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ROV enhancements

Tiburon power boost
Lead Engineer/Project Manager: Ed Mellinger

This proposal suggests a modification of ROV Tiburon’s power system to increase the available electrical power from 15 to 20 kilowatts.

The performance requirements established for Tiburon in 1991 included operating depth, transit speed, payload, and other fundamental vehicle specifications. During the subsequent design process, these requirements were used to derive values for the vehicle’s real-world physical parameters. Among these were the closely interrelated parameters of vehicle weight, size, thrust requirement, electrical power requirement, cable diameter, and cable operating voltage and current. In particular, transit speed, electrical power, and cable diameter are closely linked, and the respective final values of 0.75 knots, 15 kilowatts, and 0.68 inches represent careful tradeoffs and optimization of the selected power system and cable design approaches. In vehicle terms, 15 kilowatts provides full thrust in one axis plus maneuvering thrust in another, simultaneously with lights and the hotel load of sensors and computers.

Sea trials and initial science operations have shown the 15 kW electrical power budget to provide adequate thrust for maneuvering and transit in most situations. However, there are times when more thrust would be of benefit:
  • During vehicle recovery, strong surface currents (up to 2 knots) can severely tax the vehicle’s thrust capability. Full thrust on two axes (for example full ahead plus full turn) can be required to position the vehicle safely between the Western Flyer’s hulls, a 20 kW demand that exceeds the capability of the power system.
  • During deep transits, significant down thrust is used in place of a clump weight to counter cable lift. Large thrust values are again required in two axes simultaneously.
  • During operation of the hydraulic system, nearly 5 kW of electrical input is required, regardless of the output hydraulic load. This precludes full thrust in even one axis, reducing the vehicle’s ability to transit and maneuver in this condition. Since hydraulic power is used for more functions than the VB system originally planned, this condition occurs frequently during normal science operations.

In addition to these existing conditions, future science payloads (rock drill, clathrate heater, and others) may be able to benefit from as much power as can be provided.

Since growth paths of moderate cost are available for the power transmission system, and growth margins are already designed into other parts of the power system, a modest increase in the vehicle’s power budget is possible. This proposal suggests a boost from 15 to 20 kW, which can be achieved for the transmission system by employing feedforward regulation of the shipboard power source.