The ultimate MUM

MUM in drill corer configuration.
MUM in drill corer configuration.
MUM in control module exchange configuration
MUM in control module exchange configuration

Mums multitask; we all know that. But this particular mum, or Modifiable Underwater Mothership (MUM), takes it to a whole new level, writes Stevie Knight.

The financial argument for deploying unmanned, autonomous vessels to carry out routine tasks is well known: it avoids the cost of charting a vessel and crew. But what about taking this idea subsea?

Certainly, an intelligent drone could continue working away, 24/7, 365 days-a-year in the darkness of a seafloor, completely undisturbed by the rough and tumble of the ocean’s surface thousands of metres above.

However, developing a vessel for a distinct niche may not cut the business case, so five teams are working on a Modifiable Underwater Mothership. This could be reconfigured to meet an almost unlimited range of objectives, able to cross between the oil and gas, renewables, mining, aquaculture and research fields – plus a few more still over the horizon.

“The special thing about this MUM is that the shape is flexible,” says Florin Boeck of Technical University (TU) Berlin: “It actually consists of single units based on 20-foot containers that can be shipped as standard. So while we have basic modules for intelligence, energy provision, diving depth control and propulsion, it will have specifically designed modules for different missions.” This allows for a fast development cycle and adaptation to new, even novel, roles, he adds: third-party kits could be integrated fairly simply.

Transformer-like, even its appearance could change dramatically between deployments. Boeck’s colleague Sebastian Ritz explains that for some assignments, “the containers may be configured in a line while for others, they may be in parallel” and explains that as the idea is to assemble and launch this from a convenient harbour, MUM is expected to transit autonomously to site – so a fore and aft section is added to smooth the box shape into something more hydrodynamic.

Most importantly, it will be comfortable even at extreme depths says Boeck. “We are using different technologies for the different modules: some are constructed using systems which have the electronics encased in silicon.” This transports the pressure around the components, which in themselves are manufactured to stand up to 500 bar. “However, for others elements such as the power, we will probably need a pressure resistant housing,” he adds.

Still, additional units will, he reiterated, be tailored for the mission, and less rigorous specifications will likely lower the cost.

The five industry and research partners are tackling different elements:
The TU Berlin team is behind the mission specific design, while Atlas Elektronik, the company developing GuideMUM, taking on guidance and mission planning including system monitoring and collision avoidance. The University of Rostock, working closely with them, is responsible for AutoMUM, and develops fault tolerant control systems. EvoLogics is focusing on NaviMUM, as the project needs to be supported by underwater navigation and telemetry, a novel mobile acoustic network consisting of USBL-drones is designed.

Finally, thyssenkrupp Marine Systems, the project coordinator, is acting as designer and system integrator, along with developing the power element. MUM will be running from a hydrogen fuel cell and battery combination that should yield around 200 kW, allowing it a 6kn transit speed. However, the battery will also help shave some of the peaks as one of its specific tasks is drill sampling; Boeck explains that the standard corer will mean there’s a 130kW hotel draw to take into consideration.

Certainly, the behemoth will be able to carry a substantial weight: “The system is being designed for a payload up to 10 tonnes – that’s enormous compared to a normal AUV,” says Ritz.

This makes it useful for the oil and gas industry “as it can exchange subsea control modules which tend to be several tonnes”, says Boeck.

It could also change the face of seismic acquisition, “as instead of streamers, the large AUV could be used to deploy ocean bottom nodes” he adds. These nodes are a much more accurate method of gathering data, but rarely used till now as it relies on laying out up to 3,000 of them in a precise pattern to pick up the echo of a source sound wave – and then going back to pick them up again.

As the traditional method relies on two or three surface ships plus a couple of ROVs, the argument for replicable, exact and automated placing is hard to beat.

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