Advanced power sources for space missions

Approaches to satisfying the power requirements of space-based Strategic Defense Initiative (SDI) missions are studied. The power requirements for non-SDI military space missions and for civil space missions of the National Aeronautics and Space Administration (NASA) are also considered. The more demanding SDI power requirements appear to encompass many, if not all, of the power requirements for those missions. Study results indicate that practical fulfillment of SDI requirements will necessitate substantial advances in the state of the art of power technology. SDI goals include the capability to operate space-based beam weapons, sometimes referred to as directed-energy weapons. Such weapons pose unprecedented power requirements, both during preparation for battle and during battle conditions. The power regimes for these two sets of applications are referred to as alert mode and burst mode, respectively. Alert-mode power requirements are presently stated to range from about 100 kW to a few megawatts for cumulative durations of about a year or more. Burst-mode power requirements are roughly estimated to range from tens to hundreds of megawatts for durations of a few hundred to a few thousand seconds. There are two likely energy sources, chemical and nuclear, for powering SDI directed-energy weapons during the alert and burst modes. The choice between chemical and nuclear space power systems depends in large part on the total duration during which power must be provided. Complete study findings, conclusions, and eight recommendations are reported

Survivability of Deterministic Dynamical Systems

The notion of a part of phase space containing desired (or allowed) states of a dynamical system is important in a wide range of complex systems research. It has been called the safe operating space, the viability kernel or the sunny region. In this paper we define the notion of survivability: Given a random initial condition, what is the likelihood that the transient behaviour of a deterministic system does not leave a region of desirable states. We demonstrate the utility of this novel stability measure by considering models from climate science, neuronal networks and power grids. We also show that a semi-analytic lower bound for the survivability of linear systems allows a numerically very efficient survivability analysis in realistic models of power grids. Our numerical and semi-analytic work underlines that the type of stability measured by survivability is not captured by common asymptotic stability measures.Comment: 21 pages, 6 figure

Survivability : A Unifiying Concept for the Transient Resilience of Deterministic Dynamical Systems

16 pagesNon peer reviewedPreprin

Interbank Networks in Prewar Japan: Structure and Implications

In this paper, we explore the structure and implications of interbank networks in prewar Japan, focusing on director interlocking. We find that approximately half the banks had at least one connection with another bank through director interlocking, and that a bank that had connections with other banks was less likely to fail than a bank without a network. The quality of networks also matters in the sense that the failure probability of a bank with a network was negatively associated with the profitability of the connected banks. On the other hand, there is no strong evidence of financial contagion through networks. In addition, networks of director interlocking contributed to the stabilization of the financial system through coordinating bank mergers.

Space power technology 21: Photovoltaics

The Space Power needs for the 21st Century and the program in photovoltaics needed to achieve it are discussed. Workshops were conducted in eight different power disciplines involving industry and other government agencies. The Photovoltaics Workshop was conducted at Aerospace Corporation in June 1987. The major findings and recommended program from this workshop are discussed. The major finding is that a survivable solar power capability is needed in photovoltaics for critical Department of Defense missions including Air Force and Strategic Defense Initiative. The tasks needed to realize this capability are described in technical, not financial, terms. The second finding is the need for lightweight, moderately survivable planar solar arrays. High efficiency thin III-V solar cells can meet some of these requirements. Higher efficiency, longer life solar cells are needed for application to both future planar and concentrator arrays with usable life up to 10 years. Increasing threats are also anticipated and means for avoiding prolonged exposure, retraction, maneuvering and autonomous operation are discussed

Financing Swedish Small and Medium-Sized Enterprises: Methods, Problems and Impact

Small and Medium-sized Enterprises (SMEs) are the seeds for a vital entrepreneurial economy. The Swedish SMEs, in particular, are very important for the future development of the Baltic Region. Financing these firms is an issue of great significance and a subject to care for. In this paper, we looked at established financing methods for Swedish SMEs. We also analyzed the impact of these methods on firm survivability using the Survival Index Value (SIV) model. The SIV model is a new tool to evaluate small firm performance, introduced recently by Dr. Adli Abouzeedan. Keywords: Small and Medium-sized Enterprises, SMEs, SIV model, Financing, Debt Financing, Equity Financing, Banks, Factoring, Disintermediation, Venture Capital, Angles, Swedish, Sweden, North Europe, European Union, EU, Baltic Region

Autonomous satellite command and control: A comparison with other military systems

Existing satellite concepts of operation depend on readily available experts and are extremely manpower intensive. Areas of expertise required include mission planning, mission data interpretation, telemetry monitoring, and anomaly resolution. The concepts of operation have envolved to their current state in part because space systems have tended to be treated more as research and development assets rather than as operational assets. These methods of satellite command and control will be inadequate in the future because of the availability, survivability, and capability of human experts. Because space systems have extremely high reliability and limited access, they offer challenges not found in other military systems. Thus, automation techniques used elsewhere are not necessarily applicable to space systems. A program to make satellites much more autonomous has been developed, using a variety of advanced software techniques. The problem the program is addressing, some possible solutions, the goals of the Rome Air Development Center (RADC) program, the rationale as to why the goals are reasonable, and the current program status are discussed. Also presented are some of the concepts used in the program and how they differ from more traditional approaches

Interbank Networks in Pre-war Japan:Structure and Implications

In this paper, we explored the structure and implications of interbank networks in pre-war Japan, focusing on director interlocking. It was found that approximately 60% of the banks had at least one connection with another bank through director interlocking. These connections resulted in the construction of complex networks of banks, not to be reduced to core-periphery structures. Based on this finding, the impact of the interbank networks on the financial performance and the survivability of banks was examined. It was revealed that while a bank with a network was not always more profitable compared to a bank without it, a bank which had a network with profitable banks was more profitable. Concerning the probability of failure, it was found that a bank with a network was less likely to fail than a bank without one. In this case as well, the failure probability of a bank was negatively associated with the profitability of the connected banks. In addition, interbank networks affected on bank mergers. Namely, a bank tended to choose a bank in the same network as a counterpart of the merger, which suggests that interbank networks played a role in coordinating bank mergers.