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Fusing delay


C3PO
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Hi,

When dropping penetration bombs, or just mk84s, does a fuse delay of 5ms per floor of a building sound about right…so 15ms tail fuse to punch through three floors before detonation?

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Modules: F/A-18C / AV-8B / F-16 / F-15E / F-4E (when it lands) / Persian Gulf / Syria / Nevada / Sinai / South Atlantic

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Depends on the terminal speed, impact angle, and the post-impact slowdown. 590 knots is 1000 fps which is 1' per ms. I did a test and got about 1500 fps with a GBU-31v3 which is about 1.5' per ms.

For terminal angle divide by the sine of the angle from horizontal, e.g. +15% for 60° +40% for 45°.

Slowdown is the most nuanced. A thin, soft building won't reduce speed as much as something hard. If you knew the burying depth for a given impact (e.g. 20' at 1000fps) then you could assume it was losing 50fps per foot of hard material. Maybe think a commercial high rise is 3' worth of hard surface every floor so 6' total. Take the average of the initial impact speed, final speed 1000+900/2 = 950. Tin shack practically nothing, concrete bunker much more.

So you want to go 25' (one and a half floors) through say 6' of hard material at 1300fps average on a 60 degree impact angle. T = 25/1300 * 1/sin(60) = 22ms. That seems quite a small delay. I think 60-180ms is more common historically but that might be against hardened targets which would bring down the average velocity a bunch. 5ms per floor sounds too short as it would have to be covering an average of 2000fps of height change.

And of course this all depends what FMU is on the bomb. If it's -152 then you can program it on the fly. If it's -148 then your SMS settings don't change anything.

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Thank you - superb knowledge there.

Now: Water-cooled Ryzen 5800X + 32GB DDR 4 3200 RAM + EVGA 3090 FTW3 Ultra 24 GB + Reverb G2 + Add-on PCI-e 3.1 card + 2x1TB Corsair M.2 4900/4200 + TM HOTAS Warthog + TM TPR Pendular Rudder  'Engaged Defensive' YouTube Channel

Modules: F/A-18C / AV-8B / F-16 / F-15E / F-4E (when it lands) / Persian Gulf / Syria / Nevada / Sinai / South Atlantic

Backup: Water-cooled i7 6700K @ 4.5GHz + 32GB DDR4 3200MHz + GTX 1080 8GB + 1TB M.2 1k drive & 250GB SSD drive 500MBps 4K 40" monitor + TrackIR 5

 

 

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