Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / Includes bibliographical references (p. 141-144). / A trajectory optimization study for a soft landing on the Moon, which analyzed the effects of adding operationally based constraints on the behavior of the minimum fuel trajectory, has been completed. Metrics of trajectory evaluation included fuel expenditure, terminal attitude, thrust histories, etc.. The vehicle was initialized in a circular parking orbit and the trajectory divided into three distinct phases: de-orbit, descent, and braking. Analysis was initially performed with two-dimensional translational motion, and the minimally constrained optimal trajectory was found to be operationally infeasible. Operational constraints, such as a positive descent orbit perilune height and a vertical terminal velocity, were imposed to obtain a viable trajectory, but the final vehicle attitude and landing approach angle remained largely horizontal. This motivated inclusion of attitude kinematics and constraints to the system. With rotational motion included, the optimal solution was feasible, but the trajectory still had undesirable characteristics. Constraining the throttle to maximum during braking produced a steeper approach, but used the most fuel. The results suggested a terminal vertical descent was a desirable fourth segment of the trajectory. which was imposed by first flying to an offset point and then enforcing a vertical descent, and provided extra safely margin prior to landing. In this research, the relative effects of adding operational constraints were documented and can be used as a baseline study for further detailed trajectory optimization. / by Alisa Michelle Hawkins. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990. / Includes bibliographical references (leaves 62-64). / by William James Steptoe. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1993. / Includes bibliographical references (leaves 78-79). / by Andrew Kevin Barrows. / M.S.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998. / Includes bibliographical references. / by Jean-Marc C. Hauss. / M.Eng.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013. / This electronic version was submitted and approved by the author's academic department as part of an electronic thesis pilot project. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from department-submitted PDF version of thesis / Includes bibliographical references (p. 99-102). / Multidisciplinary design optimization (MDO) is becoming an essential tool for the design of engineering systems due to the inherent coupling between discipline analyses and the increasing complexity of such systems. An important component of MDO is effective exploration of the design space since this is often a key driver in finding characteristics of systems which perform well. However, many design space exploration techniques scale poorly with the number of design variables and, moreover, a large-dimensional design space can be prohibitive to designer manipulation. This research addresses complexity management in trade-space exploration of multidisciplinary systems, with a focus on the conceptual design of Blended Wing Body (BWB) aircraft. The objectives of this thesis are twofold. The first objective is to create a multidisciplinary tool for the design of BWB aircraft and to demonstrate the performance of the tool on several example trade studies. The second objective is to develop a methodology for reducing the dimension of the design space using designer-chosen partitionings of the design variables describing the system. The first half of this thesis describes the development of the BWB design tool and demonstrates its performance via a comparison to existing methods for the conceptual design of an existing BWB configuration. The BWB design tool is then demonstrated using two example design space trades with respect to planform geometry and cabin bay arrangement. Results show that the BWB design tool provides sufficient fidelity compared to existing BWB analyses, while accurately predicting trends in system performance. The second half of this thesis develops a bi-level methodology for reducing the dimension of the design space for a trade space exploration problem. In this methodology, the designer partitions the design vector into an upper- and lower-level set, wherein the lower-level variables essentially serve as parameters, in which their values are chosen via an optimization with respect to some lower-level objective. This reduces the dimension of the design space, thereby allowing a more manageable space for designer interaction, while subsequently ensuring that the lower-level variables are set to "good" values relative to the lower-level objective. The bi-level method is demonstrated on three test problems, each involving an exploration over BWB planform geometries. Results show that the method constructs surrogate models in which the sampled configurations have a reduction in the system objective by up to 4 % relative to surrogates constructed using a standard exploration. Furthermore, the problems highlight the potential for the framework to reduce the dimension of the design space such that the full space can be visualized. / by Cory Asher Kays. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 99-101). / Space shuttle entry guidance with an extended analytic range corrector method is presented. The guidance method is a variation of Shuttle entry guidance in which the parameters that define the drag profile are modified using quadratic splines to make the drag profile smooth and easier to customize. In general, in order to account for off-nominal entry conditions and ensure the vehicle flies the correct range to the runway, the nominal reference drag profile is modified on-line utilizing analytic expressions for the derivative of range with respect to the relevant drag profile parameter. This new profile is then used to calculate a reference drag command in the subsequent guidance algorithm cycle. Typical implementations of Shuttle entry guidance modify the drag profile using only one variable to shift the profile by a constant value. This presents problems when the vehicle is highly constrained and can easily violate constraints such as heat load and heat rate constraints due to small drag profile variations. The methods by which the drag profile is updated are changed in order to provide multiple perturbation options. In providing multiple drag profile update parameters, a memoryless range error allocator is implemented with a vector of weights as a design variable. The allocator parameters are designed to take into account heat load while remaining within constraints using a high L/D vertical takeoff horizontal landing reusable launch vehicle simulation. The resulting algorithm seeks to leverage the high-TRL Shuttle entry guidance routine by making minimal modifications to the implementation, while increasing robustness to entry interface dispersions under tight heating constraints. A discussion of the design of the drag profile is included, in which the selection of profile update parameters is explored. Results from optimization of these parameters using a genetic algorithm are presented, as well as Monte Carlo results demonstrating that the allocator can reduce failure rates due to tight drag constraints from 42% to 0%, establishing the impact and success of this analytic range corrector method. / by Erin Elizabeth Evans. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004. / Includes bibliographical references (p. 123-125). / (cont.) (incident rate and unnecessary alert rate), the MDP-based logic can meet or exceed that of alternate logics. / This thesis describes an approach to designing hazard avoidance alerting systems based on a Markov decision process (MDP) model of the alerting process, and shows its benefits over standard design methods. One benefit of the MDP method is that it accounts for future decision opportunities when choosing whether or not to alert, or in determining resolution guidance. Another benefit is that it provides a means of modeling uncertain state information, such as unmeasurable mode variables, so that decisions are more informed. A mode variable is an index for distinct types of behavior that a system exhibits at different times. For example, in many situations normal system behavior tends to be safe, but rare deviations from the normal increase the likelihood of a harmful incident. Accurate modeling of mode information is needed to minimize alerting system errors such as unnecessary or late alerts. The benefits of the method are illustrated with two alerting scenarios where a pair of aircraft must avoid collisions when passing one another. The first scenario has a fully observable state and the second includes an uncertain mode describing whether an intruder aircraft levels off safely above the evader or is in a hazardous blunder mode. In MDP theory, outcome preferences are described in terms of utilities of different state trajectories. In keeping with this, alerting system requirements are stated in the form of a reward function. This is then used with probabilistic dynamic and sensor models to compute an alerting logic (policy) that maximizes expected utility. Performance comparisons are made between the MDP-based logics and alternate logics generated with current methods. It is found that in terms of traditional performance measures / by Lee F. Winder. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / Includes bibliographical references (p. 107-112). / Model-based diagnosis of devices has largely operated on hardware systems. However, in most complex systems today, such as aerospace vehicles, automobiles and medical devices, hardware is augmented with software functions that influence the system's behavior. As these sophisticated systems are required to perform increasingly ambitious tasks. there is a growing need to ensure their robustness and safety. Prior work introduced probabilistic, hierarchical, constraint automata (PHCA), to allow compact encoding of both hardware and software behavior. The contribution of this thesis is a capability for monitoring and diagnosing software-extended systems in the presence of delayed symptoms, based on the expressive PHCA modeling formalism. Hardware models are extended to include the behavior of associated embedded software, resulting in more comprehensive diagnoses. This work introduces a novel approach that frames diagnosis over a finite time horizon as a soft constraint optimization problem (COP), which is then decomposed into independent subproblems using tree decomposition techniques. There are two advantages to this approach. First, the approach enables finite-horizon diagnosis in the presence of delayed symptoms. Second, the soft COP formulation provides convenient expressivity for encoding the PHCA models and their execution semantics, and enables the use of decomposition-based, efficient optimal constraint solvers. The solutions to the COP correspond to the most likely state trajectories of the software- extended system. / (cont.) These state trajectories are enumerated and tracked within the finite receding horizon, as observations and issued commands become available. The diagnostic capability has been implemented and demonstrated on several scenarios from the aerospace and robotic domains, including vision-based rover navigation, the global metrology subsystem of the MIT SPHERES satellites, and models of the NASA New Millennium Earth Observing One (EO-1) spacecraft. / by Tsoline Mikaelian. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / Includes bibliographical references (p. 127-129). / The information architecture of general aviation cockpits is shifting from one of independent mechanical instruments to one of digital sensors, common databuses, and liquid crystal displays. This integrated architecture presents an opportunity to improve general aviation safety through enhancements to the flight display utilizing the data, computing power, and display capabilities available on a modem integrated cockpit. A study of general aviation accident causes identified takeoff and climbout, stall, and spatial disorientation as potential root causes that could be addressed with enhancements to the Primary Flight Display of an integrated general aviation cockpit. To address these accident causes, four prototype enhancements were designed, implemented on a PFD, and flight tested in a single-engine general aviation aircraft. A Takeoff Performance Monitor prototype demonstrated the usefulness of automating the published takeoff distance calculation required of, but seldom performed by, pilots and also showed that performance deficiencies as small as a 10% reduction in power can be detected within the first few seconds immediately after throttle-up. The prototype was also able to predict takeoff distance in real-time within 200 feet by 55 knots using a simple acceleration model. A Dynamic Stall and V-Speeds prototype calculated stall speeds, best angle of climb speed, best rate of climb speed, and best glide speed given the current flight conditions and marked them on the airspeed indicator. Subject pilots reported the speeds aided in maintaining awareness of stall margin and optimal performance conditions. / (cont.) An Angle of Attack Estimator that used a speed-based method and an angle-based method to compute the angle of attack using only the data available on the PFD without additional sensors was prototyped along with two means of display; a traditional angle of attack gauge and a Pitch Limit Indicator. Both estimator methods were compared to an angle of attack vane during a series of maneuvers. It was shown that a speed-based angle of attack estimator along with the pitch limit indicator is a useful stall avoidance aid. Finally, an Unusual Attitude Alerting prototype provided specific verbal cues over the intercom when pitch or roll limits were exceeded to aid a pilot in recovery from unusual attitudes. Subject pilots preferred alerts that commanded the recovery maneuver over alerts that informed the pilot of the attitude but left the recovery procedure to the pilot, and preferred both to alerts that simply told the pilot to recover without specific information about the attitude. / by Daniel R. Craig. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1989. / Title as it appears in M.I.T. Graduate List, Feb. 1989: A study of IMU transfer alignment. / Includes bibliographical references (leaves 93-94). / by Serge M. Karsenti. / M.S.