Combined Optimization of Trajectory and Design for Dual Propulsion Spacecraft

Following the trend of miniaturization and standardization of satellite design, as well as recent successes in the use of cubesats in interplanetary missions, a cubesat design capable of reaching another planet fully independently may lead to significant cost reductions for future missions. While efficient low thrust propulsion systems exist, Earth escape using low thrust only leads to significant incident radiation doses when crossing the Van Allen belts. As such, this report aims to present the design of a dual thrust cubesat, i.e. one which employs both high thrust and low thrust propulsion systems, such that the transfer time and the number of van Allen belt crossings is within requirements, while a final orbit aroundMars remains attainable. In doing so, this report explores the theory behind low thrust trajectory optimization, and attempts to combine this with a general optimization scheme including both high thrust phases as well as the optimization of the spacecraft system design. Implementation of such a scheme has not been shown to be useful: issues in finding a good initial guess prevent convergence in many cases, and the proposed plan to alleviate the encountered issues requires an iterative approach between system design and trajectory design. As such, the proposed scheme has not been found to have any benefit over using existing trajectory design tools in an iterative way. A design approach is presented using the pykep trajectory optimizer developed at the European Space Agency (ESA). Iteration between this tool, high thrust calculations, and system design budget calculations allows for optimizing towards a feasible design that meets the requirements, starting from an arbitrary initial guess. When a list of commercial off the shelf (COTS) components is available following the CubeSat standard, it is possible to quickly generate a feasible design without significant prior work. This report presents a full COTS design for a cubesat capable of reaching Mars independently from a common piggyback launch orbit. The design in question is a 12 unit cubesat with a dry mass of 11.4 kg and a wet mass of 14.8 kg. Launched into a geostationary transfer orbit, it can reach escape velocity though 9 Van Allen belt passes, and reachMars in less than 5 years. Due to the constrained scope of the design, further work is needed to verify that the momentumdumping budget, link budget, and thermal budget are indeed sufficient. It is further recommended to improve on the work in this thesis, by finding an alternative integrated optimization scheme, or by including and automating more features within pykep. Lastly, recommendations are given for integration, testing, and launch of the proposed spacecraft design.Aerospace Engineerin