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  2. Hitoshi Kuninaka

Hitoshi Kuninaka

  (國中 均)

Profile Information

Affiliation
Director General, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
Degree
Ph.D(Mar, 1988, The University of Tokyo)
Master(Mar, 1985, The University of Tokyo)
ORCID ID
 https://orcid.org/0000-0002-6871-3133
J-GLOBAL ID
200901080116851867
researchmap Member ID
1000144511
External link

Dr. Hitoshi Kuninaka received his Ph.D from the University of Tokyo in 1988. He was promoted to Associate Professor and Professor of the Japan Aerospace Exploration Agency, Japan, in 2000 and 2005, respectively. He held concurrently the post of Professor in the Department of Aeronautics and Astronautics, University of Tokyo, Japan, from 2004 to 2018. In 2018, he became the Director General of the Institute of Space and Astronautical Science (ISAS) as well as Vice President of Japan Aerospace Exploration Agency (JAXA).
 
He researches the plasma interaction of satellites and develops electric propulsions. He participated in the satellite project, Space Flyer Unit, from 1988 to 1996, and successfully brought it back to Earth via Space Shuttle STS-72. Microwave discharge ion engines, which were invented and developed by Dr. Kuninaka, took Hayabusa explorer on a round-trip journey between Earth and an asteroid from 2003 to 2010. The engines also have been propelling Hayabusa2 explorer toward another asteroid since 2014. The Hayabusa project team has been honored with the National Science Society (NSS) Space Pioneer Award, American Institute of Aeronautics and Astronautics (AIAA) Electric Propulsion Outstanding Technical Achievement Award, NSS Von Braun Award, International Academy of Astronautics Laurels for Team Achievement, SpaceOps Organization International SpaceOps Award for Outstanding Achievement among others. He received AIAA Fellow membership in 2012 and IAA Space Engineering Section Correspond Member in 2019.

Research Interests

 3

Research Areas

 3

Major Research History

 10
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Education

 6
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Major Awards

 34
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Major Papers

 161
  • Hitoshi KUNINAKA
    Vacuum and Surface Science, 63(4) 183-188, Apr 10, 2020  InvitedLead author
    The microwave discharge plasma sources contributed to the reciprocating powered flight between Earth and the asteroids as the main propulsion system of the Hayabusa and Hayabusa2 asteroid explorers, and showed its high performance. The electron cyclotron resonance discharge only heats the electrons and does not induce ion sputtering damage. The reasons of high performance and long life are derived and proved theoretically, experimentally, and in practical use in space. In addition to further space applications, efforts are also being made for industrial applications.
  • J. Inst. Electrostat. Jpn., 44(3) 128-134, Mar, 2020  Peer-reviewedLast author
    Electric charge accumulation can cause failure during vacuum manufacturing processes. For the charge neutralization in vacuum environment, cyclical change of its pressure to produce intermittent passive discharges according to the Paschen's law is often used; however, it is still insufficient to increse production efficiency. The goal of this study is to increase the charge neutralization rate in vacuum environments (10-10-4 Pa) using an electron cyclotron resonance (ECR) plasma source developed by JAXA (Japan Aerospace Exploration Agency) to neutralize the charge of spacecrafts emitting ions from their thrusters. We investigated the charge neutralization of a 50 mm × 50 mm plate with capacitance of 1.7 μF at initial voltage of 200 V, where the plate is placed 30 cm away from the ECR neutralizer. The time required to reach 37% of the initial voltage was 0.1 s for positive charge and 27 s for negative charge. In addition, improvement of the electron extraction electrode for the ECR neutralizer led to five times higher neutralization current compared to the previous ECR neutralizer at 10 W power and 0.1 mg/s xenon flow rate.
  • Kazutaka Nishiyama, Satoshi Hosoda, Ryudo Tsukizaki and Hitoshi Kuninaka
    Act Astronautica, 166 69-77, Jan, 2020  Peer-reviewedLast author
    © 2019 IAA Japan's second asteroid explorer Hayabusa2 was successfully launched on Dec 3, 2014, to return a sample from asteroid 162173 Ryugu by 2020. Four xenon ion thrusters based on electron cyclotron resonance discharge propelled the spacecraft for 547 h during its first year in space. Hayabusa2 completed an Earth gravity assist on Dec 3, 2015, followed by 798 and 2593 h of ion thruster operation, called the first and second transfer phases of delta-v, respectively. The third transfer phase of delta-v was conducted from Jan 10, 2018, to Jun 6, 2018, in which the final 2475-h ion thruster operation was executed before the rendezvous with Ryugu. The cumulative operating times for the four ion thrusters are 6,450, 11, 5,193, and 6418 h. This paper summarizes the 6515-h powered flight by the ion engine system, which produced 1015 m/s delta-v, in terms of thruster performance change, roll torques generated by various combinations of ion thrusters, and spacecraft surface erosion history measured by two quartz crystal microbalances located near the thrusters. In parallel with the space flight operation, an engineering model of the microwave discharge neutralizer has been under long-duration testing on the ground since 2012. It has accumulated 55,170 h of diode-mode operation as of Mar 15, 2019.
  • 85(7) 553-559, 2016  Invited
  • 國中
    日本惑星科学会誌, 22(2), 2013  Invited
    宇宙工学は、宇宙への往来の実現を目指し、技術を切磋琢磨してきた。その成果の端的な例は、「はやぶさ」にて実現された地球〜小惑星間往復航行（２００３年〜２０１０年）である。それにより、科学や技術分野を越えて、より大きな世界観を得ることができた。次の新しい知見を得るために、科学的な意義はもちろんのこと、「宇宙を自在に往来する独自能力の維持発展」と「人類の活動領域の宇宙への拡大」という宇宙工学・宇宙探査に跨る目標を担い、「はやぶさ２」小惑星探査ミッションが開発中である。
  • 川口, 國中
    日本航空宇宙学会誌, 59(694), 2011  Invited
  • Hitoshi Kuninaka, Kazutaka Nishiyama, Ikko Funaki, Tetsuya Yamada, Yukio Shimizu, Jun'ichiro Kawaguchi
    JOURNAL OF PROPULSION AND POWER, 23(3) 544-551, May, 2007  Peer-reviewed
    The electron cyclotron resonance ion engine has long life and high reliability because of electrodeless plasma generation in both the ion generator and the neutralizer. Four mu 10s, each generating a thrust of 8 mN, specific impulse of 3200 s, and consuming 350 W of electric power, propelled the Hayabusa asteroid explorer launched on May 2003. After vacuum exposure and several baking runs to reduce residual gas, the ion engine system established continuous acceleration. Electric propelled delta-V Earth gravity assist, a new orbit change scheme that uses electric propulsion with a high specific impulse was applied to change from a terrestrial orbit to an asteroid-based orbit. In 2005, Hayabusa, using solar electric propulsion, managed to successfully cover the solar distance between 0.86 and 1.7 AU. It rendezvoused with, landed on, and lifted off from the asteroid Itokawa. During the 2-year flight, the ion engine system generated a delta-V of 1400 m/s while consuming 22 kg of xenon propellant and operating for 25,800 h.
  • 國中
    プラズマ・核融合学会誌, 82(5) 300-305, May, 2006  InvitedLead author
    プラズマ生成に直流放電を利用する従来式電気ロケットは、放電電極損耗という劣化要素を含み、長寿命・高信頼を必須とする宇宙機械において重大な問題を抱えていた。これをマイクロ波放電による無電極化にて根本的に解決し、日本独自のシステムとしてマイクロ波放電式イオンエンジンが開発された。「はやぶさ」小惑星探査機は、2003年５月から2年余を掛けて、太陽距離0.86天文単位から1.7天文単位に至る広範な宇宙を走破して、目的天体「いとかわ」とのランデブーに成功した。この間、主推進装置である４台のマイクロ波放電式イオンエンジンは、22kgの推進剤キセノンを消費して、総増速量1,400m/s、延べ作動時間25,800時間という世界一級の成果を挙げた。慣性（弾道）飛行していたこれまでの「人工惑星」「人工衛星」とは異なり、高性能推進機関を搭載する宇宙機は、動力航行する能力を持ち、「宇宙船」に分類されるべき新しい技術である。
  • 国中均, 堀内泰男, 西山和孝, 船木一幸, 清水幸夫, 山田哲哉
    日本航空宇宙学会誌, 53(618) 203-210, Jul, 2005  Invited
  • H Kuninaka, P Molina-Morales
    ACTA ASTRONAUTICA, 55(1) 27-38, Jul, 2004  Peer-reviewedLead author
    Lack of neutralization is one of the most common malfunctions in ion thrusters. This phenomenon has been investigated by means of a ground experiment using a 2-cm class microwave-discharge ion thruster together with a reduced-size mock-up of the MUSES-C spacecraft. Electron leakage from the plasma beam to the high-voltage solar array has been observed to cause a slight amount of charging, its magnitude being equivalent to the operational voltage of the solar arrays. In the cases with no electron emission for ion beam neutralization, full-charging was established and the extracted ions were observed to return to the thruster body. At such experimental conditions, a so-called "virtual anode" appears in front of the deceleration grid. In this research, design guidelines for both the spacecraft and the ion engine system are proposed, based on the experimental simulation results. (C) 2004 Elsevier Ltd. All rights reserved.
  • 国中均, 西山和孝, 清水幸夫, 都木恭一郎, 川口淳一郎, 上杉邦憲
    日本航空宇宙学会論文集, 52(602) 129-134, 2004  Peer-reviewed
    The microwave discharge ion engine generates plasmas of the main ion source as well as the neutralizer using 4GHz microwave without discharge electrodes and hollow cathodes, so that long life and durability against oxygen and air are expected. MUSES-C “HAYABUSA” spacecraft installing four microwave discharge ion engines was launched into deep space by M-V rocket on May 9, 2003. After vacuum exposure and several runs of baking for reduction of residual gas the ion engine system established the continuous acceleration of the spacecraft toward an asteroid. The Doppler shift measurement of the communication microwave revealed the performance of ion engines, which is 8mN thrust force for a single unit with 3,200sec specific impulse at 23mN/kW thrust power ratio. At the beginning of December 2003 the accumulated operational time exceeded 7,000 hours and units.
  • H Kuninaka, S Satori
    JOURNAL OF PROPULSION AND POWER, 14(6) 1022-1026, Nov, 1998  Peer-reviewed
    The electron-cyclotron-resonance microwave-discharge ion thruster system utilizes no cathodes to emit thermionic electrons for plasma generation in both the ion source and the neutralizer The ion source can generate xenon ions at an ion-production cost of 300 eV and a propellant utilization efficiency of 88 %, with a double-charged-ion population of 8 %. The neutralizer can output 100 mA of electron current with 10 W of microwave power and 0.5 seem of xenon now. The thruster system combining the ion source and the neutralizer operated for 300 h without detectable erosion of the screen grid and ion source. Except for the primary frequency of 4.2 GHz used to generate plasmas, the system proved experimentally compatible with spacecraft electromagnetic interference requirements in the microwave frequency range.
  • KUNINAKA Hitoshi
    Aeronautical and space sciences Japan, 46(530) 174-180, Mar, 1998  Invited
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Misc.

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Major Books and Other Publications

 5
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Presentations

 190
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Major Teaching Experience

 5
  • Apr, 2005 - Mar, 2018
    電気推進工学  (東京大学大学院宇宙航空学専攻)
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Professional Memberships

 5

Works

 9
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Major Research Projects

 17
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Industrial Property Rights

 17
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Major Media Coverage

 9
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