Design and FE Analysis of Anti-Slosh Baffles for Fourth Stage of PSLV

Polar Satellites Launch Vehicle (PSLV) is the work horse of ISRO. It is used to launch 1000 kg satellites in polar orbits and upto 1600 kg satellites in low earth orbits. PSLV is a 4 stage vehicle weighing 315 tonnes. It uses liquid propulsion for second and fourth stages. The fourth stage propulsion tank is made up of Titanium Alloy (Ti6Al4V)(1335 mm dia). The configuration of tank is monocoque, with a common bulkhead to separate the fuel and oxidiser. The top compartment is used for fuel and bottom compartment is filled with oxidiser. Anti-slosh baffles (Ring Baffles) are used in both compartments to suppress slosh .Sloshing is a common phenomenon in partially filled liquid container. The rocket motor cases, filled with liquid propellants are left with an internal ullage volume (free volume) for the pressuring gas to stabilise. This creates a free surface of liquid. Sloshing is defined as the oscillation of the free surface of a liquid in a partially filled container due to external disturbances. Baffles are essentially ?plates? fixed inside the container to arrest sloshing. The slosh waves, during the causes of travel, hits the plates breaks and dies out. This reduces the slosh forces on the walls of container. Presently the ring baffles are supported from top flange of tank for launching satellites up to 1200 kg. For this propellant loading is upto 2.5 t. Now a PS4 stage is reconfigured with 0.8 t loading to launch 500 kg satellites. In this tank the liquid levels are less. Hence ring baffles are supported from bottom flange of tank to reduce the total mass of the baffle system. So in this paper Structural design, Finite Element analysis and Modal Analysis are carried out.