For the first step of investigating TNT equivalency, blasting tests without igniting to fuel samples in the air atmosphere were carried out in order to investigate the fragmentation characteristic of the fuel blocks. PP, PMMA and FT-0070 blocks were blasted by No.6 electric detonator or No.6 electric detonator + P-4. As a result, it is revealed that the blocks are fragmented into smaller particles if the original block size is smaller and if the power of the high explosives is higher. However, the effect of power of the high explosives is small in the case of this study. It is revealed that PP is not fragmented so small, FT-0070 is fragmented to powder and the fragmented particles size of PMMA is between PP and FT-0070.
A numerical setup has been developed to rebuild the axial profile and time history of the regression rate of a paraffin-wax-based fuel in a hybrid rocket, with the main target of investigating the effect of the local radiative heat transfer from both the combustion gas molecules and soot particles. The numerical approach is based on a quasi-one-dimensional computational fluid dynamic strategy, which is coupled with chemical equilibrium combustion; the vaporization and entrainment components of the wax-fuel regression rate have been estimated with an established liquefying-fuel model. The increase of the convective heat-transfer blocking due to radiation and the effect of recirculation flow due to oxidizer injection have been introduced. Numerical results are compared with experimental data. When radiative heat transfer, blocking-effect correction, and recirculation flow effect are taken into account, the calculated and measured fuel regression rates agree well in both values and axial profiles.
Burning tests of a laboratory-scale hybrid rocket engine were carried out with gaseous oxygen and a microcrystalline-wax-based fuel to look into the feasibility of using an intrusive resistor-based sensor for measuring the fuel regression rate. This initial screening was driven by the need for real-time control of the oxidizer-to-fuel ratio in altering-intensity swirling-flow-type hybrid rocket engines aiming at performance optimization. A traditional ballistic reconstruction technique was critically revised in order to build up a framework for comparison with the measured data; with the measured aft-chamber pressure and oxygen mass flow rate time histories, the fuel regression rate and port diameter were reconstructed over the firing by estimating the combustion efficiency with the constraint that calculated and measured fuel mass consumed are equal. This technique invariably suffers from the issue of presenting multiple solutions for the fuel mass flow rate in the proximity of the optimum mixture ratio, for which a novel variable-efficiency approach is proposed. Reconstructed data show that regression rate is nearly constant in each firing, yielding dependence upon the port diameter other than the mass flux. Resistor-sensor raw data displayed large deviation from the ballistic results for the slower burning rate of the sensor support. A detailed analysis is presented.
A multi-objective genetic algorithm (MOGA) has been applied to the multidisciplinary design optimization (MDO) of a launch vehicle (LV) with a hybrid rocket engine (HRE) to investigate the ability of an HRE to serve as a sounding rocket from various perspectives. In this study, the flight evaluation was enhanced to 3-degree-of-freedom (3DoF) in order to consider the equations of motion for horizontal and vertical motion and rotation of the LV. In the consideration of the rotation of the LV, the time variation of the center of gravity due to the fuel burn was estimated. The non-dominated sorting genetic algorithm-II (NSGA-II) was used to solve multi-objective problems (MoPs). Four design problems were examined in order to understand the practical physics of hybrid rocket. As a result, tradeoff information was observed for all design problems. The results for the present four design problems indicate that economical performance of LV is limited with the HRE in terms of the maximum altitude and maximum downrange distances achievable. The hypervolume, which was used as the metric to evaluate the difficulty of the design problems, reveals that the convergence of the solutions for not only altitude maximization in the case of a vertical launch but also the maximization of downrange at higher target altitudes was affected by the severe limitation. To observe the dependence of the design problems on the constraint, the design problems were visualized using a colored parallel coordinates plot (PCP), and the LV geometries determined from the nondominated solutions were successfully examined.
The development of enhanced propulsion system for the next Epsilon rocket was progressed. The development of Enhanced Epsilon is mainly the renewal of the second stage, and also includes each subsystem's improvement. The second stage motor M-35 was newly designed and manufactured. In order to verify the design, the static firing test of the second motor M-35 under the condition of vacuum ambient was conducted in 2015. The JAXA successfully launched the first Enhanced Epsilon launch vehicle. All solid propulsion systems for the Enhanced Epsilon launch vehicle showed a very good behavior during the flight
This paper reports on the conceptual design of a three-stage launch vehicle (LV) with a clustered hybrid rocket engine (HRE) through multi-disciplinary design optimization. This LV is a space transportation concept that can deliver micro-satellites to sun-synchronous orbits (SSOs). To design a high-performance LV with HRE, the optimum size of each component, such as an oxidizer tank containing liquid oxidizer, a combustion chamber containing solid fuel, a pressurizing tank, and a nozzle, should be determined. In this study, paraffin (FT-0070) is used as a propellant for the HRE, and three cases are compared: In the first case, HREs are optimized for each stage. In the second case, HREs are optimized together for the first and second stages but separately for the third stage. In the third case, HREs are optimized together for each stage. The optimization results show that the performance of the design case that uses the same HREs in all stages is 40% reduced compared with the design case that uses optimized HREs for each stage.
Abstract Conceptual design of a launch vehicle with a hybrid rocket engine (HRE) has been implemented using design informatics approach in order to investigate the feasibility of a single-stage hybrid rocket. Two test design problems were formulated by using two objective functions: maximization of downrange and minimization of initial gross weight, seven design variables which describe geometry and initial conditions, and one constraint relative to target altitude. The optimization result reveals the economical performance of hybrid rocket is limited with HRE in terms of the maximum downrange achievable. Moreover, the data-mining result indicates the mechanism of design-variable behavior.
