Orpheus AIAA Pluto Orbiter Design Competition AOE 4166: Senior Design Instructor: Dr. Kevin Shinpaugh Pluto Orbiter Group 1 Submitted by: Rob Engebretson, Timothy Hughes, Daniel McGrath, Jon-Paul Query, Clifton Reese May 10, 2018 Daniel McGrath Rob Engebretson Team Lead Propulsion/Structures and Launch Vehicles Communications, Command and Data AIAA Member Number: 594706 Handling/Attitude, Trajectory, and Orbits AIAA Member Number: 921354 Timothy Hughes Jon-Paul Query Attitude, Trajectory, and Orbits/Power, Power, Thermal, and Environment/Structures Thermal, and Environment and Launch Vehicles AIAA Member Number: 919746 AIAA Member Number: 919779 Clifton Reese Attitude, Trajectory, and Orbits/Propulsion AIAA Member Number: 921655 Kevin Shinpaugh Faculty Advisor Copyright © 2018 by Rob Engebretson, Timothy Hughes, Daniel McGrath, Jon-Paul Query, and Clifton Reese. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Executive Summary New Horizons, launched by NASA in 2006, performed a flyby of Pluto nine years later and gathered large amounts of data from the system. Orpheus, the successor to New Horizons, is designed to enter orbit around the Pluto system and send back larger amounts of data back to scientists on Earth. The name Orpheus was chosen for its mythological resonance with Pluto. Orpheus traveled to the underworld in order to bring back his wife, Eurydice, however at the end of the journey Orpheus left the underworld leaving behind his wife. The primary goal of this project is to gather scientific data from the Pluto system while orbiting the system for at least one year. Orpheus will need to topographically and optically map Pluto's surface while inside the system. Instruments onboard the spacecraft will also thermally map and retrieve high resolution images of Pluto, Charon and its smaller moons. Since the spacecraft will spend at least one year on orbit, the spacecraft can study the dynamic evolution of Pluto's atmosphere before ejection from the system. Geological features that New Horizons missed during its flyby can be studied due to the prolonged presence around Pluto and close orbit. The project requires the mission to conclude after 25 years from launch with a minimum of one year in the Pluto system. Due to the current position of Pluto and the outer planets, as well as booster availability, a Jupiter flyby trajectory has been chosen that requires a launch date of December 2028. This trajectory requires approximately 9.18 km/s of ∆V of onboard propulsion to achieve Pluto orbit, and will take roughly 17.5 years to arrive at Pluto. With this trajectory a total of 7.5 years can be spent inside the system exploring Pluto and its moons. The high ∆V required to successfully capture the spacecraft implies that a high specific- impulse propulsion system is needed. After comparing several thrusters, the NEXT thruster system was selected because of its efficiency and long life expectancy. A set of two NEXT iii thrusters will be used so that the risk of engine failure can be minimized. To power the electric thrusters, Orpheus will employ an 8 kW reactor and a MMRTG to produce a total of 8.1 kW for the spacecraft. Only nuclear power systems were deemed viable because of the distance from the sun which makes solar power useless. Fuel cells were briefly discussed but became unnecessary once the reactor became viable. Thermal control is accomplished by passive and active system which keep the spacecraft within its operational ranges. MLI will be used to thermally insulate the spacecraft and falls under the passive thermal system. Four sets of louvers are used to radiate excess heat near the inner solar system and a set of heaters will be used in the outer solar system. Orpheus is designed to maximize performance for a reasonable cost, estimated to be be- tween $1,570 and $2,027 million, while mitigating risk for the mission. Redundant systems have been used where necessary to ensure that Orpheus is able to complete its mission, in- cluding completely redundant computers and control hardware and a spare NEXT thruster. We believe that Orpheus will meet overall mission objectives and reveal valuable new infor- mation on both Pluto and dwarf planets in general. iv Contents Executive Summary iii Contents v List of Symbols and Abbreviations vii List of Figures ix List of Tables x 1 Introduction 1 1.1 Background . 1 1.2 Requirements . 2 2 Scientific Objectives 4 2.1 Close And Long Range Optical Imager (CALORI) . 6 2.2 Thermal Imaging Spectrometer . 7 2.3 Laser Altimeter . 8 3 Concept of Operations 9 4 Trajectory and Orbits 10 4.1 Trajectory . 10 4.2 Science Orbit . 12 5 Propulsion 14 5.1 Engine Types . 14 5.2 Engine Comparison . 15 5.3 Final Propulsion Configuration . 18 5.4 Summary . 19 6 Launch Vehicle 21 6.1 Summary . 22 7 Power 23 8 Thermal Management 28 9 Structure 33 10 Communications 38 v 11 Attitude Determination and Control 41 12 Data Handling 43 13 Risk Analysis 44 14 Compliance 47 A Mass Budget 49 B Cost Budget 50 C Requirements Flowdown 51 References 55 vi List of Symbols and Abbreviations ◦ degrees µm Micrometers AU Astronomical Unit dB Decibel Bps Bits per second BPSK Binary Phase Shift Keying C3 Characteristic Energy CALORI Close And Long range Optical Reconnaissance Imager DEAP Deep Space Network Aperture Enhancement Project ∆V Change in velocity DNE Do Not Exceed DSN Deep Space Network Eb/No ratio of received energy-per-bit to noise-density GPHS-RTG General-Purpose heat source RTG Gs Gravitaion force HIRISE High Resolution Imaging Science Experiment IMU Inertial Measurement Unit Isp Specific Impulse keV kiloelectronvolt Kg kilogram Km kilometer Km2 s2 Kilometers squared per second squared kW KiloWatts LA Laser Altimeter LH2 Liquid Hydrogen LOX Liquid Oxygen m meter m2 square meters mN millinewton m s meters per second MLI Multi-layer Insulation MMRTG Multi-Mission RTG NASA National Aeronautics and Space Administration NEXT NASA Evolutionary Xenon Thruster NSTAR NASA Solar Technology Application Readiness PEPPSI Pluto Energetic Particle Spectrometer Science Investigation PPU Power Processing Unit RCS Reaction Control System REX Radio Science Experiment RS Reed-Solomon decoding RTG radioisotope thermoelectric generator vii SLS Space Launch System SPICE Spacecraft Planet Instrument C-matrix Events SWAP Solar Wind at Pluto SDC Student Dust Counter THEMIS Thermal Emission Imaging System TIS Thermal Imaging System US United States W Watts W m2 Watts per meter squared viii List of Figures 1 Ojective Hierarchy . 3 2 Concept of operations for Orpheus. 9 3 View of Orpheus trajectory from edge of ecliptic plane. 11 4 View of Orpheus trajectory from above ecliptic plane. 11 5 Late-stage mapping orbit . 13 6 Comparison of the braking time required for each engine with its required initial mass. 16 7 Comparison of time required to achieve sufficient ∆V to complete the Pluto insertion burn . 20 8 Multi-Mission Radioisotope Thermoelectric Generator . 24 9 Kilopower nuclear fission reactor . 27 10 Solar Irradiance Throughout the Solar System . 29 11 Heat needed for Spacecraft for Survivable Temperature Ranges . 30 12 Spacecraft layout . 34 13 Cutaway of the launch configuration of the spacecraft. 35 14 Orpheus stowed in Falcon Heavy payload fairing. 36 15 Base of the reactor truss . 37 16 Antenna array . 39 17 Pointing error and data rate . 40 18 Risk Matrix . 45 ix List of Tables 1 Needs, Alterables, Constraints . 2 2 Comparison of engines. 16 3 Engine trade study. 17 4 Launch vehicle comparison . 21 5 Power systems trade study . 25 6 Power budget . 26 7 The Operating and Survival Temperatures of Significant Systems . 29 8 Solar Irradiance at Earth, Jupiter, and Pluto. 30 9 Link budget for cruise, propulsive, and science modes. 40 10 Risk Mitigation . 46 11 Compliance Matrix . 47 12 Data Compliance Matrix . 47 13 Mass Budget . 49 14 Cost Budget . 50 x 1 Introduction The goal of Orpheus is to follow New Horizons and gather more scientific data about Pluto and its moons by entering an orbit within the system. Questions about Pluto remain unanswered by the flyby performed by New Horizons and this project sets out to answer them. Using an instrument payload similar to that of New Horizons, Orpheus will gather topographical and thermal data about Pluto's dark side. Using a modified camera, Orpheus will also take higher resolution images of Pluto's smaller moons - Styx, Nix, Kerberos, and Hydra. While within a close orbit of Pluto, smaller features, such as potential cryovolcanoes, will be resolved. 1.1 Background In February of 1930, Clyde Tombaugh discovered a ninth planet in the solar system by observing movement of an object in various photographs. [1] Later named Pluto, after the mythological god of the underworld, it was known as the ninth planet in our solar system for more than 70 years. In 2006, Pluto was reclassified as a dwarf planet. [2] In the same year, NASA launched its New Horizons probe to study the dwarf planet Pluto in a flyby maneuver. Its goal was to study the surface of Pluto and its relatively large moon, Charon. After completing a gravity assist around Jupiter in 2007, New Horizons arrived in the Pluto system in July of 2015. The flyby was successful in obtaining far more detailed images of Pluto and Charon's surfaces and low-resolution images of Pluto's other, much smaller, moons. It is now exploring the Kuiper Belt and will eventually study other bodies in this system. [3] 1 Table 1: Needs, alterables, and constraints for Orpheus. Category Element Launch a probe from Earth to Pluto orbit Needs Send scientific data back to Earth Trajectory Propulsion Method(s) Launch Vehicle Alterables Launch Date Structure All Subsystems Orbit Maximum mission time of 25 years Constraints Orbit around Pluto system for at least one year One launch vehicle 1.2 Requirements The primary mission requirements come from the AIAA RFP.