Piranha USV, strike and surveillance from one hull

Primary engineering baseline

Internal architecture & CAD layout

Primary use cases

Piranha works in littoral waters, island chains and approaches to ports, where a crewed boat would be at risk. Every craft carries the radar and EO/IR payload; strike craft add the warhead.

Navigation, control and warhead

A · Non-satellite sea-surface navigation

Satellite denial over open water presents unique challenges: unlike land terrain, the open sea has no static topographic features for elevation correlation. The Piranha USV employs a layered navigation stack built specifically for marine environments:

• CRPA Anti-Jam GNSS: Indigenous multi-element antenna suppresses coastal jammers by >45 dB, maintaining NavIC/GPS lock during initial transit.
• Hydro-Inertial Dead Reckoning: Tactical IMUs fused with a Doppler Velocity Log (DVL). In coastal water the DVL locks onto the seabed and measures true speed over ground, which removes current drift; beyond its bottom-lock depth it measures speed through the water, and the current becomes an estimated state.
• Coastline DSMAC: As the vessel nears target archipelagos, ports, or coastlines, high-resolution optical cameras match shoreline profiles, headlands, and navigation marks against pre-loaded commercial satellite maps.
• Optical Waterline Tracking: In the terminal run, the stabilised EO/IR gimbal locks onto the target's hull silhouette at the waterline, which chaff and most decoys do not reproduce.

B · Control: the same method, a marine controller

Piranha is controlled the way the aircraft are, with the physics changed from air to water. A guidance layer turns the route into the heading and speed to hold, a controller holds them, and the waterjets carry out the commands. As on every Apollyon platform, the controller's settings come from a model of the vehicle identified from real runs, not from textbook assumptions, and envelope limits keep demand inside what the hull and jets can actually deliver.

The hard part is the equivalent of flying near the edge of the envelope. A fast hull behaves very differently at low speed, while climbing onto the plane and at full sprint, so the control settings are scheduled across those regimes rather than fixed. The sea adds its own problems. The controller has to ignore the rocking of individual waves and follow only the real motion. It has to hold running trim so the hull stays stable at speed, and it has to keep station on the track despite current and wind pushing the vessel sideways.

• Speed follows the sea: as the sea state rises, the vessel limits its own speed to stay inside the structural limits of the hull.
• Sharing the water: in transit and on patrol it keeps clear of other traffic using its marine radar and EO/IR, and follows the rules of the road.
• When the link drops: it falls back to a pre-set safe behaviour. The decision to strike always stays with a human commander.

The hull and hardware are still in build, so these settings will be worked out in sea trials, through the same loop the aircraft use: run the vessel, compare the logs with the simulation, correct the model and the settings, and clear each change in hardware-in-the-loop testing before it goes back on the water. One method, many platforms →

C · Warhead

The strike configuration carries a 50 kg+ class high-explosive warhead in the bow bay. It is sized for small combatants, landing craft, moored vessels and jetty infrastructure, not for major warships.

• Waterline detonation: the craft is guided onto the target's hull at the waterline, where damage lets water in.
• Redundant fuzing: contact and delayed-action fuzes, so a glancing hit still detonates.
• Human decision: the decision to strike stays with a human commander.

One hull, two customers

One hull serves both jobs. Every Piranha carries the marine radar and the EO/IR gimbal. The reconnaissance configuration uses them to watch the coast and shipping lanes and comes home; the strike configuration adds the 50 kg+ warhead and uses the same sensors to find and hit the target. Coast guards, port authorities and littoral security forces get a persistent sensor picture without crewing a boat, and the peacetime fleet keeps the boatyard tooling and the crews who operate it in practice.

Subsystems powering this vessel