Analysis of Electric Propulsion Systems for Drag Compensation of Small Satellites in Low Earth Orbits The Universtiy of Manchester Teodor Bozhanov, ID: 9023890 Supervisor: Dr. Peter C.E. Roberts Final Report 02 May 2017 Abstract Small satellites, in particular CubeSats, have been the study focus of many major space agencies, universities and private organisations. Recent studies have shown that small satellites can reach up to 95% of the operational capabilities of large satellites, for only 5% of the cost. One drawback however, is that CubeSats have no onboard propulsion system and therefore no orbit maintenance and manoeuvre capabilities. This, coupled with the fact that they are usually inserted at very low Earth orbits (VLEO (under 400 km)), means that orbital lifetime is extremely limited. Consequently, small satellites and CubeSats have reduced lifetime and operational capabilities, limiting the range of their missions. Electric propulsion systems can generate the required thrust for drag compensation, while being extremely efficient. This results in a relatively low propellant fraction, reducing the negative impact on the available payload. This study focuses on using various Electric Propulsion (EP) and Atmosphere Breath- ing Electric Propulsion (ABEP) systems to increase the lifetime and usefulness of the satellites. The scope of the study is limited to VLEO ranging from 100 to 300 km. This zone is ideal for Earth observation and reconnaissance missions. In addition, it falls within the range of the ABEP system, where higher atmospheric density is more favourable. The computer model generated for this study accounts for 6 different types of per- turbations and is able to model the change of orbital parameters with high degree of accuracy. Preliminary results from several different types of EP show an increase of orbital lifetime between 200 and 600%. In some cases the associated velocity change is sufficient for performing small orbital transfers, rendezvous and docking manoeuvres. Orbit raising of about 900 - 1200 km was observed from a couple of thrusters. It was seen that a trade-off zone, between EP and ABEP, starts to form from about 250 km below, where ABEP thrusters become more effective. 1 Contents 1 Introduction 9 1.1 History of Electric Propulsion . .9 1.2 Motivation . 12 1.3 Aims and Objectives . 15 1.4 Methodology . 16 2 Physical Background 17 2.1 Space Environment . 17 2.1.1 Atmosphere and Vacuum Environment . 17 2.1.2 Neutral Environment . 19 2.2 Electric Propulsion Systems . 20 2.2.1 Electrothermal Acceleration . 21 2.2.2 Electrostatic Acceleration . 23 2.2.3 Electromagnetic Acceleration . 24 2.3 Atmosphere Breathing Electric Propulsion . 25 3 Literature Review 27 3.1 Introduction . 27 3.2 Relevant Research . 27 3.2.1 Electric Propulsion . 27 3.2.2 Atmosphere Breathing Electric Propulsion (ABEP) . 30 3.2.3 Drag and Atmosphere Models . 33 3.3 Summary . 36 4 Methodology 37 4.1 Mission Setup . 37 4.2 Methodology . 37 4.3 Assumptions and Limitations . 38 5 Preliminary Analysis 41 5.1 Atmosphere Models . 41 5.1.1 Drag Variation With Altitude . 43 2 xCONTENTS Teodor Bozhanov 5.1.2 Drag Variation With Latitude and Longitude . 43 5.1.3 Drag Variation With Solar Activity . 46 5.2 Orbital Propagators . 48 5.2.1 Energy Methods . 48 5.2.2 Gauss's Planetary Equations (GPE) . 50 5.3 EP Systems . 53 5.3.1 Pulsed Plasma Thrusters . 53 5.3.2 Ion Thrusters . 54 5.3.3 Field Emission Electric Propulsion . 56 5.4 ABEP systems . 57 5.4.1 Intake . 57 5.4.2 Thrusters . 60 6 Results and Discussion 62 6.1 Drag Compensation With EP . 62 6.1.1 ARC PPT Thruster . 64 6.1.2 RIT Ion Thruster . 65 6.1.3 IFM Nano FEEP Thruster . 67 6.1.4 Summary . 69 6.2 Drag Compensation With ABEP . 74 6.2.1 Theoretical Predictions . 74 6.2.2 Numerical Simulations . 77 6.3 Future Work . 79 7 Conclusion 81 8 Project Management 83 8.1 Semester I . 83 8.2 Semester II . 85 3 List of Figures 1.1 Number of Commercial Satellites with on-board EP system (Hoskins, W.A. et al. 2013). 12 1.2 Small satellites trends (2016-2022) (Doncaster and Shulman 2016). 14 1.3 Space Debris Population at different altitudes. Active Debris Re- moval (ADR05) of 5 objects per year needs to be conducted to main- tain current debris density (Liou, Johnson, and Hill 2010). 15 2.1 Variation of atmospheric layers with altitude (km) (Tewari 2007) . 18 2.2 Single particle momentum transfer. (Tribble 1995) . 19 2.3 Oxidised silver which is flaked off, exposing the underlying fresh ma- terial which is oxidised again (Rooij 2010). 20 2.4 1D Schematic of an Electrothermal Thruster (Jahn 2006) . 22 2.5 1D Schematic of Electrostatic Acceleration (Sforza 2016) . 23 2.6 Schematic of MPD accelerator (Sforza 2016) . 24 2.7 Schematic of a typical PPT (Sforza 2016) . 25 2.8 Atmosphere Breathing Ion Engine (Nishiyama 2003) . 26 3.1 Two Air Intake concepts: Funnel Concept a); Bypass Concept b). 31 3.2 Variation of the different atmospheric constituents with altitude (Schon- herr et al. 2015) . 31 3.3 Variation of Relative Density with Solar Activity (Tribble 1995) . 34 4.1 Analysis of Electric Propulsion Systems: Flowchart . 39 5.1 Variation of Density With Altitude for 5 Different Atmosphere Models 42 5.2 Variation of Drag Force With Altitude for NRLMSISE and MSIS. 43 5.3 Drag Variation With Latitude, at Constant Longitude and Solar Flux, for Every Hour at 300 km Altitude. 44 5.4 Drag Variation With Longitude, at Constant Latitude and Solar Flux, for Every Hour at 300 km Altitude. 45 5.5 Maximum Drag Variation With Solar Flux, at Constant Longitude, Latitude and Time. 46 4 xLIST OF FIGURES Teodor Bozhanov 5.6 Solar Flux Drag Variation at 116 km altitude. 47 5.7 Orbital Decay for 1U, 2 kg CubeSat . 49 5.8 Orbital Decay for 1U, 2 kg CubeSat using GPE . 51 5.9 Orbital Decay for 1U, 2 kg CubeSat Using Extended GPE . 52 5.10 Extended GPE Propagator: Orbital Decay of a 1U Cubesat (different mission types) . 53 5.11 NASA S-iEPS thruster: tank configuration (left) and thruster circuit arrangement (Krejci, Mier-Hicks, et al. 2015). 55 5.12 IFM Nano Thruster Family (Reissner et al. 2015). 56 5.13 BUSEK long annular intake (Hohman 2012). 58 5.14 JAXA long annular bypass intake with a conical diffusion region (Fu- jita 2004). 58 5.15 DSMC analysis with integrated turbomolecular pump, where = 0.95 and P are the molecular flow transmission probabilities of incident particles. High speed case: 3 stages turbo (Fujita 2004). 59 5.16 Schematic of Inductive Plasma Thruster (Romano, Binder, Herdrich, Fasoulas, et al. 2016). 60 2 5.17 IPT thrust variation with altitude for Air at Af = 1m , ηc = 0.35 (Romano, Binder, Herdrich, Fasoulas, et al. 2016). 61 6.1 Orbital Lifetime with no propulsion system in place. 63 6.2 PPT Drag Compensation for 1U CubeSat. 64 6.3 PPT Drag Compensation for 2U CubeSat. 65 6.4 RIT-µX Drag Compensation for 1U CubeSat. 66 6.5 RIT-µX Drag Compensation for 1U CubeSat 200 km. 66 6.6 RIT-µX Drag Compensation for 2 and 3U CubeSats. 67 6.7 IFM Nano Drag Compensation for 2U CubeSat. 68 6.8 IFM Nano Drag Compensation for 2U CubeSat 200 km. 68 6.9 IFM Nano Drag Compensation for 3U CubeSat. 69 6.10 IFM Nano Drag Compensation for 3U CubeSat 200 km. 69 6.11 Various Thruster Arrangements (Reissner et al. 2015) . 71 6.12 Lifetime percentage increase with 30 g of propellant. 72 6.13 Change of ∆V with Propellant Mass. 73 6.14 Mass flow variation with altitude (Romano, Massuti, and Herdrich 2014) . 74 6.15 Variation of Drag force for 3U CubeSat . 76 6.16 ABEP orbital lifetime at 180 km, operational for 200 h. 77 6.17 ABEP orbital lifetime at 250 km, operational for 200 h. 78 8.1 Semester 1 Gantt Chart . 84 5 xLIST OF FIGURES Teodor Bozhanov 8.2 Gantt Chart for Semester 2. 86 6 List of Tables 5.1 Percentage Difference Between 4 Atmosphere Models and the Control Model(MSIS)............................... 42 5.2 Percentage Difference Between Energy Method and Commercially Available Software . 49 5.3 Percentage Difference Between Different Orbit Propagators . 51 5.4 Comparison of different PPT systems (Colleti, Ciaralli, and Gabriel 2015), (Krejci, Seifert, and Scharlemann 2013). 54 5.5 Comparison of various Ion Thrusters (Wright and Ferrer 2015), (Kre- jci, Mier-Hicks, et al. 2015). 55 5.6 Comparison of different FEEP systems (Wright and Ferrer 2015), (Reissner et al. 2015) . 56 5.7 BUSEK results of DSMC simulation (Romano, Binder, Herdrich, and S. 2015) . 58 5.8 JAXA results of DSMC simulation (Romano, Binder, Herdrich, and S. 2015) . 59 6.1 Electric thruster selection. 62 6.2 Extended GPE Propagator: Simulation Starting Parameters . 63 6.3 Simulation data for 1U CubeSats. 70 6.4 Simulation data for 2U CubeSats. 70 6.5 Simulation data for 3U CubeSats. 71 6.6 Atmosphere Breathing Electric Propulsion, Theoretical Predictions. 75 6.7 Theoretical Predictions for ABEP Systems. 76 7 xLIST OF TABLES Teodor Bozhanov Acronyms ABEP Atmosphere Breathing Electric Propulsion ABIE Atmosphere Breathing Ion Engine AFRL Air Force Research Laboratory AO Atomic Oxygen CAT Cathode-Arc Thruster CIRA COSPAR International Reference Model COSPAR Committee on Space Research DSMC Direct Simulation Monte Carlo DTM Drag Temperature Model EP Electric Propulsion EPRB Electric Propulsion Research Building ESA European Space Agency EUV Extreme Ultraviolet FEEP Field Emission Electric Propulsion GOCE Gravity field and steady-state Ocean Circulation Explorer IPG Inductive Plasma Generators Isp Specific Impulse ISRU In Situ Resource Utilisation JAXA Japan Aerospace eXploration Agency LEO Low Earth Orbit LISA Laser Interferometer Space Antenna MPD Magnetoplasmadynamic Thrusters MIT Massachusetts Institute of Technology MSIS Mass Spectrometer Incoherent Scatter NASA National Aeronautics and Space Administration NEP Nuclear Electric Propulsion PPT Pulsed Plasma Thruster SERT Space Electric Rocket Test SMART Small Missions for Advanced Research and Technology TLE Two-Line Element VASIMIR Variable Specific Impulse Magnetoplasma Rocket VLEO Very Low Earth.