Launch vehicle navigation system design and comprehensive performance analysis

Abstract

Space transportation is one of the most important issues of today because it plays a key role in the advancement of scientific research, economic growth and international relationships. Mainly, it provides to carry satellites which are used for communication, weather forecasting, and navigation into a variety of orbits depend on the need. Moreover, deep space missions can be conducted owing to the reliability of current launch vehicles. Nowadays, there is a big challenge in the space industry which leads to fast technological progress in space transportation technology. Leading companies like SpaceX, Blue Origin, and Rocket Lab are using reusable rockets to greatly lower the cost of reaching space. Examples of these innovations include SpaceX's Falcon 9 and Starship, and Blue Origin's New Shepard and New Glenn rockets. Traditional aerospace leaders such as Boeing and Lockheed Martin are also advancing with their Space Launch System (SLS) and Vulcan Centaur rockets. This competitive environment is fueling new innovations, making space more accessible, and creating more chances for commercial and scientific projects. National launch vehicle programs are essential today to have a say and power in political, economic and military fields. From a political perspective, this type of program makes a country as a key member of the international space community, so its role can be influential to improve space policies and collaborations. Economically, space programs pioneer to technological innovation and industrial development. Due to innovations and inventions in space, related fields like materials science, electronics, and communications are developed as well. Moreover, the capability of launching satellites by itself removes dependency to foreign providers, so projects can be managed as more cost effective and safer in terms of governments. With regard to the military, national launch vehicle programs enhance national security by guaranteeing consistent access to space-based resources that are essential for communication, navigation, and surveillance. It also enhances deterrence by demonstrating advanced technological prowess. Developing its own launch vehicle gives a country complete control over its space activities, protecting strategic interests and promoting national pride and independence in the dynamic areas of space exploration and defense. Launch vehicles are really complex systems that require the working of many subsystems together in a harmony to satisfy designed mission. The main subsystems are the propulsion system, the structural system, avionics, thermal control and guidance, navigation and control (GNC) subsystem. The propulsion system generates the force to elevate the launch vehicle through sky and space. The structural system sustains the integrity of the vehicle under rough environments. Avionics handle the onboard electronics and data processing. Extreme high and low temperatures are serious issues in space, and thermal control system balance the temperature of the system. Lastly, GNC steers the vehicle to the target orbit to ensure that payloads are placed into correct orbits. Among all of subsystems, the navigation subsystem which is an important component of GNC is specifically vital. Navigation subsystem calculates the position, velocity and attitude of the launch vehicle through trajectory to enable guidance and control systems for matching ongoing orbit with target orbit. The launch vehicle may not reach its intended orbit or deliver its cargo accurately if the navigation is unreliable, increasing the chance of mission failure. Thus, robust navigation systems are necessary to ensure that space missions are successful and that the vehicle reaches its target precisely. Designing the navigation subsystem of a launch vehicle is a complex task which requires careful research, trade-off, modelling and testing to assure an system working highly reliable. Evaluating mission requirements coming from the customer, navigation subsystem requirements are derived. Considering these navigation subsystem requirements, a couple of options are determined based on research, and tested are implemented to candidate sensors and algorithms. Generally, inertial measurement units (IMU), global navigation satellite system (GNSS) receivers, and star trackers are used for navigation. Owing to high prices of these components, they are modeled in detail by using modelling environments, and model-in-the-loop (MIL) tests are conducted to analyses their performances. MIL consists of different steps like single run, multiple run and sensitivity analysis. After completing all of these steps of MIL, requirements for navigation subsystem components are derived. Regarding requirements, appropriate sensors are bought or manufactured. Then, hardware-in-the-loop (HIL) test takes place to simulate the response of navigation system under dynamic environments representing launch conditions. This thorough development process ensures that the navigation subsystem can accurately guide the launch vehicle through all stages of the flight, from takeoff to the deployment of the payload, achieving mission success. This thesis focus on designing and analyzing the navigation subsystem for a launch vehicle at MIL level. Analysing various grades of IMUs to achieve precise navigation to a designated orbit is a critical task for improving launch vehicle guidance and control systems. Testing these IMUs with and without the application of a linearized Kalman Filter (LKF) provides a clear framework for assessing the enhancements in navigation accuracy that this filtering technique can offer. LKF is particularly valuable for its ability to integrate sensor data and reduce errors. By applying the LKF to the same set of IMUs, this study methodically quantifies the performance improvements and increased robustness attributable to the filter. Conducting extensive Monte Carlo simulations adds a robust statistical layer to performance analysis, allowing to evaluate the navigation performance across a spectrum of uncertainties. This approach enables effectively gauge the reliability and accuracy of both the basic inertial navigation systems and those augmented by the LKF. Lastly, detailed sensitivity analysis included is crucial. By investigating which specific sensor error parameters—such as biases, scale factors, and misalignments—most significantly influence navigation performance, critical vulnerabilities of the system can be pinpointed. This analysis is key to understanding the relative impact of various errors both in the context of standard inertial navigation and when using the LKF. Overall, this thesis aims to deliver a thorough understanding of the key design considerations for a launch vehicle's navigation subsystem. It explores how different grades of IMUs perform under enhanced filtering techniques and identifies significant factors influencing system accuracy and reliability. Also, it promises to contribute valuable insights into the development of more sophisticated and dependable navigation systems for launch vehicles, aligning with industry needs for precision and robustness in space missions.