Sunday, December 16, 2012

"Danger Close"

Pretty much all of us have heard of the phrase, "Danger Close".  But what does it mean and how does it effect wargaming?

First off, "Danger Close" is a radio phrase to warn friendly troops that the caller of the artillery or air strike is ordering a strike close to other friendly troops, so that they take extra caution or protection for the incoming strike.  There is no restrictions to have incoming strikes come in closer, just a warning.

So what makes something be "Danger Close"?  According to the US military, any time that there is a 1% or greater chance of hitting friendly troops is considered to be "Danger Close", or in official terms, "Minimum Safe Distances (MSD)" for the US Army and "Risk Estimate Distance (RED)" for the US Air Force.

Below is the generic "Danger Close" distance for various weapons.  While I was only interested in the Vietnam era weapons for Charlie Don't Surf, I thought some of you might be interested in seeing the distances.  When you think that in Charlie Don't Surf, 1'=100m, you start to realize that the "Danger Close" for a 105mm strike is 4' on the board!  Also, the numbers can change with the distance from the cannons to the impact zone and I provided some of the alternative distances with the range.

I hope you find this interesting!

US Army Minimum Safe Distances (MSD)

M203/40mm – 100m

60mm – 200m / 330m at 2000m range or farther

81mm – 300m

4.2” – 360m at 4000m

105mm – 400m / 360m at 10,000m

155mm/naval – 500m / 650m at 18,000m

8” – 610m at 20,000m

Generic “Danger Close”

Mortars/artillery – 600m

Naval – 750m

USAF Risk Estimate Distance

Unguided bombs by type versus unprotected and protected troops (numbers in parentheses are alternate numbers I found but not explanations for the difference)

Mk 81 (250 lbs) – 630m / 215m

Mk 82 (500 lbs) – 700m (425m) / 245m (225m)

Mk 117 (750 lbs) – 830m / 215m

Mk 84 (2000 lbs) – 722m (500m) / 315m (250m)

Napalm – 115m (covers roughly 40m x 180m area, so the 115m is delivery from a perpendicular path)

CBU (Cluster bombs Mk 24/29) – 1000m / 1000m

CBU (All other) – 250m / 110m

Rockets (2.75”) – 215m / 215m

Strafing guns (20mm) – 150m / 60m (45m)

Strafing guns (30mm) – 150m / 65m (45m)



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