@garryA

The lift equation is applicable at all speed because at the core, lift is basically reaction force due to Newton law, they are used to estimate missiles agility too, not just aircraft. So your argument that i only consider aerodynamic at aircraft speed is fundamentally wrong.

Ok, I try to explain why your lift equation is not applicable.
Your lift is also applicable to high speeds, yes. Is it the only usable reaction force?
Your aircraft aerodynamics where lift is everything because the use of aerofoils and never going to stall region and beyond, plus efficiency consideration is wrong for our hypervelocity missile case.

I use your own graphs and sources to explain why: http://www.aerospaceweb.org/question/aerodynamics/q0194.shtml

This is your lift and normal force diagram for a random case:

At 15° AoA we see a stall. The max. lift value reached before stall is 1.

Here is your aerofoil lift diagram with an additional normal force vector and components/resultants, defined by N and A (more explanation is given at the website):

and here is the related diagram showing drag and axial force.

For a reaction force to create a moment towards the center or pressure, the most effective situation is thus as following:

Fin is at the AoA of 90°, drag = normal force. This is at a factor of 2 more effective than your aerofoil lift outside stall region.

This error of a factor of two is due to your usage of the lift equation for maximum steering of a hypervelocity missile.

So how it is possible that missiles moving toward something and still has their nose toward the same target?. Here is the stuff you missing. Which is step 2, look at the photo again.In the example, once the missiles nose pull up, its whole body will be at a certain AoA with the air flow. Thus, the air flow will then applied a force on the whole missiles, with much higher force than if missiles fly straight with zero AoA.This force can be thought of as 2 components :the first one is called lift, which is what make missiles changes direction toward the desired target, the second component is drag which is what slowed the missiles, aircraft down. When you keep increasing AoA the lift will keep increase up until a certain point, where it start to decrease and drag will increase. In other words, extreme AoA will not help missiles turn quicker but rather slow it down quicker

G load isn’t important, what important for a turn is ability to change direction

I understand that. Let’s just keep the discussion within context.
We have two objects with roughly the same velocity, Iskander and THAAD both do maneuvers of a certain G value.
Both are in a environment with a very low air density.
Due to the inertia of both, a relatively small change of AoA will cause a very high G load that could reach the structural limit of the airframe allowed. Hence aerodynamic losses due to the exposure of the airframe is lower at high speeds due to the smaller AoA.

Result is that the one of the two that can do a higher G maneuver may win.

When i talked about lift and AoA, i mean the force that actually help missiles change direction not the one that slow it down, that why you can’t add CL and CN together. CN is practically the combined resultant coefficient of Cl (lift ) and Cd ( drag )

Correct, I should not have added the two. Above I detailed that and I hope to have shown you why your calculation is potentially at a factor of 2 wrong because you just consider lift.

1/ MIRV if come from ICBM can move at speed of around Mach 15-20, much faster than what Iskander capable of, they will have considerably more lift for maneuver

Yes, a ICBM, IRBM, MRBM, all have more potential for maneuvering, either via lift, dynamic pressure/drag or gas steering.

2/ Iskander is a single stage missiles, so it is considerably heavier than MRIV that seperated from their carrier, thus require much more lift for the same maneuver

Actually the Iskander appears to fly a depressed trajectory going into a glide phase at terminal. It will likely remain in a altitude region where due to it’s speed a sufficient amount of dynamic pressure is available to react on its fins, as said, almost certainly outside non-stall lift region. The gas system is a secondary mean for maneuvering. Hence the lift or better said steering situation is likely quite good, just outside PAC-3 envelope.

Iskander has high speed and very high wing loading while Cl is low as well, so expect it to lose considerable amount of speed if attemped to maneuver.
It more likely that Iskander if it indeed perform evasive maneuver will do so at low altitude since it clearly doesn’t have enough lift for that at high altitude.

The Iskander will need small AoA changes for high G maneuvers at it’s speed and it’s operating altitude as well as secondary gas system will help it to keep aerodynamic losses low enough for useful anti-ABM maneuvering.

inertia is irrelevance and high speed will mean more drag since the formular for drag is also propotional to speed

Inertia is relevant because the higher it is the lower the AoA for direction change, hence the lower the losses due to exposure of airframe to drag. Interia –> G load on airframe becomes the limiting factor.

In the formula for drag, speed is with ^2, not proportional.

About your question: the air flow will collide with the vertical fin, thus point the aircraft to the same side ( if fin turn to the left then aircraft will point to the left). Once the aircraft point to same side, the air flow on the airframe and the engine thrust will make it change direction

Would you describe that T-50 case as an effect of lift or a effect of drag/dynamic pressure/ram-air-pressure as I described above?

I don’t follow Indian TBM program so i don’t know abot that, but AFAIK, LGM-30 Minuteman has a gas system, so is Trident.

I doubt the Minueteman I had a steering gas system, only retro boosters.

Btw how can you know if decoys and ECM will change Iskander CoG or not when we don’t even have a photos or diagram of the alleged system ?. Moreover, without gas system, Iskander won’t be able to follow a quarsi ballistic path either.

I can know because Iskander works. I also know because the options for other re-entry points like aft or side can be excluded due to the burnt booster at aft and warhead at tip. The result will always be a re-entry with the top, also because ECM and decoys are certainly at the top half of the tube body. A quasi-ballistic path can be a depressed one with a following glide phase as proposed for the Iskander.

Back to THAAD vs Iskander case, i don’t see how Iskander has more reserve either when it supposed to carry ECM, decoys and what not, or how is it even matter in exdo atmosphere when there is almost no air ( no drag) ?. The engagements time between a Mach 6 and Mach 8 missiles will be extremely short too so things like RF proximity sensor are unlikely to work ( and there isn’t much time to drag out many maneuvers either).

I didn’t say that Iskander has more fuel reserves for its gas system, which one can pull and endure more G and loads, if a RF proximity sensor is present and working.
These are all detail design parameters, all we can speculate about is that these things are physically possible and hence must be taken into consideration when judging both systems against each other.

I honestly, don’t see how B-1 can run away from an F-16 unless it has a few hundred km head start.

Just let them start at sea level and with a distance of 50km. The F-16 will be out of fuel at 1/3 the max. range of the B-1. This argument was against your claim that the THAAD KV has more endurance because it’s smaller.

@garryA

If you have the book, evidence, feel free to screenshot and upload it. I highly doubt that they mentioned a MARVs that can turn 50G but iam open to see the evidence. Btw, acceleration of speed due to booster at launch is not the same as acceleration of the turn, i think you may be confuse the two.

Unfortunately I have no access to it at the moment, but I recommend it. The 30-50G numbers were encountered during reentry, there of course a part of it is due to deceleration, I’m aware of that.

AIM-54 (or any air to air missiles) cannot perform two digit G maneuver at high altitude like at 24 km (let alone some where like 50 km height). Moreover, the Phoenix is also said to have terrible agility after motor burned out.
Another factor that you must consider is the ratio between fin area and weight of the AIM-54, it is considerably better than the Iskander so to perform the same maneuver the AIM-54 will need smaller CL.

You misunderstood me: The AIM-54 was designed to operate at around 12km at speeds of mach 4+, there the fins still work. So that a G load would it encounter there, what do you think? Would that G load be consistent with whats possible via your lift formula? I’m quite sure the loads on the AIM-54 @ 12km and mach 4 would be 10+ and this because of the inertia of it at mach 4.
To put it simply a 10G turn with a F-16 @ mach 0,9 would cause a e.g 45° direction change and expose it completely to the drag. A 10G turn with a AIM-54 @ mach 4 would just cause e.g a 10° direction change.

There is one issue with the inertia effect at high speeds, which cause much higher G loads due to the velocity for the same change of direction.

Then there is another issue I tried to explain. Your formula is as it seems for a wing aerofoil lift. Beside that there is a ram-air/drag aerodynamic control method, best explained by the T-50 and J-20 vertical stabilizers: These can turn at an angle which would cause stall with a wing aerofoil, but due to ram air pressure (i.e drag force at high velocity) they can offer high steering power if necessary.
Your graph is good and shows this effect e.g @ 45° to some extend however I doubt it is also representative for high velocities (but low air density).
I’m not a aerodynamic guy but I think this, “just lift” approach is the reason why your formula is not applicable in light of different sources talk about such high G numbers at those speeds.

I don’t think the quarsi ballistic trajectory can help reduce LoS since it still have the same top point and only extended the reentry length. Furthermore, let say the altitude of the depressed trajectory is 30 km, ground radar height is 15 meters, the radar horizon would already be 730 km which is longer than maximum range of Iskander already.

Quasi as with you graph of the Indian TBM not, yes. I just mentioned this effect for ballistic missiles in general, agreed that it’s not applicable for the relatively short ranged Iskander.

It will eventually come down due to gravity, the gas system however is to oriented which part of it will point toward the earth, just like on a space shuttle

The space shuttle is in a orbit, without gas system gravity and drag would decide that it land on earth in 4 or 5 years. A ballistic missile like the Iskander is on a ballistic trajectory that will take it back to earth in a accurately calculated time and place accurately to seconds not months or years. It’s CoG will make sure that it will come down with the nose first.
The gas system on the Iskander has almost certainly a anti-TBM purpose.

I can’t find any source that stage ICBM are designed to decelerate to below Mach 4 before impact, moreover, the warheads of ballistic missiles doesn’t cruise at Mach 5 at sea level, it merely comming down through the atmostphere, so likely spend a few seconds at sea level air density at most

Yes that’s not easy to find. Here is a paper describing it:

[ATTACH=CONFIG]253273[/ATTACH]

The Iskander would be the bi-conic conventional here and as you see this is for a mach 12 missile and its decelerated to less than mach 3 at impact. That delta of mach 9, minus some penalties could be used for maneuvering for this missile with the right kinematic management.

They both got gas system, however, THAAD is smaller and has a seperate stage for its kill vehicle, it also doesn’t carry ECM or decoys.Which mean lower mass. As we already know, F=ma , so generally with same force and lower mass mean better acceleration .Thus, I find no reason to believe that the gas system on Iskander can change its direction quicker than the one on THAAD. Aerodynamic control is kinda useless above 22-25 km.

You assume same gas system power for Iskander and THAAD? We can’t really find out which one has more endurance. I could as well say a F-16 has more endurance than a B-1 with that argumentation.
This is not about quicker, it’s about endurance and maybe endgame agility for a evasive maneuver. As said: Expect the Iskander to be detected, the THAAD interceptor launched and then it starts to deviated from the rendezvous point originally calculated and the THAAD has to follow. Now who wins that endurance game? Can the THAAD catch-up to the new impact trajectory that changes continuously? This is one, a exo-atmospheric anti-ABM scenario for Iskander vs. THAAD.

The AoA would pretty much depending on the air density, you will need very big AoA to turn 10 G at 50 km altitude ( if the fin even work at all ). Moreover, drag at high velocity and high AoA is much higher so the missiles will lose alot more speed than an aircraft making a turn

The velocities and inertia involved change that picture.
The Iskander will experience much higher G loads for the same angular vector change due to its high speed –> high inertia, but this also means that the final position change is also much higher due to those velocities.
The Iskanders fins will have a high drag force as reaction force beside the lift. Just due to the magnitudes higher speed compared to aircraft it will have a high steering capability even if the air density is much lower. If the air density would be much higher at 50km altitude the Iskander would just disintegrate with mach 6 drag forces.

@garryA

I highly doubt that Iskander can pull 30G with its tiny fin and tube body either, especially consider high altitude. Air to air missiles can turn high G value only at sea level. I can’t be bothered to do the calculation now but if you put the number in the lift equation, you probably end up with CL higher than subsonic airfoil for Iskander if it want to pull 30G at high altitude (pulling 30G at low altitude is kinda too late).

High G’s were witnessed by US MaRV programs too, partly due to de-acceleration and partly due to turns.
Its the high speed in the equation with ^2 that makes it possible, aerodynamic maneuvers can be done at very high altitude due to the higher speed.
The Iskander was rumored to fly a depressed trajectory and called a quasi-ballistic missile due to that. Shorter warning time due to later radar detection was one reason, but another reason is that at high speed it would remain maneuverable via it’s fins. Other missiles would have almost no function on their fins at around 50km, but Iskander could due to its speed and resulting ram air pressure.

I don’t know if Iskander has a mid body thruster or not ( since i can’t find the holes like on the space shuttle). But gas system are not indicator that it is supposed to counter exoatmospheric interceptors. For example intercontinental ballistic missile generally all have gas system in their final stage.

They have because their post boost vehicle does maneuver to place the re-entry vehicles in trajectory. The Iskander would have no reason for a gas system, any possibly necessary course corrections would be done in terminal via it’s fins. Hence the only reason would be to counter exo atmospheric interceptors or to change course to confuse/bleed endo-atmospheric interceptors. The gas system of the Iskander is at its TVC system.

Mach 3 is not the fastest impact velocity for conventional material, structure either

Rail gun for example intended to have impact velocity around Mach 5 and it has similar trajectory to most ballistic missiles

Sounds exotic. For a system without any propulsion, just with a hardened GPS guidance and hardened fins a starting speed of mach 7,5 might be possible if the heat shielding is nearly all the projectiles weight. Still a very hard task and different than missile and their airframes.

All other systems down to ICBM reentry vehicles need to de-accelerate down to around mach 3 at sea level to avoid disintegration due to thermal stress and drag forces. The Iskander is surely in that category and maybe mach 4 would be possible if it’s hardened accordingly.

Kh-15 reach terminal velocity of Mach 5 in a dive to target.
Kh-22 reach terminal velocity of Mach 4.6 in a high altitude dive to target
AQM-37 can reach terminal velocity of Mach 5 in dive too.
http://www.designation-systems.net/dusrm/m-37.html

Maybe at the start of the dive at ~10km altitude they could still have mach 5 but almost certainly not at impact, sea level.

As a theater ballistic missiles,without maneuver Iskander can probably reach around Mach 5-6 terminal velocity in impact. Consider the small fin, Iskander will need very high CL to pull high G, high CL mean either very high AoA or very thick , lift oriented air foil. From photos we can see, there is nothing lift oriented about Iskander fin. It has low aspect ratio, high wing sweep and not much thickness if there is any. The body itself is also a tube body. So the only other option is high AoA, and high AoA generate alot more drag. The missiles likely lose 2-3 Mach from each high AoA maneuver and then it has to maneuver back to still high the right target too so will lose even more speed. While Iskander can probably change course and direction, i don’t think it can do what information on Wiki seem to suggest

I guess we have to first define high G in this scenario, in relation with THAAD.
How many G’s would the gas system of the THAAD be able to pull?
How many G’s can the Iskander pull if it fly a depressed trajectory in which its aerodynamic control via fins is still possible due to the high ram air speed?

I haven’t read the Wiki article about Iskander but in this scenario there is a good chance to outmaneuver the THAAD interceptor. There is also a good chance that at the depressed trajectory the Iskander would be outside the PAC-3 interception envelope.
We have a fundamentally different understanding about how much speed is lost when doing a maneuver, you talk about 2-3 mach numbers being lost by each maneuver. You also ignore that speed lost due to maneuvering creates a more efficient drag economy.

Hence let me make some claims too:
-THAAD would only be able to do 10G maneuvers
-Iskander would be able to dodge those maneuvers by a counter 10G maneuver at depressed trajectory 60km altitude via its fins
– Each course changing 3G maneuver of the Iskander consumes mach 0,1 and each 10G evasive maneuver mach 0,3.
This speculation is not really helpful.

Btw. at speeds like mach 6 no high AoA maneuvers are necessary to create loads like 10 or 30G.

@garryA

9K720 Iskander-M ‘s mass is around 4,615 kg , assuming the mass without fuel is 1/2 of that, it is still around 2307 kg ( likely even heavier with all these alleged ECM, decoys and gas system on it). As a result a 30g turn required the force at least 2307*30 =69,225 kg or more than 69 tons.What sort of mini gas system giving that amount of thrust ? and for how long ? For reference purpose the first stage of LGM-30 Minuteman produce 91,170 kg of thrust or 91 tons
https://fas.org/nuke/guide/usa/icbm/lgm-30_3.htm
I don’t know about you but i don’t buy that a secondary gas system on the tiny Iskander can produce thrust more than half of Minuteman’s first stage

You are mistakenly simplifying the case. Soviet engineers should have known what they are doing with the gas system of the Iskander. You don’t take into consideration the offset of the gas system to the CoG.

Moreover, how does the missiles even know when to perform the high G maneuver to dodge the interceptor?, also after the maneuver does it turn back to attack the intended target or just fly randomly in a completely new direction ?
Furthermore,in exo-atmospheric condition, a gas system perpendicular to the body will change nose pointing but not the direction of travel, unless the main rear motor still operating ( see the different between how a space shuttle pointing its nose and an aircraft turning).

The gas system of the Iskander is at a strong offset to the CoG. As for the maneuvering: it may travel at a wrong ballistic course and all the maneuvering during terminal phase will the result in the right target location, hence all the random maneuvering are course corrections. It would likely fly as far away from its initial position to deplete the kinetic energy of the interceptor within denser atmosphere.

It basically trade potential energy for kinetic energy after mid phase, if you wasted this precious kinematic energy, it will not have enough to potential energy to compensate.

No precious kinetic energy is wasted. Under exo-atmospheric conditions there is no loss at all because of maneuvering as it causes no friction. In endo-atmospheric conditions speed is decreased due to maneuvering, however as the missile has to slow down anyway, the maneuvering does to some extend that what friction would have done. So you do a controlled amount of maneuvering to decease your speed to a level in which the energy is not wasted due to heatshield heat up. We have 3 parameters: Speed, heatshield temperature and gain of kinetic energy due to transformation of potential energy.
Speed must be in a efficient relation to heatshield temperature (you don’t want a heaver heatshield to do all de-acceleration) –> the result is added to the maneuvering capability.
Speed must be in a constant relation to gain of kinetic energy (you don’t want to increase your already high speed when entering dense atmosphere layer) –> the result is added to the maneuvering capability

Furthermore, regain speed in the atmosphere would take much longer time consider the fact that the air density is much higher and it keeps getting denser and denser the longer the missiles fell back into the earth.

Yes to an extend where no regain of speed is possible at all. You have to manage the 3 parameters above in a fashion that adds up to your maneuvering capability.

@bring_it_on

Power does not have to do anything here since many applications can share comparable or high levels of power but still be different. The role or design and technical aim is what matters. The TPY-2 a high power high frequency radar designed primarily for terminal intercept and discrimination and can also double up and operate independently in FBM where it provides high quality early warning and discrimination data for launch on remote and situational awareness duties.

I didn’t say anything about BMD capabilities of Voronezh vs. TPY-2, just said that Voronezh is not a OTH radar but high power BMD sensor like the TPY-2. The TPY-2 has much better resolution for discrimination, that’s right. However decimetric band might be sufficient for discrimination of decoys. X-band has more power per array area –> more compact.

Iskander is one mean to take out such high value targets and there are others.

As for THAAD vs. Iskander. We can’t know for sure. The Iskander is a maneuvering target, it has a kinematic advantage to pull G’s, plus decoys, plus ECM, different trajectories.

What is certain: The Russians won’t use fighter/bombers to take out such dangerous and well protected targets. I’m cute sure that the US will also avoid using B-2, F-22/35 against the highest tier elements of Russian IADS in case of a conflict.

We can set two boundary conditions and check if the methodical design result would be the Qaher.

1. Your engine technology is 3-4 decades behind that of your opponents.

2. Your country to defend has one of the most mountainous topographies on this planet, where mountain chains are 2000m on average.

The resulting design can be independent and no foreign companies or mainstream idol designs have influence on it.

In such a case a result could be the following:

Make use of the mountainous terrain to avoid detection by radar, IR and ESM. The design has to fly low in valleys to mask it. I wont go for the high altitude high speed game of air superiority fighters, hence no long range radar-tech/engine-tech driven BVR engagements. Now difference of speed at sea level is at best around 30% for a subsonic fighter and a advanced opponent fighter with advanced engine-tech due to the high drag. This lower speed difference compared to low engine-tech vs. high engine-tech engagements at high altitude helps to compensate.

As for the deficits with the engine, a physical effect, the ground effect is taken into the design, which effectively creates more thrust. A possible turbofan variant of the J85 at 70s tech level without afterburner, optimized for low altitude, plus the bonus by the ground effect, decreases the gap in engine-tech. It may provides mach 0,9 for a draggy internal weapon VLO design.
In a hunt, the opponents high engine-tech fighter, far from home base on short afterburner might do mach 1,3 with or without internal weapons, a short-lived difference of 30% for 30 years difference in engine technology.
Its clear that this 1:1 hunt scenario is not everything and the opponents fighter will try to shot it down from higher altitude, look-down. However the topographie will always force it to get close in order to have a direct line of sight for radar/IR and weapons and the VLO design will futher hinder long rnage shots from look-down positions. With a intact IADS and LR-SAMs the initial engagements could be limited to that low-altitude hunt scenario where the kinematic advantage of the modern fighter is decreased.

The Qaher is surely designed to make use of ground effect, its WIG like wingtips clearly point to it. Here is a technology where no experienced metallurgy is necessary, benefit by a physical effect affecting kinematics by developing a terrain avoidance system with digital maps and multiple redundant sensors. A mature terrain avoidance system for very low altitudes, state of the art.
Additional advancing communication technology with data-links and sensor-fusion/IADS could provide the Qaher with the necessary situational awareness to do its low level operation, approach a target, pop-up, attack and dive back and leave the battle (this dive/low-level escape is also a method used by the B-2).

The tandem wing design is also noteworthy for the ground effect optimization. A question is what range performance would be possible for such a ground effect operating aircraft with an non-afterburning J-85 turbofan variant. Would the ground effect operation at mach 0,9 max. provide it with the same range performance as a medium to high altitude operating fighter?
The tandem wings have a interesting design, the forward wing/canard is conventional for a fighter, but the rear wing has a very thick leading edge. The benefit for such a thick wing profile is foremost the fuel that can be carried inside it, especially for a design that has internal weaponbays in the fuselage occupying space. The forward-wing apparently “breaks” the high speed airflow, so that the thick rear wing is just confronted with a low pressure region at the leading edge which could result into a thick wing as a airflow design result.
The decision not to go with a supersonic VLO design and stick to a low-level mach 0,9 design would also be a brave one, supersonic sounds good but in a operation regime hypothesized for the Qaher the effort-benefit ratio would be too low. In high subsonic operation the design gets much cleaner and more efficient.

Then there are always questions about the cost effectiveness. How much cheaper would be two turbofan modifications of the J-85 compared to modern engines (1/10 of a F404?)? How much cheaper is a small aperture low power AESA for 80km max. range against a 1m² target? How much easier design and hence cheaper is a VLO inlet like that of the Qaher? Just due to positioning it could provide the same VLO effect in its operation regime as complex fan-face avoiding supersonic designs. What high angle of attack penalties are expected for the inlet and how important are high AoA for its operation regime?
If all these trade-offs and design elements are clarified we can judge if the methodical design result of the Qaher makes sense or not.

Iranians are known for such unconventional designs and operation regimes, so this hypothesis might not be that far from reality.

At this point the project remains up for debate, neither IRGC nor IRIAF have shown support for it and development seems to be slow. Lets see if we see a airworthy prototype soon.

Friends, I’m not here to argue about the 3rd Khordad being on pair with the Buk-M2, nor will I defend the mock-up of a long range sam shown during a parade 7 years ago.

The 3rd Khordad is modelled on the Buk-M2 (not -M1, that system is called Tabas). Iran sometimes shows mock-ups of conceptual projects of for internal consumption and prototypes for disinformation of the enemy.
Its up to people like us to see whats real and whats real and intended to be proven to be real. It’s not a coincidence that they have shown the internal radar of the 3rd Khordad, high-res photos of the missiles (which are very different to Buk series).

To that friend who cant judge a PESA from a AESA if the internals of the radar is visible, here some guidelines: if the array depth is more than one meter and intensive cooling is provided to the front of the array, you have two good indicators for a AESA. I dont claim that the AESA array of the 3rd Khordad is any better than the PESA of the Buk-M2, it just shows how different both systems are and that it’s not a simple copy.