L’Astrolabe completes first mission to Antarctica

L’Astrolabe completes first mission to Antarctica

France’s new polar logistics and patrol vessel, delivered by the Piriou shipyard in Concarneau in September this year, completed her first mission to Antarctica in November. The L’Astrolabe, which replaces a vessel more than 30 years old, was specially designed to resupply the French scientific base known as Dumont d’Urville and the Franco-Italian base at Concordia. Both are occupied all year round by teams working on major science and climate research programmes. Dumont d'Urville can house 100 or so researchers and support personnel during the Antarctic summer and 25 to 35 during the long dark winter, while Concordia can accommodate 50 to 70 people during the summer and 13 to 15 during the winter.

 

(©  Piriou)

(©  Piriou)

 

Dumont d’Urville is on the coast of Adélie Land (French: Terre Adélie). Concordia, in contrast, is 1,100km inland at an altitude of 1,300m where the environment is among the harshest on Earth. Supplies for Concordia are unloaded at the coast then carried overland by convoys of vehicles that typically take about ten days to reach their destination. The bases are cut off for much of the year by pack ice, blizzards and temperatures as low as –80°C. Resupply operations must ensure that the personnel have everything they need from food and fuel (for the generators) to all sorts of equipment and supplies, including vehicles and scientific instruments.

It is the L’Astrolabe’s job to provide this logistic support, without which the research programmes would have to be abandoned. Built specifically for ease of access to the port of Dumont d’Urville, the ship has an overall length of 72m, a moulded breadth of 16m, and a draught of 5.30m for a deadweight tonnage of 1,200t. The upper deck (410sq.m) can accommodate a dozen 20-foot containers while also serving as a helicopter flight deck. For polar missions, the hangar is usually occupied by one or two AS350 B3 Écureuil helicopters. These are used not only to embark and disembark passengers and cargo, but also to identify passages enabling the icebreaker to weave her way through the pack ice.

 

 

(© Marine nationale)

 

The hold under the upper deck is 414sq.m in area and can accommodate sixteen 20-foot and two 10-foot containers. The hold opens to a stern platform, equipped with a 5t gantry, close to the waterline. Heavy items are handled by an impressive crane above the platform rated at 35t at 12m. Four large hatches are provided for hold loading and unloading via the upper deck.

Resupply missions to Antarctica take place from October to March during the southern summer when temperatures are high enough to melt some of the pack ice, allowing the ship to make progress. Even during these months, however, large ice floes and countless icebergs often make conditions difficult. Bureau Veritas classified the hull as Icebreaker 5. The bow is designed to ride up over the ice so that the ship’s weight then bears downwards with sufficient force to open a crack. The plating is EH40 high-tensile strength steel throughout. It is 35mm thick around the bow, 70mm for the forefoot and propeller struts, then 22mm along the sides. To cope with the huge structural loads encountered during icebreaking, the frames along the ice-belt (where the hull meets the ice) are just 300mm apart, instead of the usual 600mm.

The L’Astrolabe can smash through first-year pack ice (which is less hard than older ice) up to 1.5m thick. Tests on models in an ice test tank suggest that she should be able to maintain a steady 4 knots in 80-cm ice.

 

(© Institut Polaire Français - IPEV)

 

The vessel is powered by four 1,600-kW Wärtsilä diesels driving two Wärtsilä stainless steel controllable-pitch propellers. The propellers are made of stainless steel rather than bronze as it copes better with icebreaking shocks. Onboard power is provided by two Cummins diesel-alternator sets, each developing 534kWe, and two Leroy-Somer alternators (2 x 500kWe) coupled to the main propulsion diesels. The emergency diesel-alternator set is rated at 184kWe. The two large rudders are also specially designed for icebreaking. A bow thruster ensures good manoeuvrability.

The propulsion system offers a maximum speed of 14kts, a range of 10,000nm at 12kts, and an endurance of 35 days.

Aside from the spaces reserved for cargo, the L’Astrolabe has four accommodation decks with cabins for a crew of 21 plus 40 passengers, mostly researchers and support teams going to or returning from the bases.

The design was developed by French marine architecture bureau Marine Assistance, in cooperation with Finnish company Aker Arctic. The most unusual feature is that the ship is both a logistic support and a naval patrol vessel. Operated and crewed by the French Navy, the L’Astrolabe carries a range of surveillance and military equipment. When not on missions to Antarctica, the ship will conduct sovereignty and patrol missions in the exclusive economic zones of the French Austral and Indian Ocean territories, covering around 2.3 million square kilometres.

Original by Vincent Groizeleau published on 4 December 2017. This version translated and adapted by Steve Dyson.