Programme
Six revisions of design development, a frozen configuration, and a first vessel entering construction.
Where the HD-18 is
The design is frozen at V10 and the first vessel is entering construction. Configuration, structure, arrangement and the full bill of materials are released.
Build slots in the first series are open now. Configuration is set per customer — payload fit, sensor package, endurance profile and delivery position.
Design maturity
Six revisions, and what each one settled.
| Revision A | Design study. Envelope, displacement and the broad architecture established. |
| Revision B | Payload architecture resolved: dry compartments loaded on the surface, chosen over an opening bay for stability and simplicity. |
| Revision C | Deck arrangement and closure design developed through to a full structural take-off. |
| Revision D | Arrangement reworked: payload moved to dry wells loaded on the surface, the section re-cut so hatches land on flat deck, ring frames moved onto the bulkhead stations, and the mast designed as a system rather than a weight allowance. |
| Revision E | Configuration frozen: three sealed pressure-balanced compartments, six upward-hinging dogged hatches, a three-stage mast on its own trunk. Full CAD, drawings and costed bill of materials released. |
| Revision F / V10 | Architecture settled. The battery moved forward, which closed the trim and cleared the parallel middle body of everything except payload — so the hull became stretchable, and the six-to-twelve-bay family was solved in full. Compartments deepened to 1.45 m so a module can stand on its lift and rise clear of the coaming without anyone entering the boat. Sourcing re-verified line by line against live vendor pages. |
Build sequence
Seventeen stages, and three of them are gates.
The order is not a preference. The ring frames must be set before the compartments can be landed, because the flange mounts land on the frames. The compartments must be proof-tested before installation, because a compartment cannot be tested in place. And the hatch seats must be machined and lapped after the compartments are installed and aligned, because the six seats have to end up in a plane with the deck.
The critical path is not the labour. It is the first-article hatch and the long-lead procurement, and both are gated on the design freeze. A programme that releases six hatches on a paper design saves nothing and risks everything.
5,978 hours of direct labour are carried across engineering, fabrication and assembly, and the procurement lines carry published lead times. Those two things are what a schedule can honestly be built from.
Design freeze
Production drawings, welding procedure and welder qualification to EN ISO 15614-2.
Long-lead release
Thrusters, generating set, cells, motors, compressor, sonar, velocity log and inertial unit — the published lead times, not an estimate.
Structure
CNC plate profiling; 8 ring frames and the space frame welded, fitted and aligned.
Compartments
Fabricated off the vessel, non-destructively tested, and hydrostatically proof-tested individually to 3.017 bar.
First-article hatch
One hatch fabricated, machined, assembled and pressure-tested before the other five are released. This is a gate, not a milestone.
Tankage
Tank boundaries and bulkheads fabricated and coated — 34.7 m³ gross.
Landing
Compartments landed on the four-point flanges and aligned. The alignment sets the hatch seat plane.
Closures
The remaining five hatches fabricated, all six coamings machined, seats lapped and dogs set.
Machinery
Generating set pod, battery pods, propulsion, thrusters, control planes and mast trunk installed.
Air plant
Bottles, compressor, regulator trains, relief and monitoring installed, commissioned and fault-case tested.
Electrical
Harness installation, junction boxes and the compartment connector interfaces.
Fairing and coatings
Hull fairing fitted and faired off; etch primer, barrier coat, copper-free antifouling and cathodic protection over 273.5 m².
Integration
Systems integration, software and autonomy commissioning.
Ballast
19,750 kg of fixed ballast grouted into the keel channel at the solved longitudinal centre.
Inclining
Inclining experiment and trim verification — the only physical check on KG that exists before the first dive.
Dock trials
Every sealed volume tested in the water at shallow immersion, with the vessel recoverable by crane, before any depth is attempted.
Sea trials
Two weeks with a support craft. Powering, endurance, dive and surface cycles, autonomy, communications, and the pressure-balance fault cases exercised deliberately rather than encountered.
Assurance
What gets tested, and what is still an open question.
The obligations below are scoped and costed regardless of which certification regime ends up applying. They are what any competent review would impose on a pressure boundary, and they are in the programme already.
The regime itself is deliberately open. An uncrewed submersible carrying commercial cargo does not sit cleanly in any established category: it is not a manned submersible, not a conventional cargo ship, and not a small uncrewed surface vessel. We have not invented a determination we do not have. The classification line in the programme is the cost of finding out, not the cost of complying — and getting that answer in writing from the intended flag administration is the single most valuable thing the programme can do next.
Ownership
The design is ours, end to end.
Hull form, structure, arrangement, closure design, energy system and payload interface were all developed in-house against one engineering model. There is no licensed platform underneath and no third party to renegotiate with.
That matters when a customer wants the boat changed: length, payload volume, endurance and sensor fit are parameters in the model, not a redesign. The six-to-twelve-bay family is the proof — four full solves of the same architecture, produced by changing one number.
