Today, there are many challenges. As the working depths become greater to access those fields, the complete ROV system has been inundated with new challenges. The various interests in the offshore exploration and production of Gas and Oil, subsea research, engineering, design, and manufacturing groups are increasing their investments in new innovations, technologies, and materials.
Here is where the challenge begins. The two primary sub-systems of the ROV responsible for providing the power that is required to run and control the ROV and TMS are the PDU and the umbilical. The ROV dependent upon the PDU to provide sufficient and reliable power at those depths, and is dependent upon the umbilical to deliver that power to the ROV at those depths.
The umbilical has been refined to a great extent, but is limited for covering the full range of ROV needs in deep waters. On the extreme short analysis, in this case, there is a large gap in the available umbilicals, one containing 13 cables with 6 power cables consisting of number 8-stranded wire and the other with 12 power cables of number 8-stranded wire. The difficulty herein, is that the larger 12 cabled umbilical is rather stout, designed for very large trenchers and other subsea operations that do not require the flexibility provided by the 6 cabled umbilical, which is necessary for agile maneuverability.
The PDU up until the last few years was not so well thought out of designed. The first well engineered PDU was made available in 2007. For the smaller umbilical to provide the power that is required for the ROV at the greater depths, the voltage must be stepped up. That requires a much larger and more expensive set of transformers.
The total length of umbilical cable may require two separate lengths, one from the vessel to the TMS and the other from the TMS to the ROV can consist of up to a total of approximately 11,000 meters.
Note: The “Challenger Deep” is the deepest known point in the Earth’s sea floor hydrosphere, with a depth of 10,898 m (35,755 feet) to 10,916 meters (35,814 feet) by direct measurement from submersibles, and slightly more by sonar bathymetry. It is in the Pacific Ocean, at the southern end of the Mariana Trench near the Mariana Islands group. Only 4 ROVs have ever reached the deepest known sea bottom from 1960-2012.