Quote:
Originally Posted by Hektore
What generates the heat is not the speed of the air, but the friction of the air moving against an object. Same principle as rubbing your hands together, only with air. So as long as the walls of the wind tunnel whatever happens to be in it are sufficiently low in friction then, no it won't generate a fireball.
As far as your original question though, yes you could melt a rock with air if you got the air moving fast enough and the rock was rough enough.
|
Moving air (i.e. wind) can actually heat itself through the friction of the air molecules themselves. However, not everything will combust (in general on earth , oxidise). At the speeds generated by the Lens-X wind tunnel, the air itself will become hot enough to ionise relatively quickly, resulting in a plasma. This does not happen within the air tunnel itself (I believe) due to the short bursts of the actual wind blasts. On the other hand, there is a plasma created around objects entering the earth's atmosphere (such as meteors and space shuttles). This is part of what causes the "radio blackou" on re-entry.
As well, as mentioned above, the SR-71 flew so fast that it would expand by about 12" - 18" just from the friction of the air. As a result, they never came up with any seals that could totally contain the fuel within the plane. Fueled in a hangar, they would have to put pans under it to catch the dripping fuel. Once in the air, they would fly at speed until the expansion compressed the seal sufficiently to block the leakage, then re-fuel in air, then fly the missions.