Realistic Earth escape strategies for solar sailing

With growing interest in solar sailing comes the requirement to provide a basis for future detailed planetary escape mission analysis by drawing together prior work, clarifying and explaining previously anomalies. Previously unexplained seasonal variations in sail escape times from Earth orbit are explained analytically and corroborated within a numerical trajectory model. Blended-sail control algorithms, explicitly independent of time, which providenear-optimal escape trajectories and maintain a safe minimum altitude and which are suitable as a potential autonomous onboard controller, are then presented. These algorithms are investigated from a range of initial conditions and are shown to maintain the optimality previously demonstrated by the use of a single-energy gain control law but without the risk of planetary collision. Finally, it is shown that the minimum sail characteristic acceleration required for escape from a polar orbit without traversing the Earth shadow cone increases exponentially as initial altitude is decreased

A Low-Cost Wireless Power Transmission Experiment

A solar power satellite (SPS) is a satellite dedicated to collecting solar energy on orbit, transforming it into microwave or laser energy, and beaming it to a receiving station on the ground. The transmitted energy is converted into DC or AC power for consumer use. Even a test version of the SPS would be a challenging and expensive undertaking due to the amounts of energy which need to be collected. Satellites measured in hundreds of meters and hundreds of millions of dollars are required for an accurate demonstration. It has been suggested that useful measurements can be made for substantially less if the beaming direction is reversed. A 30 kg, cubic satellite with 31 cm square faces costing under two million dollars is presented. The spacecraft is to receive, rectify and measure microwave power beamed from a highpower, ground-based radar station. Secondary payload opportunities have been analyzed in conjunction with the applicability, availability, and cost of government radar stations. Primary and back-up radar stations have been chosen. Orbital constraints recommended the selection of respective primary and back-up launch vehicles. The satellite is being designed to survive the launch environments of both launchers to increase the likelihood of mission success

A Simplified Use of Quality Function Deployment as a System Tool for Designing to Cost

The problem of designing to cost is one with which industry is still grappling. A technique of requirement development, analysis, and refinement is applied to a university-class satellite development project. A simplified form of the Quality Function Deployment process was followed and allowed to structure the entire design process. It aided in evolving a mission scope which resulted in a feasible mission. This paper presents the steps developed for a senior-level, spacecraft design course. Its application to the design of a low-cost wireless power transmission experiment will be illustrated from requirements generation well into the satellite design. Cost was the prime driver in developing a feasible mission. Use of the technique allowed a cost versus benefit analysis of mission science suggested by previous studies and helped to reduce the cost by more than a factor of four over those studies. Two conditions necessary for success in designing to cost are suggested. One pertains to the organization generating the mission requirements, and the other to a paradigm shift for designers. Potential applications for university satellites and instructors developing missions for senior satellite design courses are suggested

Application of a Genetic Algorithm to Wind Turbine Design

This paper presents an optimization method for stall-regulated horizontal-axis wind turbines. A hybrid approach is used that combines the advantages of a genetic algorithm with an inverse design method. This method is used to determine the optimum blade pitch and blade chord and twist distributions that maximize the annual energy production. To illustrate the method, a family of 25 wind turbines was designed to examine the sensitivity of annual energy production to changes in the rotor blade length and peak rotor power. Trends are revealed that should aid in the design of new rotors for existing turbines. In the second application, five wind turbines were designed to determine the benefits of specifically tailoring wind turbine blades for the average wind speed at a particular site. The results have important practical implications related to rotors designed for the Midwestern US versus those where the average wind speed may be greater

Optimal multi-objective low-thrust spacecraft trajectories

Genetic algorithms have gained popularity as effective search procedures for obtaining solutions to traditionally difficult space mission optimization problems. In this paper, a hybrid optimization method is described that integrates a multi-objective genetic algorithm with a calculus-of-variations-based low-thrust trajectory optimizer. Fronts of Pareto optimal trajectories are generated and novel trajectories identified for both Earth–Mars and Earth–Mercury missions