Worst Case: Lightning

LightningThis chapter aims to find preventions and handling to reduce risks of a lightning strike. All proposals that may help to improve it are welcome.

 

Coverage

  • safety for surface support buoy
  • safety for the support vessel
  • safety for divers outside the habitat
  • safety for the inhabitants of the habitat, the aquanauts
  • functioning of electrical/electronical systems / life supporting systems for a certain period of time
  • communication between habitat and surface/land support
  • rescue procedures

Introduction

Lightning strikes are an easily ignored danger for the operation of an underwater habitat.  They are attracted by objects protruding from the ocean surface and spread after hitting the water. But it seems like there are no sufficient information on the exact behavior of lightning energy under water.

NASA has shown with satellite imaging that the oceans rarely get hit with lightning. Apparently the surface water does not heat up enough to cause the positive charge needed for lightning to occur. Potentially, lightning is the biggest weather danger for divers.*

The parts of the underwater habitat under highest risk is the surface support buoy and divers outside the habitat. If the lightning strikes the buoy, currents could be carried until the habitat, where all electric/electronic parts could be damaged and aquanauts injured.

Divers outside the habitat could be under serious risks since the lightning current is distributed over large areas. Due to the good conductivity of water currents could spread up to distances of more than 100 meters away from the impact site and cause a shock to the diver leading to drowning.**

Aquarius Life Support BuoyThe corresponding safety measurements of the habitats La Chalupa (Jules Undersea Lodge) and Aquarius in Florida are unknown. Both survived several hurricanes already, one time with aquanauts inside LaChalupa. Ian Koblick, president of the Marine Resources Development Foundation and Jules Undersea Lodge said “the lodge was the safest place to be during Hurricane Irma. It was not going to flood and it is protected in the lagoon.” (Details on lightning protection will be requested)***

Critical phase before and after a thunderstorm

A Lightning Safety Group, which met at the 1998 American Meteorological Society convention to update safety recommendations, noted in it’s report: “Generally speaking, if an individual can see lightning and/or hear thunder, he or she is already at risk. Louder or more frequent thunder indicates that lightning activity is approaching, increasing the risk for lightning injury or death.” The report also notes that “many lightning casualties occur in the beginning, as the storm approaches — Also, many lightning casualties occur after the perceived threat has passed.” In fact, the danger can persist as long as thirty minutes after the storm has passed and the last thunder is heard.*

Preventive measures

Meteorological forecasts should continuously provided, updated and communicated. A classification table should be established to mark conditions  that require return of excursion aquanauts to the habitat or cancellation of ongoing or scheduled missions.

The buoy should be provided with a lightning arrester, that vertically protrudes over all other devices and is shielded to the rest of the buoy and communication antennae; the arrester should carry currents through the buoy into deeper water. The equipment cases of the buoy should be shielded from the water and especially from the arrester. It has to be determined if the buoy should be retractable to the sea bottom before bad weather reaches the site.

The umbilical between buoy and habitat should have over current protections on both ends to prevent any electronic from damage.

The habitat: There were no proposals for preventive measures of the habitat yet.

Excursion Divers should return to the habitat before the squall line reaches site.

The support vessel should have standard protection systems against lightning strikes.**** Information are available at all boat/yacht companies.

Help us improving/completing this article. If you have additional or opposing proposals about this subject please use the comment box below!

Sources:

* http://scuba-doc.com/lightdive.htm
** “Blitze – So können Sie sich schützen“; VDE (Verband der Elektrotechnik Elektronik Informationstechnik e.V.), p.16
*** flkeysnews.com /news/business/article182594161.html
**** Pantaenius Yachtversicherungen

Images:

  • Lightning Image: Taken from Wikimedia; © Don Amaro from Madeira Islands, Portugal, upload by Herrick 17:17, 4 December 2007 (UTC)
  • Aquarius LSB: Taken from Wikimedia; National Oceanic and Atmospheric AdministrationOceanExplorer.noaa.gov
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