The soft pulsed-jet carrier. A creeper with a cast elastomeric bell where a propeller would be, rated to 30 m, that carries one neutral 2 kg cartridge the last, quiet kilometre.
A slow, soft-bodied carrier for piers, intakes, outfalls and listeners, carried to its start point by the larger hull or launched by hand.
A cast elastomeric bell contracts on a slow stroke and refills on the recovery. Propulsor, fairing and contact-compliance layer are one moulding: no shaft to seal, no gearbox and no blade tip to cavitate.
CS-310 carries it in its bay and releases it at a surveyed point, so the expensive navigation stays on the larger hull and the creeper begins its leg close to the work.
At a 1.0 W silent-running load the vehicle runs 133.3 h and 71.1 km in still water, and at 0.5 W it runs 266.7 h and 112.9 km.
Six non-kinetic cartridges and nothing else: no warhead, no fuze, no energetic material and no mechanism whose purpose is harm. No radio and no GPS aboard.
The selected baseline of CS-320, grouped the way an integration engineer reads it: form, canister, mass, propulsion, endurance, current and drift, cradle, crossings, guidance and recovery.
Vehicle and arrangementPressure canisterMass and displacementPropulsionEndurance and energyCurrent, drift and depth controlPayload cradle and interfacesPressure-boundary crossingsGuidance and communicationsAbort, handling and environment
| Parameter | Value | Basis |
|---|---|---|
| Form | Free-flooded elastomeric bell over a rigid polymer chassis, with a dry canister inside | three bodies, one of them dry |
| Bell | Ø380 × 300 mm | design value, the general arrangement |
| Exit nozzle | Ø40 mm | design value, the general arrangement |
| Inside the dry canister | Pulser actuator · ballast pump · avionics and compute · 0.2 kWh battery | the general arrangement; everything that must stay dry |
| Outside the canister | Ballast bladder · payload cradle · drop weight | the general arrangement |
| Structure | Polymer chassis and cast elastomer bell; no metal structure | the design definition |
| Bell material | Cast elastomer | propulsor, fairing and contact-compliance layer in one part |
| Chassis and fairings | Free-flooded moulded polymer, eligible for recycled PET | non-structural; the most-plastic platform in the fleet |
| Parameter | Value | Basis |
|---|---|---|
| Architecture | Dry canister inside the flooded body | selected on serviceability over potted, oil-compensated electronics |
| Canister | Ø160 mm × 8 mm wall × 450 mm | design value, the selected baseline |
| End closures | Hemispherical, 6 mm | design value, the selected baseline |
| Canister material | Glass-filled nylon | the canister's material class |
| External pressure at 30 m | 0.302 MPa | calculated, seawater |
| Critical length | 816 mm | calculated; the 450 mm canister is a short cylinder |
| Effective unsupported length | 503 mm | calculated, the closures' head depth included |
| Collapse, short-cylinder relation | 2.94 MPa | calculated, Windenburg–Trilling, before knock-downs |
| Collapse after creep and ovality | 1.03 MPa | calculated, creep ×0.50 on modulus and ovality ×0.70 on pressure |
| Safety factor at 30 m | 3.41 | calculated |
| Closure collapse | 5.20 MPa | calculated with a ×0.25 sphere knock-down; clear of the cylinder |
| Proof test | Every canister, before its first wet use | a rule on every canister built |
| Parameter | Value | Basis |
|---|---|---|
| Canister with 6 mm closures | 3.62 kg · 11.19 L | calculated, the mass and displaced-volume ledger |
| Rigid chassis, cradle and fairings | 2.02 kg · 1.50 L | calculated |
| Elastomeric bell | 1.38 kg · 1.20 L | calculated; propulsor, fairing and contact layer |
| Battery pack, 0.2 kWh | 1.43 kg | calculated, packaged pack; inside the canister |
| Avionics, compute and optional micro-modem | 0.80 kg | ledger allocation; inside the canister |
| Pulser actuator, magnetic coupling and drive | 0.90 kg | ledger allocation |
| Variable ballast, dry and water | 1.00 kg | ledger allocation |
| Moving-mass trim | 0.30 kg | ledger allocation |
| Penetrators and harness | 0.40 kg | ledger allocation |
| Drop-weight abort, cast iron | 0.80 kg · 0.10 L | ledger allocation |
| Dry mass | 12.66 kg · 13.99 L | calculated, the sum of the ledger |
| Displacement in seawater | 14.34 kg | calculated |
| Fixed trim and reserve | 1.69 kg | calculated; 12% of displacement |
| Payload cartridge | 2.00 kg | neutral by interface rule |
| Vehicle wet displacement | 16.34 kg · 15.95 L | calculated, with the cartridge fitted |
| Fresh-to-salt buoyancy swing | 0.35 kg | calculated on this displacement |
| Routine ballast authority | ±0.5 kg | design value; the 0.35 kg fresh-to-salt swing sits inside it |
| Payload-release compensation | Up to ~2 kg | a separate ballast action; it sizes the system |
| Parameter | Value | Basis |
|---|---|---|
| Propulsor | Pulsed-jet elastomeric bell | contracts on a slow stroke and refills on the recovery; no screw |
| Stroke | 0.5 L expelled in 0.30 s through the Ø40 mm nozzle | the stroke the thrust figures are calculated on |
| Jet velocity | 1.33 m/s | calculated |
| Momentum thrust during the stroke | 2.27 N | calculated; the mean is this figure times the duty cycle |
| Overall propulsive efficiency | 0.10 | Froude efficiency of 0.203 at 0.15 m/s, about halved by drive and electrical losses |
| Drag to overcome | 0.35 N at 0.15 m/s · 0.96 N at 0.25 m/s · 3.84 N at 0.50 m/s | calculated at a drag coefficient of 0.6 on 0.05 m² frontal area |
| Top speed | 0.25 m/s | design value; the vehicle has no sprint |
| Thrust needed at 0.50 m/s | 3.8× the mean thrust a stroke delivers | calculated; still 1.41× at half the drag coefficient and the highest stroke rate evaluated |
| Drive | Pulser actuator dry in the canister, magnetic coupling to the bell | torque only; no wire and no seal cross the boundary |
| Bell strain | 25% volume change per stroke; about 7.7% linear strain | calculated, volumetric average on an isotropic conversion; local strain at crown and root runs higher |
| Refill stroke | Valved | requirement; an unvalved recovery stroke produces reverse thrust |
| Parameter | Value | Basis |
|---|---|---|
| Battery | 0.2 kWh | design value; inside the canister |
| Endurance inputs | Drag coefficient 0.6 on 0.05 m² · overall propulsive efficiency 0.10 · 200 Wh | the inputs every endurance figure here is calculated on |
| Best range at a 0.5 W hotel load | 0.118 m/s → 266.7 h, 112.9 km | calculated, 0.75 W total draw, still water |
| Best range at a 1.0 W hotel load | 0.148 m/s → 133.3 h, 71.1 km | calculated, 1.50 W total draw, still water |
| Best range at a 2.0 W hotel load | 0.187 m/s → 66.7 h, 44.8 km | calculated, 3.00 W total draw, still water |
| Best range at a 3.0 W hotel load | 0.214 m/s → 44.4 h, 34.2 km | calculated, 4.50 W total draw, still water |
| At the 0.25 m/s creep | 3.40 W → 59 h (2.4 d), 53 km | calculated at a 1.0 W hotel load, still water |
| Range against hotel load | Scales as hotel load to the power −2/3 | calculated; doubling 1.0 W to 2.0 W costs 37% of range |
| Propulsion draw at best range | Half the hotel draw | calculated relation; efficiency moves the best speed and barely moves the best range |
| Parameter | Value | Basis |
|---|---|---|
| Reachable cone half-angle | Unbounded at or below 0.25 m/s · 30.0° in 0.50 · 19.5° in 0.75 · 14.5° in 1.00 · 9.6° in 1.50 m/s | calculated, the arcsine of vehicle speed over current speed |
| Six-hour cross-track authority | 5.4 km | calculated at 0.25 m/s |
| Ground speed against the design current | −0.50 m/s | calculated, 0.25 m/s in a 0.75 m/s set |
| Arrival error, six hours in a 0.75 m/s set | ±1.62 km along-track per 10% current-speed error · ±2.81 km cross-track per 10° direction error | calculated; the two combine |
| Terminal leg in slack water | 2 km in 2.2 h | calculated at 0.25 m/s |
| Local fix for arrival | Acoustic beacon at the target · fibre tether · delivery by CS-310 to a surveyed point | required; drift serves the transit, not the arrival |
| Tide and current data | A hard dependency of every mission plan | the terminal approach is timed to slack water, run down-current or held to a low-current pocket |
| Depth-band keeping in drift | 101 J per stroke; 0.67 Wh over a six-hour drift, 0.34% of the battery | calculated: 0.1 L against 3.02 bar at 30% pump efficiency, 24 strokes |
| Primary flight control in drift | Variable ballast | sized for cycle count and duty life |
| Parameter | Value | Basis |
|---|---|---|
| Cradle envelope | 2 kg / 2 L | design value; one cartridge at a time |
| Cartridge buoyancy | Neutral, ±0.2 kg in seawater | interface rule; a scaled member of the CS-310 bay interface family |
| Interface | Mechanical mount · electrical and data connector · retention and release | defined once, so a new cartridge is tooling rather than a redesign |
| Cartridges | Passive sensor node · tag or beacon · micro relay node · environmental sampler · inspection package · emplace and retrieve | six, non-kinetic |
| Carriage in CS-310 | Inside the 20 kg / 20 L bay: 18% margin on mass, 20% on volume | calculated; one-way release, trim-neutral |
| Parameter | Value | Basis |
|---|---|---|
| Electrical crossings | 2 | the shore umbilical and the cradle wet-mate |
| Shore umbilical | Charge and data | electrical; pre-dive only |
| Cradle wet-mate | Power, data and the release command | electrical |
| Ballast port | Water in and out | hydraulic, not electrical |
| Pulser drive | No crossing | magnetic coupling, torque only |
| Depth cell | No crossing | reads through a diaphragm |
| Parameter | Value | Basis |
|---|---|---|
| Tier 1 | Preset: compass, depth cell, time and the tide table | legs planned against current predictions; the current term dominates the error |
| Tier 2 | Fibre-guided, a person in the loop | spool volume competes with the 2 L cradle |
| Tier 3 | Delivered precision | CS-310 carries the navigation and releases at a surveyed point |
| Radio and GPS | None aboard | RF and GPS do not penetrate seawater |
| Communications | Silent running by default; a micro acoustic modem as an option | never a control channel |
| Loss of confidence | Hold the depth band or bottom-sit, then surface at a planned point | safety function, inside geofenced corridors |
| Timer expiry | Return to recovery or surface | safety function |
| Critical fault | Drop-weight abort | safety function |
| Parameter | Value | Basis |
|---|---|---|
| Abort | A normally-energized hold coil retains the drop weight | cutting power releases it and the vehicle rises |
| Drop weight | 0.80 kg, cast iron | ledger allocation; every abort leaves it on the bottom |
| Recovery | A fault surfaces the machine with its core, battery and data | recoverability is a design requirement |
| Launch | By hand from a small boat or the shore, or released from the CS-310 bay | each vehicle is independently launchable |
| Recovery capture | A slow soft body is easy to net | the small platform's recovery advantage |
| Shore support | Charging and mission upload pre-dive; data offload after | over the shore umbilical |
| Design depth | 30 m | the harbour, pier and approach work band |
| Cold water | Elastomer stiffens near 0 °C | changes the bell's stroke and rate together |
Three bodies, and only the smallest is dry. Everything outside the canister floods, so the one part that answers to 30 m is a tube 160 mm across.
The bell contracts on a slow stroke, expels a ring of water through a Ø40 mm nozzle and refills on the recovery.
A glass-filled nylon canister with 6 mm closures, holding the pulser actuator, the ballast pump, the avionics and the 0.2 kWh battery: the only volume aboard at one atmosphere.
A mechanical mount, a connector and a release, defined once, with the drop weight below. Every cartridge is a sensor, tag, relay, sampler or inspection tool.
With no screw, nothing turns in the water. Everything the water touches is free-flooded moulded polymer or cast elastomer, and the vehicle carries no metal structure: the most-plastic platform in the fleet, built on the fleet's own tooling.
A cast bell and a moulded chassis make a vehicle that can be fielded in numbers. Distance belongs to another machine: CS-310 runs the long transit on its screw and carries this one in its bay.
Two architectures were open at this scale: a small dry canister inside a flooded body, or no air volume anywhere, with potted electronics and oil-compensated cells at ambient pressure. The second deletes the collapse and crossing problems, and it is not free.
| Architecture | Displaced | Buoyancy | Mass | Net |
|---|---|---|---|---|
| Dry canister with hemispherical ends | 11.19 L | 11.47 kg | 3.62 kg structure + 2.23 kg contents | +5.62 kg |
| Potted and oil-compensated, no air volume | 2.30 L | 2.36 kg | 3.40 kg | −1.04 kg |
| Buoyancy material to buy back 6.66 kg of lift | Volume | Potted-route mass | Against the dry canister |
|---|---|---|---|
| Deep syntactic, 0.40 g/cm³ | 10.7 L | 7.66 kg | +1.8 L / +1.8 kg |
| 100 m-class syntactic, 0.25 g/cm³ | 8.6 L | 5.55 kg | −0.3 L / −0.3 kg |
| Closed-cell PVC, 0.15 g/cm³ | 7.6 L | 4.54 kg | −1.3 L / −1.3 kg |
The air inside the canister is most of the vehicle's buoyancy budget. At a foam grade suited to the depth the potted route narrows to about a litre and a kilogram, and it stays open as an option, but it spends displacement, the currency this vehicle has least of, on the cheapest problem on the platform: at 30 m two millimetres of extra wall already solve collapse.
The dry canister is selected on serviceability. Potted assemblies are hard to rework and restrict component choice to parts with no air gaps and no hard-case cells, and being able to open the canister and change a component is worth more than the litre.
External pressure at 30 m is 0.302 MPa. The critical length for a Ø160 × 8 mm cylinder is 816 mm and the canister is 450 mm, so it is a short cylinder and its end restraint carries load.
| Wall | Long-cylinder relation | Short-cylinder relation | After creep and ovality | Safety factor at 30 m | Result |
|---|---|---|---|---|---|
| 4 mm | 0.21 MPa | 0.51 MPa | 0.18 MPa | 0.60 | Fails |
| 6 mm | 0.72 MPa | 1.43 MPa | 0.50 MPa | 1.65 | Below a safety factor of 2 |
| 7 mm | 1.15 MPa | 2.10 MPa | 0.74 MPa | 2.44 | Passes thinly |
| 8 mm, selected | 1.71 MPa | 2.94 MPa | 1.03 MPa | 3.41 | Passes |
The short-cylinder relation is taken over an effective unsupported length of 503 mm, the closures' head depth included, with creep at 0.50 on the modulus and ovality at 0.70 on the pressure. On a short tube the long-cylinder relation understates strength by roughly 2.5 times, and the two knock-downs take it all back.
Going from 7 mm to 8 mm costs 0.28 kg and moves the safety factor from 2.44 to 3.41, an easy purchase on a vehicle meant to be fielded in numbers. The 6 mm closures reach 5.20 MPa after a 0.25 sphere knock-down, clear of the cylinder by a wide margin, so on this machine the closures do not govern. Every canister is proof-tested before its first wet use.
Take a credible stroke: 0.5 L expelled in 0.30 s through the Ø40 mm nozzle. That is a jet velocity of 1.33 m/s and 2.27 N of momentum thrust while the stroke runs, and the mean is that figure times the duty cycle.
| Speed through the water | Drag to overcome | Against the mean thrust of the stroke |
|---|---|---|
| 0.15 m/s | 0.35 N | Met at every stroke rate evaluated |
| 0.25 m/s | 0.96 N | Met at the two higher stroke rates evaluated |
| 0.50 m/s | 3.84 N | Met at none |
Froude efficiency on this jet is 0.203 at 0.15 m/s, and drive and electrical losses about halve it, to 0.10 overall. The top speed is 0.25 m/s, and that is the whole speed the machine has. Half a metre a second would need 3.8 times the mean thrust a stroke of this size delivers, and the shortfall survives a generous drag figure: at half the drag coefficient and the highest stroke rate evaluated it is still 1.41 times. A small screw would buy a sprint and give up the no-screw identity, so the mission set is sized around a creeper without one.
A small submersible is bought twice, once in material and once in the buoyancy the material consumes, so every line of the ledger carries a mass and a displaced volume, and displacement is a sum.
The heaviest single item is the canister at 3.62 kg, and the air inside it is most of the vehicle's buoyancy. The fresh-to-salt swing on this displacement is 0.35 kg, inside the ±0.5 kg of routine ballast authority, and a separate compensation of up to about 2 kg on payload release is what sizes the ballast system.
At 16.34 kg and 15.95 L the creeper fits the 20 kg / 20 L wet bay of CS-310 with 18% margin on mass and 20% on volume. Releasing it from a 113 kg vehicle would otherwise be a 14% buoyancy transient at the moment the larger hull is trying to hold station; because every cartridge is neutral by rule, the transient is zero.
At creep the propulsion draw is under a watt, so the silent-running hotel load governs. Every figure below is still water on 200 Wh, at a drag coefficient of 0.6 over 0.05 m² and an overall propulsive efficiency of 0.10.
| Hotel load | Best-range speed | Total draw | Endurance | Still-water range |
|---|---|---|---|---|
| 0.5 W | 0.118 m/s | 0.75 W | 266.7 h (11.1 d) | 112.9 km |
| 1.0 W | 0.148 m/s | 1.50 W | 133.3 h (5.6 d) | 71.1 km |
| 2.0 W | 0.187 m/s | 3.00 W | 66.7 h (2.8 d) | 44.8 km |
| 3.0 W | 0.214 m/s | 4.50 W | 44.4 h (1.9 d) | 34.2 km |
Range scales as hotel load to the power −2/3, so doubling the silent-running draw from 1.0 W to 2.0 W costs 37% of range. Underneath it is a small exact result: at the best-range speed the propulsion draw is half the hotel draw whatever the propulsive efficiency, so efficiency moves the best speed and barely moves the best range. A watt taken out of the sleep state is worth more on this machine than any refinement of hull or bell.
At the 0.25 m/s creep the vehicle draws 3.40 W for 59 h and 53 km. Froude efficiency itself rises with speed, at 0.166, 0.203 and 0.317 for 0.12, 0.15 and 0.25 m/s, so the true optimum sits a little above the table's.
The vehicle adds at most 0.25 m/s to whatever the water is doing. After a time T its reachable set is a disc of radius 0.25·T centred U·T downstream, so the cone that bounds it from the release point has a half-angle of arcsin(v/U).
| Current set | Reachable cone half-angle | Six-hour along-track drift | Six-hour cross-track authority |
|---|---|---|---|
| 0.20 m/s | Unbounded | 4.3 km | 5.4 km |
| 0.25 m/s | Unbounded | 5.4 km | 5.4 km |
| 0.50 m/s | 30.0° | 10.8 km | 5.4 km |
| 0.75 m/s | 19.5° | 16.2 km | 5.4 km |
| 1.00 m/s | 14.5° | 21.6 km | 5.4 km |
| 1.50 m/s | 9.6° | 32.4 km | 5.4 km |
At or below its own speed the vehicle can hold station or work upstream, and the reachable set is unbounded in angle; above it the cone closes quickly. The arrival error sits in the current forecast rather than in the vehicle. On a six-hour transit in a 0.75 m/s set, a 10% error in the predicted current speed puts the vehicle ±1.62 km off along-track and a 20% error ±3.24 km, and a 10° error in direction adds ±2.81 km across. The errors combine, so kilometre-class arrival error is a floor.
At 0.25 m/s in the 0.75 m/s set the design assumes, ground speed is −0.50 m/s. Authority binds rather than navigation, and three design constraints follow.
Tidal currents are stratified by depth, so in a drift the way to steer is to change depth and ride a different stream. Moving 0.1 L against 3.02 bar at a pump efficiency of 30% costs 101 J a stroke, and 24 strokes over a six-hour drift cost 0.67 Wh, 0.34% of the battery. In drift the variable-ballast system is the primary flight control, and it is sized for cycle count and duty life rather than for authority alone.
The cradle takes one module at a time, about 2 kg and 2 L. Anything larger is the mothership's cargo, not this machine's.
Emplaces a small acoustic or environmental listener for persistent harbour and approach monitoring, at the node scale below the mothership's seabed packages.
Delivers a small inert marker, transponder or instrumentation tag to the seabed or to fixed civil infrastructure, for sensing.
Drops a small acoustic-network relay below the mothership's moored relay class.
A water-quality sonde or a small sediment sampler: the civil work, on the same cradle.
A compact camera with lighting, or a small imaging sonar. The creep that makes the machine hard to find also lets it approach a structure without disturbing it.
Low-signature delivery or recovery where a surface presence is unwanted. Export-sensitive in its own right.
The interface is defined once, as a mechanical mount, a connector, retention and release, so a new cartridge is tooling rather than a redesign. It is a scaled member of the CS-310 bay interface family, and every cartridge is neutrally buoyant to ±0.2 kg in seawater, which is what makes a release trim-neutral. The list ends there by rule: no warhead, no fuze, no energetic material, no terminal-effect payload and no mechanism whose purpose is harm.
Carriage in the larger hull is a cartridge fit, not a dock. The creeper rides in a retention cradle, leaves on a command the bay interface already carries and does not come back: CS-310 transits and releases at a surveyed point, and the creeper runs the last, quietest leg and surfaces at a planned point for its own recovery. The expensive navigation stays on the larger hull, and each vehicle stays independently launchable.
Every wire through a pressure boundary is a leak path, a pressure-test item and a cost line. The larger hull needs five electrical crossings; the creeper needs two, and a water port.
| Crossing | Type | Carries |
|---|---|---|
| Shore umbilical | Electrical | Charge and data, pre-dive only |
| Cradle wet-mate | Electrical | Power, data and the release command |
| Ballast port | Hydraulic | Water in and out |
| Pulser drive | Magnetic coupling | Torque only, not a crossing |
| Depth cell | Diaphragm | Reads pressure without a crossing |
The pulser actuator and the ballast pump both live dry inside the canister and reach the water through a magnetic coupling and a hydraulic port. A water port is a far easier seal than a multi-conductor electrical penetrator, and it is the small platform's one structural advantage over the larger hull, which comes from scale.
The abort follows the fleet's inverted doctrine. A normally-energized hold coil retains the drop weight, so cutting power releases it: a flat battery, a hung computer or a severed harness all end the same way, with the weight gone and the vehicle rising. The weight is 0.80 kg of cast iron rather than lead, because every abort leaves it on the bottom, and a fault surfaces the machine with its core, its battery and its data.
The bell, the canister, the cradle and the abort are common to every build. What differs is how the vehicle finds its start point, and whether a micro acoustic modem is fitted.
Pre-programmed legs on magnetic heading, a depth cell, time and a current prediction, with the drift planned against it. The current term dominates the error budget, so the drift plan is the mission plan.
A person in the loop over optical fibre from a payout spool, at walking-pace speeds with no launch shock. Spool volume competes with the 2 L cradle, which makes this the short-reach inspection build.
The larger hull carries the navigation, transits and releases the creeper at a surveyed point for a short, bounded final leg on preset or fibre guidance, with one or two pre-emplaced acoustic beacons as a local fix where the mission needs one.
A micro acoustic modem for scheduled, brief check-in, abort and retask contacts. Silent running stays the default, because every transmission spends the signature budget the platform exists to conserve.
These lines hold on every build of the creeper and for every customer.
The page this sheet specifies, and the sheets beside it in the line.
The page this sheet specifies, with the pictures and the reasoning.
A first conversation needs the water, the tide and current the work is timed to, the depth band, and the thing that has to be placed, sampled or looked at. Enquiries are screened before anything is discussed.
Not an offer. Enquiries are screened, international transfer is subject to Canadian government permits taken per shipment, the emplace-and-retrieve cartridge is treated as export-sensitive in its own right, and all designs, systems and technologies shown are patent pending.
