Rock is disaggregated on the seafloor by two large robotic machines that excavate material by a continuous cutting process, not unlike coal or other bulk continuous mining machines on land. The Auxiliary Cutter ("AC") is a preparatory machine that deals with rough terrain and creates benches for the other machines to work. It will operate on tracks with spud assistance and has a boom mounted cutting head for flexibility. The second machine, the Bulk Cutter ("BC"), has higher cutting capacity but will be limited to working benches created by the AC. Both machines leave cut material on the seafloor for collection by the Collecting Machine ("CM"). The CM, also a large robotic vehicle, will collect the cut material (sand, gravel, silt) by drawing it in as seawater slurry with internal pumps and pushing it through a flexible pipe to the Riser and Lifting System.

The RALS comprises a large pump and rigid riser pipe hanging from a vessel which delivers the slurry to the surface. The proposed positive displacement pump is designed and built by GE Hydril (Houston, TX). The pump hangs from a solid vertical (riser) pipe suspended beneath the support vessel. The pipe is deployed to the seabed by a derrick and draw works system on board the vessel.

On deck of the production support vessel, the slurry is dewatered. The dewatered solid material is discharged to a transportation barge moored alongside. Used seawater is pumped back to the seafloor through the riser pipes and providing hydraulic power to operate the RALS pump. Discharge of the return water at the seafloor will avoid impacts to the warm surface seawaters, minimizing environmental impact of the operation.

Undersea mining has been tried for millennia; in the third century B.C., divers extracted copper ore from a depth of 4 meters near Heybell Island in the Bosporus. However, the first time I read about it as a child was in a somewhat more dramatic narrative format:

"...I utilize the heat of coal from the earth."

"From the earth?" I said, my voice going up on the word.

"We'll say coal from the seafloor, if you prefer," Captain Nemo replied.

"And you can mine these veins of underwater coal?"

"You'll watch me work them, Professor Aronnax. I ask only a little patience of you, since you'll have ample time to be patient. Just remember one thing: I owe everything to the ocean; it generates electricity, and electricity gives the Nautilus heat, light, motion, and, in a word, life itself."

The quote about undersea mining is, of course, from the (still!) amazing 1875 novel 20,000 Leagues Under the Sea, by Jules Verne.