Feasibility study on synthermal storage of two cryogens in a single tank with a metal common bulkhead

Abstract Liquid-oxygen-liquid-methane reusable rocket technology is currently a hot topic in the field of spaceflight. Storage of liquid methane and liquid oxygen in a single tank but with a common bulkhead partition is the most compact and favorable scheme. Usually, two cryogens with different saturation temperatures are separated by a partition made of some low-conductivity materials or insulation structures, which creates difficulties in the processing and manufacturing of the tank. Instead of keeping the pressure on bilateral compartments close to each other, an idea is proposed to have the partition made of the same metal as the tank wall, which turns out a thermal equilibrium result inside both compartments. To explore the feasibility of the new method, a small-scale storage system with a stainless-steel common bulkhead tank is designed and tested by measuring the transient thermodynamic behavior inside the tank during the self-pressurization and venting processes. Experiments show that the pressures in the liquid oxygen and liquid methane compartments are 399.36 kPa and 67.86 kPa respectively (Scheme 1), which means a large pressure difference between the two compartments, and even worse a subatmospheric state in the liquid methane compartment. Consequently, appropriate amount helium is charged into the liquid methane compartment to improve the performance (Scheme 2). The results indicate that Scheme 2 significantly prolongs the storage duration, with a 38.30% increase in self-pressurization and venting time of the liquid oxygen compartments, and a 9.70% increase on the liquid methane compartment, compared with Scheme 1 with the same filling ratio and boundary conditions.