Performance of Mixture-Ratio-Controlled Hybrid Rockets for Nominal Fuel Regression

This paper discusses the impacts of oxidizer-to-fuel mass ratio (O/F) shifts on the flight performance of single-stage sounding rockets using the flight simulations of three scales of O/F-controlled and O/F-uncontrolled hybrid rockets under a nominal fuel regression behavior without uncertainty. The flight simulation code includes three factors dependent on the O/F: thermodynamic states of the burned gas (theoretical Isp), shifts in c∗ efficiency, and nozzle throat erosion. In the flight simulations, a thrust control law was applied to increase the apogee and evaluate the effects of O/F shifts in the thrust curve including throttling. For the best cases in each scale, O/F-controlled hybrid rockets slightly improved the performance by 2.03–2.42% in the averaged specific impulse. However, the performance of the O/F-controlled sounding rockets is essentially the same as the O/F-uncontrolled type under the median regression behavior: especially when considering the slight increases in the mass and complexity of the oxidizer feed system needed for O/F control. Considerable scale effects on the throat erosion and theoretical Isp were observed, but that of the c∗ efficiency was negligible. The improvement of the theoretical Isp was the primary contributor to flight performance, which was responsible for a larger than 70% share in the total Isp increase. The second largest contribution was the improvement of the c∗ efficiency with a share of 21.8–24.3%. The O/F control gave an improvement of throat erosion corresponding to 5.75% in the total Isp increase for the smallest scale; but, with increasing of the scale, the throat area increase ratio became small so that the throat erosion improvement contribution was reduced to 1.21%

Performance of Mixture-Ratio-Controlled Hybrid Rockets under Uncertainties in Fuel Regression

This paper evaluates various sources of oxidizer to fuel mass ratio (O/F) shifts in hybrid rockets and paths (physical phenomena) through which these O/F shifts affect flight performance. Moreover, the performance increase of O/F control in hybrid rockets is evaluated. Vertical launches of O/F uncontrolled and O/F controlled of hybrid sounding rockets were simulated under two uncertainty models of fuel regression behavior based on experimental data: a) systematic errors with a constant deviation within ±3σ±3σ and 2) random errors subject to a probability distribution. These simulations included all sources of O/F shifts that originated in the fuel regression behavior and all paths through which the O/F shifts affect flight performance. Residual propellant mass and decreases in specific impulse are found to be the dominant causes of performance loss under both uncertainty models. For both cases 1 and 2, the O/F-controlled hybrid rockets maintained the performance expected under nominal fuel regression behavior, whereas the O/F-uncontrolled hybrid rockets had a lower performance by upwards of 6.69 and 4.06% in ΔVΔV for cases 1 and 2, respectively. For case 2, 3008 flight simulations revealed that the worst case of the O/F-controlled hybrid rocket had a 4.06 to 4.49% larger ΔVΔV and 10.5 to 13.3% higher apogee than that of the O/F-uncontrolled hybrid rocket, and that the O/F-uncontrolled hybrid rocket had a 6.61 times larger standard deviation in ΔVΔV. These results mean that the elimination O/F shift in hybrid rockets significantly improves performance, as well as the accuracy and reliability of performance predictions

酸化剤の軸/周方向噴射を用いたハイブリッドロケットの高機能化に関する研究

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 嶋田 徹, 東京大学教授 津江 光洋, 東京大学教授 小紫 公也, 東京大学准教授 姫野 武洋, 東京大学准教授 中谷 辰爾, 東海大学教授 那賀川 一郎University of Tokyo(東京大学

Development of Mathematics Lesson Using Kahoot! as a Transformation of the Lesson through EdTech

In this study, we analyzed a case study of ICT use in a mathematics department in Singapore from a subject-specific perspective that deepens students' learning, such as adaptive learning. Based on the suggestions obtained from this study, we developed lessons using Kahoot! in Japanese mathematics classes. The results of the verification of its effectiveness suggested that the use of Kahoot! is effective in promoting students' independent learning and deep learning.departmental bulletin pape

Regression behavior of polylactic acid manufactured by fused filament fabrication for hybrid rocket propulsion

Advanced closed-loop control of thrust and mixture ratio of hybrid rockets is planned by combing a fuel mass flow rate control technique with a real-time fuel regression measurement. The latter technique is enabled by a multi-materialadditive-manufactured solid fuel with an integrated sensor probe structure. This work investigated the fuel regression behavior of polylactic acid (PLA) fuel used for the main material of this type of solid fuels. Rectangular slab fuels and cylindrical fuel grains were manufactured by Fused Filament Fabrication (FFF) and fired in an optically accessible slab burner and a lab-scale motor, respectively. The cylindrical fuel grains had more than 2 times larger regression rates than rectangular slab fuels even with the same PLA filament. One of the main factors causing this large difference can be an anisotropy in the fuel regression rate behavior of the solid fuels manufactured by FFF

Surrogate models for the magnitude of convection in droplets levitated through EML, ADL, and ESL methods

Fluid flow and heat transfer in levitated droplets were numerically investigated. Three levitation methods: electro-magnetic levitation (EML), aerodynamic levitation (ADL), and electro-static levitation (ESL) were considered, and conservative laws of mass, momentum, and energy were applied as common models. The Marangoni effect was applied as a velocity boundary condition, whereas heat transfer and radiation heat loss were considered as thermal boundary conditions. As specific models to EML, the Lorentz force, and Joule heat were calculated based on the analytical solution of the electromagnetic field. For the ADL model, besides the Marangoni effect, the flow driven by the surface shear force was considered. For ADL and ESL models, the effect of laser heating was introduced as a boundary condition. All the equations were nondimensionalized using common scales for all three levitations. Numerical simulations were performed for several materials and droplet sizes, and the results were evaluated in terms of the Reynolds number based on the maximum velocity of the flow in the droplet. The order of magnitude of Reynolds numbers was evaluated as $\text{Re} \sim 10^4$ for EML, $\text{Re} \sim 10^3$ for ADL, and $\text{Re} \sim 10^1$ for ESL. Based on the simulation results, we proposed simple formulas for predicting the Reynolds number of droplet internal convection using combinations of nondimensional numbers determined from the physical properties of the material and the driving conditions. The proposed formulas can be used as surrogate models to predict the Reynolds numbers, even for materials other than those used in this study

Serial Assessment of Immune Status by Circulating CD8+ Effector T Cell Frequencies for Posttransplant Infectious Complications

To clarify the role of CD8+ effector T cells for infectious complications, 92 recipients were classified according to the hierarchical clustering of preoperative CD8+CD45 isoforms: Group I was naive, Group II was effector memory, and Group III was effector (E) T cell-dominant. The posttransplant infection rates progressively increased from 29% in Group I to 64.3% in Group III recipients. The posttransplant immune status was compared with the pretransplant status, based on the measure (% difference) and its graphical form (scatter plot). In Groups I and II, both approaches showed a strong upward deviation from pretransplant status upon posttransplant infection, indicating an enhanced clearance of pathogens. In Group III, in contrast, both approaches showed a clear downward deviation from preoperative status, indicating deficient cytotoxicity. The % E difference and scatter plot can be used as a useful indicator of a posttransplant infectious complication

Genetic and antigenic characterisation of influenza A(H3N2) viruses isolated in Yokohama during the 2016/17 and 2017/18 influenza seasons.

BACKGROUND: Influenza A(H3N2) virus rapidly evolves to evade human immune responses, resulting in changes in the antigenicity of haemagglutinin (HA). Therefore, continuous genetic and antigenic analyses of A(H3N2) virus are necessary to detect antigenic mutants as quickly as possible. AIM: We attempted to phylogenetically and antigenically capture the epidemic trend of A(H3N2) virus infection in Yokohama, Japan during the 2016/17 and 2017/18 influenza seasons. METHODS: We determined the HA sequences of A(H3N2) viruses detected in Yokohama, Japan during the 2016/17 and 2017/18 influenza seasons to identify amino acid substitutions and the loss or gain of potential N-glycosylation sites in HA, both of which potentially affect the antigenicity of HA. We also examined the antigenicity of isolates using ferret antisera obtained from experimentally infected ferrets. RESULTS: Influenza A(H3N2) viruses belonging to six clades (clades 3C.2A1, 3C.2A1a, 3C.2A1b, 3C.2A2, 3C.2A3 and 3C.2A4) were detected during the 2016/17 influenza season, whereas viruses belonging to two clades (clades 3C.2A1b and 3C.2A2) dominated during the 2017/18 influenza season. The isolates in clades 3C.2A1a and 3C.2A3 lost one N-linked glycosylation site in HA relative to other clades. Antigenic analysis revealed antigenic differences among clades, especially clade 3C.2A2 and 3C.2A4 viruses, which showed distinct antigenic differences from each other and from other clades in the antigenic map. CONCLUSION: Multiple clades, some of which differed antigenically from others, co-circulated in Yokohama, Japan during the 2016/17 and 2017/18 influenza seasons