Taking a common-pool resources approach to space sustainability: A framework and potential policies

This paper examines Nobel Prize Winner Elinor Ostrom's principles for sustainable governance of common-pool resources (CPR), capturing the best practices of CPRs over the years, which avoid the “Tragedy of the Commons” without being either completely privatized or controlled by a Leviathan entity. Ostrom's principles highlight, inter alia, the need for clear boundary definitions, rules tailored to fit the domain, who has a say in formulation of collective-choice agreements and operational rules, monitoring of behavior, graduated penalties, and conflict resolution mechanisms. In the context of the space domain they highlight issues such as the definition of where space begins, gaps in the existing liability regime, the concept of collaborative space situational awareness, and how best to include emerging and developing space actors in negotiations and decision making. The paper concludes that Ostrom's principles highlight specific areas on which to focus initial space sustainability efforts and national and international policy. It also recommends further analysis into how best to translate her principles to the space domain, where they may not be wholly applicable because of the unique nature of space, and how to evolve space governance institutions and mechanisms to best suit the unique environment of outer space.     

Bayesian Design of Decision Rules for Failure Detection

The formulation of the decision making process of a failure detection algorithm as a Bayes sequential decision problem provides a simple conceptualization of the decision rule design problem. As the optimal Bayes rule is not computable, a methodology that is based on the Bayesian approach and aimed at a reduced computational requirement is developed for designing suboptimal rules. A numerical algorithm is constructed to facilitate the design and performance evaluation of these suboptimal rules. The result of applying this design methodology to an example shows that this approach is potentially a useful one.     

Formation of polymer micro-agglomerations in ultralow-binder-content composite based on lunar soil simulant

We report results from an experiment on high-pressure compaction of lunar soil simulant (LSS) mixed with 2–5?wt% polymer binder. The LSS grains can be strongly held together, forming an inorganic-organic monolith (IOM) with the flexural strength around 30–40?MPa. The compaction pressure, the number of loadings, the binder content, and the compaction duration are important factors. The LSS-based IOM remains strong from ?200?°C to 130?°C, and is quite gas permeable.     

Interleaved boost converter with zero diode reverse-recovery loss

A three-phase interleaved continuous-inductor-current-mode (CICM) boost converter with zero diode reverse-recovery loss is proposed. In the converter, the di/dt of the output rectifiers is controlled by an integrated magnetic component. All the output rectifiers can be turned off softly and a very high efficiency is obtained. The equivalent-circuit model of the integrated inductors, the operation principle of the converter, and the design issues are discussed. Simulation and experimental results are presented.     

Conceptualizing an economically,legally, and politically viable active debris removal option

It has become increasingly clear in recent years that the issue of space debris, particularly in low-Earth orbit, can no longer be ignored or simply mitigated. Orbital debris currently threatens safe space flight for both satellites and humans aboard the International Space Station. Additionally, orbital debris might impact Earth upon re-entry, endangering human lives and damaging the environment with toxic materials. In summary, orbital debris seriously jeopardizes the future not only of human presence in space, but also of human safety on Earth. While international efforts to mitigate the current situation and limit the creation of new debris are useful, recent studies predicting debris evolution have indicated that these will not be enough to ensure humanity?s access to and use of the near-Earth environment in the long-term. Rather, active debris removal (ADR) must be pursued if we are to continue benefiting from and conducting space activities. While the concept of ADR is not new, it has not yet been implemented. This is not just because of the technical feasibility of such a scheme, but also because of the host of economic, legal/regulatory, and political issues associated with debris remediation. The costs of ADR are not insignificant and, in today?s restrictive fiscal climate, are unlikely/to be covered by any single actor. Similarly, ADR concepts bring up many unresolved questions about liability, the protection of proprietary information, safety, and standards. In addition, because of the dual use nature of ADR technologies, any venture will necessarily require political considerations. Despite the many unanswered questions surrounding ADR, it is an endeavor worth pursuing if we are to continue relying on space activities for a variety of critical daily needs and services. Moreover, we cannot ignore the environmental implications that an unsustainable use of space will imply for life on Earth in the long run. This paper aims to explore some of these challenges and propose an economically, politically, and legally viable ADR option. Much like waste management on Earth, cleaning up space junk will likely lie somewhere between a public good and a private sector service. An international, cooperative, public-private partnership concept can address many of these issues and be economically sustainable, while also driving the creation of a proper set of regulations, standards and best practices.     

Integrating system engineering software tools

System engineering projects typically involve the use of a variety of design, analysis, simulation, and management software tools that are home-grown or commercial-off-the-shelf (COTS). Very often, these applications are hosted on dissimilar computing platforms in a network environment. An application deployed on one platform may not be easily ported to another platform, and it usually cannot be readily accessed by software on the other platform. Enhancing the inter-operation among software applications or tools will greatly increase the effectiveness of the system engineering process. The middleware technology currently being developed by the computer industry promises to provide the needed software interface for integrating tools across a heterogeneous computer network. This paper discusses the experience of applying the middleware technology to software tools used in system engineering     

An Adaptive Estimation Algorithm for Time-Varying Bit Synchronizers

This paper presents an adaptive estimation algorithm for bit synchronization, assuming that the parameters of the incoming data process are time varying. The data are linearly related to the state variable to be determined. By employing the Gauss-Markov theorem, the optimal recursive estimate (including the nonstationary property of the system), which is a matrix operation on the transformed data, is obtained. The efficiency of the estimator is measured by the amount of data required and the speed of convergence. Both of these have proved to be of satisfactory and acceptable quality.     

Design and evaluation of a hybrid passive/active ripple filter with voltage injection

Active ripple filters can substantially attenuate power converter ripple, allowing considerable reduction in passive filter component size. Investigated here is a hybrid passive/active filter topology that achieves ripple reduction by injecting a compensating voltage ripple across a series filter element. Both ripple feedforward and feedback are employed. The design of sensor, amplifier, and injector circuitry for this application is explored. The experimental results demonstrate the feasibility and high performance of the new approach, and illustrate its potential benefits. It is demonstrated that the proposed approach is most effective in cases where it is desirable to minimize the amount of capacitance in the filter.     

Effect of Sampling Time Jitter on Array Performance

The effect on array SNR of errors in sampling times (jitter) isan analyzed for the "Bryn processor." Jitter is modeled as a discrete-paramter er random process, and expressions for array SNR are determined as a function of signal and noise spectra and jitter characteristics. For a plane wave signal, it is found that jitter in the data used to design the processor has no effect on output SNR if the noise is independent between channels. However, jitter in the input (evaluation) n) data can cause a substantial loss in peak array SNR and in the array's frequency selectivity. These losses can be expected to increase as the high-frequency content of the data increases. The Bryn processor also loses its interpretation as a likelihood ratio processor in the presence of jitter. The effect of jitter can be reduced in many cases by increasing the sampling rate.     

Two-phase forward converter using an integrated magnetic component

An interleaved two-phase forward converter using an integrated magnetic component is proposed for telecommunication and computer applications. The integrated magnetic component consists of two step-down transformers and two output-filtering inductors on a single magnetic core. The z-parameter (gyrator) model and the equivalent-circuit model of the integrated magnetic component are presented. The circuit operation and design criteria of the proposed converter are described. All theoretical analyses are verified by simulated and experimental results.