In the early days of dynamic positioning, the 1960s and 70s, commercial deepsea divers soon learned how good their support vessel’s DP footprint was. Their lives depended on it. If a vessel slowly, or worse still, rapidly, moved off position, they would be pulled along with it.
Diver safety was an early motivator for developments in DP systems, but risks remained. Chris Lemons survived a worst-case scenario in the North Sea in 2012: “First, the communications cable snapped. Then the gas hose stretched to the point I had nothing to breathe. I opened the supply on my back. This happened within about 30 seconds. Soon after that the umbilical snapped like a shotgun going off and I fell down to the sea bed. Nearly 100m (approximately 300ft) down in absolute darkness…”
Amazingly, Lemons survived there for over 30 minutes until he was rescued, and it is timely to recall the effective action of those involved in his rescue as Focus Features is releasing a thriller about it on February 28.
The probable cause of the DP 2 system failure in Lemons’ case was determined to be a single fault which caused blocking of the DP system's internal data communications.
An upcoming issue of will take a look at what is driving innovation in DP system technology today.
Starring Woody Harrelson, Simu Liu and Finn Cole, and made by Longshot Films and Dark Castle Entertainment, Last Breath is based on a 2019 documentary of the same name.
