Conquer Club

johnnyrotten wrote:I'm rather pleased this is still going.

Jdsizzleslice wrote:Can we post anything in here?

Jdsizzleslice wrote:Can we post anything in here?

rdsrds2120 wrote:A gif of the Milky Way and Andromeda Galaxies colliding:




Obviously not from real footage, but interesting nonetheless.

BMO

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.

To prevent early degradation, most helicopter blades are coated with an abrasion strip. This strip, typically made of a metal like titanium or nickel, prevents the leading edge of the blade from being worn down too quickly by the various particulate hazards of the atmosphere. This abrasion strip can handle a lot of wear and tear, but the desert is a harsh environment. 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.

It turns out that the metals comprising the abrasion strips on helicopter blades can be pyrophoric—they can spontaneously ignite in air. But of course this doesn’t happen in normal circumstances; we don’t see bricks of nickel bursting into flames. Rather, the spinning blades of the helicopter generate a cloud of metal particles. Once in that form, the metal particles can ignite and light up. Like sawdust or flour, finely powered metal can and does explode.