Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1988. / Includes bibliographical references. / by John Charles Brewer. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 179-181). / For a variety of missions, vision-based navigation and similar architectures provide the advantage of detailed measurements for a fraction of the size and complexity of ground-based imagers. This thesis provides a simple navigation algorithm using no more than a visual centroid measurement to enable in-situ inspection of space objects. This work evaluates those inspection maneuvers using the Synchronize Position Hold Engage Reorient Experimental Satellites, known as SPHERES. Evaluation of hardware performance was done using data from the International Space Station, in concert with ground-based simulations. Ultimately, this work is in preparation for future experimentation using the VERTIGO vision-navigation payload for SPHERES. The first step presented is an analysis of the measurement capabilities of the SPHERES system and the predicted performance of the VERTIGO system. Using this analysis it is shown that tests run using the former system are applicable to the latter in terms of accuracy, precision, and observability. The second step is an analysis of the tests run on the Space Station, a comparison to those predicted by simulation, and an extension of those results to simulations of more complex maneuvers. Further, a determination of the robustness of the control to disturbances is also performed. Finally, this thesis reflects on the technical and programmatic challenges of developing the VERTIGO payload. From these challenges, lessons are drawn which may guide future developers and program managers, particularly in the university engineering environment. / by Michael Christopher O'Connor. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002. / Includes bibliographical references (leaves 97-99). / by Melvin Michael Henry. / S.M.

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. Thesis. 1965. Sc.D. / Bibliography: leaves 178-192. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990. / Includes bibliographical references (leaves 124-135). / by Simon Andrew Collins. / M.S.

Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics. Thesis. 1968. M.S. / MICROFICHE COPY ALSO AVAILABLE IN AERO LIBRARY. / One blank page inserted. / Bibliography: leaves 84-85. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / "June 2005." / Includes bibliographical references (p. 77-79). / Artificial gravity provided by short radius centrifugation is considered a promising countermeasure to the deleterious physiological effects of microgravity during long-duration space flight. We investigated the feasibility of dual countermeasures to address space flight deconditioning of the musculoskeletal and cardiovascular systems, by combining centrifugation with lower-body exercise. The exercise device is a small stair-stepper with constant resistance provided by dampers beneath each foot, and is the first such device to be used in centrifuge studies. We modified the existing centrifuge to support the additional stresses due to exercise and added following structural elements: support struts on the rotation shaft, a redesigned footplate to which the exercise device was mounted, and horizontal support beams. We also added a sliding mattress with linear ball bearings on rails, so that the subject's body can move up and down while stepping. Design changes and exercise feasibility were validated by having subjects exercise during centrifugation at 23 rpm. We measured heart rate, blood pressure, forces on the feet, and knee deflection due to Coriolis accelerations, for up to four subjects. As expected, heart rate and blood pressure did increase normally with exercise on the centrifuge, relative to when not exercising. However, both heart rate and systolic blood pressure were higher for exercise on the non-spinning centrifuge than on the spinning centrifuge, attributable to the necessity of pulling against the stair-stepper's dampers in order to exercise while lying supine. Approximately half the subject's weight was exerted on the footplate when not exercising. / (cont.) This was expected: since the subject's head was at zero radius and thus at 0-g radially, the 100% artificial gravity gradient along the body's longitudinal axis gave an average effective gravity of about 0.5 g. More pressure (up to 80% body weight) was exerted when the subject was stair-stepping. The measured lateral deflection of the knee during normal stair-stepping and knee bend exercises increased up to three inches compared to deflections in a non-rotating environment. This issue must be further addressed to determine if stair-stepping or knee bend exercises are to be used safely in artificial gravity. / by Jessica Leigh Edmonds. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006. / Includes bibliographical references (p. 97-101). / NASA's human lunar and Mars exploration program requires a new transportation system between Earth and the Moon or Mars. In recent years, unfortunately, human space exploration programs have faced myriad political, technical, and financial difficulties. In order to avoid such problems, future human space exploration programs should be designed from the start for affordability. This thesis addresses one aspect of affordable exploration programs by tackling the issue of high costs for access to space. While launch vehicle trades for exploration programs are relatively well understood, on-orbit assembly has been given much less attention, but is an equally important component of the infrastructure enabling human access to space. Two separate but related perspectives on in-space assembly of modular spacecraft are provided: first, the coupling between launch vehicle selection, vehicle design, and on-orbit assembly is explored to provide a quantitative understanding of this combined tradespace; and second, a number of on-orbit assembly methods are analyzed in order to understand the potential value of a reusable assembly support infrastructure. / (cont.) Within the first topic, a quantitative enumeration of the launcher-assembly tradespace (in terms of both cost and risk) is provided based on a generalizable process for generating spacecraft modules and launch manifests from a transportation architecture. An optimal module size and launcher capability is found for a sample architecture at 82 metric tons; a 28-mt EELV emerges as another good option. The results show that the spacecraft design, assembly planning, and launcher selection are highly coupled and should be considered together, rather than separately. Within the second topic, four separate assembly strategies involving module self-assembly, tug-based assembly, and in-space refueling are modeled and compared in terms of mass-to-orbit requirements for various on-orbit assembly tasks. Results show that the assembly strategy has a significant impact on overall launch mass, and reusable space tugs with in-space refueling can significantly reduce the required launch mass for on-orbit assembly. This thesis thus examines a broad but focused set of issues associated with on-orbit assembly of next-generation modular spacecraft. / by Erica Lynn Gralla. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, February 2010. / "September 2009." Cataloged from PDF version of thesis. / Includes bibliographical references (p. 135-143). / To improve capacity and efficiency of the air transportation system, a number of new systems-level changes have been proposed. Key aspects of the proposed changes are combined functionality across technology and procedures and large physical scale of deployment. The objective of this work is to examine the current safety assessment processes for systems-level changes and to develop an understanding of key challenges and implications for the assessment and approval of future systems-level changes. From an investigation of current U.S. and international safety regulatory policies and processes, a general model was created describing key processes supporting operational approval. Within this model, a framework defined as an influence matrix was developed to analyze key decisions regarding the required scope of analysis in safety assessment. The influence matrix represents the expected change in levels of risk due to changes in behavior of elements of a system. It is used to evaluate the appropriate scope of analysis in safety assessment. Three approaches to performing safety assessment of systems-level changes were analyzed using the framework: the risk matrix approach, target level of safety approach, and performance-based approach. Case studies were performed using eight implemented and pending systems-level changes. In this work, challenges expected in safety assessment of future systems-level changes were identified. Challenges include the large scope of proposed changes, which drives a need for a broad and deep scope of analysis, including the multiple hazards and conditions and complex interactions between components of a change and the external system. In addition, it can be expected that high safety expectations will increase the required accuracy of models and underlying data used in safety assessment. Fundamentally new operational concepts are also expected to expand the required scope of safety assessment, and a need to interface with legacy systems will limit achievable operations. The large scope of analysis expected for future changes will require new methods to manage scope of safety assessment, and insights into potential approaches are discussed. / by Roland Everett Weibel. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 195-200). / A body-force-based fan model for the prediction of multiple-pure-tone noise generation is developed in this thesis. The model eliminates the need for a full-wheel, three-dimensional unsteady RANS simulation of the fan blade row, allowing Euler calculations to be used to capture the phenomena of interest. The Euler calculations reduce numerical wave dissipation and enable the simultaneous computation of source noise generation and propagation through the engine inlet to the far-field in non-uniform flow. The generated shock Mach numbers are in good agreement with experimental results, with the peak values predicted within 6%. An assessment of the far-field acoustics against experimental data showed agreement of 8 dB on average for the blade-passing tone. In a first-of-its-kind comparison, noise generation and propagation are computed for a fan installed in a conventional inlet and in a boundary-layer-ingesting serpentine inlet for a free-stream Mach number of 0.1. The key effect of boundary layer ingestion is the creation of streamwise vorticity which is ingested into the inlet, resulting in co- and counter-rotating streamwise vortices in the inlet. The fan sound power level increases by 38 dB due to this distortion, while the vortex whose circulation is in the same direction as the fan rotation enhances the sound power attenuation within the inlet duct such that the far-field overall sound pressure levels are increased by only 7 dB on average. The far-field spectra are altered in the following manner due to inlet distortion: (1) tones at up to 3 times the blade-passing frequency are amplified; and (2) tones above one-half of the blade-passing frequency are attenuated and appear to be cut-off. To quantify the effects of serpentine inlet duct geometry on the generation and propagation of multiple-pure-tone noise, a parametric study of inlets is conducted. The conclusions are that (1) the ingestion of streamwise vorticity alters multiple-pure-tone noise more than changes in inlet area ratio or offset ratio do; and (2) changes in the far-field spectra relative to the conventional inlet results are only weakly affected by the duct geometry changes investigated and are instead predominantly caused by flow non-uniformities. A response-surface correlation for the effects of inlet geometry on far-field noise is also developed. / by Jeff Defoe. / Ph.D.