FEATURE: New horizons for France’s flagship deep-research vessel

From a redesigned acoustic sensor gondola to upgraded winches, laboratories and deep-sea systems, a special look inside France’s flagship research vessel has revealed the engineering behind a ship built to investigate some of the ocean’s least accessible environments.

During Sea Tech Week in the northern French port town of Brest, a select group of journalists was invited aboard the French research vessel Pourquoi Pas? (Why Not?) to see the second generation of a pioneering ship.

New lease of life

Measuring 107.6 metres in length and 20 metres across the beam, Pourquoi Pas? was built at Chantiers de l’Atlantique in Saint-Nazaire and entered service in 2005.

Owned by Ifremer, France’s national institute for ocean science, the vessel also serves the French Navy on scientific and hydrographic missions, carrying out oceanography, marine biology, seabed mapping and geological research.

Submersibles on board can be deployed to depths of 6,000 metres, one with three human beings on board.

The ship’s major mid-life refit, done at Remontowa Shiprepair Yard in Gdańsk, Poland, gave an ageing vessel a new lease of life, renewing the machinery, handling systems and scientific instruments on which its research capability depends. The refit included a replacement under-hull scientific sensor gondola, new-generation acoustic instruments, a replacement four-drum deep-sea winch, upgrades to cranes and handling equipment, and improvements to propulsion controls and electrical systems. The scientific control room and laboratory facilities were also renewed.

The diesel-electric propulsion system, with a generating capacity of 5.8MW and specialist scientific infrastructure, was also refitted, said acoustic engineer Arnaud Gaillot, leading the tour.

“Two of the engines were refitted,” he said. “And we now make fresh water using the heat from the engines. We need fresh water to transmit acoustic waves, and we also drink it. We’ve also changed the oceanographic trolls so they are outside the deck.”

Pourquoi Pas? has six decks and can accommodate up to 75 crew and scientists for six-week missions in the most remote parts of the world.

Under the hull: science of seeing through water

One of the most exciting elements of the refit is also among the least visible.

The same Polish shipyard, Remontowa, even built a special oven to build a new gondola that sits underneath the hull complete with the latest in scientific sensors, acoustic equipment and instruments to map the seabed, examine the water column and investigate everything about the oceans.

The new installation incorporates Kongsberg EM 124 and EM 712 multibeam echo sounders, EK80 scientific echosounders and current-profiling equipment. It’s a complementary way of examining the underwater environment.

Scientific echosounders can investigate targets within the water column, helping researchers study biological distributions and other structures suspended between the ship and the seabed.

“We couldn’t fit an 8m device on the hull because there wasn’t an 8m length, which we needed because acoustic devices need a special area without interference from engine noise,” said Gaillot. “So it was totally rebuilt. A special oven was built and it was put inside it to ‘relax’ the metal so it wouldn’t then expand or shrink in the different temperatures it is bound to experience.”

Exceptionally flat acoustic surfaces were needed, with tolerances of just millimetres.

Pourquoi Pas? also has a moonpool that allows equipment to be deployed from within the ship to help locate underwater vehicles. Using an Ultra-Short Baseline, or USBL, technique, the system transmits and receives acoustic signals and uses their timing and direction to estimate a vehicle’s position relative to the vessel.

Knowing where it is allows the team to coordinate its movements, relate observations to mapped locations and manage recovery.

40m sediment cores to 6,000m dives

Subsea research and equipment is a growing part of Brest’s economy in terms of research and study institutes and constant innovations going on in a port town that is home to the naval shipyards, two dry docks and a burgeoning offshore wind hub.

Physical samples of the seabed are taken in cores of up to 40 metres long, and housed in a special storage chamber at Ifremer, the research institute in Brest, where there are 18 kilometres of cores, if lined up end to end, stored at between 4-5 degrees Celsius. Built in 2017, the Centre de Resources en Echantillons et Archives Mains (CREAM) is one of four similar institutes in France.

Cores are lowered from the ship on a wire or cable that penetrates the seabed, drilling down and sucking up a column of sediment within it. The winch then brings the equipment back aboard, where scientists can document, process and preserve the sample in either of the wet or dry labs on board. The sediment sequence can provide a record of past environmental conditions, geological events and changes in marine ecosystems.

Submersibles, on the other hand, investigate particular features and retrieve selected rocks, minerals or sediment samples. Both approaches contribute to the same scientific investigation.

Nautile is 8m x 8m and made of titanium, which makes it light but capable of withstanding 600 bar of pressure, which makes maintenance and inspection particularly important.

The vehicle, which is one of just six similar vehicles in the world, Gaillot says, is checked every 100 dives – its hatches, windows, cables, wires – everything.

But surely the checks could miss something – which would be catastrophic for the three team members some 6km under water.

“We manage because it’s been done for years, it’s extremely rigorous and there are people in charge of managing every step,” one engineer said. “All of the cables are surrounded by oil, which can withstand the immense pressure on them. Everything is filled with oil.”

A remotely operated vehicle, Victor 6000 can also work at depths of up to 6,000 metres, but is tethered and uncrewed.

The third option, Uly^x, is an AUV designed and built by Ifremer. Just four metres long, the AUV follows the seabed autonomously, using onboard systems to react to its surroundings. Its reported endurance allows it to cover up to 80 kilometres during a mission at 6,000 metres.

Nautile, 2m in diameter, dives during the day with its brave trio of humans, while the uncrewed vessels are deployed night.

“It costs around €50,000 per day,” said Gaillot. “So you can’t afford to do nothing. They are all battery powered, and they are charged when they come up and another one goes down.”

Floating labs and computers

Much of the scientific work on Pourquoi Pas? takes place in laboratories and control spaces where samples, measurements and data are turned into usable research.

The ship has wet and dry laboratory facilities, areas for water sampling and coring work, and dedicated spaces for scientific data and energy storage. The scientific control room was renewed as part of the refit, alongside communications and monitoring equipment. These spaces must accommodate different disciplines, often operating simultaneously, while allowing scientists to manage instruments, process information and prepare for subsequent deployments.

The vessel’s computer infrastructure is particularly important.

“There are three different networks – one for crew, one for the scientists and one for the ship’s navigation systems,” said Gaillot. “Cybersecurity is important so we keep them separate.”

Dynamic positioning and navigation systems were also upgraded during the refit to help the ship hold its position during sensitive operations.

After the last trip on Pourquoi Pas?, an investigation into radioactive waste barrels being dumped into the deep northeast Atlantic, the NODSSUM project, Pourquoi Pas? was having the final touches done before her next six-week adventure.

This, we have just been told, will be a trip to the French island of Mayotte, in the Mozambique channel, to monitor seismic activity related to an underwater volcano discovered in 2019.

The crew and scientists at least know that for those six weeks they will be fed very well, with their own chef team cooking them three meals a day and even offering them wine on Sundays, when no one works.

It is French, after all. Et pourquoi pas?