Angels of the sky: Dazzling halo effect created by helicopter blades hitting sand and dust is named in honor of two fallen soldiers
- The Kopp-Etchells Effect was named in honor of two soldiers – one British and one American – who were killed in Afghanistan in 2009
- The dazzling photos were taken by a photojournalist who covered the war, and who decided to start calling the halos the Kopp-Etchells Effect
- When the two soldiers died, they were just 21 and 22 years old
Until recently, the dazzling visual effect caused by helicopter blades hitting sand and dust – and creating mesmerizing halos described as ‘one of the most beautiful things you’ll ever see in a war zone’ – had no specific name; observers would simply marvel at the breathtaking sight without an understanding of what was causing it – or what to call it.
Now, however – to honor the memories of two soldiers killed in the war in Afghanistan – the physics that create these types of breathtaking halos has a name: The Kopp-Etchells Effect.
The effect is named after U.S. Army Ranger Benjamin Kopp and British soldier Joseph Etchells, and was given its title by photojournalist Michael Yon – who was covering the war and captured the effect in dozens of photos – as a way to honor the fallen soldiers.
Kopp and Etchells were killed in combat in Sangin, Afghanistan, in July of 2009. At the time of their deaths, the two men were just 22 and 21 years old, respectively.
Kopp was born in Minnesota and enlisted in the Army straight out of high school, working his way up to the rank of corporal in just three short years. He completed two tours of duty in Iraq prior to his fateful tour in Afghanistan.
Etchells hailed from Greater Manchester and joined the British army in 2003. He, too, rose to the rank of corporal, and had previous deployments before the tour in Afghanistan that ultimately took his life.
The stories of the two soldiers aren’t dissimilar from many members of the armed services, and like most soldiers deployed in Afghanistan, the two men likely would have been witness to the stunning halos in the night sky that came with helicopters heading to-and-from various missions.
To honor the two men – and other brave men who, like them, spent countless nights escaping the horrors of war in the beauty of helicopter halos – Yon dedicated the effect to them.
Until recently, what caused the Kopp-Etchells Effect wasn’t entirely understood.
One pilot told the photographer that the halos were ‘a result of static electricity created by friction as materials of dissimilar material strike against each other.’
Other theories were that the extreme speed of the blades moved dust particles so fast that they burned up like meteors in the atmosphere.
Science blogger Kyle Hill at Nautilus, however, explains the effect as the result of ‘when a helicopter descends into a sandy environment, the enormous downward thrust from the blades inevitably kicks up a cloud of sand.
‘Cutting through the sand and dust, the blades smash into millions of these tiny particles, each sandblasting metal from the blade. Most of the time the only visible consequence to the helicopter is pitting on the blades, with enough damage warranting replacement. Every so often, however, the metal blasted from the blades produces a miniature meteor shower.’
He goes on to explain that, to prevent deterioration of the blades, they are often coated with an abrasion strip, typically made of metals like titanium and nickel.
‘This abrasion strip can handle a lot of wear and tear, but the desert is a harsh environment,’ Hill explains.
‘Sand is harder than the titanium or nickel that makes up the abrasion strip, so when a helicopter’s blades begin cutting through a cloud of sand, the particles hit the blades and send bits of metal flying into the air.’
Those bits of metal come in a cloud of pyrophoric (flamable) particles, which ultimately burst into flames, thus causing the wondrous Kopp-Etchells Effect.
Though beautiful, this effect is dangerous as it can blind the pilots’ night vision gear.
On truly dark nights a helicopter can land nearby and not be seen, but if the Kopp-Etchells Effect kicks in, then it suddenly becomes a more obvious target for enemy fire.
Original article: http://www.dailymail.co.uk