Is it possible to calculate 100,000 MT nuclear blast radius?

mkarger

Really, what I'm wondering is if the blast radius is a constant given an increase in output. I assume it is not. So I'm really at a loss as to how to calculate such a massive value.

The scenario is the explosion occurs at sea level on a flat desert plane.

Help?

mfb

What do you define as "blast radius"?
Radius of some specific overpressure?
Radius of some specific temperature?
Radius of some specific destruction?
In addition, all three will depend on the height of the explosion.

QuantumPion

I used the asteroid impact calculator to come up with some plausible values for an impact energy of 1e5 MT here: http://impact.ese.ic.ac.uk/cgi-bin/c...tdens_select=0

mkarger

I'm thinking of the radius within which there is "total destruction" of any objects that are not very heavily reinforced.

mfb

Nuclear explosion simulator
Does not allow to detonate nukes above 2 MT, but I did some scaling guesswork:

"Certain Mass Fires" radius:
2 MT: 821 km^2
1 MT: 417 km^2
0,2 MT: 88 km^2
0,02 MT: 10 km^2
0,002 MT: 1,3 km^2

Looks like a factor of ~9 for the area for a factor of 10 in weapon yield. If that does not change, I would expect an area of 25*10^6 km^2 or a radius of 2800 km for an explosion of 10^5 MT. However, this would need a nearly flat explosion, which is a bit unrealistic for such a high yield. Multiple bombs at different places could give that effect, of course.


Another tool, here for the shock wave:
5 psi overpressure: "Complete destruction of ordinary houses, and moderate to severe damage to reinforced concrete structures, will occur within this ring." (does not take heat into account)

100MT: 20.99 km radius
20MT: 12.28 km
2MT: 5.7 km (102km^2)
0,2MT: 2.64 km
0,02MT: 1.23 km
That corresponds to a factor of 2.15 in radius or 4.64 in area for a factor of 10 in yield. As ##10^{1/3}=2.154## and the shock wave is spherical, that looks reasonable.
Scaled to 10^5 MT:
100MT: 208 km radius


A third tool shows effects of the shock wave and heat at the same time, and indicates that indeed the burned area expands quicker with weapon yield than the shockwave. And it shows the difference between an explosion on ground and in the air.

snorkack

I expect that for bombs over a few tens of MT, the overpressure would grow less than in case of a smaller explosion - these have nearly spherical fireballs in nearly uniform air environment.

But when fireball expands past a few km and approaches atmospheric scale height, the upper part of the fireball will be ploughing up less dense air - it will travel faster and expand to lower pressure. And decreasing pressure at the top will release the pressure from the bottom and sides of fireball and slow down their propagation.