研究者詳細 - 赤星　保浩

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Study of the effects of projectile strength and density in the asteroid deflection by hypervelocity impact 査読有り国際誌

Wakatsuki Y., Akahoshi Y., Koura T., Takahara H.

International Journal of Impact Engineering 180 2023年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

In recent years, potentially hazardous asteroids (PHAs), which have orbits approaching the Earth and are a threat to humankind, have been attracting attention. It is necessary to prevent them from impacting the Earth, and asteroid deflection by hypervelocity impact is one of the best impact avoidance. This asteroid deflection needs to be greater, but momentum enhancement factor β, which represents deflection efficiency, is affected by various factors. This study focused on projectile strength and density, and experiments for small-scale impacts and numerical simulations for large-scale impacts were conducted to clarify these effects on β. In experiments, six types of projectiles with different strengths and densities and the same shape and size were impacted into brick targets at 1-3.5 km/s using a Two-Stage Light Gas Gun to investigate the effects in actual impacts. In simulations, three types of projectiles with different densities and the same shape and mass were impacted into granite targets at 3-10 km/s using AUTODTN to investigate the effects in asteroid-deflection-scale impacts, which are difficult for experiments. In conclusion, the effect of projectile strength on β is less, and the one of projectile density on β is high. It is demonstrated that projectiles whose density is close to the target density increase β, namely, are suitable for asteroid deflection regardless of impact scale. Additionally, a crater formed by hypervelocity impact is a preferably flat shape for asteroid deflection, and the effect of crater shape on β is higher at large-scale impact. Further study of this effect and the scaling one could be expected.

DOI： 10.1016/j.ijimpeng.2023.104710

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STUDY OF THE EFFECTS OF PROJECTILE STRENGTH AND DENSITY IN THE ASTEROID DEFLECTION BY HYPERVELOCITY IMPACT 査読有り国際誌

Wakatsuki Y., Koura T., Akahoshi Y.

Proceedings of the 16th Hypervelocity Impact Symposium, HVIS 2022 2023年01月

STUDY ON HYPERVELOCITY IMPACT OF SRM SLAG WITH VOIDS 査読有り国際誌

Fujii M., Nitta K., Higashide M., Akahoshi Y., Koura T.

Proceedings of the 16th Hypervelocity Impact Symposium, HVIS 2022 2023年01月

担当区分：責任著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

Solid rocket motors are mainly used for launching small satellites because they have a small number of parts, simple structures, and high responsiveness. However, there are concerns about solid rocket motors, which release solid rocket motor slag (SRM slag). The SRM slag is derived from aluminum powder in a solid matrix and released as agglomerated alumina into outer space before and after the solid rocket motor is cutoff. It has been confirmed that voids inside themselves in combustion tests in a vacuum conducted by JAXA. In this paper focusing on SRM slag with voids, we simulated its impact with diameters ranging from 1 mm to 10 mm, with porosities ranging from 0 % to 80 %, and with impact velocities of 2-15 km/s towards enough thick targets. We investigated the potential danger of SRM slag with voids using AUTODYN-2D. In addition, we calculated the ballistic limit curve (BLC) for each porosity of SRM slag based on the penetration depths obtained by the numerical simulations and compared BLCs in SRM slag and space debris made of aluminum alloy.

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材料力学教育における新しい試み

赤星保浩

工学教育研究講演会講演論文集 ( 公益社団法人日本工学教育協会 ) 2021 ( 0 ) 218 - 219 2021年01月

Evolution of ISO's space debris mitigation standards 査読有り国際誌

Stokes H., Akahoshi Y., Bonnal C., Destefanis R., Gu Y., Kato A., Kutomanov A., LaCroix A., Lemmens S., Lohvynenko A., Oltrogge D., Omaly P., Opiela J., Quan H., Sato K., Sorge M., Tang M.

Journal of Space Safety Engineering 7 ( 3 ) 325 - 331 2020年09月

記述言語：英語掲載種別：研究論文（学術雑誌）

Since 2010 the International Organization for Standardization (ISO) has been publishing a comprehensive set of international standards on space debris mitigation based on guidelines and best practices from the IADC and other bodies. This paper describes the structure and content of the ISO debris standards and how they are evolving to address the needs of space environment sustainability within the context of a rapidly changing space industry. Particular emphasis is placed on ISO 24113 (Space systems – Space debris mitigation requirements), which was published as a third edition during July 2019. The new requirements are compared with those in the previous edition and the rationale for the various changes is discussed. Most notably, the requirement for a spacecraft or orbital stage to exceed a specified threshold for its probability of successful disposal has been made more demanding. With the launch of numerous small spacecraft into LEO and the imminent launch of constellation systems comprising thousands of satellites, it is likely that the ISO debris standards will have to implement even stricter requirements in the future. The challenge is to do this in a way that is fair and reasonable for the entire space industry.

DOI： 10.1016/j.jsse.2020.07.004

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高速衝突と爆薬を併用した小惑星軌道変更策の検討

古賀想大, 池田仁哉, 吉田冬威, 高良隆男, 赤星保浩

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2019 ( 0 ) C12 2019年01月

記述言語：英語掲載種別：研究論文（研究会，シンポジウム資料等）

Near Earth Objects (NEOs) are asteroids and comets which come close to Earth's orbit each year. So there is a high possibility of impacts for example, in February 2013, an asteroid created an airburst near Chelyabinsk State in Russia, causing an estimated damage of approximately 33M$ and injuring an estimated damage of approximately 1500 people. To avoid asteroid impacts it is necessary to change NEO's orbit. Impacting at a hypervelocity is one of the methods that we consider to change NEO's orbits. Hypervelocity impacts intend to change the orbit by making a spacecraft impacts on the NEO. In our study we examined the orbit change induced by hypervelocity impacts and explosives to further improve the effect. The influence on the orbit by explosives depends on the shape of the crater created by an impactor. Thus we will optimize its shape by making impact tests with a Two Stage Light Gas Gun in order to accelerate impactors with different shapes. As a result, we analyzed of the influence by explosive with AUTODYN from the shape of craters obtained by the experiment and we found that the shape of crater has an optimum condition.

DOI： 10.1299/jsmekyushu.2019.72.C12

その他リンク： https://ci.nii.ac.jp/naid/130007801936

航空機用炭素繊維強化プラスチック材料の耐衝撃性評価

林泰斗, 赤星保浩, Lee Juhyo, 高良隆男

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2019 ( 0 ) G14 2019年01月

記述言語：英語掲載種別：研究論文（研究会，シンポジウム資料等）

To reduce fuel consumption on airplanes, we need nowadays lighter materials which absolutely need to withstand bird strikes. CFRP (Carbon fiber reinforced plastic) is one of the best materials for this, considering its high strength modulus and low density, but still lacks impact resistance. In this study, we simulated a fragment of aircraft impacting on a fan case in order to develop a CFRP with a better strength and impact resistance than conventional CFRP. For this experiment, we used the gas gun installed in our laboratory, and a rigid rectangle projectile as an impactor. Then, we compared our new lamination structure with conventional CFRP according to the amount of absorbed energy and to the delamination area (internal separation of layers). The amount of energy is obtained by the difference of energy before and after the impact, and the higher the energy absorbed, the more resistant the material is. In the case of the delaminationarea, the smaller it is, the lower the damages are. In new CFRP (called E2-E), the conventional [45, -45] degree layer is changed to a [30, -30] degree layer and a 0 degree layer is added between the 30 and -30 layers. The conventional lamination structure is [(0/45/-45/0)3(45/-45)(0/-45/45/0)3], and the E2-E's lamination structure is [(0/30/0/-30/0)2(30/0/-30)2]s. As a result, for the same amount of energy the CFRP E2-E was not penetrated unlike conventional CFRP. Moreover, the absorbed enegy was higher and the delamination area was smaller, which means the E2-E materialshowed better performances than coventional CFRP.

DOI： 10.1299/jsmekyushu.2019.72.G14

その他リンク： https://ci.nii.ac.jp/naid/130007801977

スペースデブリ捕獲銛における耐久性評価

吉田賢雄, 大森彩加, 藤井聡史, 高良隆男, 赤星保浩

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2019 ( 0 ) C11 2019年01月

記述言語：英語掲載種別：研究論文（研究会，シンポジウム資料等）

One of the promising ways to remove space debris is to attach an electrodynamic tether (EDT) to debris by shooting a harpoon from an active debris removal satellite. There is a possibility for the harpoon to be removed from the surface of debris because of the tensile load of the EDT. The purpose of this research is to evaluate the pull-out force in a novel harpoon designed for the debris capturing system. This new harpoon with a barb is composed of an inner harpoon and an outer harpoon. After the penetration, the outer harpoon is deformed by the inner harpoon and so creates a barb on the tip. Harpoon shooting tests were conducted using a debris capture gun in order to study the impact of the harpoon into the aluminum alloy plate. After firing tests, pull-out tests were conducted by the universal tensile testing machine. During these tests, the harpoon was deformed after the penetration and opened a barb on the tip so the function of barb system could be confirmed. Moreover, the maximum pull-out load the harpoon can handle without being separated from the plate is measured. For some harpoons with the barb system, pull-out load was superior to the non-barb systems. In this way, the efficiency of this design of harpoon is proved, with a maximum loading of 7000 to 16000 N.

DOI： 10.1299/jsmekyushu.2019.72.C11

その他リンク： https://ci.nii.ac.jp/naid/130007801937

Ejecta斜め衝突実験と解析によるISO11227改定案の検証

花草孝史, 赤星保浩, 田上翔悟, 村竹菜々瀬, 高良隆男

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2019 ( 0 ) C14 2019年01月

記述言語：英語掲載種別：研究論文（研究会，シンポジウム資料等）

At present, Space debris have a lot of problems in the space industry. They are the crush to spacecrafts and making the restriction of orbit in space. ISO 112227 was enacted in 2012 as a measure against microscopic secondary Space debris called Ejecta among space debris. However, this protocol did not take into account oblique impacts of projectiles, and a draft revision is made for the purpose of implementing oblique impact experiments. In this research, as a verification of the revision proposal, a 1 mm diameter projectile simulating micro debris is collided with a two-stage light gas gun at a speed of 5 km.s-1 using a target of A2024-T3, usually used as a spacecraft material. The impact angles are 0 (vertical impact), 45, 60 and 75 degrees. About the evaluation method, it is based on the generation amount of Ejecta and its distribution throughout impact marks. Since the target is a ductile body, the amount of Ejecta generated is small, and so it is difficult to calculate accurate ejecta mass at 60 and 75 degrees. Since the angle also increases the distribution of impact marks, scavenging of Ejecta is insufficient. In order to solve this problem, the way of collecting Ejecta is reviewed in oblique impact experiments.

DOI： 10.1299/jsmekyushu.2019.72.C14

その他リンク： https://ci.nii.ac.jp/naid/130007801938

Hypervelocity impact phenomena of LPSO-magnesium alloys 査読有り

Nishida M., Kodama F., Hayashi K., Akahoshi Y., Hokamoto K., Kawamura Y.

EPJ Web of Conferences 183 2018年09月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2018 The Authors, published by EDP Sciences. Hypervelocity impact phenomena of long period stacking ordered type magnesium alloys (LPSO-Mg) plates were examined at the impact velocities of 4 km/s and 6 km/s. Ejecta veil and external bubble of debris of LPSO-Mg were darker than those of aluminum alloy A6061-T6. The size of external bubble of debris of LPSO-Mg was slightly smaller than that of A6061-T6. The velocity reduction of LPSOMg was slightly larger than that of A6061-T6. However, the scatter area of projectile and targets were not determined by electron probe micro-analyzer.

DOI： 10.1051/epjconf/201818302033

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超高速衝突試験手順の国際標準化と今後の計画について

赤星保浩

日本機械学会九州支部講演論文集 ( 一般社団法人日本機械学会 ) 2018 ( 0 ) J31 2018年01月

Study of the Effects of Projectile Shape in the Asteroid Orbit Change by Spacecraft Impact 査読有り国際誌

Ikeda M., Tanaka M., Yokoo D., Koura T., Akahoshi Y.

Procedia Engineering 204 138 - 145 2017年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2017 The Authors. Published by Elsevier Ltd. NEO (Near Earth Object) are the celestial bodies which pass near the Earth. One NEO deflection method is spacecraft impact. In order to estimate its results, it is necessary to clarify mechanism of momentum change of NEO. Generally, β is used as an evaluation index in this field and affected by various factors, so this study focuses on spacecraft shape. Five types of projectile shape were tested and compared in term of two aspects. In addition, we made comparison by using scaling law in order to compare the shape effect in the speed region which is assumed to using actual NEO deflection.

DOI： 10.1016/j.proeng.2017.09.766

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Lip Formation and Ejecta from LPSO-type Magnesium Alloy Plates in Hypervelocity Impact 査読有り国際誌

Nishida M., Ishida K., Kodama F., Hayashi K., Akahoshi Y., Hokamoto K., Mayama T., Yamasaki M., Kawamura Y.

Procedia Engineering 173 65 - 72 2017年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2017 The Authors. Long period stacking ordered (LPSO) type magnesium alloys have the low density, excellent mechanical strength and ignition resistance. LPSO-type magnesium alloys have a great potential as structural materials of satellites. Lip formation and ejecta size were examined when spherical projectiles strikes thin plates made of LPSO-type magnesium alloy at hypervelocities of 5 km/s. Witness plates were placed in front of and behind each target to determine the scattering area. After impact experiments, ejecta were collected from test chamber and lips near penetration hole was examined x-ray computed cosmography (CT) in detail. Results of LPSO-type magnesium alloy plates were compared with those of aluminum alloy (A6061-T6). Images of scattering ejecta taken by a high speed video camera were also discussed.

DOI： 10.1016/j.proeng.2016.12.024

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Ejecta from LPSO-Type Magnesium Alloy Targets in Hypervelocity Impact Experiments 査読有り国際誌

Nishida M., Kodama F., Hayashi K., Akahoshi Y., Hokamoto K., Mayama T., Yamasaki M., Kawamura Y.

Procedia Engineering 204 270 - 275 2017年01月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2017 The Authors. Published by Elsevier Ltd. Because long period stacking ordered (LPSO) type magnesium alloys have the low density, excellent mechanical strength and ignition resistance, LPSO-type magnesium alloys have a great potential as structural materials of satellites. Ejecta size and crater shape were examined when spherical projectiles struck targets made of LPSO-type magnesium alloy at hypervelocities of 2km/s and 5 km/s. After impact experiments, crater surfaces and lips near craters were observed X-ray computed cosmography (CT) in detail. Ejecta collected from test chamber were measured. Results of LPSO-type magnesium alloy targets were compared with those of aluminum alloy (A6061-T6). Fracture behavior of LPSO-type magnesium alloy targets seemed to be brittle and many small ejecta from LPSO-type magnesium alloy were observed.

DOI： 10.1016/j.proeng.2017.09.735

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Discharge on Solar Array Coupon by Debris Impact 査読有り国際誌

Tagami S., Quesada M., Koura T., Akahoshi Y.

Procedia Engineering 204 323 - 328 2017年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

© 2017 The Authors. Published by Elsevier Ltd. Recently, a risk of impact between spacecraft and debris is increasing. An impact on solar arrays can cause electrical damage such as sustained arc as well as mechanical damage. If sustained arc occurs, electricity does not flow to the payload and the power generation capacity is reduced. In this study, discharge due to debris impact is reproduced by hypervelocity impact test, and plasma and discharge currents are measured. As a result, high density plasma and discharge due to impact were confirmed. Moreover, it became clear that some difference appears in the discharge current waveform depending on the impact point.

DOI： 10.1016/j.proeng.2017.09.753

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超高速衝突実験におけるLPSO-Mg板の破壊特性とイジェクタ評価

児玉史哉, 西田政弘, 石田魁人, 林浩一, 赤星保浩, 外本和幸, 眞山剛, 山崎倫昭, 河村能人

M&M材料力学カンファレンス ( 一般社団法人日本機械学会 ) 2016 ( 0 ) OS01 - 19 2016年01月

記述言語：英語掲載種別：研究論文（研究会，シンポジウム資料等）

Long period stacking ordered type magnesium (LPSO-Mg) alloys have low density, excellent mechanical strength and ignition resistance. LPSO-Mg have a great potential as structural materials of satellites. Lip formation and ejecta size were examined when spherical projectiles strikes thin plates made of LPSO-type magnesium alloy at hypervelocity of 5 km/s. Witness plates were placed in front and behind of each target to determine the scattering area. After impact experiments, ejecta were collected from test chamber and lips near penetration hole was observed. Results of LPSO-type magnesium alloy plates were compared with those of aluminum alloy (A6061-T6).

DOI： 10.1299/jsmemm.2016.OS01-19

その他リンク： https://ci.nii.ac.jp/naid/130007120202

Effects of target temperature on size distribution of ejecta in hypervelocity impact : Toward revision of ISO11227 査読有り

NISHIDA Masahiro, MIYOKAWA Naoto, KODAMA Fumiya, HAYASHI Koichi, FAURE Pauline, NORIMATSU Koichi, FUJIMURA Yusuke, AKAHOSHI Yasuhiro

Mechanical Engineering Journal ( 一般社団法人日本機械学会 ) 3 ( 6 ) 16 - 00148-16-00148 2016年01月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）

As a preliminary study, the effects of target temperature on ejecta size were examined at an impact velocity of 3.5 km/s with the goal of improving the ISO11227. At first, the size of each ejecta collected from test chamber, was examined by the image analysis software using a photograph of each ejecta (direct method). The cumulative number distributions of ejecta size were discussed. The effects of target temperature on ejecta size were small within a predictable range. After that, we compared the ejecta size distribution of the direct method with the results of the international standard method using witness plate (indirect method). The number of ejecta impact craters evaluated by the international standard method was very small at the high temperature. The results of international standard method using witness plate were easily influenced by temperature of target at the high temperature. It is highly possible that the international standard method underestimate the ejecta from target at high temperature.

DOI： 10.1299/mej.16-00148

その他リンク： https://ci.nii.ac.jp/naid/130005250539

OS0106-474 LPSO型マグネシウム合金板への超高速衝突におけるイジェクタサイズ分布

石田魁人, 西田政弘, 林浩一, 赤星保浩, 外本和幸, 河村能人

M&M材料力学カンファレンス 2015 "OS0106 - 474-1"-"OS0106-474-2" 2015年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

Ejecta size of a LPSO-type magnesium alloy were examined when aluminum alloy projectiles struck in hypervelocity. The size of ejecta collected from the test chamber was measured. We compared with the difference in ejecta size distribution by changing impact velocity. The results of LPSO-type magnesium alloy were compared with those of aluminum alloy.