Thread by @MikeBlack114

I've had folks hit me up asking for sources/background on the DPICM/UXO rate discussion. Unfortunately there's not one good gold standard source, because it's not like anyone is doing peer reviewed studies on the UXO rates of US submunitions

And the people who should know best (DoD) can't exactly be trusted given their demonstrated repeated obfuscation and repetition of incorrect statements on the subject

So this will attempt to lay out the facts as best anyone knows them and provide some of the technical background

For starters read @johnismay, he's been on this "beat" (I think he's the only one) for several years, and he's got the technical background to understand this topic specifically intimately well

Here's his piece on DPICM:

nytimes.com/2023/07/07/us/…

You can read that and get the general gist of everything else I'm about to say, but I'll pull on the thread a little further to amplify some of the stuff he lays out there

So as folk hopefully know, DPICM in this context is referring to submunition equipped 155mm artillery shells, armed with a payload of M42/M46 submunitions

(They're effectively the same thing but the M46 has some physical differences to account for different stress when fired)

It's important to be specific with what we're talking about, because many aspects of this conversation have been conflating all sorts of different systems and their UXO rate, effectiveness, target sets, etc

From a technical perspective, the M42 is about the size of a d-cell battery, contains about 30 grams of explosives (so 1 oz), is scored to fragment, and ostensibly has a shaped charge capability to penetrate armor

I say ostensibly, because while the explosive is shaped to produce a shaped charge, any shaped charge is contingent on three things: amount of explosive force and (more importantly) standoff from the impact surface and diameter of the charge

The why is "physics," and I don't want to go too far down a rabbit hole, but suffice to say a traditional non-EFP shaped charge with 1 oz of explosive, an inch and change of standoff for the jet to form, and less than an inch in diameter isn't an armor killing titan

Even the Army's glossy brochure value from the TM cites a penetration of 2.75" against the armor benchmark (RHA), which isn't going to achieve great effects even coming in from the top on most tanks

.@johnismay wrote a good article on the mythmaking surrounding DPICM, effectiveness, and "steel rain"

nytimes.com/2020/01/15/mag…

Includes this minor tidbit of the supposedly armor piercing submunitions' effects on Chevy Blazers

Given this was solidly in the Like A Rock era of Chevy ads, missed opportunity here for them to capitalize on this I think

From a UXO perspective, the M42 arming train functions in series. This is important because unlike something involving parallel processes, each step in the arming process has to function correctly, otherwise the submunition won't detonate (but may still be partially armed)

That process straight out of the TM:

(Sourced here, I can't directly vouch for it but it seems to be legit)
https://t.co/lJOD4OAFYSbulletpicker.com/pdf/TM%2043-00…

A nylon ribbon has to provide enough force to pull a firing pin (semi-armed), which then allows a slide to shift (armed), and then to detonate the submunition must impact a hard enough surface at the correct angle to provide the physical impulse to drive the firing pin

(from this document, on lower UXO DPICM replacement possibilities: )…iastorage.blob.core.usgovcloudapi.net/ndia/2016/arma…

If you're wondering why they'd come up with such an apparently basic and prone to failure design, UXO wasn't much of a consideration when the M42 was being designed, and cost is a key consideration given the scales here; 72+ submunitions per artillery shell, millions of shells...

Which is a good shift to the first source: a fascinating Army War College paper from 1993

https://t.co/ydWrZ32dPVapps.dtic.mil/sti/pdfs/ADA26…

One important caveat: this paper takes the published UXO rates at face value, so I would not use it as a source for that. What it is useful on is getting a snapshot into the mindset of DoD and UXO in Desert Storm (horrible) and the scope of UXO, even when using published rates

I'll just include some excerpts from it

This is a good pivot, because as the paper suggests, data from CMS or other cleanup contractors would indeed be useful data

Guess what GAO dug up a decade later?

With the obvious caveat that the denominator (total rounds fired) matters here, I think this table speaks pretty well for itself

https://t.co/liiJQm6Q6ogao.gov/assets/gao-02-…

more excerpts

DoD: "your data is wrong"

GAO: "please, by all means, show us where and provide alternative data, we'd be happy to include it in our report"

DoD: <...>

I find it interesting that in a report that was supposed to focus on landmines, the GAO found that UXO from submunitions was a potentially greater problem

That's a statement with a lot of nuance and situationally dependent variables ofc, but it speaks to the scope of the problem

It's worth highlighting that the stuff UKR has promised to do (avoid use in built up areas, limit use to when militarily necessary, keep detailed records of employment to facilitate cleanup) are all things we did not do sufficiently in Desert Storm and were ID'd as best practices

Some more good reporting from @johnismay

nytimes.com/2023/07/06/wor…

And if you want a look at another type of submunition (one that is significantly more effective than M42, but also I think it is fair to say has a significantly higher dud rate and is significantly more dangerous) check out his deep dive on the BLU-97/CEM

nytimes.com/2019/12/04/mag…

I'll throw in gift links to all the NYT articles on a reply below them (the link didn't appear to be parsing correctly when I added them in so didn't want to risk breaking the thread, thanks elon)

nytimes.com/2023/07/07/us/…

nytimes.com/2020/01/15/mag…

@johnismay nytimes.com/2023/07/06/wor…

nytimes.com/2019/12/04/mag…

Also I should note that this shouldn't be taken as reflexive opposition on my part to providing M42/46 equipped shells. Like I've said elsewhere it's a complicated topic with so many tradeoffs there isn't a good solution, like most things in this or any war

But the discussion and opinions on the decision to send should proceed from a common set of facts, and the discourse on here re: effectiveness and DoD's statements re: UXO rate do not align with reality

@DefenseBulletin and obviously stuff that other countries have made (Eastern Bloc specifically) is often even worse

But the one thing that is important to remember about submunitions that is different than unitary warheads is their size and failure mode

@DefenseBulletin very few people would mistake a dudded artillery shell or bomb for anything other than what it is, and it's going to be of a size that it's easily noticeable (easing cleanup). Obviously that's not true for submunitions

@DefenseBulletin second is that dudded unitary warheads generally had an interruption of the firing sequence, so while they may be partially armed and are still dangerous regardless, are unlikely to be in a fully armed state sitting around undetonated

@DefenseBulletin while that can and does happen with submunitions, it's also very possible that they fully armed but failed to detonate (soft ground/sand/mud/impact angle/etc), and are now lying around in a fully armed state, increasing hazard if disturbed relative to a unitary dud