the feasibility of pumping a liquid using a turbopump on the micro scale. This thesis presents the first data indicating positive pumping from the demonstration micro turbopump. Data pertaining to both the turbomachinery as well as the bearing systems for these preliminary tests is shown and discussed. The pressure rise through the pump, turbine pressure ratio, respective powers, and a system efficiency are presented. Bearing theory and static flow test data are discussed. The pump design is detailed. Modelling data is presented to help describe the operational difficulties with the highly coupled aft bearing system. These operational difficulties lead to the redesign of the aft bearing system, which is described in detail. Other operational procedures developed and discussed include the pump start up procedure and the use of the inverted journal bearing. / by Shana Diez. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006. / Includes bibliographical references (p. 111-113). / The notion of sequential engine shutdown is introduced and its application to lunar descent is motivated. The concept calls for the utilization of multiple fixed thrust engines in place of a single continuously throttleable engine. Downrange position control is provided by properly timed engine shutdowns. The principle advantage offered is the potential cost savings that would result from the elimination of the development cost of a throttleable rocket engine. Past lunar landing efforts are reviewed and provide the foundation for a baseline vehicle definition. A descent from a lunar parking orbit is assumed. The powered descent is divided into two phases, and a sequential engine shutdown-based guidance scheme is developed for the earlier phase. The guidance scheme consists of a biased ignition point and an algorithm for calculating shutdown times combined with a linear tangent steering law to provide full terminal position control. The performance of the sequential engine shutdown guidance scheme is assessed against two alternative approaches. / (cont.) A statistical picture of the performance of each guidance scheme is obtained via Monte Carlo trials of a lunar descent simulation that captures, to first order, the interaction between the descent propulsion system, the navigation filter, and the guidance function, allowing a direct comparison to be made on the basis of accuracy and fuel consumption. The impact of variations in the number of engines available in the sequential engine shutdown case is analyzed. While the performance observed with sequential engine shutdown does not match that observed with a throttleable engine, the results suggest that it is a viable solution to the lunar descent guidance problem. / by Philip N. Springmann. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990. / Title as it appears in the June, 1990 M.I.T. Graduate List: An exoatmospheric interceptor guidance using angle-only measurements and discrete maneuvers. / Includes bibliographical references (leaf 109). / by Anthony John Bogner. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1992. / Includes bibliographical references (leaves 82-83). / by John-Paul B. Clarke. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1993. / Includes bibliographical references (leaves 112-113). / by Patrick V. Hagelauer. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013. / This thesis was scanned as part of an electronic thesis pilot project. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 107-109). / A low power, Hall-effect type plasma thruster known as the MIT-Cylindrical Cusped- Field Thruster (MIT-CCFT) has been developed and simulated using a fully-kinetic plasma model, the Plasma Thruster particle-in-cell (PTpic) model. Similar to the Diverging Cusped-Field Thruster (DCFT) previously developed in the Massachusetts Institute of Technology Space Propulsion Laboratory, this thruster uses cusped magnetic fields aligned in alternating polarity in order to confine electrons, thus slowing their flow to the anode and readily ionizing neutral gas, which is then electrostatically accelerated by the anode. The design methodology for the CCFT will be discussed, with significant emphasis on the effects of magnetic topology on thruster performance. In particular, while the topology is similar to that of the DCFT in that it also confines the discharge plasma away from the channel walls to limit wall erosion, the CCFT was also designed to minimize plume divergence. To predict the CCFTs performance and plasma dynamics, the design has been modeled and simulated with PTpic. From multiple simulations of the CCFT under different operating conditions, the thruster performance and plume characteristics were found and compared to past simulations of the DCFT. Specifically, the predicted nominal total efficiency ranged from 25 to 35 percent, providing 4-9 mN of thrust at a fixed xenon mass flow rate of 4.0 sccm, whilst consuming 90-400 W of power and with a corresponding nominal specific impulse of 1050 to 1800 s. Preliminary observations of the particle moments suggest that the magnetic confinement of the plasma isolates erosion of the channel walls of the discharge chamber to the ring cusps locations. In addition, in contrast to the DCFT, the CCFT does not have a hollow conic plume; instead, its beam profile is similar to that of traditional Hall-effect thrusters. To supplement the efforts for optimizing longevity of the cusped-field thruster, a new diagnostic tool for erosion studies, novel to the electric propulsion community, has been implemented and has undergone preliminary validation. Ion beam analysis (IBA) allows for in-situ measurements of both composition and profile of the surfaces of the discharge region of a plasma thruster during operation. The technique has been independently tested on individual coupons with the use of the Cambridge Laboratory for Accelerator Study of Surfaces (CLASS) tandem ion accelerator. The coupons, which are composed of materials with known sputtering rates and/or are commonly used as insulator material, are exposed to helicon-generated plasma to simulate the sputtering/re-deposition found in thruster discharge region. Through comparison of ion beam analysis traces taken before and after plasma exposure, the effective erosion rates were found and validated against simulated results. / by Anthony Pang. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 105-110). / We study the flow generated when a handheld fan is waved. This fluid-structure interaction problem is investigated through precision experiments, using an oscillating semi-circular elastic plate as a reduced analog model. The aerodynamic performance of the fans is systematically characterized for a variety of geometric and material parameters, as well as the amplitude of the periodic driving. We demonstrate that the bending stiffness of the structure can be tuned to maximize the output of the generated airflow, while simultaneously minimizing the input power. A design guideline is established for this optimal conditions based on matching the driving and the natural frequencies of the plate. Closer to the handheld fans, we then consider a discrete analog model comprising an array of overlapping strips. Unlike homogeneous plates, these discrete designs deform passively into shapes with finite Gaussian curvature and further enhance the generated flow. Finally, we explored the effect of corrugation on the flapping plate and found that the fan employs the interesting mechanism of reversible buckling to simultaneously increase the velocity of the flow and reduce the load. / by Grace Swee See Goon. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. / Includes bibliographical references (p. 153-157). / (cont.) of environmental disturbances and measurement noise.The product of this thesis is a robust planning system that is tolerant of the types of uncertainty experienced by real aircraft. This robustness has been demonstrated by more than 20 successful flights on a fully automated UAV testbed. / This thesis presents the development and testing of a unique testbed consisting of a fleet of eight unmanned aerial vehicles (UAVs) that was designed as a platform for evaluating coordination and control algorithms. A hierarchical configuration of task assignment, trajectory design, and low-level, waypoint following, are used in a receding horizon framework to control the UAV system. Future UAV teams will have to autonomously demonstrate cooperative behaviors in dynamic and uncertain environments, and this testbed can be used to compare various control approaches to accomplish these coordinated missions. Flight demonstrations are made utilizing real-time mixed-integer linear programming techniques, exercising the algorithms in realistic environments with real-world disturbances. Large disturbance sources, computational delay and measurementnoise all represent significant error sources that reduce the ability of UAV teams to interact in a coordinated fashion by increasing uncertainty on higher planning levels. This thesis develops a method that explicitly accounts for this uncertainty by including feedback loops on the task assignment and trajectory design algorithms to prescribe added robustness for the uncertainty at each stage. This approach takes into account low level controller saturation limits that might cause infeasibilities in the plans created at the higher levels of the planning system. Detailed and realistic simulation environments are useful for large-scale multi-vehicle simulations, particularly when logistics prevent flight testing on that scale. This thesis validates one such hardware-in-the-loop simulation environment through the comparison of models obtained from experimentally collected flight data and detailed modeling / by Ellis T. King. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / Includes bibliographical references (p. 107-110). / Technical capabilities for improved communication, surveillance, and navigation (CNS) over the oceans are currently available. However, all aircraft operators will not equip simultaneously because of the high costs required. Consequently, as these CNS systems are integrated into oceanic air transportation architecture, the controller will have to manage the current low frequency surveillance and communication paths in parallel with future enhanced CNS. The cognitive effects of the mixed equipage environment were studied through field studies and experimental analysis. Field studies at New York Center, Oakland Center, and Reykjavik Center in Iceland were conducted to identify human-centered systems issues with the emerging mixed equipage environment. Findings show that the integration of varying communication latencies influences controller planning. The fusion of multiple surveillance sources and the application of varying separation standards based on equipage was found to limit the cognitive processes of the controller. These limitations may constrain the controller from providing full efficiency benefits to aircraft equipped with the highest capabilities, which would reduce the incentives for equipping. Experimental analysis was conducted to further study the integration of high and low frequency surveillance and the use of varying separation standards. Results show that workload increases and situation awareness degrades in the mixed surveillance environment, compared to segregated operations. The results also demonstrate that efficiency benefits attained by equipped aircraft are in fact limited in the mixed equipage environment. Implications for the design of air traffic control systems and procedures are also discussed. / (cont.) Strategies for the segregation of airspace based on equipage are suggested to alleviate controller cognitive limitations and ensure incentives for equipped aircraft. Options are given for the display of equipage information in the future environment. / by Laura M. Major. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990. / Includes bibliographical references (leaves 173-175). / by Georgia F. Denktsis. / M.S.