The LCS USS Jackson
“The ship performed exceptionally well, sustaining
minimal damage and returned to port under her own power.” (1)
On the other hand, there’s
this.
“The Jackson
Six weeks to repair damage
from a blast detonated around 100 yards from the ship seems a bit excessive
but, to be fair, I don’t know what typical shock testing damage is to any
ship. This seems excessive but perhaps
it’s not. Maybe someone out there has
some experience with this kind of testing and can tell us about it?
The repairs were conducted
by LCS manufacturer Austal under a repair contract from the Navy.
“The work was led by Austal USA Jacksonville Florida Kent
That’s $11.2M of repair work
from a not very near blast. Again, it
seems excessive.
Now, here’s an interesting
item. It appears from the video of the
test that the Jackson
 |
| LCS Shock Test |
As you know, the Navy has a
slight tendency to put a gargantuanly positive spin on even the worst
incidents. Before I pass judgment on
whether the LCS performed well or not, I’ll wait to hear what DOT&E has to
say.
________________________________
(1)DoDBuzz website, “VIDEO:
Littoral Combat Ship Withstands Wallops at Sea”, Brendan McGarry, 15-Sep-2016 ,
(2)Defense News website,
“LCS Jackson Completes Repairs, Is Back at Sea”, Christopher Cavas, 1-Sep-2016 ,
What was the weight of the explosive? Judging from the blast in comparison to the ship, Im guessing around 500lb.
ReplyDeleteAs in regards to the 57mm, they may have removed it in case the ship sank, waste not.
In the linked article, it says 10,000 lb of an unidentified explosive.
DeleteNo, it seems highly unlikely that the gun was removed to prevent losing it if the ship sank. If the ship sank, there would be a lot of other, far more valuable items lost. Plus, no one believed the ship would sink. I'm assuming they removed the gun because they knew it could not withstand the shock but that's just speculation on my part.
Just read the link, 10,000lb charges three times. Wow.
ReplyDeleteIm actually surprised that it will only take 11mil to repair.
You'll also note that the closest explosion was 100 yds away. That's a long way off to sustain any damage at all.
Delete$11M damage from a blast 100 yds away seems excessive. What does that say about the ability of the ship to absorb an actual hit?
I didn't notice in the link what type of exsplosive was used. Depending on the relative effectiveness of it, tlit could have a considerable affect on how the shock wave behaves.
DeleteI've part if some large scale demolitions, the largest of which was 7k lb plus. Somethings just aren't adding up based on the pictures I've seen on this, by chance do you know of a link on the Navy's shock test standards and procedures?
I've never seen a detailed procedure for the testing. In general terms, it involves a series (three seems to be the number) of explosions starting far away and moving closer with each one. I don't know the amounts beyond the stated 10,000 lb of ??
DeleteI wasn't able to find any listed standard either. Until we can find out more details in regards to type of explosive and depth of detonation, I would be suspicious of this test.
DeleteIn addition to that, the Independence class only has a draft of 14 ft, so not only is the shock wave having less effect then normal, the angle of it reduces the effect even further.
DeleteSo the ship might have avoided more damage by being lifted up and away from the shock wave as well.
"I would be suspicious of this test."
DeleteSuspicious of what? It's a standard test protocol that's been performed on every ship class.
First off, I not making this out as some sort of conspiracy theory as others are implying. I just want to know if any special conditions were made in regards to testing. I also put forth a theory in regards to why I might be wrong.
DeleteMy main concern with all this testing, and why im suspicious of it, is yet again with the type of exsplosive and depth. For example, since we can find no information on it, whats to say they did not use a military explosive but a commercial one. Which makes sense in MY experience which explosives because 30000 POUNDS of military grade explosive is prohibitively more expensive then ammonia nitrate. However ammonia nitrate only has an RE factor of .42, compared to C4's 1.34 and until we find out that kind of information Ill shall remain suspicious of this test.
Im just hesitant to stand by a test when I don't know all the facts. Until we establish type and depth of the explosion and the type of actual damage incurred.
DeleteFor those stating we shouldn't know the answers to those questions due classification reasons, why? How the ship reacted to a shock test or the standards for the test offer no advantage to our potential enemies.
In regards to "moonhowling", Im not claiming a conspiracy. I even suggested a possibility for why I might wrong. I just stated in my experience that details aren't adding up, hence why I would like clarification on these details.
"My main concern with all this testing, and why im suspicious of it, is yet again with the type of exsplosive and depth."
DeleteI'm still completely lost as to what you're suspicious of? Are you thinking that the test was rigged to make the LCS look better than it is? Rigged to make it look worse?
As far as we know, no one is questioning the test itself other than my question about why the gun was removed. From what I read, the test was pretty standard for all ship class shock testing.
According to "Measurement of naval ship responses to underwater explosion shock loadings", referencing "NAVSEA, Ship Post-Delivery Tests and Trials Guidance Manual,
DeleteNAVSEA 0900-LP-095-3010", the charge is 1,200 lbs of for ships under 425ft, 10,000lbs for ships between 425 to 625ft and 40,000lbs for ships greater than 625ft, all of HBX-1 explosive (RE = 1.3).
The force of the explosion cause shore based seismographs to register 3.8 and the blast wave was registered all the way to Kansas. Anyone doubting the size of the explosion is barking up the wrong tree.
Thank you. I was trying to firgure out if they were using an ammonia nitrate composition (pure AN = RE .42) or pentolite ( RE 1.3). Due the size of each of explosion being 10k lbs and pentolite being phased I was afraid that they did a bulk buy of AN composition which 1) is relatively weak and 2) adversely affect by H20 chemically.
DeleteAgain thank you, and Ill be sure to check out that link. MIL-STD 810, Test method 5.16.6 was to vague for my liking.
On a side note what are the acceptable parameters for shock testing?
ReplyDeleteOne down, one more LCS type to be tested. ?
ReplyDeleteSo what damage is "expected" during a shock test? Or is it more of an experiment to see if the engineering stood up
ReplyDeleteI think the clue is in the phrases : "I don’t know what typical shock testing damage is to any ship." and "You'll also note that the closest explosion was 100 yds away. That's a long way off to sustain any damage at all."
ReplyDeleteThe first statement is at least honest. The second is the worst sort of uninformed speculation. Do you have any idea of the relationship between charge weight, stand-off distance (and angle) and water depth? Or indeed what the actuation distance and/or lethal radius of a ground mine is?
No-one who does know that relationship or how to do shock trials is going to put that sort of information out on a public forum. Let's just remind ourselves that 5 tons of explosive is significantly higher than pretty much any UW threat weapon out there. Let's also remind ourselves that as an essentially incompressible fluid, water is very good at transmitting energy and finally that the physics of Undex are dynamic and complex. Non-contact, stand-off detonations are the ones that kill ships.
Shock trials are always a compromise between safety and cost. That doesn't mean they are "rigged" or somehow fiddled. Statements like "Until we can find out more details in regards to type of explosive and depth of detonation, I would be suspicious of this test" are the worst sort of internet conspiracy moonhowling.
On the cost of post trial rectification - have a little think about this. To properly check and repair any damage, shipyard staff are going to have to go over every compartment and every system, physically. You don't get a BITE system that (for example) detects cracks in pipes, pipe hangers, stiffeners, cable supports, equipment seatings etc. To do that you have to survey the entire ship, in detail, draining and gas-freeing tanks and fluid systems among other things. All of which costs money, because it takes lots of manhours.
I know it doesn't fit the preferred narrative that LCS is a dog and that the Navy are trying to swindle the taxpayer and hide their incompetence, but I'm afraid in this instance, the shock trials appear to have demonstrated that the ship ain't that bad.
"The second is the worst sort of uninformed speculation."
DeleteYou make this statement and then proceed to speculate on the positivity of the test without any informed knowledge. That's hilarious!
Is this idiotic or am I confused? A shock test is to identify weaknesses in a ship design that can be corrected and incorporated in future ships yet to be built. The first LCS was launched in 2006 and commissioned in 2008, so I would assume a shock test was done in 2007.
ReplyDeleteBut now we have 24 LCS in commission or near completion, and some Admiral says "Time for shock test!" Is this competence or corruption? I assume any problems identified require sending all 24 to the yards for millions of dollars of corrections.
They will shock test the first in class Ford carrier, but that idea suddenly arose when it was time to start launching aircraft. The unexpected shock test will take two years for some reason.
For reasons unknown to anyone outside the Navy, the Navy has all but abandoned test in general, when they can, and shock testing, in particular. The Navy declined to do shock testing when the first LCS's were built and had no plans to do it at any point until DOT&E stepped in and, basically, spanked them. This produced the current LCS shock testing and resulted in a mandated Ford shock test. The Navy had proposed putting off Ford class shock testing until some vague, undefined point well in the future.
DeleteYou note, correctly, that the point of shock testing is to be able to incorporate changes into the production run. Running shock tests years after the first ship is produced can't accomplish that.
I assume that the reason the Navy is resisting shock testing is because they've moved extensively into lighter weight construction and all but eliminated shock hardening from components. They know that shock testing will not go well and, therefore, don't want to do it. Just speculation on my part.
The Ford shock testing will not take two years. That's the Navy throwing a childish tantrum and trying to make people think that shock tests are some kind of huge affair. They're not. They've been routinely performed for decades.
The Navy has been trying to move to component based physical testing and full ship simulation testing instead of full ship physical shock testing. They have real reasons for doing this.
DeleteBeyond the actual cost of physical shock tests, there are lots of political/enviromental issues involved. Setting off a 10,000-40,000 lbs HBX-1 charge underwater has serious ramification for sea life and also causes significant civilian disturbance (the LCS tests resulted in a 3.8 earthquake on land for instance).
A Ford class shock test would entail 3 rounds of 40,000lb HBX-1 charges being set off which will have rather significant enviromental impact and either require them to be very far out to sea in an isolated area from all commercial traffic or have significant shock effect on shore.
The advances in computer simulation has given the Navy hope that they can avoid the massive planning and political issues surrounding real life shock tests. Most of the historical shock tests have been run in days where things like environmental concerns weren't real issues. So I don't think the speculation around lighter weight construction is really valid as a reason.
"The advances in computer simulation "
DeleteThere have been advances in simulations of all sorts, however, simulations are still found to be significantly wanting in terms of accuracy. We've simulated the construction of Ford, for example, and the simulations failed with large degrees of redesign required. We've simulated the SSDS and it's failed almost completely. We simulated the F-35 and - well, no need to comment on that. Every weapon system built in the last couple decades has been thoroughly simulated and yet found wanting when subjected to real tests. And so on.
Yes, there are environmental concerns with physical testing but there is, as yet, no practical substitute. One has only to read the litany of failures documented by DOT&E to see that.
Part 1.
ReplyDeleteAs a point of order, I'm not mocking anyone - merely pointing out that your statement on 100yds being a long way was unsupported by anything other than your own (self-admitted) lack of expertise. Your first reply kicked off any mocking on this thread.
In terms of relevant knowledge, I'm a naval engineer of 25+ years experience. I've designed warships, built warships, been to sea on warships and of particular relevance to this debate, I've specified machine-based and full-scale shock tests, attended the trials and supervised the post test and post-trial analysis. I've been to SAVIAC (now SAVE) in the US and know a few of the NAVSEA guys in the field. Perhaps you'd care to elaborate on your background?
No-one is going to outline classified standards and procedures on a public domain thread and because I don't have access to the specific trial order for the LCS shock trial I can't say how deep the charge was, nor the type of explosive, nor why the gun was landed. That data will be in classified reports, as it allows you to work out what the design shock levels might be, if you know the relevant equations.
That said, you can do two types of full-scale trial - one using large charges at slightly larger stand-off ranges or one using smaller charges at closer ranges. The advantage of the second method is that you can get more focussed effects along a specific part of the hull, whereas the former method just aims to subject the whole ship to a shock wave. the charge weights tell me that it's the first type of trial. The purpose of these trials tends to be multifold. At one level it's a proving trial to ensure that the ship and it's systems meet (or get close to) the design shock levels. It also allows you to identify unexpected points of failure in overall systems - which are usually down to factors like inadequate shock clearances for equipment, incorrectly fitted mounts, component level items that may not be correctly specified or mounted and soforth. Not show-stoppers, just things that need identifying and then fixing, like circuit breakers popping, pipe/cable hangers fracturing. You also tend to instrument the trial ship reasonably extensively, because the opportunities for trials are very limited these days and computer models need validation data. Which also helps post trial analysis if you find anything unusual.
The sorts of damage you get tend to be minor structural damage (you've done something properly wrong if you get major structural damage), like fractured welds, a bit of plate dishing, fractured stiffeners, distorted seatings, cracked castings.
Equipment damage can be caused by insufficient mount clearance or equipment clearance which means the equipment grounds out under acceleration and puts more energy into the kit than it is designed to absorb. More seriously, if your mounts or fasteners are wrong, you get loss of captivity, which is where the equipment starts moving at high speed across the compartment with usually serious if not fatal consequences. Thankfully, not a frequent occurrence, but has been known. What you usually find is cable/pipe hangers giving way, pipes or their joints failing, lagging becoming detached, bits of dustproofing / linings failing and so forth. However, it needs a whole ship check to find it, which is where you end up with effort and cost.
Not sure what you mean by combat explosives damage. It's not a term used in survivability or damage mechanism engineering.
Part 2.
DeleteI personally wouldn't use Wiki as a reference source. But on your specific point on submarines, have a think about these factors. Submarine hulls are pressure vessels designed to withstand significant design pressure, in addition to shock loads - at depth. That tends to mean that they use much thicker and higher strength plating than ships. Have a go at speculating on the difference in plate thickness and strength between your typical surface ship and your submarine. Happily surprise me....
You're also missing that there are different design levels for shock for float/move/fight functions. The float function is usually defined by hull rupture. Much lower levels of shock are capable of causing machinery and equipment to fail. The shock load experienced by equipment in a surface ship is also affected by whereabouts it is located in the ship. This is a much less prevalent effect in a submarine.
So 15ft to cause hull rupture in a WW2 submarine does not mean that a charge some hundreds of yards away will not have an effect on a surface ship and its equipment. Shock effects are dynamic and affected by stand-off, charge size, bottom topography, depth and a number of other factors. Simplistic comparisons with Wiki are I'm afraid, just that.
The cost of post trial rectification tends to be dependent on the size of the ship and complexity of its systems, the scope of the trial and any instrumentation fitted. Because we do so few trials these days, there isn't a ready-reckoner. Suffice to say that based on the size and complexity of the ship, and the damage identified in the Defense news report, the cost published is of the right order.
The LCS has reduced levels of shock hardening compared to a 2normal" warship. What is important is the scale of that reduction, which is classified. That doesn't mean by the way that the LCS will fall apart when subjected to shock. What it means is that a lower level of shock will cause equipment failures. That may be operationally important, or it may not. It depends entirely on the mode of failure and how critical it is. The likely effect may be to constrain to some degree the depth of water (ie how shallow you can go) without exposure to a mine threat that would cause unacceptable damage. It's a relative, not absolute effect and the actual numbers are and will remain classified.
Your last point on damage sustained at 100yds compared to a cruise missile hit exhibits I'm afraid a complete lack of understanding of the damage mechanisms that are in play here. Shock is primarily an UW mechanism. A cruise missile imparts very different damage mechanisms. Care to expound on what they might be?
Hopefully that's authoritative and informative enough for you......
See? Now that wasn't so hard, was it? A bit snarky still but at least helpful!
DeleteOkay, to address a couple of specific points...
"Have a go at speculating on the difference in plate thickness and strength between your typical surface ship and your submarine."
Nowhere have I suggested that hull rupture is an issue in this testing (could, theoretically, happen, I suppose, but no one expects that). The point about depth charges is that the shock transmitted to and through the hull to the equipment on board a sub would be significant. The hull thickness has little bearing other than as a transmission medium. I posed the question about correlation between a depth charge shock effect at close range and a test charge at 100 yds. I simply note that submarines suffered relatively little shock damage under those conditions and, therefore, can't help but wonder about the degree of damage to be expected from a charge 100 yds away, though admittedly a much larger charge.
"Shock is primarily an UW mechanism."
No. Shock is a vibratory mechanism. The imparted movement of a ship or its contents in response to an outside (meaning a non-normal) force is defined as shock. Shock, in this context, is typically imparted by an explosion but can occur by other mechanisms. A shell from a naval gun imparts shock to the ship when it explodes on, in, or near the ship. Similarly, a cruise missile imparts shock when it explodes. In fact, a ship's own gun imparts shock when it fires. Many ships have experienced self-damage when firing their own guns, battleships being the extreme example of this phenomenon. Thus, any explosion in, on, or near the ship will impart shock throughout the ship. The ship's structure will be subjected to vibration frequencies (whiplash, to use a descriptive word) for a period of time.
The vibration need not be high frequency to cause damage. The example of the Port Royal which grounded and suffered severe or irreparable damage to its VLS and Aegis arrays (depending on which Navy statement you believe) is an example of a very low frequency shock wave induced by the gentle rolling of the grounded ship until it was freed. Despite the very low frequency, significant damage occurred.
I do not have any idea how the magnitude of the shock of an underwater charge 100 yds away compares to the shock from a cruise missile or shell hitting (or near-missing) but this is certainly one of the points of the testing.
Continued ...
Continued ...
DeleteI assume that the point of the underwater charge 100 yds away is to eliminate shrapnel damage that would come from an air burst, stay far enough away to ensure no hull rupture, but get close enough with a large enough charge to ensure the induction of a sufficient vibratory frequency on/in the ship to be able to assess its resilience to shock from whatever source it might encounter.
Having said all that, I will repeat my pure speculation that $11M (around 3% of the reported cost of the ship construction) seems excessive from a charge 100 yds away. If that damage and cost were to scale up to the Ford, the repair cost would be $42M (3% of $14B construction cost). I have no idea whether damage scales linearly with ship size. My speculation about the degree of damage may or may not be correct but is certainly reasonable speculation. The lightness of construction of the LCS and the reduced levels of shock hardening built into the ship's components would, logically, lead one to expect more damage than would be typical for a warship. Indeed, the Navy basically said so when they stated that the damage was less than expected. They, apparently, shared my belief that greater than normal damage was possible. So, I'm left with the speculation that while the damage may have been less than expected, it was still greater than ought to occur on a warship. Again, maybe right, maybe not but certainly a reasonable speculation as opposed to your original assertion that I was engaged in the "worst sort of uninformed speculation". Quite the opposite, the speculation, clearly noted as such, was quite reasonable.
I wish you would have started with your most recent informative comment but at least you've gotten to the right place eventually.
Feel free to add additional helpful and informative commentary, if you have any. This, now, is the kind of discussion I like to encourage from readers.
You appear to be looking for an argument rather than a discussion so I'm deleting any further comments.
DeleteIndependent class LCS has aluminum hull, and AL is 1/3 of strength of common steel, so I would assume this shock test was tailor made for AL, not steel ship.
DeleteI have no idea whether the test was tailored for the particular ship though you make a good point about aluminum. I assume that the charge distance from the hull is sufficient to ensure that the hull is not damaged. The Navy doesn't want to accidentally sink a ship during testing! My vague understanding is that these tests are pretty standardized - not sure if that's true or not.
DeleteHi ComNav,
DeleteIf you want to get up to speed on underwater shock testing, this reference is as good as it gets. See section XV, and the damage-range charts for an indication of the physics of the inputs and the format of the outputs.
Enjoy.
http://ibiblio.org/hyperwar/USN/WarDamageReports/SummWarDamageSub7DEC41-12AUG45/SummWarDamageSub7DEC41-12AUG45.html#SECTION%20XV
Also, I thought anonymous, above, was a complete tool.
Thanks for that link. I read section XV and it is fascinating. Unfortunately, it only describes the underwater explosion phenomenon and stops short of explaining the mechanism of transfer of the shock wave into the ship and the subsequent damage. On the other hand, the transfer mechanism and subsequent damage is readily apparent, I think.
DeleteGreat link. Thanks!
Please be polite and respectful regardless of personal opinions!
All the public test parameters appear to be straight out of the manual including charge sizing and ship distance. The only variable we don't know is charge depth which is a variable that is different for each ship (basically they are trying to get a specific shock magnitude into the hull based on a formula with some classified constants).
DeleteAlso a 10k lbs HDX-1 explosion 100 yards away isn't something small. That's a large enough of an explosion for be detectable upwards of a thousand miles away. For comparison sake, if you were in the water 100 yards away, you would pretty much be dead instantly.
DeleteIn case anyone missed the video
ReplyDeletehttps://www.youtube.com/watch?v=4jdnG90ipo8