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第9回スペースデブリワークショップ (2021年2月24-26日. 宇宙航空研究開発機構調布航空宇宙センター(JAXA)(CAC), オンライン会議), 調布市, 東京, The 9th Space Debris Workshop (February 24-26, 2021. Chofu Aerospace Center, Japan Aerospace Exploration Agency (JAXA)(CAC), Online meeting), Chofu, Tokyo, Japan, 宇宙開発はこの半世紀において科学や工学の両面において飛躍的な発展を遂げてきた．一方，宇宙開発を今後も持続可能なものにするためにはスペースデブリ問題の対策が重要である．本研究は新たなデブリ発生を抑える非デブリ化対策として，ロケット上段や宇宙機の大気圏突入後の溶融残存物による地上被害リスクの最小化を目指している．本研究では，とくに高忠実な物理モデルをベースとした複合物理連成解析法であるリエントリ安全評価法LS-DARC（Destructive Atmospheric Re-entry Code）の開発に取組んでいる．設計パラメータ変更による安全性向上度を定量的に分析できるようにすることで，a) 上流設計段階からの溶融促進設計，b) 認知学的な不確かさの低減による高精度なリスク評価を実現することが目的である．LS-DARCにより下図に示すようなロケット上段や衛星などの複雑形状に対して溶融残存物が生じるかどうかを評価することができるが，安全評価法として実用化するためには物理モデルの検証プロセスの確立が不可欠である．本報告ではとくに熱流束モデル検証方法を提案し，高エンタルピー風洞試験による検証データ取得をはじめとした検証状況について述べる．, Remarkable progress in space exploration both for science and engineering have been made in a half century. Space debris problem is a growing concern to be tackled internationally to keep our space activity sustainable. For the improvement in the ground safety related to the survived debris after the destructive re-entry of the rocket upper stages and the spacecrafts, the comprehensive considerations on the design and the disposal operation should be made. High-fidelity model-based re-entry safety analysis tool LS-DARC is under the development in JAXA. Purpose of this study is an establishment of quantitative assessment of the design and disposal operation change effect on the re-entry risk. Consequently, a) design for demise from the initial development phase, and b) accurate risk prediction by reducing epistemic uncertainty are realized. LS-DARC is multi-physics coupling analysis code including the aerodynamic and 6DoF trajectory analysis, surface heat flux distribution analysis, three-dimensional thermal transfer analysis. Establishment of the uncertainty quantification process of the LS-DARC models is essential in order to make it practical re-entry safety analysis tool. In this report, the uncertainty quantification process especially on the heat flux model is proposed and discussed. Research activities on the validation data acquisition by the high-enthalpy wind tunnel and the model validations are discussed., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA2130003024, レポート番号: JAXA-SP-21-001

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2020-09-01, 資料番号: PA2110028000

第8回スペースデブリワークショップ (2018年12月3-5日. 宇宙航空研究開発機構調布航空宇宙センター(JAXA)(CAC)), 調布市, 東京, The 8th Space Debris Workshop (December 3-5, 2018. Chofu Aerospace Center, Japan Aerospace Exploration Agency (JAXA)(CAC)), Chofu, Tokyo, Japan, 宇宙開発はこの半世紀において科学や工学の両面において飛躍的な発展を遂げてきた．一方，宇宙開発を今後も持続可能なものにするためにはスペースデブリ問題の対策が重要である．本研究は新たなデブリ発生を抑える非デブリ化対策として，ロケット上段や宇宙機の大気圏突入後の溶融残存物による地上被害リスクの最小化を目指している．とくに本研究では高忠実な物理モデルを採用した，複雑な実機形状の複合物理連成シミュレーションによるリエントリ安全評価法LS-DARC（Destructive Atmospheric Re-entry Code）を開発している．設計パラメータ変更による安全性向上度を定量的に分析できるようにすることで，a) 上流設計段階からの溶融促進設計，b) 認知学的な不確かさの低減による高精度なリスク評価を実現することが目的である．LS-DARC を用いることで，下図に示すようにロケット上段や衛星などの複雑形状に対し，空力，6自由度姿勢/軌道，熱流束，伝熱を連成解析し，溶融・破壊による形状変化も扱うことができる複合物理連成シミュレーションを行うことができる．本報告では，LS-DARC の開発状況と安全性評価法としての実用化に向けた研究課題を議論する．, Exponential progress in space exploration both for science and engineering have been made in a half century. Space debris problem is a growing concern to be tackled internationally to keep our space activity sustainable. For the improvement in the ground safety related to the survived debris after the destructive re-entry of the rocket upper stages and the spacecrafts, the comprehensive considerations on the design and the disposal operation should be made. High-fidelity model-based re-entry safety analysis tool LS-DARC is under the development in JAXA. Purpose of this study is an establishment of quantitative assessment of the design and disposal operation change effect on the re-entry risk. Consequently, a) design for demise from the initial development phase, and b) accurate risk prediction by reducing epistemic uncertainty are realized. LS-DARC is multi-physics coupling analysis code including the aerodynamic and 6DoF trajectory analysis, surface heat flux distribution analysis, three-dimensional thermal transfer analysis. Complicated real geometry can be considered including the small curvature effect on the heat flux increase and the shape change due to structure demise. Development status of LS-DARC is overviewed and the research needs are discussed., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1830034025, レポート番号: JAXA-SP-18-011

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2019-06-03, 資料番号: PA2010044000

形態: 図版あり, Physical characteristics: Original contains illustrations, 資料番号: PA1810081000

第48回流体力学講演会/第34回航空宇宙数値シミュレーション技術シンポジウム (2016年7月6日-8日. 金沢歌劇座), 金沢市, 石川, 48th Fluid Dynamics Conference /the 34th Aerospace Numerical Simulation Symposium (July 6-8, 2016. The Kanazawa Theatre), Kanazawa, Ishikawa, Japan, A feasibility study of the interface tracking simulations of liquid oxygen (LOX) and gaseous hydrogen(GH2) coaxial combustion at a subcritical pressure was conducted. To simulate the breakup and atomization of LOX core, CIP-LSM (Constrained Interpolation Profile based Level Set and MARS) that combined CIP-CUP (CIP-Combined Unified Procedure) method with the hybrid Level-set and MARS (Multi-interface Advection and Reconstruction Solver) method for volume tracking, was employed as a solver of the governing equations of fluids. The phase change rate on the surfaces between the multi-species gas and single-species liquid was calculated. To investigate the ignition process and flame holding mechanism, chemical reaction equations were solved with the detailed chemical mechanism of oxygen and hydrogen. Results suggested that this numerical approach can be a powerful method that provides the information on ignition, breakup and atomization of LOX core, and flame holding at the steady state of LOX/GH2 coaxial combustion at subcritical pressures., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1630031027, レポート番号: JAXA-SP-16-007

東京大学ロケット・宇宙機モデリングラボラトリー(社会連携講座)シンポジウム (2016年3月23日. 宇宙航空研究開発機構筑波宇宙センター(JAXA)(TKSC) ), つくば市, 茨城, 著者人数: 20名, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA1630026006, レポート番号: JAXA-SP-16-005

Successful result of HTV small re-entry capsule (HSRC) project was presented. Computational aerothermodynamic analysis methods and its contributions to the HSRC\'s design are overviewed and discussed. Local heat flux peak and the pressure increase are generated due to the hot gas main stream collision onto the wall near the reaction control system (RCS) nozzle exit. Augmentation factor is roughly from 2.0 to 8.0, which is increased by the larger mass flow rate of the free-stream. Effect on the aerodynamic force and moment is significant, which is at least 5 times larger as comparing with the RCS thrust. Severe ablator erosion was not found and the precise GNC was achieved. TPS shell separation failure and collision risks were identified and the shell release air-bag was employed. Its importance on the reliable parachute deployment is confirmed by the post-flight analysis. Conventional MILES-type computational fluid dynamics (CFD) analysis is quantitatively accurate even for the unsteady flows such as the aeroacoustic characteristics prediction. Pressure fluctuation is induced by the unsteady shear layer whose frequency changes with the flow structures such as the local shock on the shear layer. Input sound pressure level is decided based on CFD. 6DoF trajectory analysis was carried out to evaluate the sidewind criterion to prevent the turn-over rotation at the low dynamic pressure phase just after the separation. Drop test was succeeded by meeting the side-wind criterion.

Quantitative crew safety assessment method was proposed, and continuous research efforts had been made to maximize the crew safety to keep sustainability of the challenging human space flight missions. Key physics-based models to predict the water landing accelerations and the crew injury risk for the transient dynamic loads were developed. Two hazardous scenarios are considered, the one is the large dynamic loads due to the off-nominal excessive water landing speed and the unfavourable crew module attitude and the other is due to the blast-wave over pressure generated by the launch vehicles\' failures. At first, these dynamic loads were predicted and selected as the reference conditions for the crew injury risk predictions. Multi-body dynamics and finite-element models of Hybrid III anthropomorphic test device (ATD) were validated by the comparison with the sled test with including the lateral impact, which is the specific conditions of the human space flight. Crew injury risk was evaluated for the reference dynamic load conditions, and the injury mechanisms were investigated based on the numerical and the sled test results. Quantitative crew injury risk assessment was carried out for the water landing loads of the capsule-type crew module concept. Water landing accelerations under wide range of landing conditions were obtained based on the fluid and structure interaction analysis based on Arbitrary Lagrangian Eulerian (ALE) solver and the penalty coupling method of LS-DYNA(R). Corresponding crew injury risk distributions were also predicted by using the multi-body dynamics model of Hybrid III ATD for the rigid seat. Key findings of the crew injury mechanism to improve the crew safety were obtained and presented. Finally, the design for safety studies on the spaceship seat were conducted to maximize the crew safety. Large magnitude accelerations were successfully reduced by the design optimization of the lateral and axial dampers. It was confirmed that the resulting injury metrics values even for the most severe landing condition are within the NASA\'s acceptance risk level for the off-nominal cases. It was found that the design for safety strategies such as the zero-gap concept and the adapted seat liner with the soft padding are key elements to achieve higher-level of crew safety.

東京大学ロケット・宇宙機モデリングラボラトリー(社会連携講座)シンポジウム (2015年4月21日. 東京大学山上会館), 東京, 形態: カラー図版あり, 共催: 東京大学工学系研究科ロケット・宇宙機モデリングラボラトリー(社会連携講座) : 宇宙航空研究開発機構研究開発部門第三研究ユニット, Physical characteristics: Original contains color illustrations, 資料番号: AA1530036001, レポート番号: JAXA-SP-15-007

形態: 図版あり, Physical characteristics: Original contains illustrations, 資料番号: AC1600002000

形態: 図版あり, Physical characteristics: Original contains illustrations, 資料番号: AC1600005000

In Japan, new developments of liquid rocket engines are now underway for Japan’s next flagship launch system. In the development, front-loading design process is applied to reduce development costs and to increase reliability. Therefore it is indispensable to precisely evaluate life time of a combustion chamber, which is exposed to the most severe heat and loads among engine components, in an early design phase. In order to improve accuracy in the life prediction, we focus on the interaction between thermo-fluid behaviors and structural responses, and have been developing the multi-physics coupled simulation. By applying this simulation and the linear damage rule, we have clarified the mechanisms and the dominant factors of cracks occurred in the throat, which were experienced under development of the upper stage engine. It has been revealed that the damage is caused by creep and low cycle fatigue and depends on structural temperature histories. Structural temperature overshoots in the start-up process are affected by the transient flows of both combustion gas and coolant. Due to overshooting temperature, creep and low cycle fatigue damage are accumulated., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: PA1610085000

Proceedings of Summer Program 2015 (July.20-August.05, 2015. Technical University of Munich), Munich, Germany, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AC1600048000

東京大学ロケットエンジンモデリングラボラトリー(JAXA社会連携講座)シンポジウム (2012年9月26日-27日. 東京大学), 東京, Symposium on Rocket Engine Modeling Laboratory, The University of Tokyo (JAXA public relations lecture): Advances in Rocket Engine Modeling and Simulation, and its Future (September 26-27, 2012. The University of Tokyo), Tokyo Japan, 形態: カラー図版あり, 共催: 東京大学ロケットエンジンモデリングラボラトリー(JAXA社会連携講座), 宇宙航空研究開発機構, Physical characteristics: Original contains color illustrations, Meeting sponsors: Rocket Engine Modeling Laboratory, The University of Tokyo (JAXA public relations lecture), JAXA's Engineering Degital Innovation Center, Japan Aerospace Exploration Agency (JAXA)(JEDI), Translation title: Future prospects of research in numerical simulation of rocket engine, 資料番号: AA0061924018, レポート番号: JAXA-SP-12-014

Wall-modeled large eddy simulation (WMLES) is performed toward simulation of turbulent heat transfer in liquid rocket engine flowfields. To assess the prediction capabilities of WMLES, as a preliminarily work, turbulent channel flows with heat transfer are simulated. The present results show that mean velocity and temperature profiles agree well with DNS and the log law from moderate to high Reynolds numbers. Outer-layer turbulence and its fluctuations of velocity and temperature are well captured with modeling the inner layer. Quantitative differences in the fluctuations are observed indicating that the assessment for the spatial accuracy of the numerical method is needed.

東京大学ロケットエンジンモデリングラボラトリー(JAXA社会連携講座)シンポジウム(2010年9月28日-29日. 東京大学), Symposium on Rocket Engine Modeling Laboratory, University of Tokyo (JAXA public relations lecture): New Horizon of Rocket Engine Modeling and Simulation (September 28-29, 2010. University of Tokyo), Tokyo Japan, 形態: カラー図版あり, 共催: 東京大学ロケットエンジンモデリングラボラトリー(JAXA社会連携講座), 宇宙航空研究開発機構, Physical characteristics: Original contains color illustrations, Meeting sponsors: Rocket Engine Modeling Laboratory, University of Tokyo (JAXA public relations lecture), JAXA's Engineering Degital Innovation Center, Japan Aerospace Exploration Agency (JAXA)(JEDI), 資料番号: AA0064934018, レポート番号: JAXA-SP-10-010

資料番号: SA1005174000