Optimization of Deep-sea Profiling Float based on Ballasting Methodology

Ballasting is the approach of adjusting the float weight in order to park the profiling float at the predetermined equilibrium depth of ocean surface. The criticality of this quantitative approach changes from 0.05 g to 0.15 g of float weight which results in 1m difference in the diving depth due to local density stratification of ocean water. The lateral gradients of temperature and salinity are very high under pressure that reflects over the density gradient of seawater. Eventually, to merge with isopycnal condition (coincide the float density concerning pressure and in-situ density of ocean water), a variable buoyancy system is used i.e. altering the float volume without changing float mass. This paper describes the integration and procedure of optimal ballasting and explains the weight calculation of indigenously develop deep-sea profiling float that is capable of diving upto 5000 m depth with 1000 cc capacity of variable buoyancy. Nevertheless, the initial float testing and fine adjustments are planned at 500 m depth. For 500 m diving, the ballasting procedure is to be carried out in three stages. In the first stage-Preballasting-the float is placed in freshwater to correct the stability by achieving a neutrally buoyant state at atmospheric pressure. In the second stage-Ballasting- the laboratory measurement of float compressibility under 50 bar pressure in hyperbaric chamber is interpreted. Trim mass is calculated as 109.20 g (wet mass) based on the data collected over the chain attachment methodology of ballasting experiment. In final stage- Postballasting-the difference in the water properties of the pressure chamber and in-situ water at 500 m of ocean depth is to be calculated and resulted as 1781.20 g (wet mass) which is the compensation mass. This quantitatively analyzes the ballasting procedure with the intent of estimating optimal net buoyancy. The optimal net buoyancy over precise oil transfer through ballast weight leads to effective energy consumption that results in longer endurance of profiling float and enhances overall float performance. The prototype is configured and the system mass is fine-tuned for profiling up to 500 m parking depth with 24 hours mission cycle.