Mast, comms and control
How the vessel breathes, sees and is told what to do — including the honest limits of the long-range link.
One mast, three stages, its own hatch.
The mast stows at 1.684 m inside a watertight trunk 0.60 m wide on the centreline at station 13.95 m, and extends 4.693 m. At a snorkel depth of 1.20 m that puts the masthead 3.81 m above water — high enough to clear the sea state the vessel is rated to snorkel in.
Stage diameters are 300 / 250 / 200 mm. The assembly weighs 464 kg: 135 kg of trunk, 74 kg of stages, 90 kg of head, 70 kg of actuator and 95 kg of snorkel.
It has a dedicated hinged access hatch carrying the pressure-tight gland, rather than sharing a payload opening. The mast can be serviced without breaking into a payload compartment, and a payload compartment can be opened without disturbing the mast seal.
| 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 |
Stated as it is
The long-range link is telemetry, not remote control.
At 10 km the long-range link delivers approximately 50 bps usable, with 1.5–3 s of latency. That is enough to pass vessel state, receive a waypoint list, change a mission plan and command a surface or an abort. It is not enough to fly the vessel, and we do not describe it as remote control.
Anything needing real bandwidth — payload data, imagery, a full mission log — comes off over a high-rate link with the mast up and the vessel in range, or off the hull alongside. Build the concept of operations around that and the vessel behaves predictably. Build it around a live video feed and it will not.
Higher-rate satellite and line-of-sight options are part of the configuration conversation. They change the masthead fit rather than the platform.
Air and autonomy
Breathing is a system, not an afterthought.
Diving means charging 50.74 m³ of pressurised volume to sea pressure and flooding main ballast: 100.70 Nm³ of free air to the compartments and 42.07 Nm³ to the ballast tanks — 142.78 Nm³ per complete cycle, carried with a ×1.35 margin.
Storage is 13 × 50 L bottles at 300 bar — 195 Nm³ — recharged by a 15 Nm³/h compressor in 12.85 hours while the generator runs on the surface leg. The air plant is therefore sized by the dive cycle rather than by a rule of thumb, which means the number of dive cycles available is a figure you can plan a mission against instead of discovering.
| 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 |
Links
Four independent paths, deliberately.
An uncrewed vessel that loses its only link is a salvage problem, so redundancy here is not a luxury. The mast carries a high-rate satellite path for command and video offload, a cellular path for inshore work, an independent low-rate satellite path that shares nothing with either, and a direct long-range link to a mothership or shore station.
They fail in different ways on purpose. Losing satellite coverage does not touch the cellular path; losing shore infrastructure does not touch the satellite paths; and the low-rate path stays available when everything with real bandwidth has gone.
The masthead, stated plainly
A single mast-head multiplexer combining every band this vessel carries does not exist as a catalogue product, and it cannot: the span runs from VHF to Ka band, and the satellite terminal is a self-contained phased array with no RF port to combine.
The correct architecture is separate antennas with physical separation on the mast, plus a zero-loss splitter integrated in the AIS transponder. Anyone quoting a single masthead multiplexer for this vessel has not understood the problem — and surge protection has to be banded to the frequency of the run it protects, because fitting a 1 GHz part on a 1.6 GHz run is a silent failure rather than a loud one.
Navigation
Dead reckoning that survives a long dive.
A dual-antenna inertial unit is corrected by a Doppler velocity log referenced to the bottom, which is what makes a 66-hour submerged leg navigable rather than approximate. A multibeam forward-look sonar handles obstacle avoidance, a single-beam altimeter holds height over ground, and redundant depth transmitters cross-check each other.
Two autopilots run beneath a GPU-class mission computer. Surface fixes and heading come from a dual RTK GNSS pair on survey-grade multiband antennas whenever the mast is up.
One procurement note belongs on the record rather than in a footnote: the velocity log's performance grade is export-controlled by its vendor and needs an end-user undertaking and a granted licence. It is on the long-lead list for that reason, not for manufacturing time.
Bring us the payload and we will size it.
We run your fit through the engineering model and come back with real numbers for it, not a generic figure.