A bearing failure has forced Celebrity Cruises' brand new Infinity ship into drydock for at least three weeks for repairs. Two one-week Alaskan cruises will also be cancelled, significantly impacting parent company Royal Caribbean's financial performance this quarter.

This is the second recent bearing failure in the propulsion system of a pod-drive cruise ship. It is also the latest in a series of problems plaguing Celebrity's new Millennium class.

The Millennium class represents the latest in advanced cruise ship technology and drive systems. Millennium class are 91,000 tons, 965 feet long and can cruise at up to 24 knots. They carry 1,950 passengers and 1,000 crew. The Infinity has the world's first conservatory at sea (including six Magnolia trees), a cyber cafe, 25,000 square foot spa, Internet access in every stateroom and numerous other features. They are built to Panamax standards and so are certified to pass through the Panama and Suez canals. All Millennium class will be built by the Chantiers de L'Atlantique shipyard at St. Nazaire, France. Each ship costs over USD $350 million.

The Millennium class employs two new drive system technologies.

First, they are the world's first gas turbine powered cruise ships. Power is generated by two GE LM2500+ aeroderivative gas turbine engines from GE Marine Engines division, GE Aircraft Engines. The LM2500+ is a combined gas turbine and steam turbine integrated electric drive systems (COGES). Each 22-foot, 11,000-pound engine produces 40,500 horsepower at 3600 RPM. The exhaust gas temperature is 965 degrees Fahrenheit. The gas turbines are the cleanest burning powerplants for any cruise ship in operation today.

Second, the ship is powered through the water by two Kamewa (Rolls-Royce AB) / Alstom pod propulsion systems called Mermaid™. Each Mermaid pod propulsion system consists of a 19.5 MW electric motor turning an 18-foot fixed pitch propeller. The electric motor is contained within the pod, completely submersed, and has infinitely variable speed control. Most importantly, the two pods can be rotated through 360 degrees, providing thrust in any direction. The propellers normally point forward, but their infinite speed adjustment and infinite directional adjustment allow the ship to be steered in any direction at any speed up to 24 knots. The propulsion pods not only allow the rudder to be eliminated, but putting the power unit in the pod frees up substantial space onboard.

Other advantages to the pod propulsion system are that the ship can easily dock anywhere without tugboat assistance, and that by pointing the propellers into the oncoming water, pressure pulses are reduced or eliminated. A propeller's pressure pulses create intrusive vibrations within the ship; reduction of propulsion system noise and vibration has long been a key design criteria for cruise ships.

Royal Caribbean ordered four Millennium class ships to be delivered over the next two years. The first, the Millennium, was delivered in mid-2000. The Infinity was delivered on February 26, 2001, over a month late, and was not inaugurated until April 29, 2001.

Chantiers de L'Atlantique is France's biggest shipyard and has built most of the world's largest and most advanced oil tankers, over 120 advanced technology warships and produces 40% of the world's cruise ships. The shipyard employs over 8,500 people.

Even though the shipyard's advanced technology capabilities are well established, this has not prevented the Millennium class from experiencing a series of expensive and debilitating teething problems.

The first ship, the Millennium, had to be taken out of service only a few months after inauguration due to unacceptably high vibration levels amidships, traced to the gas turbines. The ship was put in drydock at Newport News where it was fitted with a ducktail and additional buffer section in the stern. Several cruises had to be cancelled in that case.

The Infinity was in its in final stages of completion just as the Millennium's unwanted vibration problems surfaced. Infinity's launch was delayed by over a month as a solution was engineered and incorporated into the ship. Several of Infinity's early cruises were cancelled.

In January, the Millennium was once again out of service for two weeks due to an "under-performing" electric motor in one of the Mermaid propulsion units. The weak motor limited the ship's top speed to 20.5 knots instead of 24 knots, making it impossible to stay on schedule. Two cruises were cancelled during the repair.

Now the Infinity's pod drive bearing failure has sidelined it for three weeks and forced the cancellation of two more cruises. However, it was not immediately clear why the Infinity had to return to drydock for repairs. According to Rolls-Royce, the entire Mermaid propulsion system can be serviced or replaced in the water.

Bearing failures and other problems are not unique to Celebrity, lending credence to several leading experts' opinions that pod drive systems are not yet a mature product or technology.

In December, ABB Industry reached a financial settlement with Carnival Cruise Lines over a propeller bearing failure in one of the 14 MW Azipods which power the company's ship Paradise. The Paradise's Azipod bearing failure was blamed on lubrication problems, although an analysis pointed to a "series" of unspecified problems.