HD-18 specification
Every figure below is generated from the HD-18 V10 master engineering model. None is transcribed by hand.
Envelope and form
| Length overall | 18.00 m |
| Beam | 3.80 m |
| Depth moulded | 3.40 m |
| Deck corner radius | R200 |
| Bilge radius | R1,100 |
| Flat deck width | 3.40 m |
| Entrance · parallel body · run | 3.00 · 10.00 · 5.00 m |
| Prismatic coefficient | 0.819 |
| Wetted surface | 273.5 m² |
| Envelope volume | 182.7 m³ |
Hydrostatics and stability
| Submerged displacement | 82.94 t |
| Light ship | 46.19 t incl. 10% margin |
| Fixed ballast | 19.75 t · 23.8% of displacement |
| Closure residual | 0.00 kg |
| KB | 1.9088 m |
| KG | 1.2997 m |
| BG | 0.609 m |
| Righting moment | 0.8817 t·m per degree |
| LCG − LCB | 0.0000 m |
| Main ballast tank volume | 14.10 m³ |
| Installed tankage | 34.71 m³ gross |
| Surfaced reserve buoyancy | 17.4% |
| Freeboard, surfaced | 320 mm of dry deck |
| Tank permeability | 0.92 |
Payload
| Configuration | 3 sealed pressure-balanced compartments |
| Compartment envelope | 3.50 × 2.80 × 1.45 m |
| Volume per compartment | 14.21 m³ |
| Total payload volume | 42.63 m³ |
| Compartment pitch | 3.60 m · stations 2.70 to 13.50 m |
| Cargo deadweight | 17.0 t |
| Payload modules | 6 · 2 per compartment |
| Module envelope | 2.44 × 1.09 × 1.10 m · 4 mm skin |
| Module clearances | 60 mm wide, 60 mm long, 350 mm standing |
| Cargo per module | 2,833 kg |
| Lift mass per module | 3,071 kg |
| Module lifts | 6 scissor tables · 1,670 mm stroke, 250 mm collapsed |
| Reference cargo density | 399 kg/m³ |
| Mounting | Four machined flange mounts per compartment, landing on ring-frame stations |
| Connectors | SubConn / MCBH — 44 bulkhead and 44 cable ends, dry 1-atm junction boxes |
Pressure balance
| Principle | Compartments charged with air to sea pressure when submerged |
| Design differential | 1.00 bar |
| Control band | ±0.15 bar · ±1.49 m of depth |
| Relief setting | 0.5 bar |
| Proof test | 3.017 bar — 1.5× the unbalanced head |
| Boundary plate | 8 mm on 300 mm stiffening |
| Design-case stress | 70.3 MPa · SF 3.06 |
| Loss-of-pressurisation stress | 141.4 MPa · SF 1.52 |
| Material | 5083-H116 · 215 MPa yield |
| Pressurised volume | 50.737 m³ · compartments and trunks |
| Compartment mass, each | 2,027 kg |
Deck access
| Hatches | 6 upward-hinging, dogged, seated plug closures |
| Clear opening | 1.15 × 2.50 m |
| Cover | 1.35 × 2.70 m · 8 mm plate on 186.5 mm webs |
| Dogs per hatch | 14 at 19.3 kN |
| Seal | 12 mm nitrile O-ring on a machined seat, 100 mm land |
| Opening angle | 95° |
| Balancing | 2 gas springs · 13.2 kN manual effort |
| Uplift, relief valve lifted | 162.5 kN — carried by the dogs |
| Seated load at depth | 653.6 kN · 66.6 t — carried by the seat |
| Opening condition | Surface only |
| Access trunks | 6 · 1.15 × 2.50 × 0.47 m |
Propulsion and energy
| Battery pack | 750 kWh LFP |
| Usable energy | 600 kWh at 80% depth of discharge |
| Diesel generator | 150 kWe |
| Fuel | 3,960 L · 3,326 kg · pressure-compensated |
| Specific fuel consumption | 0.212 kg/kWh |
| Quasi-propulsive coefficient | 0.68 |
| Propellers | 2 × 0.80 m diameter on 1.90 m centres |
| Control planes | X-form, 1.10 m span, 1.55 m chord |
| Hotel load, submerged | 2.0 kW |
| Hotel load, payload active | 8.0 kW |
| Snorkel duty | 30% at the transit condition |
Performance
| Submerged range | 486 km at 4 kn · 65.6 h |
| Diesel transit range | 4,528 km at 6 kn · 407.5 h |
| Declared total range | 5,014 km |
| Sprint speed | 12 kn · 79.1 km · 3.56 h |
| Bus power at sprint | 168.6 kW |
| Service life | 500 h between overhauls |
Air plant
| Free air per cycle | 142.78 m³ |
| Compartment charge | 100.70 m³ |
| Main ballast blow | 42.07 m³ |
| Bottles | 13 × 50 L at 300 bar |
| Stored free air | 195 m³ |
| Compressor | 15 m³/h |
| Recharge time | 12.85 h |
| Design margin | ×1.35 on one full cycle |
| Charged-air mass | 123.4 kg — carried in the weight statement |
Mast and communications
| Stages | 3 |
| Stowed length | 1.6842 m |
| Stroke | 4.693 m |
| Snorkel depth | 1.20 m |
| Masthead above water | 3.81 m |
| Trunk | 0.60 m wide, watertight, with a dedicated hinged access hatch |
| Gland | Pressure-tight, in the mast hatch |
| Links carried | Satellite broadband, cellular, satellite short-burst data, long-range LPWAN |
| Long-range link | Approximately 50 bps usable at 10 km, 1.5–3 s latency — telemetry and waypoint command, not remote control |
Structure
| Shell plate | 8 mm |
| Stiffener pitch | 300 mm |
| Stiffener web | 184.9 mm |
| Ring frames | 8 at 12 mm, 220 mm web |
| Section modulus required | 45.6 cm³ |
| Operating depth | 20 m · 2.011 bar gauge |
| Yield depth | 30.4 m |
| Collapse depth | 54.7 m |
Programme
| Programme | Prototype — entering construction |
| Package revision | V10, 16 August 2026 |
| Model revision | Revision F — master.json |
| Engineering report | 136 pages, 90 tables, 19 sections, 6 appendices |
| Engineering deck | 44 slides |
| Bill of materials | 172 costed lines in 14 systems, 226 researched components |
| Direct labour | 5,978 hours across engineering, fabrication and assembly |
| Market designation | HD-18 |
| Engineering designation | IS-18 Revision F |
Figures. Every row above is generated from the HD-18 V10 engineering model dated 16 August 2026. Market designation is HD-18; the same platform is IS-18 Revision F in the engineering pack, and both appear on the data sheet so the two can be reconciled. See the disclaimer.