The short answer
Start from the depth and the job. The depth decides the housing material, the penetrators and the foam grade, and the job and target speed decide how much thrust you need. Then check that every cable through the pressure boundary has a matched penetrator, that the vehicle trims slightly positive, and that each sensor uses an interface your controller has free.
How much thrust does an ROV need?
Work out the drag at your target speed from the frontal area and drag coefficient, add about 50% for current, tether drag, fouling and voltage loss, and divide by the forward thrust each thruster contributes. Drag rises with the square of speed, so doubling the speed needs about four times the thrust.
- How to size an underwater thruster for an ROVSize ROV thrusters from drag, target speed and vectoring angle. Worked method for thrust per unit, thruster count and the margin real vehicles need.
- How to choose an underwater thruster for an ROVHow to choose an underwater thruster for an ROV by thrust, voltage, depth rating, ESC, rotation and mounting.
- Designing a 300-metre ROV propulsion systemPropulsion design for a 300-metre ROV: thruster count and layout, bus voltage, tether losses, sealing and the effect on buoyancy.
- Underwater and ROV thrusters in IndiaBlu-Sub and Blue Robotics underwater thrusters for ROVs, AUVs and USVs, with prices in rupees and delivery across India included.
Shop: Blu-Sub thrusters · Blue Robotics thrusters, actuators, and lights
Should the housing be acrylic or aluminium?
Acrylic when the payload has to see out through the wall and the housing stays shallow and cool, because its rating falls from about 250 m to 20 m as the tube gets larger. Aluminium for depth, heat and frequent servicing, typically rated to 1,000 m. Either way, every part in the pressure boundary needs a rating above your working depth.
- Aluminium versus acrylic subsea enclosuresAluminium and cast acrylic subsea housings compared on depth rating, optical access, heat, servicing and cost.
- Selecting a subsea enclosure for marine research payloadsHow to choose a subsea enclosure, end caps, seals and penetrators for research payloads, and how to test them before fieldwork.
- Subsea pressure and depth conversion guideConvert depth to pressure in bar, psi, MPa and atmospheres. Reference table, the formula behind it, and how depth ratings and test pressures relate.
Shop: Blu-Sub enclosures · Blue Robotics enclosures, buoyancy, and ballast
Cable penetrator or underwater connector?
A penetrator for every cable that stays on the vehicle, and a wet-mateable connector only where a cable must come off in the field without opening the housing. Count the end-cap entries early, because space runs out before the budget does.
- Cable penetrator versus underwater connectorWhen to use a subsea cable penetrator and when to use a wet-mateable connector: cost, serviceability, depth rating and failure modes compared.
Shop: Blu-Sub cables & connectors · Blue Robotics cables, penetrators, and connectors
How much buoyancy foam does a vehicle need?
Subtract the vehicle's mass in air from the mass of water it displaces, aim for between a few hundred grams and a kilogram or two positive, and make up the difference with foam rated for your depth. Deeper-rated foam is denser, so it lifts less per litre and you need more of it.
- ROV buoyancy and ballast calculation, worked throughA worked ROV buoyancy and ballast calculation: net buoyancy from mass and displacement, foam volume for a target trim, and how to measure displaced volume.
- Buoyancy and ballast for custom ROV and AUV research platformsHow to calculate buoyancy and ballast for a custom ROV or AUV, and how to choose syntactic foam by depth rating.
Which depth sensor and lights?
Choose the depth sensor's range at about 1 bar per 10 m of seawater, then match its interface to the controller: I2C at 3.3 V or serial at 5 V. For lights, move them off the camera's axis before adding brightness, because backscatter, not darkness, is what usually spoils the picture.
- How to choose an ROV depth sensor: pressure range, accuracy and interface compatibilitySelect an ROV depth sensor by pressure range, overpressure limit, accuracy and interface. Compares Blu-Sub M8, M10 and M14 sensors with a worked error budget.
- ROV lighting: reducing backscatter before adding more lumensPlan underwater ROV lighting around camera distance, beam placement, dimming and power. Includes a Blu-Sub light example and a repeatable in-water test.
Shop: Blu-Sub sensors · Blu-Sub lighting · Blue Robotics sensors and cameras
What does a complete build look like?
Our build guides put all of this together: a tethered student ROV, a competition AUV and an autonomous survey boat, each with the design numbers worked through and a parts list priced in rupees.
- Building an underwater ROV for a student project: parts listA tethered six-thruster ROV for a college project or pool and lake work: thrusters, pressure housing, penetrators, controller, tether, camera, lights and sensors, priced.
- Building a competition AUV for SAUVC or RoboSub: parts listAn eight-thruster autonomous underwater vehicle for SAUVC, RoboSub or a university AUV team: hull, kill switch, mission switches, cameras, computers and a priced parts list.
- Autonomous survey boat for depth and water-quality mapping: student parts listA small ArduPilot boat that runs survey lines on its own, logging depth and water temperature against position: hull, thrusters, autopilot, echo sounder and a priced parts list.
What these parts cost in India: price ranges, cost per kilogram of thrust and bulk-order savings →