std7mag said:
Alas it is not just the shock wave, but where on the bullet does the shock wave occure?
If you watch a fighter jet, the shockwave doesn't appear untill about the cockpit.
That's happening
as the plane speeds up toward Mach 1. It happens because air diverted around the shape of the cockpit has to travel a longer distance than air moving along the sides, so the air over the cockpit is moving at supersonic speed before the body of the plane is. That creates a shockwave because air moving that fast can't move away as fast as more air comes into place. As the plane speeds up further, more of the air passing over its surface is supersonic and the pileup moves toward the rear of the plane, creating the stern shockwave. But when the plane body passes Mach1, a second shockwave, the bow shockwave, forms up in front of it due to the direct nose pressure wave, and that typically has the most energy in it. Indeed, shadowgraphs will show the stern shockwave often isn't all that dense right at the bullet surface, being fed a bit off to the side, so the bullet or plane doesn't see much extra heat from it. The bow, though, gets the full brunt of the temperature rise, being right in the hot compressed air.
On the Concorde, flying at Mach 2.04, the greatest heating was at the pointed nose.
Scroll down this page to see an illustration of the skin temperature distribution. The nose hit 127°C. Everywhere else was less. It's because the front of the nose is closest to pushing the air straight forward, creating the greatest compression in the bow shockwave. It was moving at about the speed of a 170-grain 30-30 bullet.
The differences between the plane and the bullet are the supersonic bullet is already going above the speed of sound when it plunges into the air from the muzzle blast sphere. It gets both a bow and stern wave immediately. However, the bullet is not in the air as long as the airplane is, so it doesn't have time to for the bow shockwave temperature to be fully transferred to it. Indeed, it is constantly losing speed, so the temperature gets lower.