Suppose that ground-penetrating weapons (such as the bunker buster bombs) designed to go through several feet (or maybe even several dozen feet) of concrete/earth instead are dropped into the ocean. Would they penetrate several hundred meters before detonating (since water is softer than concrete), or just never go off at all?
Well, bombs have lousy buoyancy, so I suspect the bunker buster will sink. As will a non bunker buster.
The main components of a bunker-buster are hardened casing and fusing. If the continuing act of going through the water sets off the fuse, then it’ll explode. I wonder what salt water will do to the electronics of thr fuse, nothing good one would imagine.
If it goes off, it will be bad news for some nearby ocean life, if its shallow enough at point of detonation, some boat and or some very surprised and unlucky submarine (*Comrades, the Americans are using amphibious bombs *).
Better qiestion IMO, is what effect does the local water table have on such a bomb.
Water is actually pretty hard - unlike, say, soil, it doesn’t compress. A bomb hitting water would almost certain go off.
There’s the impact which starts the delay timer. Once the timer goes off, boom. Given the speeds involved not a lot of time goes by.
Like Alessan, I think the impact with the water would almost certainly be enough.
Note that there are different ways the timer/fuze can work. Old school ones have a propeller that’s turned by the air. When the propeller stops turning, the timer starts. Water would do that.
They are doing “smart” timers now. Fancy stuff like count the number of “floors” hit before going off, delaying until an empty area between floors is felt, etc. It would seem idiotic to not have a bomb go off if none of the key conditions are met. A misplaced boom is better than no boom at all.
FWIW, a previous thread … from 2001.
Interesting. Do you think nuclear MIRVs (multiple independently targeted reentry vehicles) mounted on ICBMs could be given a bunker-buster mode?
^
Hmmmm… some 100 kiloton bombs would weigh less than 1,000 kg. Tall Boy (WW2) weighed 4,000 kg, while the Desert Storm GBUs weighed around 1,800 kg. A recent GBU version weighs 15,500. And therefore bunker busters appear too heavy when delivered in a cluster.
OTOH, a single warhead in the megatons range would weigh between 1,000 and 10,000 kg. So a single nuke bunker buster might be feasible. My figures are from a private blogger who seems to know what he’s writing. Kilotons per kilogram | Restricted Data
According to the internet, reentry bodies of ICBMs and Submarine launched ballistic missiles weight between 350-800 lbs. I am sure they could be made penetrating to some minimal degree, but nothing as penetrating as real bunker busters. I would say they would rely upon the energy release to do the damage.
Bunker busters are designed to go through rock and concrete, not just granular material.
Not necessarily. I would imagine a ground penetrating bomb is rather like an armor piercing shell which is designed not only with a short delay (to allow penetration into the bowels of the target) but also a significant deceleration to trigger the fuse in the first place. In the Battle Off Samar the Japanese fleet mistook the US destroyers and DEs as cruisers and the escort carriers as fleet carriers, and fired AP shells initially. The hits failed to detonate, passing entirely through their unarmored targets entirely. After several for-sure hits failed to make their targets go blooie, they realized their mistake and switched to high explosive shells which had the desired result.
Now, while getting a hole from 6 to 18 inches in diameter punched through your ship is not going to make your day, given that you were hit at all, it’s the best possible outcome. While smacking into water is hard, I don’t know if the deceleration would be enough to detonate the bomb.
There are two types of fuses for bunker busters - Delay fuses and Hard Target Smart Fuses (HTSF)
Delay fuses are pretty simple - an accelerometer detects impact and delays the explosion for a predetermined amount of time. These would work on water, as impacting water at those speeds is no different than a structure or the ground. Exactly how deep the bomb is when it goes off will be different based on the density of the material its going through, but it’ll go of at the same time.
HTSFs include a microprocessor capable of counting voids as well as timing functions, so if they were programmed to say, count 5 impacts (floors) before exploding but for some reason they were dropped in the ocean instead, they will not go off since the programmed conditions were not met, unless there is a function included to “go off after x milliseconds regardless of anything else”.