By Karen Moltenbrey
for nearly a week last August, the world held its collective breath as international organizations and governments tried to save 118 sailors trapped aboard the crippled Russian submarine Kursk, grounded on the bottom of the Barents Sea. But hope turned to despair when divers finally reached the sub, only to find the vessel devoid of life.
Nevertheless, the tragic story of the Kursk is not over yet. Although divers recovered a dozen bodies during the rescue operation, others remain in the watery grave. Even more discouraging are the long-term consequences. Just as the Barents Sea flooded the vessel's chambers, so too might the nuclear-powered Kursk flood the sea with contamination.
An experienced international salvage team is now writing what it hopes to be the final chapter to this tragic story. Aided by 3D computer modeling and simulation, a consortium of Russian, Dutch, Norwegian, and US companies is planning a complex recovery operation that will raise the Kursk, thereby providing closure for the sailors' families and preventing possible widespread nuclear contamination of the fertile Barents Sea fishing grounds in the Arctic Ocean.
|An international consortium is using 3D modeling and animation to simulate its plan to raise the doomed Russian sub Kursk from the sea floor before leakage from the vessel's nuclear reactors causes widespread contamination of the sea. |
Pending acquisition of the funds and final approval by the Kursk Foundation, which is coordinating the mission, the group plans to perform the maneuver this fall if granted the project. Other consortiums and individual companies may also present plans to the Kursk Foundation in hopes of securing the contract.
Established last November by the Government of the Russian Federation, the Kursk Foundation comprises an international group of experts in submarine technology and former senior politicians. Its goal is to neutralize the potential environmental dangers resulting from the badly damaged submarine's two nuclear reactors, which carry a considerable amount of deadly uranium, plutonium, strontium, and cesium. The Russian government contends that no nuclear weapons are onboard, but the vessel is heavily armed nonetheless.
Experts believe that the reactors were "extensively affected" by a series of explosions in the Kursk's forward compartment prior to its sinking. The blasts, thought to have been equivalent to 2 tons of TNT, at the very least have weakened the structural integrity of the reactors.
The first explosion, registered by seismologists, likely occurred in the for ward torpedo compartment during a failed naval exercise. This, in turn, probably triggered the second blast, which ripped through the confined space of the submarine. While the foundation believes the reactors are stable for now, the situation could change for the worse because of the weakened structure of the vessel and the natural corrosion that will occur.
"Our intention is to prevent any [radiation] leakage while it is still possible to do so," explained foundation co-chairman Alexander Bessmertnykh of Russia. While no contamination has been found yet in the biologically active waters near the wreckage site, Russian research vessels will be monitoring the area for signs of radiation until the salvage operation is completed.
|The salvage team used 3D modeling and visualization to help plan and test its complex recovery operation. The usefulness of the simulation was dependent on the accuracy of the 3D model of the submarine.|
Based on site surveys by divers and remotely operated vehicles, the level of destruction inside the submarine appears extensive. At this time, nobody is sure whether the hull was weakened from the explosion, which occurred in the relatively shallow waters (108 meters, or 356 feet) of the Barents Sea during a training exercise. However, the fact that the submarine is resting in a few feet of sand is evidence that the vessel hit the sea bottom with extreme force.
Because of the volatility of the situation, extensive planning of the entire salvage operation is essential to prevent further structural damage. Indeed, just raising such a large vessel-twice the size of a 747 airplane-from the sea bottom presents a formidable challenge. So 3D animations of this complex process were created at the request of Halliburton Subsea, a leading member of the international salvage consortium. These visualizations, made by AGS of Horten, Norway, have enabled the group to test and revise its recovery methods virtually, without a risk to the environment.
Using Autodesk's Inventor software, AGS first created a detailed 3D model of the Kursk based on documents supplied by the Russian company that built the sub in 1994. Though necessary, handing over sensitive weapons designs was understandably difficult for the Russians. To help safeguard its military secrets, the Russian government required that all parties privy to the design data sign nondisclosure agreements.
|The engineers used finite-element analysis to determine whether the sub's hull could withstand the stress resulting from their lifting solution. |
AGS initially built the virtual model based on dimensions from paper documents, but later revised those figures after receiving digital construction blueprints containing more precise dimensions. Rather than rebuilding the model from scratch to accommodate the revisions, the AGS team adjusted the parameters, and the software automatically reconfigured the model to reflect the new information.
"It was vital that the model be 100 percent accurate for the calculation of the resulting stresses in the finite-element analysis and to figure out the weight and balance ratios for lifting the sub," says Tore Bornick, AGS's owner and general manager.
Even with the correct dimensions in hand, the group still had difficulty re-creating the complex shape of the submarine's curved hull. In fact, the overall design of the submarine made the 3D solid-modeling task quite complicated. "The vessel is double-hulled, with 3 feet of separation between the inner and outer hulls," notes Bornick.
|Animators created accurate models of all the salvage equipment to precisely plan the interaction of the recovery vessels during the lift operation. |
The vessel's complexity required the group to input a large amount of data into the virtual model. For the initial application, the team did not re-create the inside infrastructure of the hull. However, Bornick expects to incorporate those details in the future if the consortium is given the green light to continue with the project. "When the operation begins, the salvage team will need to know what's behind the walls because they'll have to make cuts in the hull to obtain the strong points of the submarine's rib structure, which are really the superstructure of the submarine," he adds. "They have to know what they're cutting into and how that affects the lifting process."
In addition to modeling the Kursk, AGS also created virtual replicas of the crane that would be used to lift the submarine, as well as the barge that would tow the disabled sub ashore and the diving ship that will control the operation. "We needed all these models so we could animate the interaction of the vessels throughout the process," says Bornick.
According to Halliburton's Birger Haraldseid, the salvage team members would position a giant barge from Smith International, reconstructed specifically for this operation, over the submerged vessel. Then they would engage the world's largest crane vessel, from Heerema Marine Contractor, to raise the Kursk off the seabed using cables fastened to custom-made lifting clamps on the hull's rib structure. The crane, with a lifting capacity of 16,000 tons, would not lift the 154-meter, 18,000-ton Kursk out of the water. Rather, it would position the submarine underneath the barge, where it would be fastened and then towed to the Russian port of Murmansk.
|One of the most important functions of the simulation was to determine where on the hull to attach cables for lifting the sub. A remote-controlled vehicle would assist in that action.|
Prior to AGS creating a simulation of this exercise, engineers at Halliburton transferred the 3D model of the sub into a finite-element analysis program from Ansys, to determine whether their lifting solution was structurally feasible. Using the software, the engineers calculated the amount of force that would be placed on the superstructure of the sub marine and the amount of structural weight the lifting gear could hold. This data was then incorporated into the Inventor model, which was used in the simulation.
Within the virtual environment, the engineers have determined how and where to attach the lifting clamps, the amount of stress that can be placed on the hull, and how the sea currents may affect the submarine and recovery craft during the lift. This was done by importing the Inventor models of all the participating vessels into Discreet's 3D Studio Max animation software.
"Using the simulation, we could test as many details as possible," says Bornick. Once the optimal lifting points are determined, holes would be cut into the submarine at these locations, so that the customized lifting clamps could be attached. With the simulation, the team can ensure that the procedure avoids mechanical contact with the section of the hull containing the two nuclear reactors.
|The simulation is still a work in progress, as new methods of raising the fractured 18,000-ton vessel continue to be devised. |
AGS is also using the animation to sim ulate the cutting and recovery of the damaged bow section, which must be completed prior to the lifting operation so that no fragments break off when the vessel is lifted, Bornick notes. In fact, Halliburton gained valuable knowledge and experience in working with the submarine's exterior when it participated in the mission last Aug ust, when the bodies of 12 sailors were re moved from a hole the group cut into the hull. That effort gave the company an opportunity to assess the condition of the vessel.
Because Halliburton is still in the pre-engineering phase of the operation, the simulation model is in a state of flux. "There are several engineering approaches to solving the lifting process," says Bornick. "We can easily adjust our 3D model to meet any new request." AGS is currently simulating a new lifting method devised by Halliburton that may be more appropriate given the weakened state of the submarine's structure, which would also make it easier for the divers to work at this particular depth. The overall cost of executing a specific method will also affect its viability, given the financial state of the Russian government. In fact, the cost of the operation could prevent it from occurring at all, notes Haraldseid. If the consortium is granted the projected, Bornick expects to test numerous methods and ideas either on location or through a remote connection as new scenarios unfold during the actual operation.
"Without 3D modeling, the alternative would have been to make a miniature physical model and conduct the testing in a water tank. But that alternative is expensive, time-consuming, and far less accurate," Bornick maintains. "And that would have made the operation far riskier."
Once the engineers have determined the best method of raising the submarine, they will present their plans to the Kursk Foundation for approval. According to Haraldseid, Halliburton will use the simulation as the main focal point of its presentation, which should help make the complex procedures easier for the foundation members to understand. "It's a very diverse group, so the visualization will be quite powerful when it comes to presenting the concept, especially to the nonexpert personnel [who comprise the majority of the foundation]," he says. The animation also will be used to generate the necessary funding, estimated at $70 million, which will be shared by Russia and international donors.
Yet time is of the essence. The Russians are anxious to recover the bodies of their fallen sailors, although, because of the explosions, it is unknown how many remains will be found. And, the longer the Kursk sits at the bottom of the sea, the more prone it is to structural deterioration. Furthermore, because of the long polar winter, there is a limited window of availability in which to conduct the mission. If that timeframe is missed, the recovery team will have to wait several months for safer conditions.
"The most important thing, though, is to conduct the operation as safely as possible without endangering the environment and those participating in the process, and the visualization is vital in allowing us to accomplish that goal," says Haraldseid.
Neither Halliburton nor AGS-nor the world for that matter-has been involved in such an ambitious and dangerous endeavor before. Yet the lessons they learn will be invaluable for future situations, and could be used to recover numerous other nuclear submarines that litter the ocean.
For instance, the Russian submarine Komsomolets, which sank in 4500 feet of water off the northwestern coast of Nor way more than a decade ago, is slowly leaking plutonium. At that depth, marine life is scarce, so presently it poses less of a threat to the environment than the Kursk. Nonetheless, these sunken nuclear hazards are ticking bombs.
|By simulating the lifting operation, the engineers hope to prevent further damage to the submarine's hull. |
"Simulating complex processes such as these in a digital form is extremely valuable, particularly when these processes take place offshore and under water, where skill is essential. In these harsh conditions, it's very costly to create [physical] prototypes in order to 'practice' solutions under water, a method frequently used by oil companies involved in subsea activities," explains Bornick. "By maintaining virtual control of these processes, companies will save both time and money-two necessary factors in most projects."
Karen Moltenbrey is a senior associate editor at Computer Graphics World.