How depth is controlled

The vehicle is trimmed slightly positively buoyant. It does not rely upon forward speed alone to remain safe.

1. At the surface, two 50 L ballast tanks admit water through their flood openings while air leaves through controlled vent valves.
2. Two 12 L piston trim tanks adjust fine displacement and fore/aft trim.
3. Vertical thrusters provide immediate depth and hover control while the automatic controller holds the demanded depth.
4. For surfacing, compressed air expels water from the main tanks. In an emergency, the independent 20 kg drop weight is released.

How the submarine moves

Six guarded electric thrusters are mixed by the onboard control allocator. The operator requests a movement; the computer calculates the direction and power required from every thruster.

Twin 6 kW stern propulsors provide forward/reverse thrust and differential yaw. Two vertical thrusters control ascent, descent, hover and pitch. Two lateral thrusters control sideways movement and close docking.

Where the order comes from

The Remote Operator creates a signed mission containing waypoints, target depth, speed, minimum altitude, geofence and recovery corridor. At the surface it is sent through encrypted 4G/5G, satellite or Wi-Fi to the gateway and vehicle. Underwater, short bounded commands use the acoustic modem.

How the vehicle obeys

The command gateway first checks identity, sequence number, age, operating limits and available energy. Accepted commands pass to the guidance computer. It compares the demanded position with INS, DVL, depth, altimeter and acoustic fixes, then sends force demands to the thruster allocator. Motor controllers report actual speed/current, and the control loop continuously corrects the error.

A command that is unsafe, unauthenticated, outside the geofence or incompatible with energy reserve is rejected. The UUV returns an acknowledgement or reason for rejection.

Radio above water; acoustics underwater

Ordinary radio cannot provide a dependable underwater control link. The land ROC therefore communicates by internet/VPN with a surface gateway on a support vessel, buoy or USV. The gateway translates bounded commands and acknowledgements to the acoustic link.

High-rate sonar and video are stored onboard. Only essential status, alarms, command acknowledgements and selected thumbnails are sent acoustically. This prevents dangerous dependence on continuous joystick steering through a delayed link.

What happens if communication stops

For the first 20 seconds the vehicle maintains a safe trajectory and retries the link. It then stops survey actions, reduces speed and holds safe depth or altitude. If the link remains absent it backtracks toward the last good communication point. After the mission-specific timeout it follows the approved recovery corridor and surfaces only where overhead clearance permits.

Severe leak, loss of navigation or exhausted recovery margin can cause the independent safety controller to command HP ballast blow and/or drop-weight release.