This thesis examines the current technological and legal issues concerning orbital debris (space debris). The unique physical characteristics of the space environment are identified and explained. The thesis then explores the causes of orbital debris and examines the risk posed by debris to the most frequently used orbital areas. Significant environmental, legal, political, and economic consequences of orbital debris are described. The current technical and legal controls on the creation of debris are discussed and evaluated. Finally, proposed solutions are considered and critiqued. The thesis concludes with a non-binding treaty-based proposal for a new legal debris control regime that can encourage compliance and enhance accountability.

Thesis (M.S.)--Oregon State University, 1997. / Typescript (photocopy). Includes bibliographical references (leaves 62-67). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1999. / Typescript (photocopy). Includes bibliographical references (leaves 117-121). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2005. / Printout. Includes bibliographical references (leaves 45-48). Also available via the World Wide Web.

Thesis (M.S.)--Florida State University, 2005. / Advisor: Sherwood W. Wise, Jr., Florida State University, College of Arts and Sciences, Dept. of Geological Sciences. Title and description from dissertation home page (viewed Jan. 27, 2006). Document formatted into pages; contains ix, 93 pages. Includes bibliographical references.

Every space launch increases the overall amount of space debris. Satellites have limited awareness of nearby objects that might pose a collision hazard. Astrometric, radiometric, and thermal models for the study of space debris in low-Earth orbit have been developed. This modeled approach proposes analysis methods that provide increased Local Area Awareness for satellites in low-Earth and geostationary orbit. Local Area Awareness is defined as the ability to detect, characterize, and extract useful information regarding resident space objects as they move through the space environment surrounding a spacecraft. The study of space debris is of critical importance to all space-faring nations. Characterization efforts are proposed using long-wave infrared sensors for space-based observations of debris objects in low-Earth orbit. Long-wave infrared sensors are commercially available and do not require solar illumination to be observed, as their received signal is temperature dependent. The characterization of debris objects through means of passive imaging techniques allows for further studies into the origination, specifications, and future trajectory of debris objects. Conclusions are made regarding the aforementioned thermal analysis as a function of debris orbit, geometry, orientation with respect to time, and material properties. Development of a thermal model permits the characterization of debris objects based upon their received long-wave infrared signals. Information regarding the material type, size, and tumble-rate of the observed debris objects are extracted. This investigation proposes the utilization of long-wave infrared radiometric models of typical debris to develop techniques for the detection and characterization of debris objects via signal analysis of unresolved imagery. Knowledge regarding the orbital type and semi-major axis of the observed debris object are extracted via astrometric analysis. This knowledge may aid in the constraint of the admissible region for the initial orbit determination process. The resultant orbital information is then fused with the radiometric characterization analysis enabling further characterization efforts of the observed debris object. This fused analysis, yielding orbital, material, and thermal properties, significantly increases a satellite’s Local Area Awareness via an intimate understanding of the debris environment surrounding the spacecraft.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第17866号 / 工博第3775号 / 新制||工||1577(附属図書館) / 30686 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 中川 一, 教授 藤田 正治, 准教授 川池 健司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Sediment material around the base of a bridge pier is moved by the flow velocity and associated turbulence. This phenomenon is generally termed as local scour and can lead to undermining the structure and increase its possibility of failure. Numerous factors can affect bridge pier scour and they have been investigated for decades. Debris jams, one of these factors, could significantly contribute to bridge failure as some field examples and experimental investigations pointed out. Woody debris accumulation on the front of either single or multiple bridge piers can result in deeper pier scour and extra load exerted on the pier. Several studies have already investigated the influence of woody debris on pier scour in terms of static woody debris. In addition, HEC-18 (2012) also proposed a design code to estimate scour depth in the presence of woody debris jam. However, in these studies, the woody debris jam was considered to be static, whereas a woody debris jam accumulates piece by piece, growing to a debris jam with a shape most akin to a half-cone, and then may even eventually break up and be carried in pieces downstream. Therefore, this research investigated the evolution of the loading onto and scouring around a bridge pier in the presence of dynamic debris jams. In this study, the temporal evolution of the bridge pier scours was monitored during the development of dynamic debris jams. Experimental modeling was conducted to explore the influence of dynamic debris jam on bridge pier scour using a scale of 30 by employing both dowels and seedling trees. It was found that the dynamic debris jam of dowels could last 10-20 minutes and reach a critical size, then fail and subsequently reform. In addition, the first debris jam had an obvious influence on scour depth which correlated to the blockage generated by the debris jam; however, the influence of the subsequent debris jam depended on its size compared to the previously formed one. For the dynamic debris jam using seedling trees, the debris jam lasted for a longer time once it formed, and it could lead to twice the maximum scour depth compared to that generated in the absence of the debris jam, which is the same with dowels debris jam. In addition, the hydraulic head induced by the debris jam was correlated to the blockage of the debris jam and the flow Froude number irrespective of whether the dynamic debris jam was made of dowels or seedling trees. Additionally, blank control tests in the absence of a debris jam were used along with previous data gleaned from the literature to develop and test new multigene genetic programming (MGGP) models for the temporal evolution of scour. The MGGP model, using the non-dimensional variables from the empirical equations, can reach a better accuracy than the empirical equations, which indicates the ability of the model to optimize the empirical equations. The temporal evolution of load exerted onto the bridge pier with a dynamic debris jam was also measured. Experimental tests were performed to investigate the additional debris jam drag force exerted onto the bridge pier using both dowels and seedling trees in the presence of a fixed flume bed. Likewise, the dynamic debris jam of dowels lasted for about 10-20 mins, while those formed by the seedling trees, once formed, could last over 50 mins. The investigation demonstrated that the drag coefficient of the seedling trees jam was higher than that of the dowels jam. More importantly, a spike in the drag force was also observed irrespective of whether the jams were formed by dowels or seedling trees. Detailed investigation of the flow field around the debris jam and pier provided insight into the mechanics of debris jams. Three half-cone-shaped debris jams of the same dimensions were designed and built. The three jams were fabricated using: a) 20 cm long dowels, b) 30 cm long dowels, or c) a 3D printer. For each jam, four sections were measured using an Acoustic Doppler Velocimeter (ADV). The results indicated that the flow fields around the 20 cm length dowel jam and the 30 cm length dowel jam were similar. In addition, the section behind the pier and debris jam showed divided zones termed herein as the accelerated high-velocity zone, the high shear transition zone, and the wake dead zone. As for the drag coefficient, the 20 cm length dowels jam and 30 cm length dowels jam shared a very close magnitude of 1.7, but the drag coefficient of the 3D printer debris jam was only 0.88 which indicated the debris jam built by individual pieces behaved differently than the block jam.

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