Jun’ichiro Kawaguchi, JSPEC, ISAS/JAXA

1. Solar Power Sail - Hybrid Propulsion and its Applications - A Jovian Orbiter and Trojan Asteroid Flybys ISSS 2010 Jun’ichiro Kawaguchi, JSPEC, ISAS/JAXA

2. A Solar Power Sail Mission proposed at JAXA A Proposal from the Solar Power Sail Working Group (WG) at JSPEC, ISAS/JAXA. A Conceptual Study is summarized here. The Mission aims at Technology Demonstration of A Combined Solar Electric/Photon Powered Sail to Jupiter for Science Mission. This briefly introduces the Ikaros demonstration flight.

3. What’s new in ‘Solar Power Sail to Jupiter’ Proposal • World’s First Solar Powered Jovian Explorer, but Juno. • World’s First Combined Jovian Orbiter / Flyby Mission, • World’s Highest Performance Ion Engines, • World’s First Photon/Electric Hybrid Sail Propulsion, • World’s First Background Emission Mapping, • World’s First Access & Rendezvous to Trojan Asteroids, • World’s First Formation Flight in Jovian Magnetosphere. (TBD)

4. A Prospect for Solar Sail Technology Utilization • Sooner or later, Nuclear Propulsion represented by Fission / Fusion Reactors will prevail for Large and Heavy Interplanetary Transportation in 21st century. • However, Nuclear Propulsion weighs heavy and not efficient for smaller spacecraft, and Solar powered electric propulsion continues to be sought for the time being. • Contemporary Ion Engines performance characterized in terms of specific impulse will shift for higher region dramatically. Ultra-High specific impulse era does come. • Pure Solar Photon propulsion is useless for rendezvous and orbiter missions and the applications will be confined to smaller flyby probes. • This Prospect infers : Solar powered high-specific-impulse Ion Engines combined with Solar photon propulsion will be utilized for medium-to-smaller missions in near future. (Hybrid Propulsion)

5. Comparison : Proposed Solar Power Sail and Ulysses Ulysses: Mass: 370 kg, Powered by: RTG, Launched by STS-41 with Double Upper Stage (1990), Trajectory : ballistic. Proposed Solar Power Sail: Mass: 650 kg including a Jovian Orbiter, Powered by Thin Film Solar Cells, Launched by Expendable Smaller ELVs, Trajectory : Hybrid Combined SEP (Solar Electric Propulsion) with Photon

6. Solar Power Hybrid Sail Approaching to Jupiter

7. Major Technology Demonstration Itmes • A Large Membrane Space Structure including Deployment strategy, • A Hybrid Propulsion using both Photon and High Performance Ion Engines, • Thin Film Solar Cells, • Reaction Control System (Jet) functioning at very Low Temperature, • An Integrated Propulsion/Power System using Fuel Cells. • Formation Flight in Jovian system, (TBD) • Electric Delta-VEGA technique departing for outer solar system, • Ultra Stable Oscillator for 1-way range or VLBI orbit determination, • Ka-band for Interplanetary Missions, • Radiation-Resistant Technology for Jovian Orbiter, * Ultra High Speed Entry Probe for Jovian Atmosphere. (optional)

8. Thin Film Solar Cells and Large Membrane Space Structure • Developing Thin Film Solar Cells leads NOT ONLY to solar powered planetary missions BUT to a new space era represented by Solar Power Satellites etc. • The use of Thin Film Solar Cells should be used NOT for a mere demonstration, BUT for a real and essential space science.

9. 108 (km) 8 Jupiter 6 4 Sail 2 Earth 0 -6 -4 -2 2 4 108 (km) 0 Future Solar System Voyage Deep Space Port, Infrastructures (Outline)Deep Space Port built at L2, and Earth-to-Planetary Reusable Transportation System (Strategy)Large Spaceships are never launched from ground. Propulsion will be driven by nuclear power. Completely Reusable spaceships will be operated in future. (Prospect)Flight/Voyage will fly through Relay Port (Deep Space Port) Multi-objective On-orbit Stations are constructed. The traffic infrastructure will include commuter craft between gravity-well to the Port. Example: Round-Trip to Jupiter

10. Thin Film Solar Sail Thin Film Solar Cells Ikaros Jupiter and Trojan Asteroids Explorer Solar Sail Film Cells Trojan Asteroids Explorer Jovian Probe Evolution of Solar Power Sail ・Solar Power Sail combines photon propulsion with electric propulsion by taking the advantage of thin film solar cells technology, which optimizes highly efficient delta-V-fuel characterized by the solar photon sail through higher thrust nature to accomplish the missions within admissible period.

11. Preparing for the Real Mission • Detail the Science Requirements for both Cruise, Jupiter and Trojan Sciences. • System Design • Satisfying the science requirements, • Enhancing payload capability. • Elemental Studies at the Working Group • Schedule • WG Studies until 2011, • Pre-Project Activity from 2011 to 2013 • PM(EM) Design & Fabrication, TTM/MTM: 2013~2015 • FM Design and Fabrication: 2016~2017 • FM IVV: 2018~2019 • Launch: 2019~2020 • Cruise Science: 2020~（beyond main belt asteroids in 2025～） • Arrival at Jupiter & Orbiter Measurements : 2026~28 • Rendezvous with Trojan Asteroids : 2030.

12. Single EDVEGA 1st SW 5.4km/s Launch Double EDVEGA Typical Transfer Sequence

13. Beyond Main Belt Asteroids Cruise Observation Cruise Observation Trojan Asteroids Launch→Single EDVEGA→Jupiter Swingby Jupiter →Trojan asteroid rendezvous Trajectory Examples

14. Mother spacecraft (Trojan Rendezvous and Cruising Observation) Jovian Orbiter (Magnetosphere Measurement) Jupiter and Trojan Asteroids Explorer • Mission Scenario • Single EDVEGA Strategy： to assure ample science payload • By 4.5 years flight, the mother spacecraft jettisons the Jovian orbiter, which independently decelerates the orbital speed to stay around the Jupiter for scientific observation. • The mother spacecraft leaves the Jupiter for the Trojan Asteroids by 5 years flight.

15. Jupiter Entry Probe (option) Sail Drum Spacecraft Hub HGA Jovian Orbiter Aux. Solar Cell Cable to Petals Ion Engines Tables Damper Solar Power Sail (COSPAR04-A-01655, Paris, 2004 ) • Hybrid Propulsion combining Electric Propulsion with Photon Propulsion • Deploying Large Membrane including Thin Film Solar Cell, spanned by Centrifugal Forece • Rotor / Stator Spacecraft

16. System Block Diagram

17. Jovian Small Orbiter Outline Spin-Stabilized : Size : 700mmf in diameter. Operational Temperature : -30degC (243degK) Heater power : 80W assumed. Power required : 150W (no- communication), 250W.(with communication XPA: 20W) Cells Film : 60m2. (~9mf) No Drum Structure required. Ka-band TLM via HGA fixedly mounted. Routine operation assumes 0.5 hr/day. Heavy duty period is backed up by Fuel Cells aboard.

18. Orbiter Trajectory (Jupiter-Sun FixedCoordinate) (Ticks in 10 days) Phase Angle in Approach is 110 degrees.

19. Scientific Objectives in Solar Power Sail Mission • A Mapping Observation of Background Emission, • In-situ Jovian Science : Magnetosphere, Jovian Satellites, Jovian Atmosphere (option) • Rendezvous with Trojan Asteroids and Main-belt Asteroids, (Extended Flight Segment) • Gamma-Ray Bursts Detectors, (was aboard Ikaros) • A Large Area Dust Counter. (was aboard Ikaros)

20. Technology Development Example–1 Microwave-driven m10 engine to m10HIsp 15kV Acceleration m10HIsp Grid m10 Grid m10(Hayabusa Heritage) to m10HIsp(15kV, Isp 10,000sec, 2.5kW)

21. Technology Development Example–2 Jupiter Entry Probe - Aerodynamic Heating Ultra-High Heat Flux Environment qc =195 MW/m2 qr =320 MW/m2 Total = 490 MW/m2 Flight Environment Comparison

22. Solar Electric Hybrid Sailor – Roadmap What was attempted at JAXA: Aug. in 2003 Sounding Rocket (S310-34) Dynamic Membrane Deployment (10m) Spinner Feb. 2006 Subpayload on M-V#8 Quasi-Static Membrane Deployment (10m) Deployment resulted in Partial Success. Aug. 2006 Balloon Experiment on B200-7 Quasi-Static Membrane Deployment (20m) Deployment resulted in Success. Sept. 2006 Piggy-back ultra-small satellite on M-V#7 Thin Film Solar Power Generation Film Deployed. Functioned for 6 hrs using Battery. Resulted in Failure.

23. Sail Deployment Experiment • ISA/JAXA conducted the sail deployment experiment in space via a sounding rocket via a sounding rocket S-310#34 that carried two types of sails whose diameter is 10m. Deployed Clover-Type Sail S-310#34 Sounding Rocket

24. Clover Sail Flight Demonstration via S-310-34 Aug., 2004 Square Sail Deployment Demo. via Balloon Aug., 2006 1st Deoloy 2nd Deoloy Series of Preliminary Experiments

25. Membrane Deployment Experiments Clover Sail（ISAS） Pseudo Logarithmic Sail（ISAS） Fundamental Experiments were Repeated. Membrane deployment is one of the keys in Solar Sails. Double Accordion Sail (TMIT)

26. How JAXA Sail is characterized? • It is spanned by Spin, Centrifugal force without use of any spar. Exclusion of spar leads to significant mass reduction. • There is a drawback in adopting spin for extension. Hard to control huge angular momentum. (But we found a solution for it.)

27. Ikaros Background – How it is appropriated? • While we had made a proposal of putting a Solar Power Sail to the Jupiter, the proposal hardly passed through due to its high technology risks. Agency is always sensitive to the risks. • The study team (WG) then decided to propose a technology demonstrator to show if the deployment of large membrane is feasible. To this end, the WG proposed a small spacecraft carried by a smaller independent vehicle of JAXA. At that time, the demonstration was sought on Earth orbit. The proposal cost proposed was about $40M excluding the vehicle cost. • However, the proposal still did not go through, just because the cost is high in view of the risks. • When Akatsuki (PLANET-C) was decided launched via H-IIA, large payload surplus was identified, and JAXA almost decided to carry a dummy mass on the vehicle. • I, at that instance, raised my hand to propose a further low-cost solar sail demonstration by taking the advantage of this opportunity. The cost was proposed reduced down to about $20M. • The development period was just 2.5 years with this small amount of budget. The development was not easy. • I left the development to the younger generation with my participation as an adviser.

28. “Ikaros” : Mission Definition This Mission aims at the following four key targets． (1) Deployment of Large Membrane Sail Minimum Success Criteria • Deployment and Expansion of a Large Membrane in space using similar mechanical device and procedures to those in Solar Power Sail craft. • Obtaining a number of data indicating the expansion status of the membrane. (2) Collecting Power from Thin Film Solar Cells • Demonstrating Solar Power from Thin Film Solar Cells • System Verification with the same current as that in Solar Power Sail craft. (3) Demonstrating Photon Propulsion Full Success Criteria • Verification of Reflectance as well as Comparison of them with Diffuse & Specular Property. • Measurement of overall Reflectance with the rigorous relation examination of the temperature and surface status (4) Demonstrating Guidance, Navigation Control Skills for Solar Sail Propulsion • Navigation / Orbit Determination under continuous and small acceleration • Acceleration Direction Control via Steering via appropriate attitude control means

29. Venus Full Success during half a year 5) Trajectory Control Demonstration with Steering capability Minimum Success during several weeks Earth 4) Demonstrating Photon Propulsion 1) Launch via HIIA, Sun-Pointing, Spin-Separation 3) Minimum Success: Deploying Membrane with Thin Film Solar Cells `Power Generation. 2) Initial Inspection Ikaros – Its Mission

30. Ikaros flying toward Venus Launched in May to June of 2010, as an Extra Payload with PLANET-C (Venuc Climate Orbiter) toward Venus on H-IIA.

31. Tip Mass Released Separated from Vehicle Tip Mass Spin-down 1st Deployment Extraction Guide 2nd Deployment

32. Sail Membrane Tether Harness Deployed Extraction Guide Roller Full Deployment of Ikaros Sail Captured by Camera Aboard Where the Camera is?

33. 2nd Deployment Switching Doppler Measurement Photon Acceleration was Confirmed. Photon acceleration was legibly confirmed immediately after the 2nd deployment of the sail membrane.

34. Spin-down Spin-up Diffusion Radiation Effect drifted Attitude Motionas Expected. Circular shaped attitude motion caused by the Diffusion Radiation Effect was observed as predicted.

35. Tip Mass weighs 0.5kg each. Dust Particle Sensor (Piezo-electric device) Tethers Thin Film Solar Cells (25 micron) Liquid Crystal Steering Experiment Device Membrane made of 7.5 micron poly-imide. Ikaros Photographed in Space

36. Subsequent Speakers will report on Ikaros Achievements. • J. Kawaguchi on General Solar Sail Activity at JAXA, • O. Mori on Missions Operation, • H. Sawada on Sail Deployment Device, • Y. Shirasawa on Deployment Dynamics, • R. Funase on Liquid Crystal Reflection Control Device demonstrated, • Y. Mimasu on New Steering Law based only on Spin Rate Control. * Ikaros Demonstration Team is lead by O. Mori with our colleagues. The Ikaros was also success in nurturing the next generation.

37. Summary and Remarks A Solar Power Sail consisting of : Thin-Film Solar Cells in Large Area Membrane deployment technology taps for a new era. Baseline : Aiming at demonstrating a new strategy for outer solar system exploration by means of Solar Power, Hybrid propulsion spacecraft, also aims at background emission and Trojan asteroids flybys. World’s First & First Class Scientific output and Technology demonstration expected. Ikaros Demonstrator Mission was successfully placed. We are ready to host joint WSs with International Partners, such as the Planetary Society.