Masashi Wakita

Fuel Regression Characteristics of a Novel Axial-Injection End-Burning Hybrid Rocket

The regression characteristics of axial-injection end-burning hybrid rocket were experimentally investigated using a laboratory-scale motor. The axial-injection end-burning type fuel grains were ma...

Verification Firings of End-Burning Type Hybrid Rockets

The authors have previously proposed the concept of end-burning-type hybrid rockets, which would use cylindrical fuel grains consisting of an array of many small ports running in the axial directio...

Driver Gas Reduction Effect of Pulse-Detonation-Engine Initiator Using Reflecting Board

To reduce driver gas usage of a pulse detonation engine operating in airbreathing mode, the authors experimentally examined a combination method of a reflecting board and overfilling of the driver gas. This method has the potential to reduce the predetonator diameter by half and shorten the overfilling distance h to the reflecting board position w. Experiments with stoichiometric hydrogen–oxygen and hydrogen–air mixtures as driver and target gases, respectively, showed that the overfilling distance necessary to have a planar detonation wave propagate in a detonation chamber is reduced to 30 mm when a reflecting board is used with a reflecting board clearance of w 10 mm. With an overfilling distance of 30 mm, the transformation of the detonation wave from cylindrical to toroidal did not occur because of the mixing effect of the driver gas and the target gas around the reflecting board. A 100-mm-thick reflecting board prevents the mixing effect, and a successful transformation from cylindrical to toroidal becomes possible with an overfilling distance as small as 17.2 mm.

Development of Regression Formulas for CAMUI Type Hybrid Rockets as Functions of Local O/F

Regression formulas for solid fuels in CAMUI type hybrid rockets were developed as functions of local O/F. The alternative fuel grain design used in this rocket consists of multiple stages of cylindrical fuel blocks with two ports. A fuel block in a CAMUI type grain has three burning surfaces, i.e., the upstream end face, port inner walls, and the downstream end face. A series of static firing tests by a laboratory model motor revealed controlling parameters to develop a regression formula for each burning surface. Some empirical constants in the regression formulas depend on local O/F. Based on these findings, regression formulas as functions of local O/F were developed for a 2500 N thrust class flight model motor. Obtained regression formulas contribute to obtain an optimal design of a grain configuration to minimize the weight of residual fuel mass and c * loss due to the O/F shift during firing.

Method for Determining Nozzle Throat Erosion History in Hybrid Rockets

The authors of this paper introduce a new reconstruction technique titled nozzle-throat reconstruction technique to estimate nozzle-throat-erosion history and oxidizer-to-fuel-mass-ratio history in...

Detonation Transition Around Cylindrical Reflector of Pulse Detonation Engine Initiator

To achieve reliable transmission of detonation waves to a pulse detonation engine combustor (detonation chamber), the authors propose a pulse detonation engine initiator that uses a cylindrical reflector downstream of a predetonator exit. The detonation wave propagates around the reflector to change the wave shape in three transition stages: from a planar detonation wave in the predetonator to an expanding cylindrical detonation wave, from the cylindrical wave to a planar toroidal detonation wave, and from the toroidal wave to a planar detonation wave in the detonation chamber. The cylindrical wave propagates along a cylindrical path between the reflector and front wall of the detonation chamber, and the toroidal wave propagates along an annular path between the reflector and sidewall of the detonation chamber. The purpose of this study was to examine the influence of the gap width L of the annular path on the transition stages from cylindrical to toroidal and from toroidal to planar. A series of experime...

Proposal of procedure of thermal design on micro and nano satellites pointing to Earth

A procedure for the thermal design of micro and nano satellites is proposed in order to complete the thermal design of micro and nano satellites for about 1 year. Two concepts of thermal design are considered to keep the temperature change of components within the design temperature range of components. One concept is to decrease the temperature change using the whole heat storage of the micro and nano satellite. The other is to decrease the temperature change of the inner structure where the components with the narrow design temperature range are mounted. The temperature of micro and nano satellites designed in the former concept is calculated using one nodal analysis method. The temperature of micro and nano satellites designed in the latter concept is calculated using two nodal analysis method. The combinations of optical properties on structures and components to keep the temperature within the design temperature range of components are clarified using one or two nodal analysis. Then, the multi-nodal analyses are carried out to be designed in detail based on the optical properties clarified from the one-nodal analysis and two nodal analysis. This procedure of thermal design is applied to Hodoyoshi-1 satellite. Hodoyoshi-1 satellite is the micro satellite that is about 50 cm in width, 50 cm in depth, 50 cm in height, is about 50 kg in mass, has two inner plates, has solar cells on the body, flies on the sun-synchronous orbit of the 500 km of altitude and is pointing to the Earth. The thermal design of Hodoyoshi-1 satellite has been completed for about ten months. The validity of this procedure is confirmed and the problems of this procedure are clarified.

Emissivity of Wavelength-Selective Radiator With Periodic Microcavities

A periodic microstructure of the cubic cavity 6.0 μm wide, 6.0 μm deep, and 6.0 μm high is built on an ultraviolet curable resin via UV nanoimprinting. The 200 nm thick gold film is sputtered on the periodic micro structure. The hemispherical spectroscopic transmittance and reflectance of the periodic microstructure with the gold film are measured using a Fourier transform infrared spectrometer with an integrating sphere. The hemispherical spectroscopic transmittance is 0.0 from 2 to 15 μm wavelength. The hemispherical spectroscopic reflectance is 1.0 from 2 to 8 μm wavelength and from 12 to 15 μm wavelength. The bottom of the hemispherical spectroscopic reflectance is 0.4 near 10 μm. Assuming Kirchhoff’s law, the maximum normal emissivity of the periodic microstructure is 0.6 near 10 μm. It is clarified that the periodic microcavities with a gold film built via UV nanoimprinting and sputtering can enhance maximum spectral emissive power of radiation.© 2013 ASME