On-Orbit Performance of a Miniature Propulsion System on a 70 Kg

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IMAGE: ©Hodoyoshi-3&4, The University of Tokyo SSC15-P-45 1 by Hiroyuki KOIZUMI On-orbit Performance of a Miniature Propulsion System Email: [email protected] Hiroki KAWAHARA1, Kazuya YAGINUMA1, Jun ASAKAWA1, on a 70 kg Space Probe to Explore Near-Earth Asteroids Yuichi NAKAGAWA1, Junichi NAKATSUKA2, Satoshi IKARI1, Ryu FUNASE1, and Kimiya KOMURASAKI1 The University of Tokyo1 & JAXA2

What is the micro-space probe, What is the unified-micropropulsion, Nominal mission Requirements to Propulsion I-COUPS? PROCYON? Verification of bus technologies of micro- space probe: communication, attitude control, Multiple thrusters I-COUPS [άɪkúːz] (Ion thruster and COld-gas thruster Unified Propulsion System) is a orbit determination, power generation, micropropulsion system equipped with ion thruster and multiple cold-gas thrusters to . University of Tokyo, in 2003, for RCS (reaction control system) developed and launched the world's thermal control, and micropropulsion The ion thruster and cold-gas thrusters shares the same gas first cubesat, XI-IV, into the orbit. High ΔV system, xenon gas. For downsized-propulsion system, MIPS-FM on H4 Advanced mission OUR mass of gas-feeding system becomes dominant In 2014, we challenged the world’s for orbit transfer of gravity assist rather than propellant. Hence, reducing first microsatellite, PROCYON, to Verification of technologies for deep-space- SOLUTION Total mass: 8.1 kg dry-mass of gas system is a key of develop micro-deep-space- exploration by a micro-space probe High thrust micropropulsion system. Xenon: 0.9 kg exploration. • GaN high-eff.-deep-space communication for TCM (trajectory correction maneuver) Volume: 39 x 26 x 15 cm3 • Fast-fly-by observation of asteroid • Orbit transfer by micropropulsion Power: 27 W PROCYON (2014) Thrust: 200 μN The first interplanetary Science mission Xenon Gas system1 Isp: 740 s microsatellite Geocorona observation by Lyman-alpha 2.57 kg (Tank) 2.01 kg Gas system Delta V: 140 m/s 10 km 4.5 kg !! Cold-gas (for 50 kg S/C) + XI-IV (2003) THE UNIVERSITY OF TOKYO thrusters ×8 The first cubesat 0.41 kg Gas system2 (others) Extremely simple structure of cold-gas thrusters and DEVELOPMENT Line-of-sight Power supplies 2.25 kg MIPS (Miniature Ion Propulsion System) is a micropropulsion gas sharing with ion thruster enabled light weight and SINCE 2013 SEPT. control 1.31 kg system equipped with an ion thruster developed for the 60-kg, compact micropropulsion system that provides full-set LEO-satellite HODOYOSHI-4, and the ion thruster successfully propulsion ability: orbit transfer, reaction control, and Controller Ion thruster conducted its first operation in space on Oct. 28th, 2014. The high thrust. 0.95 kg 0.38 kg The PROCYON & I-COUPS, I-COUPS was developed based on this MIPS. Earth gravity assist VERIFICATION Developed & Launched? 2015 END (TBD) The first interplanetary micro-spacecraft, Launch Dec 3 (2014) In-Flight Operation 0.12 25.00 Doppler shift/mm s-1 Initial checkout of the propulsion system started on Dec. 5th, 20.00 2014, two days after the launch. In one month, the project team 0.10 INTO Unloading successfully finished the checkout of the COTS-based high- maneuver DEEP SPACE 15.00 366±3 μN pressure gas system, cold-gas thrusters, and the ion thruster. 0.08 T. coefficient: 0.927 Torque by the cold-gas thrusters was confirmed by the angular 10.00 momentum change of the space probe and thrust of the ion Norm of the angular momentum/Nms Ion beam current/mA thruster was confirmed and measured by Doppler shift of the 0.06 communication wave. 5.00

©JAXA The ion thruster accumulated the total operation time up to 0.04 0.00

223 hours after solving problems #01-04. The averaged ion beam SPS-I (mA) / 1 NPS-V (V) / 10 CPS (kPa) / 200

Xenon gas current was 5.62 mA corresponding to the thrust of 346 μN. The LOCAL.ANGULAR_MOMENTUM_X LOCAL.ANGULAR_MOMENTUM_Y LOCAL.ANGULAR_MOMENTUM_Z I-COUPS; ITU全運転(5分平均プロット ) 論文用 from Dec 28 (2014) to Mar 12 (2015); 運転判定条件:SPS-I (mA)>1.00 (2.5 kg Ion thruster thrust coefficient γ_T was updated to 0.964 according to the

by 7.75 MPa@30℃) Thrust 300 μN thrust estimated from the Doppler data. The beam current 250 Simultaneous8.00 operation 0.4

showed a trend of gradual decrease by 1.7% over 200 hours.

Specific impulse 1080 s of ion thruster and cold-gas thruster

223 h

200

P Number of thrusters 1 ←Ion cur./mA

Problems exposed in the flight operation of the ion thruster 6.00 0.2 Mechanical Regulator (0.3 MPa) Power consumption 32 W 1. Leakage at the ion thruster valve 2. Error control of the pressure regulation valve 150 Z-Ang. Mom.→

Cold-gas thruster 2 3. Occasional freeze of the controller 4.00 0.0

Y-Ang. Mom.→

Low Pressure Gas Cold-gas Thruster Unit 4. Gradual increase of the neutralizer voltage 100 ←Neut. volt./V

Cold-gas thruster 1 Tank

5. High voltage anomaly of the ion thruster

Cold-gas thruster 6 P

2.00 -0.2

(30 kPa) P T 50

T P 01-04 were found in the initial checkout and solved by

# changing the operating conditions/methods. #05 appeared after ←Cold-gas P./100kPa X-Ang. Mom.→

Cold-gas thruster 8 time/hours operating Total 0 0.00 -0.4

Ion Thruster Unit the 223-h operation. Recovery operation for the problem #05 has time/hours operation Accumulated

Ion thruster continued to clear the expected cause, grid-short.

Achievement, up to today

Cold-gas thruster 5 The miniature propulsion system has operated for Ion thruster Cold-gas thruster Neutralizer Cold-gas thruster 7 more than 6 months, as the first interplanetary misalignment torque unloading ROCYON has no gimbal system and cold-gas Cold-gas Thrusters 1-8 Cold-gas thruster 4 micropropulsion. P Ion source thruster unloading is necessary, typically once a two • COTS-based micro-EP subsystems, including the Cold-gas thruster 3 days. Gas ejection from the cold-gas thrusters had Valves of the cold-gas thrusters have redundant systems for high-pressure gas system, have been in good health. potential to increase the gas pressure surrounding open failures of thruster valves. Cut-off valves are equipped at Cold-gas thruster unit has 8 cold-gas thrusters allocated at the center of • The cold-gas-thrusters are successfully working the space probe and to disturb the operation of the upstream of the thruster valves, which divided into two groups. each side of the probe as. Nozzle directions of all the thrusters were over 103 operations ion thruster. The unloading maneuver was conducted The cut-off valves have parallel configuration prepared for their canted from the panel surface to provide both of rotational force for RCS with continuous-operation of the ion thruster and it close failures. and translational force for TCM. • The ion thruster operated in 223 hours showed no interference with its operation.