This thesis examines the way legal space risks are managed in commercial space transportation provided by major carriers, such as, NASA, the US private launch sector, and Arianespace, as well as in the system envisaged for Australia. Its purpose is to show that even if all systems tend to provide a favorable risk allocation scheme to the space launch industry, there are several alternatives for the telecommunications satellite operators. It also attempts to show that, even if all these risk sharing regimes have been modeled after NASA's, there are certain important differences, which stem from the different political objectives of each of the countries where these carriers are inserted.

Thesis (M.A.)--University of North Texas, Dec., 2007. / Title from title page display. Includes bibliographical references.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 2000. / Computer printout. "April 2000." "March 7, 2000"--Cover. Includes bibliographical references (p. 360-377).

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<p>The commercial CubeSat industry has experienced explosive growth recently, and with falling  costs  and  growing  numbers  of  launch  providers,  the  trend  is  likely  to  continue.  The scientific missions CubeSats could complete are expanding, and this has resulted in a demand for reliable  high  specific  impulse  nanosatellite  propulsion  systems.  Interest  in  liquid-fed  pulsed plasma thrusters (LF-PPTs) to fulfill this role has grown lately. Prior work on a nanosatellite LF-PPT was done in the Purdue Electric Propulsion and Plasma Laboratory, but its high operational voltage and electrode size would be disadvantageous for integration on a CubeSat, which have strict volume limitations and provide only tens of Watts in power at low voltages. This work aims to address those disadvantages and further advance the development of a nanosatellite LF-PPT by reducing the operating voltage and removing long plate electrodes to prevent energy losses on components other than the expelled plasma sheet. Two major objectives are pursued: to construct a  coaxial  pulsed  plasma  thruster  operating  with  10s  to  100s  of  volts  and  to  characterize  the temporal evolution of the discharge parameters in this low-voltage operation scenario. </p> <p>It  took  three  experimental  design  iterations,  all  of  which  used  a  260  <em>uF</em> ,  400 <em>V</em> film capacitor, to arrive at a functional coaxial pulsed plasma thruster. First, a button gun was tested. It produced  a  peak  current  of ~16<em> kA</em>,  which  serves  as  the  expected  maximum  for  the  later experiments. Due to the presence of parasitic arcing, it revealed that electrical lines needed to be removed from vacuum chamber to enable testing at a wide range of pressures. Second, a coaxial PPT was designed, built, and tested. This design confirmed operation at discharge voltages <100 <em>V</em> across the plasma, achieving one of the project’s aims, and produced a peak current of 7.4 <em>kA</em>. However,  necessity  to  better  align  the  cathode and  provide  an  unobstructed  camera  view  for observation of the discharge column attachment to the cathode surface forced additional system redesign. Third, a revised coaxial PPT was built and tested. Using air as a propellant, the discharge generated a peak current of 10.4 <em>kA</em> at a mass flow rate of 2 mgs. The PPT cathode was imaged with an ICCD camera over a wide range of pressures, and the photos indicated “spotless” diffuse arc attachment to the cathode, which serves as evidence to expect low erosion rates. The direct measurements of the cathode erosion rate are planned for future. </p>

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<p>Activity planning for space mission operations has traditionally been a human-in-the-loop effort, conducted by ground operators. Over the past two decades, advances have been made toward automating the mission planning process, in an effort to improve the efficiency of the mission operations system, while increasing the mission return. In keeping with NASA’s goals, some aspects of onboard mission planning are increasingly used for complex missions, particularly for planetary surface missions that are subject to long communication delays.</p> <p>This dissertation research develops an automated mission planning framework and applies it to two spacecraft scenario case studies: a science orbiter and a science rover mission. Mission plans are optimized on the basis of science return, accommodating spacecraft movement</p> <p>to sites of scientific interest according to ground-team preferences, while staying within rover engineering and traverse-related constraints. Automated mission planners offer the capability to schedule engineering and science activities onboard, without ground-in-the-loop interaction. Resource modeling and path planning can be done onboard, reducing the need for modeling and verification by ground operators. Further, automated mission planners</p> <p>may incorporate an optimization executive that maximizes the mission return within the available resource constraints. The proposed planners may be utilized onboard autonomous spacecraft and rovers with limited human support. Also, they may be run on the ground by</p> <p>mission planning teams to provide additional insight during the planning process. Utilizing a variety of optimization approaches, the developed automated mission planners establish the planned sequence of activities, including and engineering activities, while adhering to constraints imposed by orbital geometry or planetary pathing requirements and resource availability. The focus of the work is on remote, robotic missions in which human-in-the loop decision input is delayed or at times unavailable. Two major classes of robotic missions are examined: Orbital science missions in which primary science activities are performed periodically at a specified rate, and a planetary rover mission in which a larger variety of science activities are interspersed with unique terrain navigation activities. The automated mission planning framework is designed to be adapted based upon the application. Optimization methods suitable for different mission planning problems are presented, comparing methods on the basis of computation speed, resources required and solution value.</p> <p>The Aerospace Systems Engineering definitions for “robustness” and “flexibility” are given quantifiable, mathematical definitions and are incorporated into the framework as quality metrics to provide criteria with which to evaluate and compare the produced activity plans.</p> <p>The metrics “reliability” and “latent performance index” provide additional criteria for plan evaluation. A variety of automated mission planning algorithmic approaches are developed and described functionally and mathematically. Planning tools capable of plan verification, Monte Carlo simulation-based verification and plan variation analysis are developed and described in detail. Two detailed, step by step case studies are developed, applying and</p> <p>running all the mission planning and analysis tools to provide planning solutions and analysis of generated plans for the science orbiter and science rover scenarios. The application of the developed planning solutions to the presented missions, including the determination</p> <p>of the quality metrics, are seen as the primary contributions to the advancement of the</p> <p>state of the art in automated mission planning. The Automated Mission Planning and plan analysis techniques and practices are summarized into a User’s Guide to Automated Mission Planning. The guide aids the user in developing their own automated mission planning framework and applying it to their unique mission planning problems. Numerous avenues for future work are proposed to extend this research into other, useful areas. Two areas of road mapping—tasks that must be done to enable a future vision for improved automated planning—are discussed.</p>