A Big Ship Chop Shop On The Georgia Coast

April 4, 2021 by Roger Cheng 16 Comments

Last week we saw a hapless container ship vaulted to fame, where people converged on its combination of mind-boggling size suffering an easily relatable problem of getting stuck. Now that it is moving again, armchair engineers who crave more big ship problem-solving should check out [David Tracy]’s writeup on the salvage operation of an overturned car carrier ship, the MV Golden Ray published by Jalopnik. If the ship’s name doesn’t ring a bell, the writeup opens with a quick recap.

Written for an audience of gearheads, [Tracy]’s writeup walks through some technical aspects of the salvage plan and initial results of execution. Citing from the official entity in charge, the St. Simons Sound Incident Response Unified Command, and augmented with information from elsewhere. Even though the MV Golden Ray is “only’ half the length and a third of the gross tonnage of our meme darling MV Ever Given, it is still a huge ship. Every salvage operation this big is unique, requiring knowledge far beyond our everyday intuition. At this scale, most Internet “Why don’t they just…” comments range from impractical to absurd.

Fortunately, people who actually know how to perform salvage work designed plans, submitted by multiple bidders, each making a different tradeoff in cost and speed among other factors. The chosen plan was to cut the ship into sections small enough to be carried by barge for further processing elsewhere. This required a huge floating crane, a chain pressed into cutter duty, custom fabricated lugs for lifting, and similarly custom fabricated cradles for the barges.

But we all know that no plan survives contact with reality. While this plan was seemingly chosen for speed, it hasn’t gone nearly as fast as advertised. Certainly the pandemic was a huge hinderance, but cutting has also been slowed by pieces built far stronger than spec. Delays also meant more sediment buildup inside the wreck, compounding headaches. Other bidders have started saying that if their plan had been chosen the job would be done by now, but who’s to say their plan wouldn’t have encountered their own problems?

In time St. Simons Sound will be cleared as the Suez Canal has been. Results of their respective investigations should help make shipping safer, but salvage skills will still be needed in the future. At least this operation isn’t as controversial as trying to retrieve the radio room of RMS Titanic.

Aireon Hitchhikes On Iridium To Track Airplanes

December 27, 2017 by Roger Cheng 21 Comments

SpaceX just concluded 2017 by launching 10 Iridium NEXT satellites. A footnote on the launch was the “hosted payload” on board each of the satellites: a small box of equipment from Aireon. They will track every aircraft around the world in real-time, something that has been technically possible but nobody claimed they could do it economically until now.

Challenge one: avoid adding cost to aircraft. Instead of using expensive satcom or adding dedicated gear, Aireon listen to ADS-B equipment already installed as part of international air traffic control modernization. But since ADS-B was designed for aircraft-to-aircraft and aircraft-to-ground, Aireon had some challenges to overcome. Like the fact ADS-B antenna is commonly mounted on the belly of an aircraft blocking direct path to satellite.

Challenge two: hear ADS-B everywhere and do it for less. Today we can track aircraft when they are flying over land, but out in the middle of the ocean, there are no receivers in range except possibly other aircraft. Aireon needed a lot of low-orbit satellites to ensure you are in range no matter where you are. Piggybacking on Iridium gives them coverage at a fraction of the cost of building their own satellites.

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The Foghorn Requiem

May 30, 2016 by Anool Mahidharia 16 Comments

Foghorns have been a part of maritime history since the 19^th century, providing much needed safety during inclement weather to mariners out at sea. Over time, their relevance has slowly reduced, with advanced navigational aids taking over the task of keeping ships and sailors safe.

The sounds of the foghorns are slowly dying out. Artists [Joshua Portway] and [Lise Autogena] put together the Foghorn Requiem, a project which culminated on June 22^nd 2013, with an armada of more than 50 ships gathered on the North Sea to perform an ambitious musical score, marking the disappearance of the sound of the foghorn from the UK’s coastal landscape.

Up close, a foghorn is loud enough to knock you off your shoes. But over a distance, its sound takes on a soulful, melancholy quality, shaped by the terrain that it passes over. The artists tried capturing this quality of the foghorn, with help from composer [Orlando Gough] who created a special score for the performance. It brought together three Brass Bands – the Felling Band, the Westoe Band and the NASUWT Riverside Band, almost 50 ships at sea and the Souter Lighthouse Foghorn to play the score.

Each of the more than 50 vessels were outfitted with a custom built, tunable foghorn, actuated by a controller box consisting of a TI Launchpad with GPS, RTC, Xbee radio and relay modules. Because of the great distances between the ships and the audience on land, the devices needed to compensate for their relative position and adjust the time that they play the foghorn to offset for travel time of the sound. Each controller had its specific score saved on on-board storage, with all controllers synchronized to a common real time clock.

Marine radios were used to communicate with all the ships, informing them when to turn on the controllers, about 10 minutes from the start of the performance. Each device then used its GPS position to calculate its distance from the pre-programmed audience location, and computed how many seconds ahead it had to play its horn for the sound to be heard in time on the shore. The controllers then waited for a pre-programmed time to start playing their individual foghorn notes. The cool thing about the idea was that no communication was required – it was all based on time. Check out the video of the making of the Foghorn Requiem after the break, and here’s a link to the audio track of the final performance.

This is a slightly different approach compared to the Super Massive Musical Instrument that we posted about earlier.

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