published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

The space elevator has been proposed as an alternate method for launching cargo into space. However, the construction of such a structure requires a material much stronger than any currently in existence. Instead, a partial elevator is considered for satellite placement. In the first part of the thesis, the fundamentals of very long tethered systems are studied. From static analysis on a simple two-body system, it is demonstrated that an assumption made in the conventional analysis does not apply to very long tethered systems. For a uniform tether, the axial stress distribution is obtained. Following the Lagrangian approach, the equations of motion governing the planar librations of a multi-body tethered system are derived. From a linearization of these equations, the libration frequencies are found. Then, by solving the nonlinear equations numerically, the responses to various changes in the system parameters are determined. In the second part of the thesis, the use of a partial elevator in satellite placement is studied. In the case of single climber transit, residual librations occur, which alter the shape and size of the orbit of a satellite launched from the climber. An approach using two climbers is investigated in order to decrease the residual libration and thereby reduce orbit placement errors. Also, some energy calculations are done to determine whether the partial elevator offers significant advantages.

Within the first decade of the 21st century, the aerospace community has seen many more opportunities to launch small spacecraft in the 10 to 100 kg mass class. Coupled with this has been consistent interest from the government in developing small-spacecraft platforms to expand civil and military mission possibilities. Small spacecraft have also given small organizations such as universities an increased access to space. Because small satellites are limited in size, power, and mass, new and often nontraditional capabilities must be explored and developed to make them viable and attractive when compared with larger and more proven spacecraft. Moreover, small organizations that wish to contribute technically are often limited by the small size of their teams and available resources, and need creative solutions for meeting mission requirements. A key need is in space-to-ground communications. Complex missions typically require large amounts of data transfer to the ground and in a timely fashion. Available options trade hardware cost, available ground stations or networks, available operating-frequency range, data-rate performance, and ease of use. A system for small spacecraft will be presented based upon Radio Frequency Integrated Circuits (RFIC) that minimizes development effort and maximizes interface control to meet typical small-spacecraft communications requirements. RFICs are low-cost components that feature pre-built radio hardware on a chip that can be expanded easily by developers with little or no radio experience. These devices are widespread in domestic applications for short-range connectivity. A preliminary design and prototype is presented that meets basic spaceflight requirements, offers data rates in the 55 to 85 kbps range, and has completed basic proof-of-concept testing. While there are higher-data-rate alternatives in existence, the solution presented here strikes a useful balance among data rate, parts cost, and ease of use for non experts, and gives the user operational control necessary to make air-to-ground communications time effective.

Thesis (LL.M.). / Written for the Institute of Air & Space Law. Title from title page of PDF (viewed 2008/07/28). Includes bibliographical references.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references. Also available via the Internet.

Thesis (M.S.)--Oregon State University, 1988. / Typescript (photocopy). Includes bibliographical references (leaves 80-82). Also available on the World Wide Web.

Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, Dec. 2004. / Thesis Advisor(s): Brij N. Agrawal. Includes bibliographical references (p. 103-104). Also available online.

Thesis (M.S.)--Rochester Institute of Technology, 2008. / Typescript. Includes bibliographical references (p. 239).

Project report (M. For.)--Virginia Polytechnic Institute and State University. M.S. 1993. / Abstract. Includes bibliographical references (leaves 32-62). Also available via the Internet.

WASP-39b is a hot Saturn-mass exoplanet with a predicted clear atmosphere based on observations in the optical and infrared. Here, we complete the transmission spectrum of the atmosphere with observations in the near-infrared (NIR) over three water absorption features with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) G102 (0.8-1.1 mu m) and G141 (1.1-1.7 mu m) spectroscopic grisms. We measure the predicted high-amplitude H2O feature centered at 1.4 mu m and the smaller amplitude features at 0.95 and 1.2 mu m, with a maximum water absorption amplitude of 2.4 planetary scale heights. We incorporate these new NIR measurements into previously published observational measurements to complete the transmission spectrum from 0.3 to 5 mu m. From these observed water features, combined with features in the optical and IR, we retrieve a well constrained temperature T-eq = 1030(20)(+30) K, and atmospheric metallicity 151(46) (+48) solar, which is relatively high with respect to the currently established mass-metallicity trends. This new measurement in the Saturn-mass range hints at further diversity in the planet formation process relative to our solar system giants.