Print Email Facebook Twitter Reachability Analysis to Enable Zero-Wait Entry Guidance Title Reachability Analysis to Enable Zero-Wait Entry Guidance: Orbital Aborts to Enhance Mission Safety Author González Puerta, A. Contributor Mooij, E. (mentor) Faculty Aerospace Engineering Department Space Engineering Programme Astrodynamics & Space Missions Date 2017-03-17 Abstract The role of traditional entry guidance systems is to ensure that the vehicle is brought from a nominal entry interface point (EIP) to the neighborhood of a designated landing site at an acceptable energy state. Such systems are designed in such a way that the landing site can be safely reached even if off-nominal conditions are present at the EIP or during the descent flight. A common aspect of traditional guidance systems is that they heavily rely on prior knowledge of the nominal entry trajectory and often require significant planning time prior the de-orbit burn. Due to the nature of abort scenarios, not only is prior knowledge of the entry conditions usually unavailable, but also there is often limited time to plan and execute any entry procedures. In addition, the range of entry conditions that may be encountered in an abort situation is significantly large, meaning that planning a trajectory to an alternative landing site may be required if the vehicle needs to be brought to safety in due time. The goal of this thesis is to develop and test a dedicated guidance system for abort entry missions, focusing on flights that originate from a low Earth orbit. Due to the limited computational power of current flight hardware, performing on-board trajectory optimization is not feasible, especially in an abort situation. This issue is tackled using the concept of on-board trajectory generation via Adaptive Multivariate Pseudospectral Interpolation (AMPI), which attempts to achieve the optimality and accuracy of solutions obtained on the ground with a feasible computing speed. The AMPI-based trajectory interpolator feeds off a large database of optimal trajectories computed off-board, where the selection of the appropriate database sub-space is made according to the projected entry conditions at the moment of the abort. The AMPI method is reduced to bivariate interpolation and thus uses a database that simply covers off-nominal latitude and longitude values. Dispersions in the remaining entry state variables are addressed by a combination of a Linear Quadratic Regulator (LQR) tracking law and a simple lateral guidance implementation. The developed guidance system is capable of planning a reference trajectory in the order of a few milliseconds, proving its capability to run on-board. Furthermore, the system can handle multiple abort scenarios, since the trajectory planner is capable of selecting the most appropriate reference trajectories from the database based on information provided by the navigation system. Thorough testing of the system showed that while the constraint compliance is marginally affected by the density of the trajectory database, the position dispersions at the terminal point are strongly correlated with the chosen density. Despite this, the AMPI algorithm employed in the trajectory planner allows for a loss-less compression of the database. Consequently, manageable database sizes can be achieved even for fine spacings, ranging from only 18 MB for a database spacing of 5 deg to 900 MB for a spacing of 0.1 deg. Subject adaptive entry guidanceorbital abortstrajectory optimizationadaptive multivariate pseudospectral interpolation To reference this document use: http://resolver.tudelft.nl/uuid:a18416c5-d5f5-4f7c-b482-f50a45975a7c Embargo date 2018-02-28 Part of collection Student theses Document type master thesis Rights (c) 2017 González Puerta, A. Files PDF ThesisFinal_GonzalezPuerta.pdf 16.1 MB Close viewer /islandora/object/uuid:a18416c5-d5f5-4f7c-b482-f50a45975a7c/datastream/OBJ/view