The tether is the second crew member

Buyers price a confined space ROV job as one machine and one pilot. The manufacturers' own piloting guides describe a two person job with a practice budget and a bag of accessories, and an honest quote says so before the first dive.

Confined space is where an underwater robot earns its keep: potable water tanks, ballast tanks and cargo holds, intakes and culverts, the inside of a wreck. The whole point is that a diver stays out. But everything that makes the space dangerous for a person makes it awkward for a machine, and the awkwardness lands on the one thing a robot cannot leave behind, the tether.

VideoRay, which builds the Mission Specialist line the Navy and the Coast Guard standardized on, sends a short piloting guide to anyone who asks for it. It is refreshingly unglamorous. Its first instruction is to practice in a swimming pool before the real job: fly through a weighted hula hoop until you can judge the opening against the vehicle without touching it, wrap your own tether around a submerged spar on purpose and free it with the manipulator, then fly out, turn around, find the tether and follow it home. The reasoning is plain. A mistake in a pool costs an afternoon. A mistake inside a tank costs the robot, and sometimes the tank.

The second lesson is the one buyers miss. The guide calls the tether handler the person who decides whether the mission succeeds: someone who knows exactly how much slack the vehicle needs as it maneuvers, who keeps the loop behind the robot small on the way out so it does not catch, and who never pulls hard enough to drag the vehicle off its line. Pilot and handler are meant to practice together. That is a two person crew, and a day rate that assumes one person is a day rate that will be renegotiated on the dock.

The tether itself is a specification, not an accessory. Neutral tethers float slightly in salt water and carry thinner conductors; the thin performance versions drag less but move less power. Which one comes in the case, and whether this job needs a different one, is a fair question to put to any dealer, including us.

Third, planning. Entry and exit, where the vehicle turns around or whether it has to back out, which side of a torn opening is smooth enough to protect the tether, and the decision that should be made on dry land: if the tether snags and will not come free, do you attempt a recovery, possibly with a second vehicle carrying a manipulator jaw, or do you cut it? An operator who answers that question calmly and adds that they will abort and regroup rather than risk the vehicle is an operator who has done this before.

Fourth, the accessories that turn a camera on a tether into an inspection tool: a manipulator to clear a path and untangle a snag, sonar to build a map of a space nobody has drawings for, extra cameras so the pilot can see sideways without turning, and the lights those cameras need. Each one changes the quote. On a confined space job the base vehicle is rarely the whole invoice.

Here is what we take from it as a dealer. If your organization opens a tank twice a year, a rental program that arrives with a practiced two person crew, the manipulator and the sonar already on the vehicle will almost always beat owning a robot that sits in a case getting unfamiliar. If you are a dive team or an inspection contractor doing this monthly, own the machine, but budget the pool hours and the accessories from the start, and measure the manway before you fall in love with a vehicle that will not fit through it. The matrix behind Joe and Abe carries VideoRay, Deep Trekker and their competitors side by side, and either of them will tell you which vehicles fit a 600 millimeter opening before you ask anyone for a price.