Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1996. / Includes bibliographical references (p. 194-198). / by Bryan Heejin Kang. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1993. / Includes bibliographical references (p. 165-168). / by Matthew Edward Fox. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 93-94). / This thesis provides a numerical algorithm to solve fluid-structure interaction problems in the Cartesian grid. Unlike the typical Immersed Interfaced Method (IIM), we define thin non-stretchable solid interface with the Level Set function. In addition, we developed a partial differential equation which represents the bending rigidity of the interface. The interface is assumed very thin and has zero elastic stress when it is flat. The interface gives singular forces to the incompressible viscous fluid and the fluid solver handles discontinuities across the interface. Instead of solving two dynamic systems (i.e., fluid and solid), we solve the fluid field only and solve a convection equation of interface with the local fluid velocity. This idea is valid because of viscous fluid (i.e., velocity is continuous across the interface) as we can see frequently in the IIM. The result shows that elastic interface vibrates and converges to an equilibrium state. The oscillatory motion of the interface depends on the viscosity of fluid, Young's modulus and thickness of interface. The results looks correct physically, and they match with the existing IIM results. / by Jae Hyung Kim. / S.M.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1984. / Microfiche copy available in Archives and Barker. / Includes bibliographical references. / by William James Usab, Jr. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2003. / Includes bibliographical references (p. 151-153). / by Shaun Shiao Sing Goh. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1996. / Includes bibliographical references (p. 71-72). / by Ali A. Merchant. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (p. 103-108). / This thesis discusses the design of a ten milli Newton chemical propulsion system for providing approximately 200 m/s delta velocity to a five kg satellite. The nozzle is the focus of the experimental work, which involves building and testing ten 20x upscale 2D nozzles. The ten nozzles involve three classes, an ideal contour for 2D expansion, a 15 degree cone, and the ideal contour widened for the displacement thickness, each cut to 25%, 50% and 100% axial lengths. The last nozzle is a 100% axial length, ideal contour class, that is twice the thickness to see the effect of end wall boundary layer growth. The nozzles are tested in the MIT Space Propulsions Lab's vacuum chamber at sub atmospheric chamber pressures to match the throat Reynolds number with the micro nozzles. For the purposes of this specific design the Reynolds number is on the order of a 1,000; however, tests are done over a range of 200-1,400 to provide additional data to the community. The nozzle's coefficient of thrust efficiency is approximately 80% for Reynolds numbers greater than a 1,000 and the data suggest the efficiency drops below 50% at 200. The error becomes significant at low Reynolds number due to pressure measurement error, which reduces the quality of the results. The entire system is compared to the state-of-the-art in milli Newton class space propulsion systems and recommendations are given for propellant choice, valve and pump designs, and thermal management. For small delta velocity missions ( 200 m/s), a monopropellant chemical propulsion system is advantageous to current electric propulsion and cold gas thrusters due to the low system mass. / by Alexander Robert Bruccoleri. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 207-218). / Measurements of atmospheric temperature, pressure, water vapor, and composition are important to users in the Earth science, defense, and intelligence communities. Nanosatellites (with mass < 10 kg, such as CubeSats) can support miniaturized instruments for atmospheric sounding and characterization. Nanosatellite constellations can improve spatial and temporal coverage of Earth and can produce data consistent with the current state of the art at reduced cost compared with larger satellites. Nanosatellites are also used for on-orbit technology demonstrations due to low cost and higher risk posture. We focus on CubeSats as a host platform for instruments and technology demonstrations for three kinds of atmospheric sensors: (i) passive microwave radiometers, (ii) atmospheric occultation experiments and (iii) coronagraphic direct imaging of exoplanets. Microwave radiometers (MWR) measure brightness temperatures in multiple channels across bands centered on atmospheric absorption features. MWRs require stable cold and warm calibration targets for accurate measurements. CubeSat MWRs, such as MicroMAS (the Micro-sized Microwave Atmospheric Satellite) and MiRaTA (Microwave Radiometer Technology Acceleration), use deep space as a cold target with a noise diode as the warm target instead of larger calibration targets. However, noise diodes drift, and a better calibration method is needed to meet the desired measurement precision. Occultation experiments measure electromagnetic signals received from a transmitter as it passes behind the Earth from the perspective of the receiver. In the neutral atmosphere, the measurements yield profiles of temperature, pressure and in certain configurations, composition. We consider radio and optical wavelengths. GPS Radio Occultation (GPSRO) instruments measure phase delay in signals transmitted from GPS satellites that travel through the atmosphere to a low earth orbit (LEO) receiver. GPSRO measurements are inherently well calibrated, because the primary interaction is of an electromagnetic wave through a medium, and have high accuracy and vertical resolution. We show that it is possible to make several GPSRO measurements per day that are collocated spatially and temporally with space-based MWR measurements and that using these measurements enables better MWR calibration by measuring noise diode drift. Occultation observations using several near infrared optical wavelengths can measure absorption features to characterize atmospheric species and abundances. Intersatellite optical links are used for these measurements, but transmissions deep in the atmosphere experience scintillation and distortion. Wavefront control systems could be used to compensate for atmosphere-induced aberrations. Wavefront control systems are also needed to obtain reflection absorption spectra of exoplanet atmospheres, where photons from the host star are reflected by the planet. A space-based telescope equipped with an internal coronagraph can make high contrast measurements off-axis using high spatial frequency wavefront control systems to correct for speckles, imperfections, and other distortions that would degrade the measurement. High actuator count deformable mirrors (DMs) are needed, and Microelectromechanical systems (MEMS) DMs can provide a cost-effective, compact solution. We describe our design for a nanosatellite platform using a wavefront sensor to characterize the on-orbit performance of MEMS DMs. We present results from these new approaches to improve atmospheric sounding and characterization missions using nanosatellites. Our hardware analysis for MiRaTA demonstrates that the CubeSat GPSRO instrument noise performance supports the calibration of the noise diode to improve the CubeSat MWR measurement accuracy from > 0.75 K to 0.25 K. We simulate and experimentally demonstrate a CubeSat wavefront control system using a MEMS DM that can be used to characterize the performance of MEMS DMs, sensitive to 10's of nm motion and up to three times the 1.5 pm-stroke of the DMs, which is useful for future applications in both atmospheric near infrared occultation as well as in exoplanet direct imaging space telescopes. Each of these contributions improves current nanosatellite capabilities or uses nanosatellites to advance technologies in future larger systems for atmospheric sounding and characterization of Earth and exoplanets. / by Anne Dorothy Marinan. / Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 123-128). / CubeSats are a specific subset of nanosatellites, and their common form factor and canisterized deployers have made it possible to undertake higher risk, lower cost missions that can supplement the current generation of large, monolithic, expensive satellites. Our objective in this thesis is to improve attitude estimation on CubeSats using Unscented Kalman filters. CubeSats have evolved from their relatively low complexity and low computational power beginnings. This progression motivates us to revisit attitude determination estimation approaches commonly used for CubeSats, and to implement an alternative Kalman filtering method. Our goal is to improve the current state of the art in attitude estimation on previous MIT Space Systems Laboratory CubeSats by at least two orders of magnitude from about 1-5* attitude knowledge error down to 0.050 or better. This improvement benefits applications that require precise pointing, such as imaging and active tracking of specific targets, laser communications, and coordinated activity and observations among multiple CubeSats. We were able to achieve better than our pointing error goal of 0.05', and found that the proposed Unscented Kalman filter performed significantly better at high angular rate estimation than the Extended Kalman filter (already implemented on some CubeSats). The quaternion estimates were converted to Euler angles to improve ease of interpretation. For the majority of the missions, the mean total Euler angle estimation error improvement ranged from 83% - 98% with error variance decreased by as much as 98%. One implementation had more than a two order of magnitude improvement, to achieve 0.01* mean error, better than the desired pointing accuracy. We present a detailed assessment of these estimation errors, along with changes in quaternion error that accompany varying the unscented filter parameters. / by Weston Alan Navarro Marlow. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001. / Includes bibliographical references (leaves 131-133). / by Thomas John McGuire. / S.M.