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ougoah

Colonel
Registered Member
The boost phase last up to only 1.5 to 2km. Past the boost phase, the missile is an unpowered projectile. It's not much of an advantage.

Missile or DART, one will have the advantage over the other depending on which part of the engagement envelope you are looking at.

Sorry I missed the part where we were discussing DART. Yeah it depends on the engagement envelope.
 

ohan_qwe

Junior Member
Sure why not?

How much velocity an unpowered projo loses is a function of it's ballistic coefficient. Shape matters (Cd). Heft (Sd) matters as well.

Do you expect a snub nose 9mm parabellum round to maintain their velocity like a 30:1 l/d DU APFSDS round?

The velocity loss of the AIM-9L is charted per my previous post.
The velocity loss of the DART round is deduced from the statement by Leonardo that ToF to 5km is 5s. Given initial velocity of 1,100m/s, you can infer the velocity loss to 5km to be -200m/s. Nett velocity @ T+5s of 900m/s or 20%ish

There are open source statements that the initial muzzle velocity of DART is 1,200m/s which will make "5s to 5km" work out to 800m/s at 5km or a velocity loss of 33% over 5s. I'm more inclined to take this figure as the eyeball test of the DART projectile places it as somewhat similar to a DM13 APFSDS penetrator.

Look at the chart below for an indication of the velocity curve of the DM13.

View attachment 72536

The graph is v/d, but do a bit of maths and you can figure out the v/t.
Ballparking the figures, the Dm13 loses about 30% at T+5s while the M829 with better Sd only loses 20%. So the 20% velocity loss you seem so incredulous over is not that far fetched if you are shaped and weighted like an APFSDS.

Why is the missile so much worse? Probably because while it is shaped like an APFSDS (kind of), the Sd penalty of a hollow rocket body on the missile doesn't help.
I think that you error in velocity estimation comes from that turning bleeds much more energy than low drag APFSDS flying straight.

If the rocket turns while motor is still burning it could have better post turn kinetics.

A slower projectile also turns sharper with less radius compared to a fast one if both turn at 40G.

Looking at the size of the steering fins DART have much smaller fins and probably can only turn 40G at 1100m/s while missiles probably could turn 40G at slower velocities.
 

Heliox

New Member
Registered Member
I think that you error in velocity estimation comes from that turning bleeds much more energy than low drag APFSDS flying straight.

Nope. No error.
Those are for all examples flying straight and true.
There are separate curves for missiles pulling 5/10/15/20G. Trust me I didn't mix them up.

If the rocket turns while motor is still burning it could have better post turn kinetics.

Yes, I agreed that the missile defo has better kinematics up to T+5s or 1.5~2km while the rocket is still lit.

What I don't understand is why this is turning into a this vs that contest. I am not arguing if one system is better than another. I am just replying to misunderstandings and clarifying how things actually work vs how people think they work (wrongly).

Far as I'm concerned, there are more than a couple of hard kill methods for point defense and all of them have pro/cons that influence the adoption choice.


A slower projectile also turns sharper with less radius compared to a fast one if both turn at 40G.

Yes, but ....
This isn't ACM where you're trying to get your nose around for a guns/fox solution at the bogey.

Hard Kill Point Defense is an intercept maneuver. Not necessarily hit-to-kill but close as makes no difference. If you are turning tight and slow, you have just shrunk your engagement envelope against a faster missile.

Looking at the size of the steering fins DART have much smaller fins and probably can only turn 40G at 1100m/s while missiles probably could turn 40G at slower velocities.

Nuh uh.

At sea level, at slower velocities (anytime past T+8s, <~550m/s), the AIM9L is no longer capable of pulling 40G turns.
 

ohan_qwe

Junior Member
Nope. No error.
Those are for all examples flying straight and true.
There are separate curves for missiles pulling 5/10/15/20G. Trust me I didn't mix them up.
I ment assuming straight velocity while in practice it will turn. Because if it don't turn it won't hit anything past 3KM.
Specifically "DART, T+5s to 5km, V=800m/s"
Yes, I agreed that the missile defo has better kinematics up to T+5s or 1.5~2km while the rocket is still lit.
From pure energy perspective a bullet have highest energy when leaving the muzzle while rockets have most when the motor burns out. But when they start to turn I don't know anymore.
What I don't understand is why this is turning into a this vs that contest. I am not arguing if one system is better than another. I am just replying to misunderstandings and clarifying how things actually work vs how people think they work (wrongly).

Far as I'm concerned, there are more than a couple of hard kill methods for point defense and all of them have pro/cons that influence the adoption choice.
I just want to clarify the facts, sorry if you don't like the tone.
Yes, but ....
This isn't ACM where you're trying to get your nose around for a guns/fox solution at the bogey.

Hard Kill Point Defense is an intercept maneuver. Not necessarily hit-to-kill but close as makes no difference. If you are turning tight and slow, you have just shrunk your engagement envelope against a faster missile.
Assuming that the AShM is maneuvering like the latest missiles, turning radius may still matter.
Nuh uh.

At sea level, at slower velocities (anytime past T+8s, <~550m/s), the AIM9L is no longer capable of pulling 40G turns.
Yes, but can DART pull 40G at 550m/s or is it more like 1000m/s. Assuming that DART which you compare with an APFSDS is high density then the small wings must have downsides. Just look at a image of AIM9 compared to DART.
 

Heliox

New Member
Registered Member
I just want to clarify the facts, sorry if you don't like the tone.

Lighten up. There was no "You" pronoun in my reply.
Nothing wrong with your tone but that said, I don't like the direction this is going (see below)

I ment assuming straight velocity while in practice it will turn. Because if it don't turn it won't hit anything past 3KM.
Specifically "DART, T+5s to 5km, V=800m/s"

From pure energy perspective a bullet have highest energy when leaving the muzzle while rockets have most when the motor burns out. But when they start to turn I don't know anymore.

This was in answer to questions a unpowered guided projectile cannot do what a powered guided missile can because it can't match the kinematics of a powered missile. Not to state that the DART can outperform an AIM9L analogue (although it does at certain points).

The salient point being at T+5s, the missile is an unpowered projectile and that at a similar point in time, the unpowered DART has a better energy state than a post burn out AIM9L analogue.

Yes, they all lose energy turning but, ceteras parabus, starting from a higher energy state puts you in a better position than lower.


Assuming that the AShM is maneuvering like the latest missiles, turning radius may still matter.

I think you are still caught up in ACM imagery ;)

I don't know how wildly you picture AShMs to be maneuvering but again, this isn't ACM where the target is an aircraft with full freedom of movement cos all the aircraft wants to do is evade. Outside of a scenario with high off-bore targeting solutions, an aircraft will turn and turn to get outside your targeting cone and therefore turning radius is important.

OTOH, an AShM (the target here) needs to hit to kill. Which means the AShM, while performing evasive maneuvers, has an overriding constraint - it needs to minimise terminal miss distance.

A few things are at work here ...

Best case and typical AShM evasive maneuvers, eg. sinusoidal weave or conical barrel rolls, are deigned to provide lateral displacement, minimise profile presented to interceptors, while still maximising propagation towards the target.

These manuevers, while increasing the AShM missile survibability, also increases ToF to the target which increases the engagement window available to the target to bring it down. But it's considered a good trade off (for the AShM).

Anything more wild than that will only present a bigger side profile to the interceptor (a big win for dumb projos like CIWS) or significantly increase the ToF which dramatically reduces the "terror" of Supersonic/Hypersonic AShM. Either way, those are all wins for the defending platform.

Given the speed that the AShM is incoming and the type of maneuvers, it's lateral displacement and not turning radius that counts.

Yes, but can DART pull 40G at 550m/s or is it more like 1000m/s. Assuming that DART which you compare with an APFSDS is high density then the small wings must have downsides. Just look at a image of AIM9 compared to DART.

Have you even stopped to ask yourself why we even need to consider whether the DART can pull 40G at 550m/s? (which I didn't even assert btw)

You are trying to pull out a single datum point as a red herring which will lead us down a spiralling hole of point vs point arguments when I am trying to keep the discussion on principles vs principles.

It's like the way arguments erupt over platform evaluations in isolation instead of in context to systems.

I'll restate the point I was making at the start.

There are 2 traditional point defence hard kill solutions.
i) Small calibre guns with high ROF but unguided projos. ie. CIWS
ii) Short Range guided missiles

You need to start considering the possibility of also
iii) Medium to large calibre guns with slow ROF but using guided sub calibre munitions.

Much of the answers I have given is to clear up how people think missiles work or how a guided sub-calibre round can be effective.

I haven't claimed a missile is not effective.
I don't claim (iii) to be the superior solution to all.
I still think they all have pro/cons that determine their suitability for the task based on platform/system constraints.
 

Heliox

New Member
Registered Member
Btw is this thread for the PLAGF or just news for the PLA as a whole (including PLARF, PLAN, PLAAF, PLAGF)

Not to throw anyone under the bus but someone posted a picture of a CIWS here so here we are ;)

But will appreciate the mods moving the relevant post to the PLAN CIWS thread. Makes more sense there.
 

Sunbud

Junior Member
Registered Member
Well the relevancy of a CIWS is there across all services. US bases around the world are defended with CRAMs, and the PLAGF, PLAN and PLAAF have CIWS systems deployed to protect ground assets, not just ships. Bases and convoys (more like large vehicular formations than a convoy) for the PLAGF, airfields for the PLAAF, and ships, naval bases and anti-ship missile batteries for the PLAN. Something of this nature is not necessarily restricted to the PLAN. You will often see non-naval Chinese CIWS deployed on large, towable platforms.
Not to throw anyone under the bus but someone posted a picture of a CIWS here so here we are ;)

But will appreciate the mods moving the relevant post to the PLAN CIWS thread. Makes more sense there
 

by78

Lieutenant General
Deploying a mobile bridge. This brings out the kid in me.

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