GBU-28 Development History

Thanks for this video!
I remember well, when I as a teenager in the mid-90's read this development history in the book 'Tom Clancy – Fighter Wing – A Guided Tour of an Air Force Combat Wing'.
 
The thing about this project that always amused me is the guy saying, "I know where there's a field of howitzer barrels. . ." (The original barrels removed from the M110s when they put the new ones on.) Really puts a spotlight on the importance have having the right people talking to each other, and also not throwing stuff away that might be useful down the road.
 

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I've been looking at Paveway recently and (OK, OK, yes, yes, it's Wiki) on the Wiki page for the GBU-28 it says:

'It proved capable of penetrating over 50 metres (164ft) of earth or 5 metres (16ft) of solid concrete'

Donning my Geologist's (hard) hat - what is 'earth'?

Chris
 
Maybe it's a translation from German language ?
Here "Erde" (earth) means our planet, as well as that usually dark, dirty and
somehow crumbly substance, you call "soil"
 
Maybe it's a translation from German language ?
Here "Erde" (earth) means our planet, as well as that usually dark, dirty and
somehow crumbly substance, you call "soil"
Harry Harrison at one time lets one of his protagonists - professor Coypu - refer to mankind's legendary home as 'Dirt or Earth or something like that' (The Stainless Steel Rat saves The World). 'Blown up in an atomic war ages ago'.
 
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as well as that usually dark, dirty and
somehow crumbly substance, you call "soil"
That's my understanding of 'earth' but I'm struggling to find somewhere with 160ft of soil. The Loess in China? The podzols and chernozems of Ukraine? Sand dunes? There's not many places with soil that deep.
 
I've been looking at Paveway recently and (OK, OK, yes, yes, it's Wiki) on the Wiki page for the GBU-28 it says:

'It proved capable of penetrating over 50 metres (164ft) of earth or 5 metres (16ft) of solid concrete'

Donning my Geologist's (hard) hat - what is 'earth'?

Chris
In this case it's, "hard dirt in the desert". IIRC it dug itself so deep they didn't bother digging it up.
 
There's probably a NIST reference standard somewhere, but yeah, as sferrin says, the testing was out in the Western US (at Tonopah, specifically) so that's probably what they were measuring against.
 
I do wonder whether it's actually meant to be a meaningful statement in its own right, rather than either the thing buried itself 50 metres deep at the test range, or 'the book' says that 1 metre of concrete is equivalent to 10 metres of earth/dirt/soil/whatever.
 
Well, there's also the fact that when tested with a rocket sled, a GBU-28 blew straight through 22ft/6.7m of reinforced concrete and kept going for half a mile downrange. And yeah, the first dummy drop at Tonopah punched a hole deep enough that it wasn't worth trying to dig up.
 
I don't know any more than you do - the title of the post and the link.

@fredymac hasn't posted in 3 years, so probably not going to answer, even if somehow he remembers the title of a video he posted a link to 7 years ago.
 
Ahem, topsoil is generally the uppermost, organic rich <2ft of the land that supports plant life. Definitely not 50m deep. In this case it's fairly uncompacted alluvial deposits, so 50m penetration isn't surprising. I wonder how a GBU-28 performs against granite. I bet that's classified.

View: https://www.youtube.com/watch?v=TKn5otfZHxE


Chris
 
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What was its' title and what was it about? If I know the title I can then do a search on YouTube.
Sometimes it's just gone. I posted a link to a video that had several good shots of Nike Zeus A launches in 2017. Noticed a while back that that channel was deleted. Odds are I've got the video downloaded. . .somewhere. Haven't been able to find it though.
 
That's my understanding of 'earth' but I'm struggling to find somewhere with 160ft of soil. The Loess in China? The podzols and chernozems of Ukraine? Sand dunes? There's not many places with soil that deep.
Most of the US Midwest has soil that deep. So does eastern Washington and northern Idaho (Camas and Palouse prairies).

But specifically, the dry lake they dropped the thing at in Nevada.
 
If that's the case it's lake sediments, definitely not soil (ie the organic rich upper layers). Let's call it alluvium. I'm surprised it only went 50m.

Anyone got a number for granite?

Chris
 
Granite yield strength is on the order of 20k psi, which is similar to some high-strength concretes used in bunkers. So, penetration in granite is usually estimated as being similar.
 
Granite yield strength is on the order of 20k psi, which is similar to some high-strength concretes used in bunkers. So, penetration in granite is usually estimated as being similar.
I thought concrete went way higher than 20ksi. I recall them testing super hard missile silos at 50ksi.

huh:


"Cooper said present Minuteman silos, in which the new MX missiles are to be placed beginning in December 1986, could withstand "about" 2,000 pounds of pressure per square inch (psi) from a nuclear blast. Recent tests on a one-fifth scale silo using the new cement and steel construction techniques "indicate we should be able to realize hardnesses up to 100,000 psi," Cooper said."
 
Concrete yields are extremely variable. Those 50kpsi and up versions are very exotic, with things like steel fibers in the mix. I think 20k is about the baseline for "typical" hardened military facilities.

See, for example:


As Air Force Brigadier General Scott Vander Hamm explained to Air Force Magazine, the MOP “is specifically designed to go after very dense targets-solid granite, 20,000 (pounds per square inch) concrete, and those hard and deeply buried complexes-where enemies are putting things that the President of the United States wants to hold at risk.”
 
Concrete yields are extremely variable. Those 50kpsi and up versions are very exotic, with things like steel fibers in the mix. I think 20k is about the baseline for "typical" hardened military facilities.

See, for example:

At risk of going OT (though not too much as we're talking about bunker busting):


Interestingly enough, the concrete there at the end, with the metal fibers, matches the description of "Fondag" fragments found around Boca Chica after the first Starship launch. Oh, and this:

 

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