Attempting to recover three massive Apollo F-1 engines in water depths over 14,000 feet or 4,300 meters is no easy feat. Marine salvage is a highly specialized skill with only a handful of experienced companies able to execute deepwater salvage. The challenge was to locate the assets which could successfully recover rocket motors potentially weighing nine tons from the deep ocean.
So what’s it take to recover three nine-ton engines from over 14,000 fsw (feet of sea water) in the deep ocean?
The first requirement is to obtain a vessel that has the capacity to stage one, if not two, remotely-controlled deep ocean robots. These robots are known as remotely operated vehicles or by the acronym ROV, and had to be capable of working three miles beneath the ocean’s surface. The ship must also include the capability to retrieve heavy loads. Even with today’s advances in ocean technology and shipbuilding, this combination of requirements is rare. Most vessels that support the oil and gas industry limit operations to approximately 10,000 fsw or slightly more than 3,000 meters. Special equipment is essential to work deeper and to be able to make a recovery of this magnitude.
In addition to the sub-surface capabilities, the final prerequisite for the ship was a sub-meter navigation system, providing absolute control of the ship’s position and heading critical to a deepwater salvage operation.
This high-tech navigation is known as dynamic positioning (DP), which utilizes GPS and a host of other sensors to maintain the ship’s position precisely over a target located two miles below her keel. Not only did the recovery vessel have to meet all the technical capabilities but additional requirements included office and conference room space along with the ability to feed and house over sixty personnel for 30 continuous days at sea.
One vessel which met all the aforementioned requirements was the M/V Seabed Worker based in Bergen, Norway. The ship had successfully performed numerous deep water salvage operations and was the best-equipped single vessel for the team’s requirements.
The Seabed Worker towers six stories over the ocean’s surface. The vessel is over 290 feet long, weighing in at almost 4,000 tons. She is a technological marvel from her seven-million-dollar ROVs to her bridge equipped like the Starship Enterprise.
The traditional ship’s wheel has been replaced with a joystick and dozens of computer screens. Every aspect of the ship is monitored and controlled by computer systems. A series of thrusters and her unique Voith Schneider propulsion system can maintain that position even when wind and currents are pushing her massive bulk eight knots sideways.
The Voith Schneider system is unique in that there are no propellers nor rudder, only vertical blades which rotate and change pitch. These rotating vertical blades provide thrust from any azimuth, eliminating the need for rudders, affording excellent maneuverability, especially when trying to maintain an exact position.
With the vessel decision astern, the team concentrated on developing a recovery plan tailored to the ship’s unique capabilities. Lifting the engines to the surface would require several hours with the transition from water to deck being the most critical period where an engine could be damaged or lost. These artifacts needed a safer way to the surface.
To ensure the security of engines and artifacts, each would be placed in a cradle or recovery basket on the bottom. Placing the engines into these devices would ensure they were protected during the long ride to the surface. Existing recovery baskets were good for loose artifacts but too small for a complete engine, so the team designed and custom-built modular recovery cradles that could handle an intact engine.
The baskets and cradles would be hoisted to the surface by the ship’s deepwater recovery winch. A mammoth spool weighing 40 tons, the size of a tractor trailer, was welded to the aft deck. The winch was equipped with 5,000 meters of synthetic rope with a breaking strength of 60 tons.
Prior to the advances of synthetic fibers, deepwater recoveries were significantly more complicated due to the weight of the lifting wire. Miles of heavy steel wire would add tons to the total lifting weight, making operations on a ship this size impossible. With the advent of stronger-than-steel synthetic fibers, the weight of the lifting wire was significantly reduced, making the ship and winch combination a viable alternative for our operation.
The stars of the show were two deepwater ROVs each sporting a 150-horsepower hydraulic system with a depth rating of 5,000 meters. Both units were equipped with lights, multiple cameras and two manipulator arms. While nearly identical, each system was customized for a specific job. The HD28 had been was equipped with a deepwater dredge and equipment compartment. It was the workhorse of the operation, excavating engines and rigging the artifacts for lifting.
The second ROV, HD23, was equipped with a custom camera system and would work on documenting the submerged engines in super high-definition video. The camera system had a resolution of 4,000 pixels which is almost IMAX quality. Supporting the camera was a custom lighting system. The combination of camera and lights produced absolutely stunning images. HD23 deployed through a large hole through the ship known as a moon pool. This 18 by 20-foot opening is covered by a hatch when at sea. During ROV operations the hatch slides aside allowing the ROV to descend through the ship.
HD28 launched via the Seabed Worker’s port hanger bay. Think of a garage door on the side of the ship which opens with an A-frame extending out over the water. Once on the bottom, equipped with the deepwater hydraulic dredge, this ROV’s primary job was to excavate the engines. After falling for over two miles, the engines had impacted the bottom with an impaling force, burying sometimes as much as a meter into the bottom. Once excavated, the engine could be rigged for lifting. HD28 would rig and move the engine, while the HD23 would film the operation.
Fiber optic cable sheathed in layers of steel wire connected the ROVs to the ship. Use of the fly by wire system eliminates the delay between commands from the surface and a response by the vehicle on the bottom. The fiber optic cable also allows the transmission of large amounts of real-time video data back to the surface. These thin glass strands even when encased in steel wire were the most fragile link in the system. As the ship heaved and pitched in high sea states there was enormous strain on the cable. Additionally, the heaving of cables make the ROVs and lifting baskets unstable as the rise and fall of the ship is transferred to the systems below.
To alleviate stress and motion problems, each system incorporated heave compensation. Motion sensors on the ship control the winches which adjust the cable length to match the ship’s motion, minimizing the strain and reducing the motion of the ROVs and recovery baskets. Heave compensation allows each system to spool cable out as the ship rises up on a wave, then spool cable in as the ship settles down into the trough of a wave, keeping the robots and lifting load steady.
The ship and all of her systems were a fantastic package of technology. Before any the mission could begin, all of these complex systems had to be rebuilt and tested to ensure faultless operation at sea. Additionally, we took on various salvage supplies such as custom recovery cradles, lifting straps and plumbing supplies to continuously wet the recovered artifacts to prevent deterioration. Even well-preserved artifacts recovered from the ocean are subject to significant corrosion when exposed to air. Hundreds of everyday items had to be loaded since there are no are hardware stores offshore. We loaded hoses, sprinklers, shackles, duct tape and plastic wrap and everything we could think of to support both people and equipment.
Once mobilisation was complete, the ROVs and the ship’s dynamic positioning underwent shallow water testing off Norway to ensure all systems were functioning. The recovery team would not board until the ship arrived in Bermuda. A second series of deepwater tests were planned enroute to Bermuda. However, like any work at sea, Mother Nature always has the final say. Traveling from Norway to Bermuda, the ship encountered storms and 50-foot seas. In between two storms, both ROVs managed a full ocean depth test but not nearly as long as the operators would have liked.
Follow the continuing story in our next post and join the ship in Bermuda alongside the recovery team as they work to bring Apollo F-1 engines to the surface for the first time since they splashed into the deep ocean four and a half decades ago.
© Copyright 2014 Vincent Capone
With Permission from Bezos Expeditions
Missed earlier posts in this series?
The story begins here: How Do you Recover An Apollo Rocket Engine from 3 Miles Beneath the Bermuda Triangle?
The search gets underway here: Finding An Apollo Rocket Engine in the Deep Ocean