Keita Terashima

Mechanical Behavior of Composite Lattice Cylinders

The effect of local rotational deformation of the ribs on compressive buckling behaviors of lattice cylinders is investigated. This type of local deformation may not be embraced in the context of either the global buckling based on smeared/homogenized conventional shell analysis or the local Euler buckling analysis, which are used in the current design methodology of lattice cylinders. Experimental evaluation of the compressive behavior of representative lattice cell structure demonstrated that the rib rotation actually may take place. Beam elements are used in the finite element modeling in order to include the effect of local rib rotational deformations. The consequence of considering the effect is the possibility of non-negligible decrease in the buckling load estimation compared to that based on combined methodology of conventional shell buckling, rib local Euler buckling and rib failure strength. The addition of thin skin to the lattice structure is also proposed in order to prevent or reduce the infection of the local deformation nature of the ribs. The merit of supplementing the skin may also arise when the lattice structure is applied to the aircraft fuselage with cabin containment or pressurization requirements.

Stability of Skin Added Lattice Structure

Composite lattice structure, consisting of helical and hoop ribs intersecting each other in a regular pattern, is considered to be a superior candidate as the lightweight aerospace structure such as payload attachment adapter and inter-stage structure of launch vehicles. The present study focuses on the buckling behaviors of lattice cylinders under compressive loading. The buckling modes of lattice structures are deeply affected by the local rotational deformation of the ribs. In order to prevent this local rotation effect, the addition of thin skin to the lattice cylinders is proposed. The buckling load of the skin-added lattice cylinders significantly increases. A parametric study is also carried out to obtain the optimal designs of skin thickness and cross-sectional dimensions of the ribs. It is shown that the addition of skin has different effects on the improvement of bucking loads depending on the rib dimensions. As a result of parametric study, the new lattice model which has no hoop ribs is proposed and the buckling behavior of the structure is investigated. The elimination of hoop ribs is also meaningful from the manufacturing point of view. It may leads to the drastic reduction of the fabrication cost.

Improvement of aero-vibro acoustic simulation technique for prediction of acoustic loading at lift-off

Aero-vibro acoustic simulation for the prediction of harmful acoustic loading at lift-off of launch vehicle is developed. In this simulation technique, high-fidelity large-eddy simulation with computational aeroacoutics based on full-Euler equations is employed for computing jet aeroacoustics and their propagation to the outside of payload fairing. Acoustic field inside the payload fairing is computed by the coupled vibro-acoustic simulation based on finite element method. A simplified fairing model is used for the validation of the present method. An impact hammer test and acoustic vibration test using a loudspeaker in an anechoic chamber are conducted for validating the structural model. Then, the accuracy of this method is validated by using the acoustic vibration test result with a subscale rocket engine.Aero-vibro acoustic simulation for the prediction of harmful acoustic loading at lift-off of launch vehicle is developed. In this simulation technique, high-fidelity large-eddy simulation with computational aeroacoutics based on full-Euler equations is employed for computing jet aeroacoustics and their propagation to the outside of payload fairing. Acoustic field inside the payload fairing is computed by the coupled vibro-acoustic simulation based on finite element method. A simplified fairing model is used for the validation of the present method. An impact hammer test and acoustic vibration test using a loudspeaker in an anechoic chamber are conducted for validating the structural model. Then, the accuracy of this method is validated by using the acoustic vibration test result with a subscale rocket engine.

Experimental study of acoustic reduction technique for H3 launch vehicle

A subscale Acoustic test, the H3-scaled Acoustic Reduction Experiments (HARE), was conducted to predict liftoff acoustic environments of the H3 launch vehicle currently being developed in Japan. The HARE is based on 2.5% scale H3 vehicle models, which is composed with a GOX/GH2 engine and solid rocket motors, Movable Launcher (ML) models with upper deck water injection system and Launch Pad (LP) models with deflector and lower deck water injection systems. Approximately 20 instruments measured far/near field acoustic and pressure data. Last year the results of the first campaign of the HARE, which aims at understanding the effects of elevation, the shape of ML, were presented. This year, the results of the second campaign which aims at studying the effects of acoustic reduction techniques such as acoustic shields and water injection will be presented.A subscale Acoustic test, the H3-scaled Acoustic Reduction Experiments (HARE), was conducted to predict liftoff acoustic environments of the H3 launch vehicle currently being developed in Japan. The HARE is based on 2.5% scale H3 vehicle models, which is composed with a GOX/GH2 engine and solid rocket motors, Movable Launcher (ML) models with upper deck water injection system and Launch Pad (LP) models with deflector and lower deck water injection systems. Approximately 20 instruments measured far/near field acoustic and pressure data. Last year the results of the first campaign of the HARE, which aims at understanding the effects of elevation, the shape of ML, were presented. This year, the results of the second campaign which aims at studying the effects of acoustic reduction techniques such as acoustic shields and water injection will be presented.

Validation of aero-vibro acoustic simulation technique using experimental data of simplified fairing model

To predict harmful acoustic loading observed at lift-off of the launch vehicle, aero-vibro acoustic simulation technique is developed. High-fidelity large-eddy simulation with computational aeroacoustics based on the full Euler equations in time domain are employed to predict generation of the acoustic waves and their propagation to the fairing. Coupled vibro-acoustic analysis based on finite element method are applied to compute the transmitted acoustic wave into the fairing both in the time and frequency domains. Acoustic measurement of a simplified fairing model with a subscale liquid rocket engine is conducted, and validation study of the present technique is performed. Reasonable agreement is obtained for peaks of the acoustic spectrum taken inside the fairing model. Such peaks are found to be related to the internal acoustic modes and ring modes of the faring structure. However, further study is required to obtain quantitative agreement.

Results of subscale model acoustic tests for H3 launch vehicle

A subscale acoustic test, the H3-scaled Acoustic Reduction Experiments (HARE), was conducted to predict liftoff acoustic environments of the H3 launch vehicle currently being developed in Japan. The HARE is based on 2.5% scale H3 vehicle models, which is composed with a GOX/GH2 engine and solid rocket motors, Movable Launcher (ML) models with upper deck water injection system and Launch Pad (LP) models with deflector and lower deck water injection systems. Approximately 20 instruments measured far/near field acoustic and pressure data. Preliminary results are presented in this presentation.

Development of aero-vibro acoustics methods for predicting acoustic environment inside payload fairing at lift-off

Prediction of harmful acoustic loading to payloads inside launcher fairing due to intense acoustic wave generated from propulsion systems at lift-off is an important design issue. Aero-vibro acoustics method developed in this study for predicting the acoustic loading consists of four elements. Hydrodynamics of jet flowfield generating aeroacoustic wave is computed by the high-fidelity Large-Eddy simulation. Computational aeroacoustics based on the full Euler equations is conducted to simulate propagating acoustic wave from the jet to the payload fairing. Then, finite element method is applied to simulate the structural vibration that radiates acoustic wave inside the fairing. Finally, acoustic behavior inside the payload fairing is also computed by the finite element method. An overview of the methods and recent work for validation and verification will be presented.

Results of scale model acoustic tests using supersonic cold jets for H3 launch vehicle

Acoustic test using Mach 2 cold jet was conducted for the H3 launch vehicle currently being developed in Japan. Effect of the clustered engines and the newly built movable launcher on the lift-off acoustics was investigated. The overall acoustic level taken by the farfield microphones did not show proportional increase in the number of engines, especially for the angles corresponding to the Mach wave radiation from the free jets. The observation here disagrees with the empirical prediction model. The computational fluid dynamics was also employed to analyze the acoustic mechanism of clustered engines.

Evaluation of Japanese current primary launch vehicle liftoff acoustic environment change due to launch pad facility modifications

H-IIA, Japanese primary launch vehicle, has been successfully launched 21 flights with a success rate of 95.4%. During 12 years of its operational phase, extensive acoustic measurements on the vehicle and on the ground have been conducted to refine conventional prediction methods and to evaluate the effect of vehicle/pad configuration changes. In this presentation, the evaluation of the effects of major pad configuration modification on H-IIA liftoff acoustic environment is presented. The effect of water injection is also evaluated.

Validation study on computational aeroacoustics of acoustic waves from sub-scale rocket plumes

In this paper, the comparative study of prediction based on computational aeroacoustics (CAA) and experimental results for acoustic waves from modeled rocket motors is conducted, and prediction accuracy of CAA is discussed in the framework of JAXA-CNES collaboration. Experimental data of flow and acoustic fields of solid motor by JAXA and H2-AIR liquid motor by CNES are used as the reference. Two types of computational codes are adapted in this study. The predictions of sound pressure level by both computational codes agree reasonably with corresponding experimental data, whereas the errors are approximately less than 5 dB. In addition, each aeroacoustic field of CAA results in this study is discussed in detail.