PUMA - Ultimate IFV presented

[Falstaff]

As a post OT...
Energy is the integral of force wrt position, so if you have the energy, you are saying something about the magnitude of forces that have acted across the path of action

You're mixing up energy and mechanical work which indeed means integrating a force along a "path" or mathematical curve.
The amount of kinetic energy a mass posesses is a mere product of mass and squared velocity, as what counts is the final amount of energy, not what happens during the acceleration phase.
Momentum (linear momentum) is the product of mass and velocity.

Though flagstaff, regardless of the porportion between mass and velocity I think my argumentation holds since it concerns the total kinetic energy delivered, thus the kinetic energy avaliable for the penetration process.

Well I didn't want to say that you're wrong. I just wanted to state is that there is another feasible way to make a gun more powerful than adding caliber, esp. when penetration power is concerned. That's all.

 

[Palnatoke]

You're mixing up energy and mechanical work which indeed means integrating a force along a "path" or mathematical curve.

No, I am trying to connect the energy to the deformation of the material. Simple example: we are pushing a rod through some bucket of magnetic balls (no gravity). everytime we push a ball aside, we would need to exert a force greater than the magnetic binding force that keeps the ball in place. We do this until we reach the bottom of the bucket. The energy we would have spendt would be the integral of the force (needed in every step (position) to push a ball aside).

I am just trying to derive why, as you say, it's the integral of the force wrt position (that'll be the energy) and not time (momentum) that's the interesting meassure.

 

[Falstaff]

Simple example: we are pushing a rod through some bucket of magnetic balls (no gravity). everytime we push a ball aside, we would need to exert a force greater than the magnetic binding force that keeps the ball in place. We do this until we reach the bottom of the bucket. The energy we would have spendt would be the integral of the force (needed in every step (position) to push a ball aside).

No, that would be the mechanical work you'd have to invest. The amount of energy you'd need would be the sum of magnetic potential energy you're creating by seperating the balls.

I think you're making it too complex. What happens when you want to punch a hole into steel at very high speeds is first elastic, then plastic deformation, liquidation under immense pressure and temperature, displacement. The energy our rod has is transformed into the according amounts of different kinds of energy (thermal, chemical, and so on). Think of flame-cutting, just that the required energy is provided by (transformed from) the energy the rod had at the time of impact. Or think of steel machining with very high cutting speeds.

 

[Palnatoke]

No, that would be the mechanical work you'd have to invest. The amount of energy you'd need would be the sum of magnetic potential energy you're creating by seperating the balls.

I think that would be the same, mechanical work=energy ; I only offer a generalised description, trying to sort out the momentum/energy discussion.

I think you're making it too complex. What happens when you want to punch a hole into steel at very high speeds is first elastic, then plastic deformation, liquidation under immense pressure and temperature, displacement. The energy our rod has is transformed into the according amounts of different kinds of energy (thermal, chemical, and so on). Think of flame-cutting, just that the required energy is provided by (transformed from) the energy the rod had at the time of impact. Or think of steel machining with very high cutting speeds.

Yes, that's complex

 

[Firn]

IMO the momentum can't be an indicator because the material failure process that leads to the penetration isn't a matter of (Newton's) motion mechanics.

Explaining ideas in physics in English seems to be for me harder than usual

Saying that momentum is a better "indicator" than kinetic energy for the penetration power of projectile, let us say fired by the L55 of Rheinmetall might be not correct. Momentum is certainly a far better yardstick than kinetic energy to judge the "penetration power" of things like musket bullets, arrows and similar implements. But you surly rightly point out the elements of the process which happen when such a heavy and dense rod hits at 1500 m/s + an armor are so that KE becomes the better yardstick or indicator.

I think you're making it too complex. What happens when you want to punch a hole into steel at very high speeds is first elastic, then plastic deformation, liquidation under immense pressure and temperature, displacement. The energy our rod has is transformed into the according amounts of different kinds of energy (thermal, chemical, and so on). Think of flame-cutting, just that the required energy is provided by (transformed from) the energy the rod had at the time of impact. Or think of steel machining with very high cutting speeds.

I assume that the specific actions (especially the liquidation) the heavy launched rod performs to penetrate a thick modern armor require a certain amount of kinetic energy with a high amount of for the component "speed". Still there seems to be a lot of balancing between the mass and the velocity and a aweful lot of other factors. Things like how large must the cross section of the rod with a given hardness and KE/momentum be to perform flawlessy. How small can the cross section be to achieve a higher velocity and thus the KE without transforming the stored work of the explosives too ineffeciently?

All in all really an interesting topic, with good imput. Let us hope the men in the Puma never have to be at receiving end of such complex physics...

 

[Falstaff]

I think that would be the same, mechanical work=energy ; I only offer a generalised description, trying to sort out the momentum/energy discussion.

Uhm, well, I feel a littlebit uncomfortable with this. While work and energy share the same dimension I'd feel better saying that "work" is the difference between two states of mechanical energy such as kinetic and potential energy. As there are other kinds of energy involved, I think that "energy" is easier to handle.

All in all really an interesting topic, with good imput. Let us hope the men in the Puma never have to be at receiving end of such complex physics...

Did you forget we're working on it the other way round?

 

[Firn]

Did you forget we're working on it the other way round?

Certainly not, and I think it will be a huge step forward. Of course other aspects are still important. Good for the crew that the Puma is also in this regards the new benchmark

Such projects are also partly the reason why I think that the machine cannons shoud be able to penetrate the frontal arc of every AFV bar an MBT and have a ROF high enough to overwhelm the active defense systems.

 

[Palnatoke]

Fallstaff

I don't think we disagree, we are saying the same thing with different words. As I read you, I think you have a more analytic or hamiltonian approch to mechanics, than the "classical" mechanic.

 

[Falstaff]

I don't think we disagree, we are saying the same thing with different words. As I read you, I think you have a more analytic or hamiltonian approch to mechanics, than the "classical" mechanic.

Wise words to close this discussion- I'm due for bed anyway

Firn, thanks for the link, I somehow missed that one. BTW both links lead to the same one- intentionally?

 

[Firn]

Wise words to close this discussion- I'm due for bed anyway

Firn, thanks for the link, I somehow missed that one. BTW both links lead to the same one- intentionally?

Corrected.

P.S: The second one also reminded me that sheer weight is in itself a big mitigating factor against blast mines or IEDs, as it can greatly reduce the savage acceleration of the vehicle and thus the one of the crew. The 40ms of shock also require excellent seats. Overall I rather liked the presentation.

The Stryker was already a huge leap forward in protection compared to an uparmored IED deathtrap aka Humvee. It is rather strange that the USA proved unable to take into account the many lessons of past conflicts and to equip their infantry forces with a decent wheeled APC before the Iraqi mess started. Quite a few, if not most European countries and companies proved to be far more farsighted in this regard.

 

[Firn]

This video of the F35's EO - DAS suite shows among other things how the pilote can see "through" the plane thanks to the thermal images projected on his helmet mounted display. Now that would be a neat thing to have in an heavily AFV.

Effective vision concept



Various optical and optronic devices provide the entire crew with an excellent 360° all-around surveillance, recognition and identification of targets by day and night and all weather conditions. Targets identified through vision blocks can immediately be displayed to the commander for further identification by operating the target allocator.

The primary panoramic sight of the commander is the independently stabilized n x 360° rotatable periscope with an optical daysight channel, which can be displayed on all monitors inside the vehicle by means of a CCD camera. The gunner’s sight with an optronic daysight channel is also independently stabilized. Both sights – with several fields of view – are equipped with identical thermal image sights and laser range finders.

Targets detected and identified by the commander using the periscope can be designated to the gunner for engagement. Immediately after target designation, the commander is ready to observe and identify new targets (hunter-killer function).

The vision concept combined with the innovative control and display concept for displaying of all optronic images on various monitors in the vehicle ensures the best possible situational awareness of the entire crew.


Allocation of sights


* Commander:

Glass optical sight (primary allocation)
images displayed on monitors: optronic daysight of commander and gunner, thermal image of commander and gunner, rear-mounted cameras
5 vision blocks and open-hatch view


* Gunner:

Glass optical sight (secondary allocation)
images displayed on monitors: optronic daysight of commander and gunner, thermal image of commander and gunner, rear-mounted cameras
1 vision block and 1 glass block


* Driver:

3 vision blocks, open-hatch view, 1 image intensifier and a display for the reversing camera


* Infantry squad:

2 displays for optronic images, 4 rear-mounted camera and 1 reversing camera, 2 vision blocks and 1 vision block rotary-mounted/1 image intensifier, open-hatch view (sliding hatch and partially opened rear ramp)

Certainly a most impressive array, I especially like the integration of the under armor infantry squad in the SA concept and the shared optronic images on the many displays.

First Bundeswehr tests

 

[eckherl]

Because at that time when greater energy was needed it was easier to increase the diameter instead of handling the increase in pressure that would have been needed. It always is.
But today as we understand material technology and simulation etc. much better, you can go for bigger propellant charges rather than bigger diameter.
It's a question of how much pressure your gun tube and breech can handle, and that as an alternating load when firing multiple rounds in automatic mode.
I'm not working with Rheinmetall but I guess that 2 decades ago the 120mm L55 gun would not have been doable with reasonable effort. Today it is.



Actually I didn't want to contradict you at all, my remark was more of an addition... Speaking of penetrating power, a more powerful 30mm would be feasible. Concerning the other points, well that's another matter.

Do you really think that propellant charges are getting bigger(in volume) or is it a matter of better, even distribution of ignition of the propellants. And why would the L55 not be doable two decades ago.

 

[eckherl]

Okay Waylander or Kato,

Just how many roadwheels is the final proto type/production Puma sporting. There are photos circulating showing 6 per side versus the usual proto type 5.

 

[Falstaff]

Okay Waylander or Kato,

Just how many roadwheels is the final proto type/production Puma sporting. There are photos circulating showing 6 per side versus the usual proto type 5.

Hi eckherl, the picture you provided shows the usual 5 roadwheels. Please consider that due to the unusual arrangement of the roadwheels one can easily have the impression that there are 6. Are there any other pictures?

 

[kato]

The current 5-wheel carriage is considered "too soft" by the WTD testing the prototypes, and a 6-wheel carriage was developed. This 6-wheel carriage was then tested and found to comply with requirements, and will therefore be on the production systems (or at least this is what the below source implies - "functionality : carriage performance qualified (due to improvement 6-wheel carriage)").

Can be found e.g. in "Infobrief Heer 03/09", page 15 (in German, no pics).

Haven't seen any pics of the prototype with 6 wheels, but its damn hard to find any pics of the Puma taken after 2007 anyway.

 

[Falstaff]

Haven't seen any pics of the prototype with 6 wheels, but its damn hard to find any pics of the Puma taken after 2007 anyway.

I haven't seen any either. After running some improvement routines to remove the dust cloud eckherl's pic shows a 5 wheeled Puma (still somwhat foggy, but I'm pretty sure). I'd really really like to see a picture with 6 roadwheels though.

 

[eckherl]

Here you go Falstaff, looks like they also shrouded the auto cannon. Thanks kato, do you know if this is the standard module armor layout that is shown in the photo.

 

[Waylander]

The picture shows the current layout of the C armor configuration.

As usual Kato was quick and already told that they added a 6th roadwheel.

IMHO they tried a gamble and hoped that they could safe some weight with just 5 roadwheels. But right from the start they also had plans for 6 wheels if the 5 wheels should prove to be too soft.

I have to say I have no idea why they gave the gun such a mantle. IIRC they encountered some accuracy problems during early trials and maybe the mantle helps to resolve them.

This photo is the newest one available as far as I know. But it doesn't show the twin spike launcher which is going to be on the left side of the turret.

 

[kato]

Official link to same pic in BIG:

http://www.kmweg.de/images/PUMA_Pressebild_02.jpg

The "mantle" around the gun is to better stabilize the barrel against vibration.

 

[Waylander]

So it is as I expected.
I wonder how the additional roadwheel and the gun mantle affect the overall weight of the vehicle...