丸 祐介

Supersonic parachutes are a critical element of planetary mission whose simple structure, light-weight characteristics together with high ratio of aerodynamic drag makes them the most suitable aerodynamic decelerators. The use of parachute in supersonic flow produces complex shock/shock and wake/shock interaction giving rise to dynamic pressure oscillations. The study of supersonic parachute is difficult, because parachute has very flexible structure which makes obtaining experimental pressure data difficult. In this study, a supersonic wind tunnel test using two rigid bodies is done. The wind tunnel test was done at Mach number 3 by varying the distance between the front and rear objects, and the distance of a bundle point which divides suspension lines and a riser. The analysis of Schlieren movies revealed shock wave oscillation which was repetitive and had large pressure variation. The pressure variation differed in each case of change in distance between the front and rear objects, and the change in distance between riser and the rear object. The causes of pressure oscillation are: interaction of wake caused by front object with the shock wave, fundamental harmonic vibration of suspension lines, interference between shock waves, and the boundary layer of suspension lines.

平成29年度宇宙輸送シンポジウム（2018年1月18日-19日. 宇宙航空研究開発機構宇宙科学研究所（JAXA)(ISAS)）, 相模原市, 神奈川県資料番号: SA6000210024レポート番号: STCP-2017-024

A robust fiber Bragg grating (FBG) hydrogen gas sensor for reliable multipoint-leakage monitoring has been developed. The sensing mechanism is based on shifts of center wavelength of the reflection spectra due to temperature change caused by catalytic combustion heat. The sensitive film which consists of platinum-supported silica (Pt/SiO2) catalyst film was obtained using sol-gel method. The precursor solution was composed of hexachloroplatinic acid and commercially available silica precursor solution. The atom ratio of Si : Pt was fixed at 13 : 1. A small amount of this solution was dropped on the substrate and dried at room temperature. After that, the film was calcined at 500 degrees C in air. These procedures were repeated and therefore thick hydrogen-sensitive films were obtained. The catalytic film obtained by 20-time coating on quartz glass substrate showed a temperature change 75 K upon exposure to 3 vol.% H-2. For realizing robust sensor device, this catalytic film was deposited and FBG portion was directly fixed on titanium substrate. The sensor device showed good performances enough to detect hydrogen gas in the concentration range below lower explosion limit at room temperature. The enhancement of the sensitivity was attributed to not only catalytic combustion heat but also related thermal strain.

In this paper, the authors propose a novel landing method named “Two-step Landing Method” for small lunar lander which is needed to be designed considering constrains from envelope area of rocket and the weight of the lander. The proposed method enforces intentional body tumbling at the contact of main leg. We analyzed its dynamics by three-dimensional simulations which consider lander's attitude and lateral velocity and landing site's slope angle. Numerical simulation models have been designed on Mechanical Dynamics Software “ADAMS”, and lander models refer to “SLIM” which is a small lander proposed by ISAS/JAXA. It is found that the proposed landing method can land on steep slope by tilting body attitude toward inclination direction of landing site. Especially in the case of landing with lateral residual velocity, the proposed method has higher landing stability than conventional landing method.

<p>SLIM (Smart Lander for Investigating Moon) is the Lunar Landing Demonstrator which is under development at ISAS/JAXA. SLIM demonstrates not only so-called Pin-Point Landing Technique to the lunar surface, but also demonstrates the design to make the explorer small and lightweight. Realizing the compact explorer is one of the key points to achieve the frequent lunar and planetary explorations. This paper summarizes the preliminary system design of SLIM, especially the way to reduce the size.</p>

大気球シンポジウム 平成29年度（2017年11月9-10日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)）, 相模原市, 神奈川県資料番号: SA6000103016レポート番号: isas17-sbs-016

<p>JAXA has constructed an experimental facility to pressurize and supply liquid hydrogen at a maximum pressure of 90 MPa to conduct experimental research on the injection of high pressure liquid hydrogen into the atmosphere. Liquid hydrogen has a property that its density greatly changes depending on pressure despite being a liquid phase. In addition, the high pressure hydrogen gas is in a supercritical state and has an intermediate property between a gas and a liquid. Therefore, it is a difficult question whether to treat the injection of high pressure liquid hydrogen as a gas phase phenomena or as a liquid phase phenomena. As a result of the experiment, it was found good to apply the liquid orifice equation to predict the discharge flow rate of high pressure liquid hydrogen.</p>

<p>将来の火星着陸探査への適用を想定した超音速パラシュートのサブスケール模型の特性を，遷音速および超音速風洞実験で評価した．本稿では，風洞実験の方法と結果について紹介する．また，パラシュートの設計や検証における風洞実験の重要性についての，著者らの見解を述べる．風洞実験，数値解析と自由飛行実験を有機的に結合した，パラシュートの特性評価方法の必要性について議論する．</p>

<p>将来の火星着陸探査ミッションに必要となる超音速パラシュートを開発するために我々はキー技術として空力性能，構造性能，放出機構に大別し検証を行ってきた．まず遷音速風洞，超音速風洞試験を実施しマッハ2程度まで損傷なく安定に開傘できることを確認した．またより大きな模型を用いて大型低速風洞試験を実施し，火星等価動圧環境で損傷なく開傘できることを確認した．一方で抵抗係数に関して動圧が増加するにつれて減少することが確認されており，今後，流体構造連成解析を用いて検証を行っていく計画である．放出機構に関しては自動車用インフレータを用いる放出機構を提案し，能代ロケット試験場での大気圧環境下鉛直放出試験を実施しその妥当性を検証した．2016年10月には総合試験として大樹航空宇宙実験場にてヘリコプターからの投下試験を実施し自由飛行環境下における空力性能データを取得することができた．</p>

大気球シンポジウム 平成28年度（2016年11月1-2日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)）, 相模原市, 神奈川県資料番号: SA6000057016レポート番号: isas16-sbs-016

For landing a rover on the Mars ground, supersonic parachute has been developed in JAXA. Key technologies are categorized in aerodynamic performance, mechanical strength, ejection system, and validation method of the design for pre-flight model. So far, we have performed experiments in low-speed, transonic, and supersonic wind tunnels in Chofu aerospace center and ISAS. From these experiments, we have investigated aerodynamic performance such as drag coefficients, opening load factor, and stability of the parachute. We have also evaluated the mechanical strength in these wind tunnel tests. In addition, ejection system with automobile airbag inflator has been developed and a vertical ground test is performed in Noshiro Rocket Testing Center.

<p>In this paper, it is discussed, in order to apply wind tunnel testing results to design and validation of parachutes, whether characteristics of parachutes can be acquired and evaluated using sub-scale models in a wind tunnel testing in which size of a test model is strictly limited. Using Disk-Gap-Band (DGB) type parachutes, transonic and supersonic wind tunnel testing was conducted so that drag coefficient at steady state, unsteady vibration, and opening behavior and shock force at opening of parachutes. As a result, a series of characteristics of parachutes can be evaluated. On the other hand, the necessity of considering a physical similarity rule is emerged so as to apply the results from the wind tunnel testing to design of full-scale parachutes.</p>

<p>In this paper, leak detection system of hydrogen fuel in a future reusable rocket is examined. Identification of a leaking engine line is a fundamental requirement considering specifications and characteristics of the rocket system. Design of the leak detection system satisfying the requirement is examined. Specification of the detection system is examined through considering comprehensively causes of leaking in the rockets and evaluating the influences of those. Demonstration experiment of the identification function is conducted using full-scale mock-up model.</p>

<p>国立研究開発法人 宇宙航空研究開発機構（JAXA : Japan Aerospace Exploration Agency）宇宙科学研究所（ISAS : Institute of Space and Astronautical Science）の高速気流総合実験設備（風洞設備）はISAS/JAXAプロジェクトにおける高速飛翔体の開発研究に供されるとともに，全国の大学共同利用施設として学術研究にも広く利用され，国内における空気力学研究の拠点となっている．本稿では，ISAS/JAXAの風洞設備の概要と，ロケット開発，大気圏突入機開発，さらには将来の宇宙輸送システム研究や大学共同利用による空気力学，計測方法に関する研究など本設備にて得られたこれまでの成果，ならびに，今後の展望について述べる．</p>

A highly sensitive hydrogen gas sensor based on a fiber Bragg grating (FBG) has been developed. Various potential hydrogen sensor materials were screened by assessing the catalytic activities of oxide-supported platinum particles prepared by a sol-gel method. It was determined that a Pt/SiO2 film was the most appropriate sensor material; exposure of this film to 4 vol% H-2 in humid air for 30s at room temperature produced a temperature change of 65 K. In addition, the Pt/SiO2 was able to respond to a concentration as low as 0.1 vol% H-2 in dry air. Two types of sensor structures were fabricated and evaluated. The device incorporating a quartz glass substrate covered with the sensor film on one side was able to detect 0.4 vol% H-2 in dry air at room temperature with a response time of approximately 25 min. The other device, in which the sensor film was immobilized on the periphery of the FBG section, exhibited rapid response to 0.6 vol% H-2 within 20s. (C) 2014 Elsevier B.V. All rights reserved.

本論文では再利用型ロケット(RVT)用ワイヤレスヘルスモニタリングシステムにおける信号干渉について検証を行った。提案しているデュアルバンドWiCoPTシステムは25GHz帯のアップリンクによって高速データ伝送を行い,下り信号(5GHz)ではコマンドと無線電力伝送を行うという特徴を有している。今回は無線センサシムテム内で発生するアップリンクとダウンリンク間の信号干渉について検討を行った。その結果,無線センサヘルスモニタリングにステムにおいてICタグ内を回りこむFSK信号を0dBm以下,ICタグ送信機から受信機へ回りこむQPSK信号を-25dBm以下に抑えれば良いことを明らかにした。

平成26年度宇宙輸送シンポジウム（2015年1月15日-16日. 宇宙航空研究開発機構宇宙科学研究所（JAXA)(ISAS)）, 相模原市, 神奈川県資料番号: SA6000036026レポート番号: STCP-2014-026

A microgravity experiment system using a high altitude balloon has been developed. In order to accommodate payloads larger than previous system which employed three- dimensional drag-free control, one-dimensional drag-free control has been applied. The first test flight was conducted in Aug. 2014. A gravity level below 10(-3) G was obtained for more than 30 seconds during the free-fall of the capsule. A combustion experiment was conducted during the low gravity condition.

In this paper is presented a microgravity experiment system utilizing a high altitude balloon. The feature is a double shell structure of a vehicle that is dropped off from the balloon and a microgravity experiment section that is attached to the inside of the vehicle with a liner slider. Control with cold gas jet thrusters of relative position of the experiment section to the vehicle and attitude of the vehicle maintains fine microgravity environment. The design strategy of the vehicle is explained, mainly referring to differences from the authors' previous design. The result of the flight experiment is also shown to evaluate the characteristics of the presented system.

第58回宇宙科学技術連合講演会（2014年11月12日-14日. 長崎ブリックホール), 長崎市, 長崎県資料番号: AC1500062000レポート番号: JSASS-2014-4168