Shigeru Aso
(Kyushu University, Japan)

Recently developments of micro-satellites, whose weight is less than 100 kg, become quite active. As micro-satellite uses commercial, inexpensive components, the cost of micro-satellite becomes cheap and also the size of subsystem of micro-satellite becomes smaller and smaller. The latest micro-satellite for single mission becomes very useful for commercial use.
Above situations of micro-satellite begin to request low-cost launcher to low earth orbit because a combination of low cost micro-satellite and low cost launcher can do develop micro-satellite business market. For this request hybrid rocket is one of the most promising propulsion system.
However, still some problems remain in hybrid rocket such as low regression rate, optimum scale rule , large thrust, vibration in the combustion chamber. The hybrid rocket working group of ISAS, JAXA has been working to solve those problems. The present authors proposed a new method for increase of regression rate of hybrid rocket. The new method is to introduce swirling flow at multi-sections along fuel and has been applied for high density polyethylene fuels and paraffin fuels with gaseous oxygen. The results show the new method is quite useful for the increase of the regression rate and the increase of the thrust of hybrid rocket engines.

Harunori Nagata
(Hokkaido University, Japan)

The authors have been developing CAMUI type hybrid rockets as explosive-flee small rocket motors. A main purpose is to drastically downsize the cost and scale of rocket experiments to realize a cascade structure of space technology development as Fig.1 shows. Because the launch site cost is independent of the scale of a rocket, the percentage of the launch site cost increases with decreasing the scale. A main cause of the high launch site cost is the need of special ground facilities for safety control. If a rocket does not use any explosives nor hazardous material, the special ground facilities are not necessary and one can take the cost advantage of small-scale rocket experiments. A key idea of CAMUI type hybrid rockets is a distinctive fuel grain design to accelerate gasification rates of solid fuels. The grain design, designated as CAMUI as an abbreviation of "cascaded multistage impinging-jet", makes the combustion gas collide repeatedly with fuel surfaces, resulting in intense heat transfer to the fuel. The first example for a research purpose is a successful subsonic flight experiment of ejector-rocket projected by JAXA, on March2009. A flight experiment of a winged vehicle will follow as the second example in fiscal 2011.

Apollo Fukuchi
(IHI Aerospace Co., Ltd., Japan)

It is reported that hybrid rockets have advantage of environmental friendliness. However, there are little reports, estimating CO2 emission quantitatively. Therefore, to confirm the environmental advantage of hybrid engines, the authors investigated CO2 emission of major propellants. We can conclude that CO2 emission of hybrid engine is greatly less than that of solid rocket motor and of LOX/LH2 engine.
The authors try to reduce recurring cost by using LOX as oxidizer and low cost plastics and liquid polymers as fuel. We examined fuel production characteristics, mechanical properties and combustion characteristics by hot firing tests. HTPE and thermo plastic elastomer were selected as low cost hybrid fuels. These fuels can reduce the propellant cost from 1/10 to 1/5 of usual hybrid fuel as HTPB. We compared regression rates by hot firing tests with calculated values by expression considering vaporization and blowing. The regression rate of test result of thermo plastic elastomer is larger than that of calculated value. It is possible that shear flow influenced transportation of melting layer on thermo plastic elastomer.
We will discuss the issues on low cost development way of hybrid engine by using the existing component techniques for large solid motor or liquid engine.