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Analysis of Crewed Missions Enabled by a Bimodal Nuclear Thermal Electric Propulsion System

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Analysis of Crewed Missions Enabled by a Bimodal Nuclear Thermal Electric Propulsion System Undergraduate Honors Thesis Presented in Partial Fulfillment of the Requirements for Graduation with Distinction in the Department of Aerospace Engineering at The Ohio State University Authored by: Justin Clark May 2019 Advisor: Dr. John Horack i Abstract From bone decay, to radiation exposure and muscle atrophy, long duration spaceflight poses significant health risks to humans. Technologies and practices have been developed that limit the impacts of some of these health issues, but perhaps the simplest method would be one of avoidance. Reducing mission durations through nuclear propulsion technologies has been researched since the 1950s, when NASA’s NERVA program tested various nuclear thermal engines for crewed applications. The technology showed significant promise but fell by the wayside due to political and environmental reasons. However, interest in nuclear thermal propulsion (NTP) has been renewed as of late, with NASA’s Marshall Space Flight Center and private companies such as BWX Technologies developing a new cryogenic NTP system for use with crewed Mars missions, possibly reducing one-way trip times from 6 months to 4 months. And while this would be a significant improvement, it’s possible that a standalone NTP system doesn’t meet the full potential of a nuclear fission powered spacecraft. Instead, a combined nuclear thermal and nuclear electric propulsion (NEP) system, also known as a bimodal nuclear propulsion system, could prove to be more efficient, and offer shorter mission times than just a single NTP system. A spacecraft with a bimodal nuclear propulsion system would have a single nuclear reactor and the capability to switch between both modes, altering the heat output of the reactor based on the required propulsion system. The NTP system would offer high thrust and an ISP in the 900s, and would be useful for escaping the sphere of influence of a planet. The NEP system, on the other hand, would offer very low thrust, but would provide long periods of propulsion in interplanetary space, as well as an ISP in the 5000s. In this paper, mission opportunities gained by a combined NTP/NEP system will be explored. Specifically, trajectories of crewed missions to orbit Mars and Jupiter using such a ii system will be analyzed, with the intent to minimize overall mission time. Fuel and payload weight calculations will also be performed to ensure that the delta-v budgets for these missions are adhered to. Some focus on the design of the reactor/propulsion system will also be given, and the overall performance and benefit relative to chemical and standalone NTP powered craft will be presented. iii Acknowledgements Over the course of this endeavor, many individuals helped in one way or another, and without their assistance, this project would not have been possible. First, I’d like to extend much love and many thanks to my wonderful family for all their support, not just for the duration of this undergraduate thesis, but also for the entirety of my undergraduate career here at Ohio State. There have been many strenuous moments over the past four years, and it’s always been reassuring to know that they’re there for me at all times. So, to mom, dad, Logan, Clayton, Lynn, Patrick, and Mee-Maw, thank you. Next, I’d like to thank the Battelle Center for Science, Engineering, and Public Policy for sponsoring this research and offering guidance throughout this process. To Dr. Elizabeth Newton, thank you for your constant support, and I’m ever so grateful for our insightful conversations about leadership and the human machine. To Jenny Shields, thank you for not just your logistical support with events and conferences, but your moral support to keep pushing through this research even when it seemed too difficult. To Dr. John Horack, thank you for giving me the courage to pursue my interests when I wasn’t confident in my ability to innovate. The wisdom and knowledge you’ve imparted on me concerning the technicalities and human patterns in astronautical engineering have inspired and emboldened me to continue down this career path. Finally, to everyone, thank you for your constant encouragement and kind words. They say you become like those you’re around, and if that’s the case, then the person I’m growing into is going to be insightful, kind, supportive, and knowledgeable, and I only have you all to thank for that. iv Table of Contents Abstract ......................................................................................................................................................... ii Acknowledgements ...................................................................................................................................... iv List of Figures ............................................................................................................................................... vi List of Tables ............................................................................................................................................... vii Chapter 1: Introduction ................................................................................................................................ 1 Chapter 1.1: Applications and Significance ................................................................................................... 7 Chapter 1.2: Overview of Thesis ................................................................................................................. 10 Chapter 2: Methodology ............................................................................................................................. 11 Chapter 2.1: Designing BNTEP Mission Architecture .................................................................................. 11 Chapter 2.2: Designing NTP Mission Architecture ...................................................................................... 15 Chapter 2.3: Designing Chemical Propulsion Mission Architecture ........................................................... 15 Chapter 2.4: Payload and Initial IMLEO Mass Consideration ..................................................................... 15 Chapter 3: Results ....................................................................................................................................... 17 Chapter 3.1: BNTEP System Results ........................................................................................................ 17 Chapter 3.2: Standalone NTP System Results ......................................................................................... 21 Chapter 3.3: Chemical Propulsion System Results ................................................................................. 25 Chapter 4: Discussion .................................................................................................................................. 30 Chapter 5: Conclusions and Future Work ................................................................................................... 33 References .................................................................................................................................................. 34 Appendix A: BNTEP MATLAB Script ............................................................................................................ 35 v List of Figures Figure 1: Average Delta-V Requirements as Functions of Mars Stay Time (Houts et al., 2018) ................. 3 Figure 2: Bimodal Nuclear Thermal Reactor and Propulsion Schematics (Houts et al, 2018) ..................... 5 Figure 3: Components and Schematic of the VASIMR Engine (Castro Nieto et al., 2013) ......................... 6 Figure 4: Configuration of a Bimodal Nuclear Thermal Electric Propulsion System (Borowski, 2003) ..... 8 Figure 5: Example Mars Mission Utilizing BNTEP Technology (Borowski, 2003) .................................... 9 Figure 6: Crewed Habitat Mass as a Function of Mission Duration (Arney et al., 2017)........................... 16 Figure 7 Earth Departure Trajectory of a BNTEP Craft ............................................................................. 18 Figure 8: Heliocentric Trajectory of a BNTEP Craft .................................................................................. 19 Figure 9: Mars Bound Trajectory Parameters and Flight Path Angle Optimization ................................... 19 Figure 10: BNTEP Mars Arrival and Departure Orbit and Hyperbola ....................................................... 20 Figure 11: Return Trajectory and Flight Path Angle Optimization ............................................................ 20 Figure 12: Short Duration NTP Earth Departure Trajectory ...................................................................... 22 Figure 13: Short Duration NTP Heliocentric Trajectory ............................................................................ 22 Figure 14: Short Duration NTP Mars Arrival and Departure Trajectories ................................................. 23 Figure 15: Long Duration NTP Earth Departure Trajectory ....................................................................... 23 Figure 16: Long Duration NTP Heliocentric Trajectory............................................................................. 24 Figure 17: Long Duration NTP Mars Arrival and Departure Trajectories ................................................. 24 Figure 18: Short Duration Chemical Earth Departure
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