A novel method of reducing the spin of a rotating symmetric body, similar to many earth orbit satellites, is by allowing small, despin weights to unwind from about the satellite so that they absorb some, or all, of the satellite angular momentum. This technique which has been used successfully on several U.S. satellites is commonly referred to as yo-yo despin. Several studies of the motion of a system such as this have been published where it was assumed that the motion was two-dimensional (i.e., without coning). This dissertation presents a comprehensive study of the yo-yo despin problem which includes a derivation of two-dimensional results as well as a three-dimensional or exact solution. The results presented are sufficient for rudimentary design computations and provide examples of the corrections necessary to apply to two-dimensional computations for their applications as estimates for the general motion. An approximate solution of the three-dimensional equations of motion is also presented along with an example of the accuracy obtained by the approximation. The equations of motion are derived in a straightforward manner using the vectorial methods of Newtonian mechanics. The Euler equations for a rigid body are used to describe the motion of the rigid body itself. The moment acting on the body through the tension in the yo-yo cables is unknown and it is necessary to apply the second law of Newton to a despin weight so that sufficient independent differential equations are available for the solution of the problem variables. These relations give three first-order differential equations and two second-order ones. An expression for the cable tension is also obtained. This system of equations is integrated numerically by a standard Runge-Kutta process. Two singularities require special attention: first, at the initial instant the fundamental inversion matrix for the Newton equations is singular; and second, special care must be taken at a point in the integration where a discontinuity is found to occur. Outside of these special points, the integration process is quite routine although some cases require precautions near the end of the despinning process in order that the integration is stopped before violent tumbling occurs. In order to discuss the motion relative to a fixed reference axis the Euler angles, and Euler angle rate equations are also integrated. A point of interest concerning the derivation of the equations of motion is that the Lagrange technique cannot be used without modification due to internal constraints which do work. After a numerical study of several typical examples, one concludes that for initial coning angles of less than 10° a two-dimensional analysis is sufficient for determining many important design variables such as maximum cable tension and despin time, although the cable length is somewhat overestimated and problems may occur in the release of the weights if only a two-dimensional analysis is considered. If one desires information on the angular trajectory of the body in inertial coordinates, a study of the problem must be made using the exact three-dimensional relations or the approximate three-dimensional relations. The approximate expressions save the investigator a great deal of effort and apparently provides excellent results. / Ph. D.

In this work, we describe all the possible radiative processes occurring in a low temperature hydrogen plasma. Some of the fundamental concepts involving ionized gases and collision phenomena are presented, and a rigorous approach is used to show that classical mechanics is quite appropriate to our study. As an application to a laser engine, we investigate the effects of the maximum temperature, the temperature gradient, the stretching of the plasma shape, the engine pressure, and the equivalent sphere radius, on the total emitted power, including absorbing mechanisms through the equation of radiative transfer. Graphs related to spectral radiative exitances are included, and a complete set of graphs of the total power, permitting interpolations with respect to the above relevant parameters, are also provided. / Master of Science

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / This paper reviews the performance requirements that provided the baseline for development of the onboard data system, RF transmission system, and ground segment receiving system of the Midcourse Space Experiment (MSX) spacecraft. The onboard Command and Data Handling (C&DH) System was designed to support the high data outputs of the three imaging sensor systems onboard the spacecraft and the requirement for large volumes of data storage. Because of the high data rates, it was necessary to construct a dedicated X-band ground receiver system at The Johns Hopkins University Applied Physics Laboratory (APL) and implement a tape recorder system for recording and downlinking sensor and spacecraft data. The system uses two onboard tape recorders to provide redundancy and backup capabilities. The storage capability of each tape recorder is 54 gigabits. The MSX C&DH System can record data at 25 Mbps or 5 Mbps. To meet the redundancy requirements of the high-priority experiments, the data can also be recorded in parallel on both tape recorders. To provide longer onboard recording, the data can also be recorded serially on the two recorders. The reproduce (playback) mode is at 25 Mbps. A unique requirement of the C&DH System is to multiplex and commutate the different output rates of the sensors and housekeeping signals into a common data stream for recording. The system also supports 1-Mbps real-time sensor data and 16-kbps real-time housekeeping data transmission to the dedicated ground site and through the U.S. Air Force Satellite Control Network ground stations. The primary ground receiving site for the telemetry is the MSX Tracking System (MTS) at APL. A dedicated 10-m X-band antenna is used to track the satellite during overhead passes and acquire the 25-Mbps telemetry downlinks, along with the 1-Mbps and 16-kbps real-time transmissions. This paper discusses some of the key technology trade-offs that were made in the design of the system to meet requirements for reliability, performance, and development schedule. It also presents some of the lessons learned during development and the impact these lessons will have on development of future systems.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / This paper describes a high altitude experimental flight test platform developed by the University of Kansas (KU) and the National Nuclear Security Administration’s Kansas City Plant (NNSA’s Kansas City Plant) for high altitude payload flight testing. This platform is called the Kansas University Balloon Experiment Satellite (KUBESat). The paper describes the flight test platform and experimental flight test results captured at Fort Riley, KS from characterization of the KCP developed Distributed Transmitter (DTX).

Approved for public release, distribution is unlimited / Nuclear power is the next enabling technology in manned exploration of the solar system. Scientists and engineers continue to design multi-megawatt power systems, yet no power system in the 100 kilowatt, electric, range has been built and flown. Technology demonstrations and studies leave a myriad of systems from which decision makers can choose to build the first manned space nuclear power system. While many subsystem engineers plan in parallel, an accurate specific mass value becomes an important design specification, which is still uncertain. This thesis goes through the design features of the manned Mars mission, its power system requirements, their design attributes as well as their design faults. Specific mass is calculated statistically as well as empirically for 1-15MWe systems. Conclusions are presented on each subsystem as well as recommendations for decision makers on where development needs to begin today in order for the mission to launch in the future. / Lieutenant, United States Navy

A new generation of compact and highly efficient power production and propulsion technologies are critically needed in enabling NASAs long-term goals. Nuclear fission power technologies as part of project Prometheus are in development to meet this need. Proposed reactor concepts utilize a combination of refractory metals and stainless steels. One such refractory alloy, Niobium 1% Zirconium (Nb-1Zr), will be used because of its strength at high temperatures, neutron absorption properties, and resistance to corrosion by liquid alkali metals. One potential problem in using Nb-1Zr is that it undergoes rapid high temperature oxidation, even in low oxygen concentrations. Long-term oxidation of the niobium matrix can significantly deteriorate the mechanical properties of the alloy. This thesis reports on experimental studies of the high temperature interaction of 316 stainless steel (316 SS) and Nb-1Zr under prototypic space fission reactor operating conditions. Specifically, how the high temperature oxidation rate of Nb-1Zr changes when in contact with 316 SS at low external oxygen concentrations. The objective of the project is to determine if transport of gaseous contaminants, such as oxygen, will occur when Nb-1Zr is in contact with 316 SS, thereby increasing the oxidation rate and degrading material properties. Experiments were preformed in a realistic non-nuclear environment at the appropriate operating conditions. Thermal Gravimetric Analysis techniques were used to quantify results. Coupons of Nb-1Zr and Nb-1Zr in contact with 316 SS foil are subjected to flowing argon with oxygen concentrations between 4-15ppm and heated to a temperature of 500, 750, and 1000oC for 2 to 10 hours. Experiments were conducted at the Early Flight Fission Test Facility at NASA Marshall Space Flight Center. The experimental results indicate that a complex oxidation process, which depends greatly on temperature and oxygen concentration, occurs at the expected operating conditions. Non-linear regression techniques were applied to experimental data in order to derive correlations for the approximate oxidation rate of Nb-1Zr and Nb-1Zr in contact with 316 SS as a function of time, temperature, and oxygen concentration.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 4 uppsatser.

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