Authorship：Lead author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (bulletin of university, research institution)

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.actaastro.2021.06.031

Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)

Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2021-3665

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1007/s00193-020-00978-5

Scopus

Other Link： https://link.springer.com/article/10.1007/s00193-020-00978-5

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.B37970

Kyutacar

Scopus

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.B37665

Kyutacar

Scopus

Other Link： https://arc.aiaa.org/doi/abs/10.2514/1.B37665

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2020-3741

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2020-1169

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2020-2160

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2020-0688

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Scopus

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2019-4100

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2019-1498

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2019-4264

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2019-1509

Scopus

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1299/jfst.2018jfst0031

Kyutacar

Scopus

Other Link： https://www.jstage.jst.go.jp/browse/jfst/-char/en

Language：English   Publishing type：Research paper (international conference proceedings)

UK   Dublin   2018.07.29  -  2018.08.03

DOI： 10.1016/j.proci.2018.09.024

Other Link： https://www.sciencedirect.com/science/article/pii/S1540748918306291

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.B36889

Kyutacar

Scopus

Other Link： https://arc.aiaa.org/doi/abs/10.2514/1.B36889

Language：English   Publishing type：Research paper (scientific journal)

<p>In this study, we developed a high-performance and high-thrust hybrid rocket motor using low-melting-point thermoplastic (LT) fuel and swirling oxidizer flow. LT fuel has excellent mechanical and adhesive properties, as well as a high regression rate compared to conventional hybrid rocket fuel. In this study, we conducted several firing tests using swirling oxidizer flow to obtain the fuel regression rate and evaluate its effects on the geometric swirl number (<i>S_g</i>). We determined that the average regression rate of the LT fuel with <i>S_g</i> = 37.3 was ~2.9 times larger than the axial flow test value. The LT fuel was more susceptible to swirling flow than polypropylene, presumably due to the different physical properties of the fuels. In the swirl flow experiment, we confirmed that the local fuel regression rate behind the fuel is uniform, and it differs from the regression rate seen in the axial flow experiment. For the range of oxygen mass flux values <i>G_oxlo</i> = 30–72, <i>ṙ_loave</i> was fitted to a conventional formula. The results of this fit suggested that the local regression rate at the head region of low-melting-point fuel, such as the LT fuel, cannot be represented only by chemical reactions; therefore, the fluid dynamics of liquefied fuel must be included in the model.</p>

DOI： 10.2322/tastj.16.267

CiNii Article

CiNii Research

Other Link： https://www.jstage.jst.go.jp/article/tastj/16/3/16_267/_pdf

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2018-4928

Scopus

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.2514/6.2017-5051

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1061/(ASCE)AS.1943-5525.0000612

Other Link： https://ascelibrary.org/doi/pdf/10.1061/%28ASCE%29AS.1943-5525.0000612

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1051/eucass/201608283

Language：English   Publishing type：Research paper (international conference proceedings)

Scopus

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Scopus

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2322/tastj.12.Pa_53

Other Link： https://www.jstage.jst.go.jp/browse/tastj/-char/en

Event date： 2019.07.28 - 2019.08.02   Language：English  

Event date： 2019.07.28 - 2019.08.02   Language：English  

Event date： 2019.06.15 - 2019.06.21   Language：English  

Event date： 2019.06.15 - 2019.06.21   Language：English  

Event date： 2019.06.15 - 2019.06.21   Language：English  

Event date： 2019.03.14   Language：Japanese  

Event date： 2019.01.01   Language：English  

Event date： 2019.01.01   Language：English  

Event date： 2018.10.24 - 2018.10.26   Language：Japanese  

Event date： 2018.10.24 - 2018.10.26   Language：Japanese  

Event date： 2018.10.24 - 2018.10.26   Language：Japanese  

Event date： 2018.10.24 - 2018.10.26   Language：Japanese  

Event date： 2018.07.09 - 2018.07.11   Language：English  

Event date： 2018.01   Language：Japanese  

CiNii Article

Event date： 2018.01   Language：Japanese  

CiNii Article

Event date： 2017.09.25 - 2017.09.29   Language：English  

Southeast Asia is a region that is severely affected by a variety of natural disasters, such as typhoons, heavy rain, earthquakes, and volcanic eruptions. Synthetic-Aperture Radar (SAR) has a large advantage in speed of data acquisition and observation because it can observe in the night or through clouds. SAR has been implemented only on large satellites so far. However, recently, a new concept of SAR and a high-speed downlink system using single small satellites has been developed. This technology can drastically decrease development costs of SAR satellites, increase the frequency of observations using a constellation of SAR satellites, and enable many developing countries to have SAR satellites. Moreover, this technology enables Southeast Asian countries to construct a shared rapid disaster observation system internationally. In this paper, a possible business model from the viewpoints of Japanese manufacturer and governments that utilize a feasible SAR satellite system based on MicroXSAR is described. A cost-benefit analysis is conducted and presented from the perspective of the manufacturer. Besides, the price of the whole observation systems is also calculated using a cost-estimation method of satellites, and is evaluated from the aspects of economic powers of Southeast Asian countries.

Event date： 2017.01.01   Language：English  

Impacts of various types of O/F shifts on flight performances of a single stage sounding rocket with a scale of S-520 sounding rocket series were comprehensively evaluated by flight simulations of O/F controlled and uncontrolled hybrid rockets. Before the simulation, sources of O/F shifts and factors affected by O/F shifts were classified and discussed in order to clarify the respective sets of simulations. O/F shifts along with the median fuel regression rate behaviors, systematic errors of the behaviors, and random errors of fuel regression rates were statistically modelled using multiple regression theroy. Shifts of thermodynamic states of productive gases after combustion, shifts of c ∗ efficiency, and nozzle throat erosion were modelled as factors affected by O/F shifts. Operations of propulsion systems were assumed to include throttling. In the presence of O/F shifts along with a median regression rate equation, shifts of thermodynamic states of productive gases were the dominant factor causing performance losses of O/F uncontrolled rockets. In the presence of systematic or random errors of fuel regression rates, residuals of propellants were the other dominant factor to decrease flight performances. Especially in the random error cases, as a result of 3000 times of flight performances, the guaranteed highest altitude of the O/F controlled rocket was 5.2% higher than that of uncontrolled rocket within ±3σ. This result shows that the O/F controlled hybrid rockets have about 2.6% higher acceleration than the O/F uncontrolled rockets. Accuracy of acceleration of the O/F controlled hybrid rocket was 10 times higher than that of the O/F uncontrolled hybrid rocket. These results indicate that the significance of O/F shifts elimination of hybrid rockets from both the aspects of expectancy and accuracy of flight performances.

Event date： 2016.01.01   Language：English  

Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. A spectrometer was used to measure the emissions emanating from the plume and combustion chamber of a paraffin-based hybrid rocket. Flame emissions were captured between 200-900 nm at numerous points during the 3-7 second ground tests. Time-resolved blackbody emissions were obtained, as well as emission and absorption peaks associated with combustion products, emanating from the plume and combustion chamber. Plume measurements were taken seven inches aft of the nozzle exit plane at the center of the plume. The rocket is described in Narsai et al. [1] and utilizes paraffin and additives as fuel along with gaseous oxygen as the oxidizer. Chamber pressure and oxidizer flow rates were varied in order to validate results over a wide range of operating conditions. The blackbody emissions were fit to Planck's law in order to estimate flame temperature. The observed temperatures matched well with simulations run via a chemical equilibrium solver [2] . Further validation of the algorithm used to estimate flame temperature was provided by capturing emissions from a tungsten filament. Additionally, numerous species of interest were identified, including igniter materials and combustion products which contributed to erosion of the nozzle. Two other techniques for estimating flame temperature were investigated: (1) the analysis of OH emission bands near 315 nm and (2) the analysis of the sodium D-lines around 590 nm. Trace amounts of sodium chloride were added to the melted paraffin wax prior to spin-casting in order to attempt to produce D-line emissions. Absorption spectroscopy was conducted on paraffin and a blackener dye used to improve the absorption of thermal radiation at the exposed surface of the fuel grain. Absorption spectra were acquired between 0.2 and 22 microns. These absorption spectra were compared with flame emission spectra within the combustion chamber in order to gain insight into how heat is transferred from the flame to the fuel surface.

Event date： 2016.01.01   Language：English  

© 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. A bread board model of Altering-number Swirling Flow Type (A-SOFT) hybrid rocket engine has been newly developed and the static burning tests have been conducted. A-SOFT hybrid rocket engines have controllability of both thrust and O/F without any replacement of components in the engine. This advantage is acquired by controlling oxidizer mass flow rate and effective swirl number. The purpose of this set of experiments is to confirm the continuity, monotonousness and predictability of the performances of A-SOFTs. The A-SOFT BBM showed a favorable fuel regression behavior. The fuel regression averaged along spatial direction fit the shape of regression rate function proposed before the experiments within ±3.5% errors, and the fuel regression rates are continuous and monotonous along swirl number and oxidizer mass flux. The O/F and thrust data also respectively fit the prediction formulas within ±4.2% and ±4.7% errors. c* efficiency is evaluated with the Isp efficiency - nozzle efficiency ratio η Isp / η C F in order to compensate the pressure sensing errors caused by the centrifugal forces of swirling flows. Though η Isp / η C F in the cases of weak swirl injection was clearly larger than in the cases of axial injection, its dependence on effective geometric swirl number was not clear in strong swirl conditions.

Event date： 2015.01.01   Language：English  

© 2015, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. In practical usage of conventional hybrid rocket engines, the oxidizer-to-fuel ratio (O/F) shift occurs by either the fuel port diameter increase or throttling because the fuel regression rate is not proportional to the oxidizer mass flux. As a promising technique to eliminate the O/F shift in a wide throttling range, Altering-intensity-Swirling-Oxidizer-Flow-Type (A-SOFT) hybrid rocket engines are proposed. A-SOFTs control O/F, independently of thrust, with the swirl intensity of oxidizer from the injector, as well as the mass flow rate of the oxidizer. In this paper, the increase rates of engine performance caused by O/F shift eliminating technique are evaluated with a vertical launch simulation for single stage sounding rockets. This simulation includes the throat erosion and c* efficiency models which can be affected by O/F shifts. The statistical uncertainty of fuel regression model is also included to evaluate the robustness of A-SOFTs and SOFTs. The increase rates of total impulse and maximum altitude of A-SOFTs compared to SOFTs depends on maximum oxidizer mass flow rate and are about 2% and 4% respectively. The most effective indicators in this evaluation to the flight performance are residuals of propellants and c* efficiency. Owing to the sensitivity of the flight performances to residuals, the fuel regression errors can cause risks of large losses of the highest altitude in SOFTs, and it is found that the feedback control of A-SOFTs have robustness to the fuel regression errors to some extent. c* efficiency dependent on L* is also sensitive to O/F shifts because O/F shifts affect combustion chamber volume and increase of throat area.

Event date： 2015.01.01   Language：English  

As a technique to eliminate O/F shifts, Altering-intensity Swirling Oxidizer Flow Type (A-SOFT) hybrid rocket is proposed using the combination axial and tangential oxidizer injection. In this paper, the possible geometric design point of the motor is considered about 2-tons class single stage A-SOFT hybrid rockets, and the nominal performance increase by eliminating O/F shifts is evaluated. The highest altitude of the A-SOFT is 450 [km] and the averaged ISP is 284[s] with 100[kg] payload, and this performance is several percent higher than the ones of S-520 with 95[kg] payload, Japanese 2-tons class solid sounding rocket. Though A-SOFTs increase the nominal flight performance by 1% from Swirling Oxidizer Flow Type hybrid rockets, which cannot O/F shift, their feedback control prevents the large performance losses caused by fuel regression errors and residuals, and this function is not found in the conventional hybrid rockets. In this paper, a planning of steady state burning tests of A-SOFT bread board model is also explained. The purpose of the burning tests are to demonstrate the concept of A-SOFTs. The test motor is 250[N] scale and uses polypropylene and GOX and its burning duration is 5[s] . In more than 10 times steady state tests, 50% throttling conditions with effective geometric swirl intensity between 0 and 37.3 are inculded.

Event date： 2014.01.01   Language：English  

© 2014 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. In this paper, first, a theoretical prediction method of regression rates and heat flux to solid fuels of uni-directional vortex injection hybrid rocket engines is developed by introducing a new swirl intensity decline model toward axial direction. Next, a linear propagative relation of heat flux to solid fuels with disturbances of oxidizer mass flux, fuel regression, and initial swirl intensity is derived. The couple of this response model and another unteady response model of solid fuel gasification amplifies oxidizer mass flux disturbance in the form of regression rate oscillation. This is the basic mechanism of low frequency instability unique to hybrid rocket engines. The linear stability analysis for uni-directional vortex types simulating both ILFI amplification source and main stream model is conducted. The result of this analysis shows that uni-directional vortex injection hybrid rocket engines have the same linear unstable mode as axial hybrid rocket engines.

A prototype pulse detonation engines are developed to be applied for the green reaction control systems for upper stages of small satellite launchers. This contract research is aimed at the conceptual demonstration of a new semi-valveless pulse detonation engine using a liquid fuel as well as the identification of challenges of this type of engines.