Study of CFRP application to the cryogenic propellant tank of reusable launch vehicle

National Space Development Agency of Japan (NASDA) is conducting a feasibility study of CFRP application to the cryogenic propellant tank of reusable vehicle system (RLV). We started the study in 1997 and have obtained a promising data for CFRP applicability. We have obtained a basic CFRP material property and chosen the most promising material - highly toughened Epoxy IM600/#133 at the moment under collaboration work with National Aerospace Laboratory (NAL). We are conducting a small tank test with 600mm diameter lay up tanks with NAL and 300mm diameter filament winding (FW) tanks under collaboration work with Italian Aerospace Research Center (CIRA). For lay-up tank test, the tank was filled with LN2 and pressurized up to 0.98 MPa, and then helium leakage data was obtained at room temperature. The data indicated there was no leak path on the lay-up tank by cryogenic temperature. For FW tank test, the first phase test was conducted in 1999. There was considerable leakage after chilled down to LN2 temperature. Manufactual malfunction of the first series of FW tank was analyzed and the second phase test are being conducted under collaboration work with CIRA. Improvements of design and manufacture process were realized and the first tank of the collaboration work was completed excellently. The tank will be served for cryogenic and pressurized test in a few months. We are also studying the property of promising insulator inside or outside of the propellant tank and most proper adhesives for bonding CFRP at cryogenic temperature. The recent outcome about the study is the data of basic property of promising insulator, including AIREX which seems to be applicable. We are also getting the data of several promising adhesives. Shear stress strength data of those adhesives were obtained at room temperature, LN2 temperature, and LHe one.