Step 4: The Ascent – Returning with Freshwater

Once the filtration process has reached its planned completion, the NEAT + WATER submarine begins the next stage of its mission: preparing for the journey back to the surface.

The first part of this transition is the management of the concentrated saltwater, or brine, produced during the reverse osmosis process. The brine is discharged from the submarine through a controlled outlet, allowing the dedicated brine chamber to be emptied and prepared for the next mission.

With the brine discharged, the submarine begins changing its buoyancy.

Air is introduced into the submarine's buoyancy chambers. As these chambers fill with air, the submarine becomes more buoyant. This gradually changes the vehicle's movement from its downward trajectory into an upward one.

The transition is carefully controlled. Rather than making a sudden change in direction, the submarine is designed to gradually adjust its buoyancy and begin its ascent toward the surface.

At the same time, the freshwater produced during the filtration process remains safely contained inside the dedicated freshwater storage tank. The submarine now carries its freshwater payload while beginning its journey upward.

As the submarine rises, onboard sensors continuously monitor its depth, orientation, pressure, buoyancy, and tank levels. The control system can regulate the amount of air in the buoyancy chambers to help maintain a controlled ascent.

This creates an important part of the NEAT + WATER operating cycle:

Descend → Filter → Discharge Brine → Increase Buoyancy → Ascend with Freshwater

The submarine is now on its way back toward the surface, carrying the freshwater it has produced from seawater.

The ascent is more than simply a return journey. It is an essential part of the system's efficiency. By using controlled buoyancy rather than relying solely on powered propulsion for every part of the vertical journey, the NEAT + WATER concept is designed to reduce the energy required to move the submarine through the water column.

As the submarine approaches the surface, it prepares for the final stage of the mission: returning to the support vessel, transferring its freshwater cargo, and preparing for another deployment.

One underwater mission is coming to an end—but the next one can begin soon after.

NEAT + WATER – From the ocean's depths, bringing freshwater back to the surface.