Military History | How To Make War | Wars Around the World Rules of Use How to Behave on an Internet Forum
Surface Forces Discussion Board
   Return to Topic Page
Subject: Would it be better to build more Burkes rather than DDG 1000s?
Charles99    3/17/2008 6:53:39 PM
Or an incremental improvement of hte Burke? Given the economy and the already high expense of the DDG-1000's, we might end up with a very small number of high end platforms. The Burkes aren't going to be as capable, but on the other hand, we might be able to build more of them, and I'd lay odds that they'll still be the most powerful surface combatant on the oceans for a good long time. Would it make sense to go for more of the good as opposed to a little of hte best, or does the DDG-1000 give such a tremendous leap in capability that it would be better to buy them, even if only a few?
 
Quote    Reply

Show Only Poster Name and Title     Newest to Oldest
Pages: PREV  1 2 3 4 5 6 7 8 9 10 11 12 13   NEXT
B.Smitty       3/20/2008 2:13:15 PM


The gun may use propellant more efficiently, but is it more cost effective, when you tally up the additional complexity, weight and volume of the mount, and the significant engineering challenges of developing a guided, gun-launched missile?

Yes. With a shell you have a small boost engine and either an aerodynamic or reaction control system steering jets and the GCU whereas with the rocket you have a large propulsion motor in addition to all of the above-yielding a much larger projectile diminishing the cargo/propellant ratio of the projectile [rocket boosted shell shell can be as 70/30% by mass whereas the  rocket  for the same range rarely is  80/20%]  This is in spite of the thicker walls that a shell requires to withstand the extremely large magnitude sudden acceleration forces that throw it in the first step [stage].  The cost of a $30,000 shell  is also cheaper than the $80,000 equivalent rocket matching the SAME performance.


Does this look like a "small boost engine"?

http://www.globalsecurity.org/military/systems/munitions/images/lrlap-image8.gif">


Also, where do you get your prices for equivalent systems? 


 
Quote    Reply

B.Smitty       3/20/2008 2:15:51 PM
Also note the image above does NOT include the gun propellant required to launch LRLAP. 
 
Quote    Reply

doggtag    cost per system?   3/20/2008 4:27:29 PM
That's something I'm taking into effect.
Economies of scale dictate that LRLAPs are only going to be produced for a small number of DDG1000 hulls, and maybe any CG(X) hulls (providing they don't come at $10B a pop).
 
But a POLAR or P44-sized munition can be bought by anybody who can fire SeaSparrows and ESSM.
Much more money to be made over a longer production run (more customers),
and such numbers would equate to a lower overall cost per round manufactured (defense contractor can spread out overall program price across a broader number of munitions).
Thus, a POLAR or P44 could possibly (more than likely, by the numbers) come in cheaper than LRLAPs.
 
Quote    Reply

Herald12345    Manufacturers.   3/20/2008 5:22:40 PM





The gun may use propellant more efficiently, but is it more cost effective, when you tally up the additional complexity, weight and volume of the mount, and the significant engineering challenges of developing a guided, gun-launched missile?

Yes. With a shell you have a small boost engine and either an aerodynamic or reaction control system steering jets and the GCU whereas with the rocket you have a large propulsion motor in addition to all of the above-yielding a much larger projectile diminishing the cargo/propellant ratio of the projectile [rocket boosted shell shell can be as 70/30% by mass whereas the  rocket  for the same range rarely is  80/20%]  This is in spite of the thicker walls that a shell requires to withstand the extremely large magnitude sudden acceleration forces that throw it in the first step [stage].  The cost of a $30,000 shell  is also cheaper than the $80,000 equivalent rocket matching the SAME performance.




Does this look like a "small boost engine"?

http://www.globalsecurity.org/military/systems/munitions/images/lrlap-image8.gif">



Also, where do you get your prices for equivalent systems? 



Here.

ERGM was a failure in 2005 and has since been rebooted to try to get the costs per shell way down.

Costs of rocket assisted projectiles here.

Yes that is a small boost engine in comparison to this.

ATACM

Small cost as well.

Herald

 
Quote    Reply

Herald12345    Manufacturers.   3/20/2008 5:28:33 PM

Rockets are superior for range. The reason is that the amount of chamber pressure you can manage and the amount of acceleration you can produce in a fraction of a second is VERY finite. In a gun, you only have the length of a barrel with which to accelerate the projectile. In a rocket you can take minutes to do so if you wish. The advantages of throw weight per unit assembled ammunition volume or weight is also often off set by the size, weight, complexity and dedicated nature of a gun mount. For instance, instead of a 155mm mount and magazine you can use the space and weight for 360 10" class VLS to deliver firepower at a higher rate to a longer range. There is no turrent, no hoist, none of that. The VLS can also be used for other AshM, SAM or whatever ordnance unlike space in a gun magazine. The disadvantage is that per shot COST is much higher even for rockets with no terminal seekers -- one guided only by post launch TVS and GPS steered fins to impact.


A gun mount that can throw 327 shells occupies the same volume as 100 not 300 rockets as you describe [See PDF discussing USS Thorn conversion on the MIT PDF in the previous including COSTING that I provide you. That design study has been done.]

Herald.

 
Quote    Reply

ArtyEngineer    Herald   3/20/2008 6:10:08 PM
That MIT paper is a very good find, thanks for posting!!!  Brought back a lot of memories from my days dealing with big floaty things as opposed to things which go bang  ;)
 
Quote    Reply

B.Smitty       3/20/2008 11:48:17 PM


A gun mount that can throw 327 shells occupies the same volume as 100 not 300 rockets as you describe [See PDF discussing USS Thorn conversion on the MIT PDF in the previous including COSTING that I provide you. That design study has been done.]

Herald.


Hmm, ok, maybe I'm missing something. 

Option 1 in the Thorn conversion was to replace the 61 cell VLS and the 5" gun with an AGS and 320 rnds.  

The VLS alone could hold as many as 244 POLARS (a much more powerful munition than LRLAP), not counting ERMs on the 5" mount (if it was converted to MOD 4).

If we developed a ~7" diameter missile and a 9-packed container, the forward VLS could hold up to 549 rounds.  So the baseline Spruance could carry 549 x 7" missiles in the VLS, plus a full load of 5" rnds.

Replacing both with AGS only gives you 320 LRLAPs.

What am i missing? 

I'm not sure what you intended by posting a link to ATACMS.  Of course LRLAP has a smaller rocket motor than ATACMS.   LRLAP only weighs 230-260lbs, with a 24lb warhead.  ATACMS weights up to 3000lbs, with a 500lb unitary warhead.   Plus ATACMS has a range of up to 300 km, LRLAP - only half that.  So the two systems are not strictly comparable.


 
Quote    Reply

Herald12345    Individual launch cell size.   3/21/2008 12:06:14 AM
That is what you are missing. READ it again.,

Herald

 
Quote    Reply

B.Smitty       3/21/2008 9:26:26 AM
Herald,

I think you're going to have to spoon-feed it to me.

By my read, Mk41 cells can accomodate 21" diameter missiles up to 3000lbs.  They can also accomodate 4 x 10" diameter munitions (ESSM, POLAR).  What's the problem with taking this a step further and developing a canister to house 9 x ~7" diameter munitions in a 3 x 3 arrangement?   Weight might be an issue if we want to push the range of a P44-like missile out to 140km+.   P44 is a 70km+ missile weighing 220lbs.  We could lengthen it by 80lbs to 300lbs to accomodate a larger motor.  9 missiles would then be 2700lbs, which should be within Mk41's limits.



 
Quote    Reply

doggtag    would love to pick the pdf's Appendix A apart (pp 23-27), but it'll take sooo long!   3/21/2008 9:14:37 PM
...so I'll start small:
 
page 25, Anti-Surface Warfare / Strike Warfare
last few sentences:
"It might be possible to fit the DDG-51 with one of the 155mm guns to be carried by the DDG-1000; it would likely require the removal of both the DDG-51's 5-inch gun and its forward (32-cell) VLS. In this configuration, the DDG-51 might carry about 120 of the gun's 155mm shells.
 
   The 155mm guns on the DDG-1000 could be replaced in the future with an electromagnetic railgun or directed-energy weapon. The DDG-51 does not have enough electrical power to support such weapons."
 
A lot more speculation in there than proven fact:
"might be possible", would likely require" and "might carry about" aren't proof-positive, solid-numbers answers.
Sounds like a lot of estimation thrown in moreso than actual engineering facts (guesstimates based loosely around generalized equipment specs).
Estimation, speculation, and semi-educated guesses is something you expect from someone like me,
not from someone supposedly high up in a given military branch who's trying to make a hard-sell case for a specific weapon system or program.
 
Another issue is the power.
Yeah, as it sits now, a Burke is designed around 8MW of electrical generation.
(but remind me again the actual output capacity of those LM2500s: something like 33,000shp a piece?
That's what?
, if kW = hp x 0.746-ish, that's about 24&1/2 MW apiece,
providing they're coupled to adequate generators that can handle that mechanical torque.
In a perfect world, that's 98MW, if the Burke had room for the generators!)
 
Way back in the day, post-WW2 saw the USN undergo the FRAM Fleet Rehabilitation And Modernization,
in which many hulls were upgraded and improved:
excess gun mounts were replaced by early missile systems,
anaolg gun directors were replaced with early electronics equivalents,
radars were added,
better ASW systems,
some vessels even received the first shipborne helicopters in the USN.
And certainly, as those vessels became more power intensive, the means were found to incorporate additional power generation (even if not on the scale of the difference between a current Burke and what's anticipated in a DDG-1000).
 
Seeing as a single AGS mount and a full magazine is obviously not going occupy both the volume and weight of both the Mk45 and its systems and a 32-cell Mk41 VLS,
what're the odds that an additional newer-generation power generation system could be installed there also?
Let's not assume that the intention is solely to power a 64-MJ railgun: if that gun does ever manifest onto the DDG-1000, then rest assured that there will be numerous other railguns built of lesser calibers and power requirements, just as there are multiple calibers of chemical propellant guns today.
Same goes for directed-energy weapons: every laser, particle beam, or whatever kind of electron cannon or undiscovered particle technology gun isn't going to require 60+ MW of power to operate, not as we learn to refine the power efficiencies of its components.
And by that timeframe, it's well possible that military budgets will not be able to afford $15-20B on single ships equipped with these fanciful weapons, so it should be almost logical (and cost practical) to have some kind of future FRAM in the works in that day and age (more than just SLEP-ing a hull).
And it's a safe assumption that, even if the earliest production Burkes are reefs or third-world navy vessels by then, it's safe to assume that the most recently-built hulls will still be in USN service (especially if we expect to maintain a 300-ish ship navy for a few decades somewhere in the coming future).
 
The more high-tech bells, whistles, and gee-whiz gizmos that we develop in the coming years, the more expense they'll add to the next generation of completely new designs.
So certainly we need to expect that at some point they will need to be backwards-compatible enough to still be installed into that day and age's currently-in-service vessels.
 
Why do we need to assume that we'll only ever use a railgun on the DDG-1000?
Can't future powerplant designs offer much more juice than the Burke's current 8MW?
And will they be so utterly big to the point that there's no chance in hell they could be specifically engineered in mind to be
insta
 
Quote    Reply
PREV  1 2 3 4 5 6 7 8 9 10 11 12 13   NEXT



 Latest
 News
 
 Most
 Read
 
 Most
 Commented
 Hot
 Topics