Sunday, January 24, 2016

"The largest man-made moving object on earth"


That's what Polarcus calls its seismic survey ship Polarcus Amani, currently working off the coast of Myanmar.  It's an odd-looking critter.




Popular Mechanics reports:

Registered in the Bahamas, Polarcus Amani is 300 feet long and displaces almost 8,000 tons. Her four propellers are rated at 3,000 horsepower apiece, providing enough pulling power to tow an array of seismic "streamers" more than a mile wide and 11 miles long. Altogether, the survey covers an area of about 6.8 square miles at a time, which is how Polarcus claims the record.

The streamers are the sensing part of a system that evolved out of submarine-hunting sonar. The working principle involves a similar use of reflected sound: The survey vessel generates pulses of high-intensity sound with underwater "air guns" made by Bolt Technology. The air guns may be fired every 20 seconds or so during surveying.  The sound waves are reflected off the sea bed and get picked up by a series of microphones towed by the survey vessel.

The line of floating microphones is known as a streamer. Were earlier research vessels had a single streamer, modern vessels like Polarcus Amani tow multiple streamers to build up a complete 3D picture of the sea bed below. They can also carry out so-called 4D surveys in which the same area is mapped several times and the images overlaid to build up a more detailed picture.

There's more at the link, and in a news release from Polarcus.

I was curious to learn more about the ship, and found this video clip from the company that built her for Polarcus.  If you're a geek technologically inclined, I think you'll find it interesting.





I hadn't realized that specialized marine geological survey ships had gotten so advanced.  I went to sea in the pre-GPS days of sextants and shooting compass bearings of coastal features, with a little help from Decca Navigator if you were lucky and the receiver was functioning (something that couldn't be guaranteed).  The Polarcus Amani operates in a very different technological environment . . . but I can't help wondering how she'd cope if the radar and GPS went out!

Peter

16 comments:

Pawpaw said...

How would she cope if the tech went out? Hopefully, the Captain is a mariner. A compass, binnacle and sextant are fairly low tech.

Cambias said...

It looks like an armored ram of the ironclad era.

J Melcher said...

As oil exploration becomes less profitable the survey results can be sold to the telecom industry on routes for undersea cables.

Did you know? Once an oil pipeline company fed fiber optic data cable thru their pipes as a maintenance technique but discovered the bandwidth was so greatly in excess of need it could carry voice signal. Became the "Sprint" long distance phone company ...

Who could plan such things?

SiGraybeard said...

The first thing I noticed was that unusual bow design. I've never seen a ship with that sort of design before. Several ships on Ulstein's website have that sort of design so it's either more effective in the design environment, or it's design for its own sake.

I don't know if there's much ship building done in America anymore but we used to be good at it. Not to take anything away from Ulstein, who apparently builds in Norway.

Rusty Gunner said...

Willard Bascom's "The Crest of the Wave" is out of print but available, a very entertaining memoir of a post-WWII ocean scientist and a good snapshot of how the work was done then. The chapter on sea-monster fishing with John Steinbeck contains one of history's finest moments of trolling (in the Internet sense).

Sam Helm said...

The bow looks like a variation on the tumbledown design, which was (is) used on the DDG 1000 (Elmo Zumwalt). It is supposed to be good for foul weather, but I have no idea how good it is. It seems to me to be a throwback to the early days of steam (compare with early battleships).

Rusty Gunner said...

I knew I'd seen that somewhere before, it's a species of inverted bow (think Zumwalt-class destroyer) that Ulstein markets as the X-bow. It Is apparently more stable and fuel-efficient in rough seas.

Duke of URL VFM#391 said...

"The largest man-made moving object on earth", bullshit.
The USS Nimitz: Overall length of 1092 feet and full-load displacement of over 112,000 tons.

Rusty Gunner said...

Try the SS Seawise Giant, 1504' in length and displacing 657,019 tonnes fully loaded. Too large to fit through the Panama or Suez canals, or for that matter the English Channel. Sent to the breakers in 2010.

Charlie Mitchell said...

That's an X bow, as noted by Rusty Gunner. Polarcus stole that "largest moving object" line from my company, the rats. By that, they mean the ship and all of its towed equipment taken as a unit. The former head of my company was one of the founders of Polarcus.

Da Curly Wolf said...

been a long time since i've used this account. lol but I gotta say Peter. that ship ain't odd. That's that's....ugly

Paul, Dammit! said...

X-bows are ugly as sin, but for a compromise between normalizing buoyancy (it supposedly minimizes pitch at angles where traditional bows start becoming less efficient at it) and increasing internal volume for revenue-generating space, it's absolutely the new hotness for small ships.

I hate hate hate seismic ships. They require a massive amount of sea room, and there have been plenty of times when we've been pushed out of designated traffic zones and started slaloming between oil rigs with a loaded tanker.

It is funny though, that navy guys think their ships are big. The Nimitz is only 1/4 the size of the larger classes of crude oil tankers. The newest oil platform service vessel is 6 times heavier, 4 times wider and a couple hundred feet longer. The amount of fuel that a large container ships burns off between China and Los Angeles weighs the same as an Aegis cruiser.

Rolf said...

Duke - VFM 391 - it's talking about the dimension of the towed sonar array, not the ship itself. The streamers are a mile wide and 11 long. Yeah, it's marketing-speak, which means it is technically true even if misleading because it's using a very specific meaning for "largest." Not talking mass or volume.
Eh, still kind of cool.

Anonymous said...

Fascinating technology. Can't help wondering however about effects of the sensing process on whales and other marine life. The U.S. Navy has altered their sonar practices I believe and this vessel would appear to produce a much larger effect.

scipioamericanus said...

Anon, it's the extremely intense pulses in military active sonar that (under certain circumstances) cause undue harm to certain marine mammals. Imagine a car driving by you making a periodic noise so loud your house shakes. For this application the intensity is far lower - like the same car, just with the radio on instead.

LCB said...

What others have said about the ships size! She only looks about 1/3 as big as the biggest cruise ships today. And no where close in size to container ships and oil tankers.