Assisted-Launch Performance Analysis: Using Trajectory and Vehicle Optimization

55 years have passed since the launch of the first man-made space vehicle, Sputnik 1. While spaceflight has changed significantly in many ways, further improvement in rocket technology is still being pursued. Launch-assist systems, which give the launch vehicle a combination of initial velocity and initial altitude, could create such an improvement. There are two factors that come into play when determining if this might be true. Firstly, the cost of building and operating both the assist platform and the launch vehicle and secondly, the total system performance. This thesis focuses on the performance of the entire system. The definition of the performance of a system utilizing the assisted launch technique was chosen to be the payload mass-to-initial mass ratio of the launcher. This was maximized by optimizing various parameters of the launch vehicle and the launch trajectory using a differential evolution algorithm. Optimization was performed for launchers using either kerolox propellant or hydrolox propellant using a variety of initial altitude and initial velocity combinations. To show continuous trends of the vehicle design parameters through the whole range of simulated launchers, all launchers consist of only one stage. The end result of the thesis provides insight of the relationships between the performance, the launch vehicle design, the trajectory profile and the magnitude and type of the assist. It also provides a comparison between the performance of launchers using low specific impulse and high density propellant, such as kerolox, and high specific impulse and low density propellant, such as hydrolox. The results are intended to be used as a tool to base design decisions on during future concept studies.