Development of a capillary tube orifice for high pressure and a low flow rate in a launch vehicle

•A unique capillary tube orifice is proposed in a launch vehicle.•The operating condition of the orifice is 22 MPa and 1.1 g/s.•The empirical correlation provided in this paper can be used to design capillary tube orifices.•The friction factor in the internal flow of the capillary tube orifice is investigated. The purpose of an orifice is to reduce the flow rate and the pressure. A tiny hole with a 0.1 mm diameter is necessary when the up-stream pressure is very high at 22 MPa, and the required flow rate is very low at 1 g/s. The machining of such a tiny hole with a 0.1 mm diameter as the orifice has a poor processability, and the flow passage is easily clogged by particles when the orifice size is too small. A new capillary tube orifice was developed to resolve the above mentioned problems. The fabricated capillary tube orifices were tested at room and cryogenic temperatures to measure its performance with helium gas. The effective cross sectional area of the tested orifices was constant in various test conditions. The cross sectional area of the fabricated capillary orifices was observed with a microscope, and the friction factor was analysed.