Issues associated with establishing control zones for international space operations

Cooperative missions in Earth orbit can be facilitated by developing a strategy to regulate the manner in which vehicles interact in orbit. One means of implementing such a strategy is to utilize a control zones technique that assigns different types of orbital operations to specific regions of space surrounding a vehicle. Considered here are issues associated with developing a control zones technique to regulate the interactions of spacecraft in proximity to a manned vehicle. Technical and planning issues, flight hardware and software issues, mission management parameter, and other constraints are discussed. Also covered are manned and unmanned vehicle operations, and manual versus automated flight control. A review of the strategies utilized by the Apollo Soyuz Test Project and the Space Station Freedom Program is also presented

Macroeconomic framework for an oil-based economy : the case of Bahrain

Bahrain's economy is characterized by producer and consumer subsidies and, possibly misaligned currency. These subsidies have resulted in lower savings rates than would be consistent with the country's endowment in oil and gas. In addition, the misaligned real exchange rate has encouraged imports, at the same time creating incentives biased against the non-oil tradable sectors. So, Bahrain's economy remains largely dependent on a rapidly depleting hydrocarbon resource base. The authors espouse a macroeconomic consistency framework to focus on the behavior of Bahrain's economy along two paths. Part one is based on the assumption that the government's present macroeconomic policy will continue. In that case, the solution exhibits bubbles - fiscal and current account imbalances that would be unsustainable over time. Meanwhile, real appreciation of the dinar would suppress non-oil exports. As a result, the need for foreign borrowing would be more pressing. In an attempt to restore the equilibrium, the government would need to contain aggregate demand by compressing imports and investment, thereby worsening the economic situation. Path two is based on a reform strategy that includes policies to raise the domestic savings rate, improve the fiscal situation (by rationalizing expenditures and introducing income taxes and cost recovery measures), and correct the misaligned exchange rate. The results show that the expenditure-switching effect of the exchange rate alignment would shift resources in favor of the tradable sectors. Non-oil GDP and exports would register high growth rates while economic diversification, in the context of a growing and more dynamic economy, would foster investment efficiency. This would help Bahrainis maintain a high standard of living as the oil income dries up, without too much loss of consumption for the present generation.Economic Stabilization,Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Macroeconomic Management

Bahrain - Managing a nonrenewable resource : savings and exchange-rate policies

Bahrain's oil-producing economy is vulnerable to terms-of-trade shocks for oil in the short to medium run. But the country's dependence on nonrenewable hydrocarbon resources represents a more basic constraint on Bahrain's prospects for long-term economic growth and welfare. To maintain economic growth and welfare in the post-oil era, Bahrain must save more of its oil revenues and assets and use them to invest abroad and to support economic diversification. The authors derive optimum domestic savings rates for Bahrain in the context of a two-assets (oil and non-oil) intertemporal welfare-maximizing model. Based on these derived rates, they recommend that the current suboptimal savings ratios be raised by about 10 percent of GDP. Achieving such a high savings rate is probably not economically feasible or politically sustainable in a stagnant economy, because it implies significantly reducing absolute levels of real consumption. Such austerity would not be necessary in a growing, efficiently restructured, and diversified economy, in which the real exchange rate policy played a key role by stimulating non-oil tradable sectors that could replace oil when it dries out. But the success of real exchange rate depreciation itself depends on a sufficiently high savings rate, to free up resources to switch to the production of other tradables. The authors present an empirical three-sector model of the real exchange rate, which permits links between the equilibrium real exchange rate and the optimum savings rate. They use this model to compute what real depreciation is required consistent with the derived optimum savings ratios. Their model predicts that a real depreciation of about 31 percent would be needed between 1992 and 2005 to avert serious overvaluation over this period.Macroeconomic Management,Environmental Economics&Policies,Economic Theory&Research,Banks&Banking Reform,Economic Stabilization

Ground Robotic Hand Applications for the Space Program study (GRASP)

This document reports on a NASA-STDP effort to address research interests of the NASA Kennedy Space Center (KSC) through a study entitled, Ground Robotic-Hand Applications for the Space Program (GRASP). The primary objective of the GRASP study was to identify beneficial applications of specialized end-effectors and robotic hand devices for automating any ground operations which are performed at the Kennedy Space Center. Thus, operations for expendable vehicles, the Space Shuttle and its components, and all payloads were included in the study. Typical benefits of automating operations, or augmenting human operators performing physical tasks, include: reduced costs; enhanced safety and reliability; and reduced processing turnaround time

External control of semiconductor nanostructure lasers

Novel semiconductor nanostructure laser diodes such as quantum-dot and quantum-dash are key optoelectronic candidates for many applications such as data transmitters in ultra fast optical communications. This is mainly due to their unique carrier dynamics compared to conventional quantum-well lasers that enables their potential for high differential gain and modified linewidth enhancement factor. However, there are known intrinsic limitations associated with semiconductor laser dynamics that can hinder the performance including the mode stability, spectral linewidth, and direct modulation capabilities. One possible method to overcome these limitations is through the use of external control techniques. The electrical and/or optical external perturbations can be implemented to improve the parameters associated with the intrinsic lasers dynamics, such as threshold gain, damping rate, spectral linewidth, and mode selectivity. In this dissertation, studies on the impact of external control techniques through optical injection-locking, optical feedback and asymmetric current bias control on the overall performance of the nanostructure lasers were conducted in order to understand the associated intrinsic device limitations and to develop strategies for controlling the underlying dynamics to improve laser performance. In turn, the findings of this work can act as a guideline for making high performance nanostructure lasers for future ultra fast data transmitters in long-haul optical communication systems, and some can provide an insight into making a compact and low-cost terahertz optical source for future implementation in monolithic millimeter-wave integrated circuits.\u2

Characterization of early graft damage after pancreatic transplantation

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