The 177 litre hydrazine surface tension tank. Model OST 31-1 from Orbital Propulsion Centre is a Spacecraft & Satellite Propellant Tank with Operating Pressure 24 Bar, Propellant Volume 132 Litres, Total Volume 177 L, Burst Pressure 48 Bar, Proof Pressure 36 Bar. More details for 177 litre hydrazine surface tension tank. Model OST 31-1 can be seen below.