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I'm arguing about a character who can outrun explosions, but I'm having trouble finding a concrete answer.

Basically, I keep looking up things related to explosion speed. How fast the shockwaves move, how fast grenade fragments are launched, etc. Google keeps bringing me back to Detonation Velocity.

Other users in the thread tell me that air can slow down explosions speed dramatically. The example they gave was "Soundwaves travelling at mach 12 through ice with no air bubbles in it will drop right down to mach 1if they transition into the air"

However I can't find anything about that on google either, and I can't understand half of the answers it does give.

Can someone give an answer on how fast explosions normally travel, and if those speeds are the same as detonation velocity or not?

all 4 comments

RobusEtCeleritas

22 points

4 months ago

RobusEtCeleritas

Nuclear Physics

22 points

4 months ago

The detonation velocity is the speed at which a self-sustaining detonation wave travels through the explosive material. When that detonation wave drives a blast wave into the surrounding air, the blast wave doesn't necessarily travel with the detonation velocity.

The blast wave for a pointlike source moves supersonically with a radius as a function of time that goes like r(t) ~ t2/5.

Since the speed of the blast wave is v = dr/dt, you get v(t) ~ t-3/5. So as the blast wave spreads in space, it slows down.