A GenCorp Company Solar Electric Propulsion: Introduction, Applications and Status Dr. Roger Myers Executive Director, Advanced In-Space Systems [email protected] 425-702-9822 Agenda • Solar Electric Propulsion Overview • Benefits and Applications • Power Level Trends and Mission Drivers • System Challenges • Summary 1 What is Solar Electric Propulsion? Use of solar electric power to create and accelerate ions to exhaust velocities >5x chemical rockets Thruster options* • Resistojet • Arcjet • Hall • Gridded ion • others *Each thruster option has different capabilities and system requirements 2 Three Classes of Electric Propulsion Electrothermal Electrostatic Electromagnetic Gas heated via resistance Ions created and accelerated Plasma accelerated via Element, discharge, or RF in an electrostatic field interaction of current and interactions and expanded magnetic field through nozzle Pulsed Plasma Resistojets Hall Thrusters MPD/LFA Arcjets Gridded Ion Engines Pulsed Inductive Microwave, ICR, Colloid Thrusters Helicon Primary Systems Today are Resistojet, Arcjet, Hall, and Gridded Ion Systems Electric Propulsion Options and Trades • Benefits: • Much higher specific impulse • Arcjets – 600s • Hall Thrusters – 1500 – 3000s • Ion thrusters – 2500 – 10,000s • Other concepts (VASIMIR, MPD, PIT) in same range • Higher Isp results in much lower propellant mass • Trades: Optimum Isp for a given • Need external source of power and thrust (acceleration) electronics to match to the thruster Optimum • Thrust increases linearly with power • Trip time decreases as thrust increases Total mass • Power increases quadratically with Isp Prop Mass mass Power System for a given thrust Mass • Propellant mass decreases exponentially with Isp for a given DV Specific Impulse Typical Earth-space missions optimize between 1500 – 3000s Isp Why Consider Solar Electric Propulsion? Typical Spacecraft Mass Fractions LEO MISSION GEO MISSION PROPULSION PAYLOAD/OTHER PAYLOAD/OTHER PROPULSION POWER POWER In-Space Propulsion Dominates Spacecraft Mass Impact increases for Deep Space Missions Some Factors Influencing Spacecraft Mass Allocations: Mission: DV, duration, environments Technology changes: launcher size/capability, payload mass/volume, power system Policy changes: deorbit requirements, debris removal, insurance rates About one-half of Everything Launched is In-Space Propulsion It is a Major Opportunity for Mission Affordability Improvement SEP Adoption Driven by Competitive Advantage • General use started for station keeping • Vehicle power levels 5 - 10kW • EP thruster powers 0.5 – 2kW • First commercial use in 1980s • Enabled launch vehicle competitions • Reduced launch costs by reducing size of required launcher • Low power SEP used on: • >250 satellites in Earth Orbit • Deep Space-1 • Smart-1 • Dawn • Hayabusa 6 7 Recent Events Driving Acceptance of High-Power SEP • Launch Costs Continue to Increase • Successful Rescue of DoD AEHF SV1 using Hall Thruster System for Orbit Raising – Baseline mission saves >2000lbf by doing ~50% of orbit raising using EP – SV-2 launched and operational – SV-3 launched and orbit raising now LM’s AEHF • Boeing’s Announcement of All-Electric 702-SP – Use gridded ion engines (L-3) – Enables dual-launch on Falcon-9 • Emergence of New Exploration Missions Requiring Efficient High-Mass Payload Delivery Within Constrained Budgets Source: Space News 8 Critical Trends for Future SEP Systems • Mission Parameters Power*Efficiency Thrust ~ Isp Forecast • Trip time ~ Mass/Thrust ~Mass/Power Actua 20kW l SEP Thruster 10-15kW Adopted • So, Faster SEP Trip Times Require SEP Thruster Higher Power/Mass Ratios and Power Adopted 5kW Conversion Efficiency SEP Thruster • Need lighter weight, high power solar Adopted 2kW SEP arrays Thruster Adopted • Need lightweight, efficient power management and processing Spacecraft Power Level • Trip times through radiation belts are Increasing long • Radiation tolerance critical 9 Near-Term Higher Power SEP Benefits & Trades Analysis Example: Payload delivered to Earth-Moon L2 Total Delivered Mass = SEP curves of total LV Launch Mass – Fuel SEP curves are at delivered mass are Req’d to get to fixed EP power and independent of S/C destination thruster performance design. Think of this as the max mass that can be 12, 18, 27kW EP Power: Delivered Mass to L1/L2 off Atlas 551 divided up into 13000 S/C and Payload 12000 11000 MORE MASS MORE Increasing SEP 10000 Delta IV H power increases 9000 All Chem 90day WSBTdelivered * mass and 8000 All Chemical Transfers to L2 reduces trip times 7000 (Reference) 6000 Atlas V 551 All Chem 90day WSBT * 5000 LESS TRIP TIME Atlas V 531 All Chem 90day WSBT * 4000 SEP curves are based (kg) L1/L2 Deliveredto Mass Total All chemical 3000 on LV launch mass from Falcon 9 transfers for 2000 All Chem 90day WSBT * very highly eccentric 0.0 0.5 1.0 1.5 2.0 2.5 3.0 comparison (bot. left) to LEO (top Trip Time to L1/L2 (Years) 12kW EP Power (4 Thr @ 3kW ea) 1870s, 56mN/kW [~18kW OTS Bus] right) orbits * All Chemical WSBT Transfers to L2 Assumed Bi-prop 328s Isp, 232m/s, 18kw EP Power (4 Thr @ 4.5kW ea) 2000s, 56mN/kW [~26kW Bus] for Lunar/Final Insertion, 90d Transfer, and NASA published LV 27kw EP Power (6 Thr @ 4.5kW ea) 2000s, 56mN/kW [~38kW Bus] Performance Launch Mass for C3=-0.7 Performance Curves Show Trades between Power, Trip Time, and Delivered Mass for a Given Launch Vehicle and Destination 10 Ex #1: High Power SEP Application Example: Delta IV-H and Atlas 6000kg Space Vehicle: GTO GEO Mission • Using a S/C with 27 kW EP to thruster • Using a S/C with 18 kW EP to thruster gives a transfer time of 4.5 months gives a transfer time of 6.7 months Switching to SEP allows for a ~65% reduction in launch vehicle costs XR-5 Isp of 1816 s and T/P of 62.22 mN/kW. GTO is 185x35786 km (28.5°). GEO is 35786x35786 km (0°) Example #2: EML-2 Habitat Logistics Supply Deliver 20mt over 5 yrs using the TRL-9 Hall Systems 1.10 1.02 1.00 CHEMICAL 1.00 1.0y 0.94 90d SEP, 27 kW Thruster Input Power Potential 4Flts 0.90 90d 10Flts total 4Flts 0.80 0.77 campaign 0.73 1.6y 2.0y 90d cost 0.70 3Flts 3Flts 7Flts 0.65 1.1y 6Flts 0.61 savings of 0.60 1.1y 59% vs. 5Flts 0.53 1.4y 0.52 5Flts 0.50 chemical 0.50 1.6y 1.3y 2.0y 4Flts 0.41 7Flts (up to 0.40 4Flts 1.5y 2.1y* 2.5y 6Flts 6Flts $1.4B) 0.30 3Flts NO 0.20 *EP Total LV + S/C Cost (normalized) Cost S/C + LV Total CHEM Perf Solution 0.10 at On 2600s F9 v1.0 Isp 0.00 Delta IV H Atlas 551 Atlas 531 Falcon 9 v1.0 SEP solutions enabled significant total campaign cost savings of up to ~$1.4 BILLION for this notional campaign Approved for Public Release, Log # 2013-036 12 Example #3: Impact of In-Space Propulsion Technology on Launcher Requirements for Mars Crew of 4 to Low Mars Orbit and back 1600 Direct Return LEO Return Cryo Crew/Cargo Cryo Crew/SEP Hall Cargo 1406 1400 Cryo Crew/SEP Gridded Ion Cargo NTR Crew/Cargo 1200 NTR Crew/SEP Hall Cargo NTR Crew/SEP Gridded Ion Cargo 1000 LEO Return 800 748 Direct Return IMLEO, t IMLEO, 588 590 600 494 375 400 331 336 304 280 200 173 155 0 Direct Return LEO Return Separating Cargo and Crew, and using SEP for Cargo and High Thrust Chemical or NTR for Crew, decreases launcher requirements by 2X Approved for Public Release, Log # 2013-036 13 High-Power SEP Dramatically Improves the Affordability of Space Missions for Multiple Customers Robotic Missions Validate Large NEOs/Phobos/ Moon/other Technologies Payload Delivery NASA SMD/HEOMD for Higher DoD/NASA HEOMD/SMD/ Power SEP Commercial NASA HEOMD 30-50kW-class SEP Space Vehicle Space Space Environments Situational Satellite & Depot Orbital Mapping Awareness Servicing Debris DoD/NASA DoD DoD/NASA/ Removal Commercial 30-50 kW SEP Vehicles Reduces Cost for Many User Communities Exploration Mission Needs It’s All About Affordability • Establish an efficient in-space transportation system to reduce mission cost – Use SLS and other launch vehicles along with efficient in-space transportation to reduce cost and increase science mission and exploration capability • Near Term (next 5 years): 30 – 50kW SEP Vehicles for – Logistics in cis-lunar space – Larger scale robotic precursors (Asteroid Re-Direct Mission) – NOTE: These systems have broad applicability to DoD and other civil missions • Mid-Term (5 – 15 years): 100 – 200kW SEP Vehicles for – Cargo pre-placement at destinations (Martian Moons, Lunar Orbit, etc.) • Long-term (15- 20 years): 200 – 600kW SEP Vehicles for – Large cargo pre-placement (habitats, landers, Earth Return stages, etc.) – NOTE: “Vision System” includes reusability – multiple trips through belts Evolutionary Growth of SEP Systems will Keep Missions Affordable 15 A GenCorp Company SEP Subsystem Options and Trends Power and Propulsion 16 Power System Architecture Options To date, vehicle power systems are dominated by payload power: For Vehicles where SEP Vehicle/Payload Power Power is Dominant: 1) Combine PMAD & PPU? 2) “Direct Drive” EP from arrays? SEP Vehicle Power System Architecture May Need Re-evaluation When SEP is Dominant Power Consumer 17 SEP Power System Technology Challenges (1/3) High Power Arrays • Cell Efficiency – Currently ~40% in lab – Target is ~50% BOL • Lightweight Structures – Current array P/M is ~ 70W/kg – Target is 200 – 400W/kg • Launch Vehicle Packaging and Deployment Mechanisms – Current Stowed Volume is <20kW/m3 – Target is 60 – 80 kW/m3 • Radiation tolerance – Capability and affordability will be enhanced if degradation can be reduced from current ~15% per trip to ~5% per trip without a large mass penalty