{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/132571"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/132571","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Optimal control techniques for multimode propulsion mission design in cislunar space","abstract":"Multimode spacecraft propulsion is an emerging, enabling, and enhancing technology that combines two or more propulsive modes (e.g., chemical and electric) into one system using a single propellant. The primary benefit of this technology is that it can provide reduced propellant consumption for a given transfer in comparison to an all-chemical approach and reduced transit time in comparison to an all-electric approach. It can also significantly increase the maneuvering capability domain of a spacecraft in comparison to single mode (i.e., all-chemical or all-electric) propulsion systems. Additionally, multimode propulsion provides mission flexibility and adaptability because the propellant may, in principle, be used in any mode at any time. Despite these benefits, there is presently a lack of mature techniques for designing optimal multimode transfers—particularly for chemical-electric multimode systems. In this dissertation, indirect optimal control techniques are developed for solving optimal multimode orbital transfers. Using an indirect approach results in the automatic selection of the burn sequence (i.e., which mode should be used at every instant). This yields more optimal transfers in comparison to the traditional approach in which the burn sequence is manually selected. Two types of optimal control problems are solved: minimum-fuel and propellant-constrained minimum-time (PCMT). The former is the primary focus of this dissertation and examples are shown for interplanetary, geocentric, and cislunar transfers for systems with large performance differences (i.e., thrust and specific impulse) between the modes. Forward single shooting is used to solve the example interplanetary and geocentric transfers in combination with hyperbolic tangent smoothing (HTS) for the throttle. To solve multimode cislunar minimum-fuel problems, a new technique is developed using modified equinoctial elements (MEE), HTS, forward-backward multiple shooting, two reference frames (Earth-centered and Moon-centered), and highly consistent dynamics. The method is demonstrated with multiple two-mode transfers as well as a three-mode transfer. The PCMT problem is particularly relevant for mission recovery efforts (e.g., after a launch injection failure) or spacecraft with hybrid propulsion systems (i.e., systems with two or more modes that are not integrated and do not share propellant) with fixed propellant budgets. To solve this problem, a penalty function approach was combined with HTS to enforce a maximum propellant usage constraint on the highest thrust, lowest specific impulse mode. The method is demonstrated with a three-dimensional transfer from a geostationary transfer orbit (GTO) to geostationary orbit (GEO) that was solved using MEE and forward single shooting. Finally, note that the techniques developed here are agnostic to the propulsion system. As a result, the methods apply equally well for spacecraft with hybrid propulsion systems as to those with multimode propulsion. While multimode propulsion is still a maturing technology, there are many spacecraft currently flying with hybrid propulsion. Accordingly, the methods developed here are applicable not only to future multimode missions, but also to near-term missions with hybrid propulsion.","abstract_html":"Multimode spacecraft propulsion is an emerging, enabling, and enhancing technology that combines two or more propulsive modes (e.g., chemical and electric) into one system using a single propellant. The primary benefit of this technology is that it can provide reduced propellant consumption for a given transfer in comparison to an all-chemical approach and reduced transit time in comparison to an all-electric approach. It can also significantly increase the maneuvering capability domain of a spacecraft in comparison to single mode (i.e., all-chemical or all-electric) propulsion systems. Additionally, multimode propulsion provides mission flexibility and adaptability because the propellant may, in principle, be used in any mode at any time. Despite these benefits, there is presently a lack of mature techniques for designing optimal multimode transfers—particularly for chemical-electric multimode systems. In this dissertation, indirect optimal control techniques are developed for solving optimal multimode orbital transfers. Using an indirect approach results in the automatic selection of the burn sequence (i.e., which mode should be used at every instant). This yields more optimal transfers in comparison to the traditional approach in which the burn sequence is manually selected. Two types of optimal control problems are solved: minimum-fuel and propellant-constrained minimum-time (PCMT). The former is the primary focus of this dissertation and examples are shown for interplanetary, geocentric, and cislunar transfers for systems with large performance differences (i.e., thrust and specific impulse) between the modes. Forward single shooting is used to solve the example interplanetary and geocentric transfers in combination with hyperbolic tangent smoothing (HTS) for the throttle. To solve multimode cislunar minimum-fuel problems, a new technique is developed using modified equinoctial elements (MEE), HTS, forward-backward multiple shooting, two reference frames (Earth-centered and Moon-centered), and highly consistent dynamics. The method is demonstrated with multiple two-mode transfers as well as a three-mode transfer. The PCMT problem is particularly relevant for mission recovery efforts (e.g., after a launch injection failure) or spacecraft with hybrid propulsion systems (i.e., systems with two or more modes that are not integrated and do not share propellant) with fixed propellant budgets. To solve this problem, a penalty function approach was combined with HTS to enforce a maximum propellant usage constraint on the highest thrust, lowest specific impulse mode. The method is demonstrated with a three-dimensional transfer from a geostationary transfer orbit (GTO) to geostationary orbit (GEO) that was solved using MEE and forward single shooting. Finally, note that the techniques developed here are agnostic to the propulsion system. As a result, the methods apply equally well for spacecraft with hybrid propulsion systems as to those with multimode propulsion. While multimode propulsion is still a maturing technology, there are many spacecraft currently flying with hybrid propulsion. Accordingly, the methods developed here are applicable not only to future multimode missions, but also to near-term missions with hybrid propulsion.","abstract_has_math":false,"creators":["Cline, Bryan Christopher"],"institution":"University of Illinois Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Aerospace Engineering","degree_department":null,"school":null,"contributors":["Woollands, Robyn M","Rovey, Joshua L","Allison, James T","Coverstone, Vicki L"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-12","date_published":"2025-12","updated_at":"2026-07-22T22:25:07Z","subjects":["Optimal Control","Indirect Optimal Control Techniques","Space Mission Design","Space Trajectory Optimization","Cislunar Space","Multimode Propulsion"],"languages":["en"],"rights":["Copyright 2025 Bryan Christopher Cline"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/2142/132571","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Woollands, Robyn M","Rovey, Joshua L","Allison, James T","Coverstone, Vicki L"]},{"key":"dc:creator","label":"Author","values":["Cline, Bryan Christopher"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2025-12","2025-12-04"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Aerospace Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Optimal Control","Indirect Optimal Control Techniques","Space Mission Design","Space Trajectory Optimization","Cislunar Space","Multimode Propulsion"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2025 Bryan Christopher Cline"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://hdl.handle.net/2142/132571"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Multimode spacecraft propulsion is an emerging, enabling, and enhancing technology that combines two or more propulsive modes (e.g., chemical and electric) into one system using a single propellant. The primary benefit of this technology is that it can provide reduced propellant consumption for a given transfer in comparison to an all-chemical approach and reduced transit time in comparison to an all-electric approach. It can also significantly increase the maneuvering capability domain of a spacecraft in comparison to single mode (i.e., all-chemical or all-electric) propulsion systems. Additionally, multimode propulsion provides mission flexibility and adaptability because the propellant may, in principle, be used in any mode at any time. Despite these benefits, there is presently a lack of mature techniques for designing optimal multimode transfers—particularly for chemical-electric multimode systems. In this dissertation, indirect optimal control techniques are developed for solving optimal multimode orbital transfers. Using an indirect approach results in the automatic selection of the burn sequence (i.e., which mode should be used at every instant). This yields more optimal transfers in comparison to the traditional approach in which the burn sequence is manually selected. Two types of optimal control problems are solved: minimum-fuel and propellant-constrained minimum-time (PCMT). The former is the primary focus of this dissertation and examples are shown for interplanetary, geocentric, and cislunar transfers for systems with large performance differences (i.e., thrust and specific impulse) between the modes. Forward single shooting is used to solve the example interplanetary and geocentric transfers in combination with hyperbolic tangent smoothing (HTS) for the throttle. To solve multimode cislunar minimum-fuel problems, a new technique is developed using modified equinoctial elements (MEE), HTS, forward-backward multiple shooting, two reference frames (Earth-centered and Moon-centered), and highly consistent dynamics. The method is demonstrated with multiple two-mode transfers as well as a three-mode transfer. The PCMT problem is particularly relevant for mission recovery efforts (e.g., after a launch injection failure) or spacecraft with hybrid propulsion systems (i.e., systems with two or more modes that are not integrated and do not share propellant) with fixed propellant budgets. To solve this problem, a penalty function approach was combined with HTS to enforce a maximum propellant usage constraint on the highest thrust, lowest specific impulse mode. The method is demonstrated with a three-dimensional transfer from a geostationary transfer orbit (GTO) to geostationary orbit (GEO) that was solved using MEE and forward single shooting. Finally, note that the techniques developed here are agnostic to the propulsion system. As a result, the methods apply equally well for spacecraft with hybrid propulsion systems as to those with multimode propulsion. While multimode propulsion is still a maturing technology, there are many spacecraft currently flying with hybrid propulsion. Accordingly, the methods developed here are applicable not only to future multimode missions, but also to near-term missions with hybrid propulsion.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2026-02-19 without embargo terms","The student, Bryan Cline, accepted the attached license on 2025-12-03 at 20:02.","The student, Bryan Cline, submitted this Dissertation for approval on 2025-12-03 at 21:36.","This Dissertation was approved for publication on 2025-12-04 at 11:23.","DSpace SAF Submission Ingestion Package generated from Vireo submission #23050 on 2026-02-19 at 18:28:19"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Optimal control techniques for multimode propulsion mission design in cislunar space"]}]}],"canonical_facts":{"dc:contributor":["Woollands, Robyn M","Rovey, Joshua L","Allison, James T","Coverstone, Vicki L"],"dc:creator":["Cline, Bryan Christopher"],"dc:date":["2025-12","2025-12-04"],"dc:description":["Multimode spacecraft propulsion is an emerging, enabling, and enhancing technology that combines two or more propulsive modes (e.g., chemical and electric) into one system using a single propellant. The primary benefit of this technology is that it can provide reduced propellant consumption for a given transfer in comparison to an all-chemical approach and reduced transit time in comparison to an all-electric approach. It can also significantly increase the maneuvering capability domain of a spacecraft in comparison to single mode (i.e., all-chemical or all-electric) propulsion systems. Additionally, multimode propulsion provides mission flexibility and adaptability because the propellant may, in principle, be used in any mode at any time. Despite these benefits, there is presently a lack of mature techniques for designing optimal multimode transfers—particularly for chemical-electric multimode systems. In this dissertation, indirect optimal control techniques are developed for solving optimal multimode orbital transfers. Using an indirect approach results in the automatic selection of the burn sequence (i.e., which mode should be used at every instant). This yields more optimal transfers in comparison to the traditional approach in which the burn sequence is manually selected. Two types of optimal control problems are solved: minimum-fuel and propellant-constrained minimum-time (PCMT). The former is the primary focus of this dissertation and examples are shown for interplanetary, geocentric, and cislunar transfers for systems with large performance differences (i.e., thrust and specific impulse) between the modes. Forward single shooting is used to solve the example interplanetary and geocentric transfers in combination with hyperbolic tangent smoothing (HTS) for the throttle. To solve multimode cislunar minimum-fuel problems, a new technique is developed using modified equinoctial elements (MEE), HTS, forward-backward multiple shooting, two reference frames (Earth-centered and Moon-centered), and highly consistent dynamics. The method is demonstrated with multiple two-mode transfers as well as a three-mode transfer. The PCMT problem is particularly relevant for mission recovery efforts (e.g., after a launch injection failure) or spacecraft with hybrid propulsion systems (i.e., systems with two or more modes that are not integrated and do not share propellant) with fixed propellant budgets. To solve this problem, a penalty function approach was combined with HTS to enforce a maximum propellant usage constraint on the highest thrust, lowest specific impulse mode. The method is demonstrated with a three-dimensional transfer from a geostationary transfer orbit (GTO) to geostationary orbit (GEO) that was solved using MEE and forward single shooting. Finally, note that the techniques developed here are agnostic to the propulsion system. As a result, the methods apply equally well for spacecraft with hybrid propulsion systems as to those with multimode propulsion. While multimode propulsion is still a maturing technology, there are many spacecraft currently flying with hybrid propulsion. Accordingly, the methods developed here are applicable not only to future multimode missions, but also to near-term missions with hybrid propulsion.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2026-02-19 without embargo terms","The student, Bryan Cline, accepted the attached license on 2025-12-03 at 20:02.","The student, Bryan Cline, submitted this Dissertation for approval on 2025-12-03 at 21:36.","This Dissertation was approved for publication on 2025-12-04 at 11:23.","DSpace SAF Submission Ingestion Package generated from Vireo submission #23050 on 2026-02-19 at 18:28:19"],"dc:format":["application/pdf"],"dc:identifier":["https://hdl.handle.net/2142/132571"],"dc:language":["en"],"dc:rights":["Copyright 2025 Bryan Christopher Cline"],"dc:subject":["Optimal Control","Indirect Optimal Control Techniques","Space Mission Design","Space Trajectory Optimization","Cislunar Space","Multimode Propulsion"],"dc:title":["Optimal control techniques for multimode propulsion mission design in cislunar space"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Aerospace Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:07Z"}