By introducing various innovative ideas, the difficult-to-develop small hybrid-type rocket is successfully developed. The main purpose is to drastically reduce the cost of rocket experiments and thus attract potential users such as metrological and microgravity researchers. A key idea is a new fuel grain design to accelerate the gasification rate of solid fuel. The new fuel grain design, designated as CAMUI as an abbreviation of "Cascaded Multistage Impinging-jet", is that the gas flow repeatedly collides with the solid fuel surface to accelerate the heat transfer to the fuel. To install a regenerative cooling system using cryogenic liquid oxygen as coolant in a small launcher, the authors devised a valveless supply system (with no valves in the liquid oxygen flow line). Four serial successful launch verification tests by 10 kg vehicle equipped with a 50 kgf thrust CAMUI motor have shown the feasibility of the motor system. The meteorological observation model of 400 kgf class motor is under development and the development of microgravity experiment class of 1.5 to 2 tonf motor will follow subsequently. The authors plan to complete the development of the 400 kgf class motor for meteorological observation model by the end of FY2005.

No abstract

Accuracy of a reconstruction technique assuming a constant characteristic exhaust velocity (c *) efficiency for reducing hybrid rocket firing test data was examined experimentally. To avoid the difficulty arising from a number of complex chemical equilibrium calculations, a simple approximate expression of theoretical c * as a function of the oxidizer to fuel ratio () and the chamber pressure was developed. A series of static firing tests with the same test conditions except burning duration revealed that the error in the calculated fuel consumption decreases with increasing firing duration, showing that the error mainly comes from the ignition and shutdown transients. The present reconstruction technique obtains  by solving an equation between theoretical and experimental c * values. A difficulty arises when multiple solutions of  exists. In the PMMA-LOX combination, a  range of 0.6 to 1.0 corresponds to this case. The definition of c * efficiency necessary to be used in this reconstruction technique is different from a c * efficiency obtained by a general method. Because the c * efficiency obtained by average chamber pressure and  includes the c * loss due to the  shift, it can be below unity even when the combustion gas keeps complete mixing and chemical equilibrium during the entire period of a firing. Therefore, the c * efficiency obtained in the present reconstruction technique is superior to the c * efficiency obtained by the general method to evaluate the degree of completion of the mixing and chemical reaction in the combustion chamber.

No abstract

The authors have been developing CAMUI (Cascaded Multistage Impinging-jet) type hybrid rockets, explosive-flee small rocket motors. This is to downsize the scale of suborbital flight experiments on space related technology development. A key idea is a new fuel grain design to increase gasification rates of a solid fuel. By the new fuel grain design, the combustion gas repeatedly impinges on fuel surfaces to accelerate the heat transfer to the fuel. To demonstrate flight performance of a newly developed 5000 N thrust class motor and accumulate flight data around the sonic speed, a launch test was conducted from a coast to the sea. Basic technologies for the sea recovery are staged braking by parachutes, suspending the fuselage on the ocean, and locating the fuselage by an electric beacon and sea marker. Test results were successful and all of the fuselage was recovered. A typical drag coefficient profile around the sonic speed was obtained.