Next generation earth-to-space telecommand coding and synchronization: ground system design, optimization and software implementation

The Consultative Committee for Space Data Systems, followed by all national and international space agencies, has updated the Telecommand Coding and Synchronization sublayer to introduce new powerful low-density parity-check (LDPC) codes. Their large coding gains significantly improve the system performance and allow new Telecommand services and profiles with higher bit rates and volumes. In this paper, we focus on the Telecommand transmitter implementation in the Ground Station baseband segment. First, we discuss the most important blocks and we focus on the most critical one, i.e., the LDPC encoder. We present and analyze two techniques, one based on a Shift Register Adder Accumulator and the other on Winograd convolution both exploiting the block circulant nature of the LDPC matrix. We show that these techniques provide a significant complexity reduction with respect to the usual encoder mapping, thus allowing to obtain high uplink bit rates. We then discuss the choice of a proper hardware or software platform, and we show that a Central Processing Unit-based software solution is able to achieve the high bit rates requested by the new Telecommand applications. Finally, we present the results of a set of tests on the real-time software implementation of the new system, comparing the performance achievable with the different encoding options.

The Viability of Providing 24-Hour Electricity Access to Off-Grid Island Communities in the Philippines

Techno-economic viability assessments of rural electrification projects, especially those that integrate renewable energy technologies, typically look at system design optimization that would yield the most favorable cost and investment scenarios. However, the true viability of these projects relies more importantly on their impact to the rural communities while ensuring positive financial returns to the project developers. This paper aims to expand the viability assessment of electrification projects in off-grid island communities in order to mainly address the apparently opposing needs of the major stakeholders at play by developing a viability assessment framework considering the techno-economic dimensions as well as the socio-economic impacts to the consumers. The analysis follows a two-phase approach, where system design optimization and financial impact calculations are done in the first phase and the socio-economic viability is accomplished in the second phase. Results suggest that high capital investment for renewable energy has a better pay-off when there is higher demand for electricity. On the other hand, consumers also tend to receive higher economic benefit as they consume more electricity. However, the low income of rural consumers strains their capacity to pay, which necessitates their engagement in more economically-productive uses of electricity. The viability assessment framework can be a useful tool for both investors and consumers as this provides important insights which can be translated into impactful interventions that may include government support through improved policy implementation that can positively sustain electricity access in off-grid communities through renewable energy.

Hybrid Rocket Engine Design Optimization at Politecnico di Torino: A Review

Optimization of Hybrid Rocket Engines at Politecnico di Torino began in the 1990s. A comprehensive review of the related research activities carried out in the last three decades is here presented. After a brief introduction that retraces driving motivations and the most significant steps of the research path, the more relevant aspects of analysis, modeling and achieved results are illustrated. First, criteria for the propulsion system preliminary design choices (namely the propellant combination, the feed system and the grain design) are summarized and the engine modeling is presented. Then, the authors describe the in-house tools that have been developed and used for coupled trajectory and propulsion system design optimization. Both deterministic and robust-based approaches are presented. The applications that the authors analyzed over the years, starting from simpler hybrid powered sounding rocket to more complex multi-stage launchers, are then presented. Finally, authors’ conclusive remarks on the work done and their future perspective in the context of the optimization of hybrid rocket propulsion systems are reported.

0D Modeling of Fuel Tank for Vapor Generation

Petrol vapor emissions are the main source of pollution for both standard and hybrid vehicles. They are mainly generated by gasoline evaporation from the fuel tank of both running and parked vehicles; it is mostly driven by fuel temperature variation due to daily temperature changes (if parked) and heat from engine (if running). To prevent its dispersion in the environment, the vapor generated in the fuel tank is usually stored in a carbon canister filter that must be periodically “purged” in order to prevent its saturation, by venting it to the intake manifold. Canister management, made by the Engine Control Unit (ECU), becomes even more critical for hybrid-electric vehicles because thermal engine is often off, thus purging cannot take place. A pressurized fuel tank is often used for hybrid applications, to further isolate vapor from environment, making the fuel system even more complex to model. System design optimization is usually based on experience and experimental correlations, which require time and cost. Thus, comes the need for a comprehensive predictive model useful for both vehicle components (fuel tank and carbon canister) and ECU software design. A 0D Matlab® model is proposed, which can predict vapor generation from an arbitrary tank in standard and arbitrary thermal cycles, with arbitrary tank capacity, geometry and construction and at different filling levels. It is based on a system of thermo-fluid-dynamic differential equations and semi-empirical correlations that is iteratively solved in time. Model calibration has been performed by using a small size test tank and validation has been completed on full size tanks for both standard and hybrid-electric applications. The main driving force for vapor generation has been shown to be the amount of empty volume on top of the tank; other significant effects come from tank volume, material, external surface as well as fuel properties. Ongoing work is to develop and integrate a carbon canister loading/purging model, with the aim to build a full model of the vapor system.

A SYSTEM DESIGN OPTIMIZATION MODEL FOR INTEGRATED NATURAL RESOURCE CONSERVATION AND DEVELOPMENT IN AN AGRICULTURAL COMMUNITY

Integrated Natural Resource Conservation and Development (INRCD) Projects are efforts at worldwide locations to promote economic development of local communities consistent with conservation of natural resources. This umbrella term includes Integration Conservation and Development Projects (ICDPs) introduced by the World Wide Fund to combine social development and conservation s through the use of socio-economic investments, and the Integrated Natural Resource Management (INRM) research and development efforts that have employed a systems approach for quantitative modeling and optimization. In the spirit of the INRCD framework, we describe the development of a system-level agriculture and energy model comprising engineering and economic models for crop, irrigation, and energy subsystem designs for a community in Central Uganda. The model architecture is modular allowing modifications for different system configurations and project locations. We include some initial results and discuss next steps for system optimization, refining model assumptions, and modeling community social benefits as drivers of such projects.

Multi-objective System Design Optimization via PPA and a Fuzzy Method

System design deals with various challenges of targets and resources, such as reliability, availability, maintainability, cost, weight, volume, and configuration. This paper deals with the multi-objective system availability and cost optimization of parallel–series systems by resorting to the multi-objective strawberry algorithm also known as the Plant Propagation Algorithm or PPA and a fuzzy method. It is the first implementation of this optimization algorithm in the literature for this kind of problem to generate the Pareto Front. The fuzzy method allows helping the decision maker to select the best compromise solution. A numerical case study involving 10 subsystems highlights the applicability of the proposed approach.