Air-to-Air Missile Discussion

[*Rage*]

over susceptibility to chaff as well.

[141st_Eko1]

So Result ? :)

[kk0425]

Really could use some updates on this. I decided to try flying online for the first time in ages with the F-15 (essentially I gave up on BVR a while ago due to the uselessness of missiles). Flew up to around 20k feet when I saw a bandit at 11k fairly close. He was head on and by the time I fired my first missile he was about 13 NM away from me, still head on. I decided to go for broke since I wasn't doing so hot anyway and fired the remaining 5 AIM-120Cs that I had. So from 20k feet at a bandit at 11k 6 missiles were shot in a matter of several seconds. Last missile came off the rail at about 9 NM distance. Lock was of course maintained at all times but I had to bug out shortly after the last missile since he launched at me. And to my extreme disappointment all 6 missed. 6 AIM-120Cs all missed. Now I understand he probably notched a couple but I find it extremely unlikely to notch all 6 while still being able to fire on me. I'm certainly not a great pilot at BVR and I know when I screw up but this doesn't seem acceptable. Missiles that just decided to not work this much doesn't make for an enjoyable experience.

[GGTharos]

Why shouldn't he able to notch 6 missiles that are all coming from the same direction?

 

It isn't the missiles that aren't working here, it's your tactics. You spamraamed and ran. Any vpilot worth their salt will ditch your missiles if you do that.

 

Now I understand he probably notched a couple but I find it extremely unlikely to notch all 6 while still being able to fire on me.

[kk0425]

How big of a notch are we talking about about? And I wasn't aware you could launch at targets at a 90 degree angle. I ran because he fired at me.

[GGTharos]

What do you mean how big of a notch? You put the bandit on the 3-9 line and you're in the notch. He drops off the radar. You're the one who said he notched.

[kk0425]

Considering 6 missiles were fired at him while he was head on I figured he notched, unless missiles are worse than I thought. I never actually lost my lock until he went off my scope. That's when I'm guessing he notched to avoid at least the first missile but I can't say for sure since I'm guessing. How else do 6 missiles miss at that range with that altitude advantage? My first missile was off the rails at 13 NM. My last one was at about 9 NM. He fired shortly after my last missile, about 15 seconds since my first one.

 

I'll continue this tomorrow night. It's late here.

[USARStarkey]

He has a point here about the missiles. It has been stated before that within 10-15nm a Amraam or anything else really should be about 100% Pk or close. The problem with him notching all the missiles is a matter of geometry. This is just one of the reasons it is more difficult IRL to notch at close ranges. But just based on geometry it goes something like this: to get into the notch, you arent just 3-9 lining it. Farther out, you dont have to be as precise because the relative angle between the bandit and the radar is less exagerated at farther distances. IE: you dont have to be as close to exactly 90deg to fall into the relative velocity gate. In close, either to a missile or aircraft radar, you would have to be closer and closer to spot on, to the point at which it would be practically impossible to be precise enough to get into the notch. Furthermore, if several missiles are fired, they wont all have the same exact trajectory, so it is extremely unlikely that every single missile would be spoofed. The first one would miss, but the second and third would see you at a different aspect, expecially since you had to maneuver in the first place to get into the notch. If you read account from red flag, or there is at least one I know of from 1991, pilots talk sometimes about how bandits will attempt to notch in close but will fail because of the distance. For a missiles or volley of missiles that dont even go active till they are 10nm out, the effect is exacerbated.

[TAW_Blaze]

Kinematics being utterly broken is just a thing you can adapt to very easily.

 

However the broken guidance, along with not having a lot of essential radar features (like TWS radar memory) is not something you can really adapt to.

[runny]

Really could use some updates on this. I decided to try flying online for the first time in ages with the F-15 (essentially I gave up on BVR a while ago due to the uselessness of missiles). Flew up to around 20k feet when I saw a bandit at 11k fairly close. He was head on and by the time I fired my first missile he was about 13 NM away from me, still head on. I decided to go for broke since I wasn't doing so hot anyway and fired the remaining 5 AIM-120Cs that I had. So from 20k feet at a bandit at 11k 6 missiles were shot in a matter of several seconds. Last missile came off the rail at about 9 NM distance. Lock was of course maintained at all times but I had to bug out shortly after the last missile since he launched at me. And to my extreme disappointment all 6 missed. 6 AIM-120Cs all missed. Now I understand he probably notched a couple but I find it extremely unlikely to notch all 6 while still being able to fire on me. I'm certainly not a great pilot at BVR and I know when I screw up but this doesn't seem acceptable. Missiles that just decided to not work this much doesn't make for an enjoyable experience.

 

You fired 6 missiles and then he fired one (or more) so you turned and ran.

 

Basically you didn't wait to see what he did so how can you say the missiles suck? For all you know he flew along a ravine out of sight to your missiles. There's plenty of ways to defeat 6 missiles that are legitimate and realistic. If you didn't even track him then I don't know how you can blame this on the missile.

 

I agree there are some issues but I wouldn't take this story as proof of them. I'd work on some tactics that don't involve turning around as soon as the RWR missile launch warning sounds.

 

Also "how much notch" doesn't make sense. You are either in the notch or you are not.

[USARStarkey]

ah ok. Speed wise, you can run in the game. Good luck trying to escape a Amraam at 10nm IRL.

[Frostie]

Really could use some updates on this. I decided to try flying online for the first time in ages with the F-15 (essentially I gave up on BVR a while ago due to the uselessness of missiles). Flew up to around 20k feet when I saw a bandit at 11k fairly close. He was head on and by the time I fired my first missile he was about 13 NM away from me, still head on. I decided to go for broke since I wasn't doing so hot anyway and fired the remaining 5 AIM-120Cs that I had. So from 20k feet at a bandit at 11k 6 missiles were shot in a matter of several seconds. Last missile came off the rail at about 9 NM distance. Lock was of course maintained at all times but I had to bug out shortly after the last missile since he launched at me. And to my extreme disappointment all 6 missed. 6 AIM-120Cs all missed. Now I understand he probably notched a couple but I find it extremely unlikely to notch all 6 while still being able to fire on me. I'm certainly not a great pilot at BVR and I know when I screw up but this doesn't seem acceptable. Missiles that just decided to not work this much doesn't make for an enjoyable experience.

 

This all a bit sketchy to draw conclusions from don't you think. He was about, he probably are pretty inaccurate. You say you launched from 13NM at about 20k, if the bandits 11k he stands a good chance of split S to outrun that missile, could well have been just as you fired your next 5. He could have dropped behind a mountain or even been damaged from that first shot. Another bandit may also have been engaging you. Sorry just nowhere near enough conclusive fact to claim 6 120C missed from 10NM when they should have hit.

[Frostie]

ah ok. Speed wise, you can run in the game. Good luck trying to escape a Amraam at 10nm IRL.

 

Are you sure you don't mean another sim which you're basing real life on.

From medium altitude and subsonic speed you're cutting the missiles balls.

[*Rage*]

Turn and run is feasible from that range at low altitudes. Also spamraaming 6 missiles makes BVR panda sad.

[Falcon_S]

I found this on a forum (I do not know who are the people on it), I do not know how OP (Cola) knows the subject (i don`t :) ), but it is an interesting text:

 

"Originally Posted by Cola"

There has been a lot of arguments over the performance of A2A missiles here --

some of which are well backed by facts, some are so far out there it is like claiming that

they fly on hyperdrive.

 

I want to take this opportunity to introduce everyone to a very simple formula that

can be used for estimating the performance of a missile. It goes like this:-

 

Change in Velocity (Delta V) = 10 x Specific Impulse x LN (initial weight / final weight) m/s

 

This assumes that all the fuel is used to get the missile as fast as possible and

none is used to provide just enough thrust to sustain a given velocity.

In otherwords, it assumes an all-boost motor not a boost sustain motor.

 

For example, let'a take a look at the AIM-120A AMRAAM which we have some decent info on...

 

Launch weight = 335 lbs (Published stats)

Motor weight = 156 lbs (WPU-6/B HTPB rocket motor weight as per Raytheon)

Approximate specific impulse = 245 seconds (typical of HTPB solid motors)

Approximate fuel fraction of motor = 85% (typical of robust aluminum cased aerospace rocket motors)

 

OK... if 85% of the motor's mass is the fuel, we have about 132 lbs of fuel in the AMRAAM-A

-- roughly a 39.4% fuel fraction (sounds about right). So let's run the numbers...

 

Delta V = 10 x 245 x LN(335/(335-132)) = 1227 m/s

 

The formula predicts that the AMRAAM will go about 1227 m/s (~Mach 3.7) faster than it started.

If it is launched at say Mach 1.5 it'll be going Mach 5.2.

In reality the AMRAAM doesn't go that fast.

The reason is that not all the fuel is used to get it as fast as possible.

The AMRAAM's motor is a boost-sustain design.

It is probably grained to take the weapon to abut Mach 2.5~2.8 faster than it started at

(Mach 4+ in a typical Mach 1.5 release).

The rest of the fuel is shaped to burn much more slowly to keep it's velocity at

or near the achieved maximum out to a longer range before the motor burns out.

 

 

Well, for any given fuel fraction and specific impulse,

a designer can decide how fast he wants to go and how long he wants to stay at

or near the peak velocity achieved. For instance, if a missile carries 40% of its launch weight

as fuel and uses the typical a modern HTPB propellant motor, it can:-

 

(1) Spend 25% to get an approximate Mach 2.1 delta V and 15% on sustaining that speed for a relatively long while.

(2) Spend 30% to get an approximate Mach 2.7 delta V and 10% on sustaining that speed for a shorter while.

(3) Spend 40% to get an approximate Mach 3.8 delta V have no sustain burn time at all.

 

BTW, in reference to the above comment on deceleration... it doesn't really work that way.

If a missle starts at Mach 4 at burn out and decelerates 25% to Mach 3 after 10~15 seconds,

it WILL NOT decelerate to Mach 2 (another 33% from Mach 3) after 20~30 seconds.

This is impossible because aerodynamic drag (Fd = Cd x A x 0.5 x P x V^2) is a function of

the square of velocity.

As velocity decreases, drag force decreases exponentially in relation to it.

Hence, if the drag for at Mach 4 causes a 25% loss in velocity in 10~15 seconds,

there is no way a much lower drag force at Mach 3 will cause a 33% loss in velocity after

another 10~15 seconds.

What happens is that deceleration is non-linear;

you start off steep and the slope flattens out over time as velocity and hence drag drops.

It'll take a missile a heck of a lot longer to decelerate from Mach 4 to Mach 2 compared to

say Mach 2 to Mach 1 for instance.

 

 

 

Actually it also depends a heck of a lot on altitude (air density)...

Let's plug some numbers shall we?

 

Question: How much thrust is needed to sustain Mach 3.0 in an AAM like the AMRAAM?

 

Drag force (Newtons) = 0.5 x P x V^2 x Cd x A

 

P = Density of Air (kg/m^3) ; ~1.29 kg/m^3 @ sea level; ~0.232 kg/m^3 @ 12,000 m

V = Velocity (m/s) ; Mach 1 = 340 m/s @ sea level; ~295 m/s @ 12,000 m

Cd = Co-efficient of Drag ; ~ 0.6 to 0.95 for rockets depending mostly on finnage,

nose and tail profile

A = Sectional Area (m^2) ; ~ 0.025 m^2 for a 7" diameter missile.

 

For an AMRAAM like AAM going at high altitudes (40,000 ft)...

 

Drag Force @ Mach 3 = 0.5 x 0.232 x (295x3)^2 x 0.70 x 0.025 = 1590 Newtons = 357 lbs

Drag Force @ Mach 2 = 0.5 x 0.232 x (295x2)^2 x 0.70 x 0.025 = 707 Newtons = 159 lbs

Drag Force @ Mach 1 = 0.5 x 0.232 x 295^2 x 0.70 x 0.025 = 177 Newtons = 39.8 lbs

 

The same missile going Mach 3 at Sea Level...

 

Drag Force @ Mach 3 = 0.5 x 1.29 x (340x3)^2 x 0.70 x 0.025 = 11,744 Newtons = 2640 lbs

Drag Force @ Mach 2 = 0.5 x 1.29 x (340x2)^2 x 0.70 x 0.025 = 5,219 Newtons = 1173 lbs

Drag Force @ Mach 1 = 0.5 x 1.29 x 340^2 x 0.70 x 0.025 = 1,305 Newtons = 293 lbs

 

Assuming that there is no sustainer,

the deceleration experienced at Mach 3 by the 203 lbs (empty) missile is

 

Deceleration @ Mach 3 = -F / mass = -1590 / (203 x 0.454) = -17.3 m/s^2 = - Mach 0.059/sec @ 40,000 ft

Deceleration @ Mach 2 = -F / mass = -707 / (203 x 0.454) = -7.67 m/s^2 = - Mach 0.026/sec @ 40,000 ft

Deceleration @ Mach 1 = -F / mass = -177 / (203 x 0.454) = -1.92 m/s^2 = - Mach 0.0065/sec @ 40,000 ft

 

Deceleration @ Mach 3 = -F / mass = -11744 / (203 x 0.454) = -127 m/s^2 = - Mach 0.39/sec @ sea level

Deceleration @ Mach 2 = -F / mass = -5219 / (203 x 0.454) = -56.6 m/s^2 = - Mach 0.17/sec @ sea level

Deceleration @ Mach 1 = -F / mass = -1305 / (203 x 0.454) = -14.2 m/s^2 = - Mach 0.042/sec @ sea level

 

OK... enough of the math and the formulas... what does all these mean?

Well, it means that while coasting at Mach 3 an AAM is going to lose about less than 2% of

its velocity a second at high altitudes while it stands to lose about 13% of its velocity at

sea level! Huge difference isn't it?

Remember though that the rate of deceleration actually DECREASES as the

missile's velocity decreases.

It is easy to see that one can claim that a missile can burn out burn out its booster

and sustainer and be effective out to over 100 km at high altitudes or be useful only

against helos after 10km on the deck!

 

Also, we can make a pretty educated guess as to how much thrust the sustainer has to make.

An AMRAAM class missile with a 400 lbs sustain thrust will be able to stay

above Mach 3 at high altitudes and stay about Mach 1.2 at sea level.

An AMRAAM class missile carrying about 10% of its launch weight as sustainer

grained propellant will be able to keep this level of thrust lit for 20.5 seconds

in addition to whatever the boost time was using the 30% of its fuel to get a

roughly Mach 2.7 Delta V after launch.

A missile like this when fired at Mach 1.5 will reach Mach 4+ and keep

above Mach 3 for the duration of the sustainer at high altitudes.

It will also reach about Mach 2.5 and keep above about Mach 1.2 at sea level.

A motor grained for this thrust profile can have a 10 second boost at ~ 2460 lbs thrust and

a 20 second sustain burn at 400 lbs thrust -- this is a 5:1 boost sustain ratio.

This is also about right for thrust profiles of star grain vs

core burn solid propellant burn rate profiles.

 

 

 

 

Another rough rule of thumb:-

 

The time it takes for a missile to lose 25% of its velocity after burn out at supersonic speeds.

 

Never @ > 100,000 m (~300,000 ft) ; in space

~150 seconds @ 24,000 m (~80,000 ft)

~70 seconds @ 18,000 m (~ 60,000 ft)

~25 seconds @ 12,000 m (~ 40,000 ft)

~10 seconds @ 6,000 ft (~20,000 ft)

~5 seconds @ Sea Level

 

Remember, fractions over time are not additive.

In otherwords, if a missile loses about 25% of its velocity in 10 seconds,

in the 10 subsequent seconds (t =20s) the missile loses approximately another 25% of

the remaining 75% not a 100%. Total velocity loss is ~43.75% not 50%.

 

This is highly collated to the fall in air density.

Drag = 0.5 x P x V^2 x Cd x A.

Holding everything else constant Drag falls proportionally to density.

Drag also falls exponentially with Velocity which accounts for the loss in velocity

in the given time slices being about 25% instead of closer to 40%.

Edited July 13, 2014 by Falcon_S

[Frostie]

To get an idea on missile performance at different altitudes the Astra missile has open information on its performance.

 

Head on max range

@50,000ft = 60NM range - tail chase 11NM

@16,000ft = 23NM range

@sea level = 11NM range

 

http://en.wikipedia.org/wiki/Astra_(missile)

[TAW_Blaze]

To get an idea on missile performance at different altitudes the Astra missile has open information on its performance.

 

Head on max range

@50,000ft = 60NM range - tail chase 11NM

@16,000ft = 23NM range

@sea level = 11NM range

 

http://en.wikipedia.org/wiki/Astra_(missile)

 

That's not information, that's bullshit. Lethal range is not a one parameter equation..

[GGTharos]

Rtr for 120A is ~14nm at 20000'. Is it shorter if the bandit's at low altitude? No one who knows is talking, but at 9nm, that's well inside this Rtr AND the missile is going down-hill. This is not reflected in-game for any of the missiles.

 

Are you sure you don't mean another sim which you're basing real life on.

From medium altitude and subsonic speed you're cutting the missiles balls.

[GGTharos]

No such thing has been stated. This is a lot of bad information in one spot, not to mention bad math that results from not doing the math, while talking about the math.

 

He has a point here about the missiles. It has been stated before that within 10-15nm a Amraam or anything else really should be about 100% Pk or close. The problem with him notching all the missiles is a matter of geometry. This is just one of the reasons it is more difficult IRL to notch at close ranges. But just based on geometry it goes something like this: to get into the notch, you arent just 3-9 lining it. Farther out, you dont have to be as precise because the relative angle between the bandit and the radar is less exagerated at farther distances. IE: you dont have to be as close to exactly 90deg to fall into the relative velocity gate. In close, either to a missile or aircraft radar, you would have to be closer and closer to spot on, to the point at which it would be practically impossible to be precise enough to get into the notch. Furthermore, if several missiles are fired, they wont all have the same exact trajectory, so it is extremely unlikely that every single missile would be spoofed. The first one would miss, but the second and third would see you at a different aspect, expecially since you had to maneuver in the first place to get into the notch. If you read account from red flag, or there is at least one I know of from 1991, pilots talk sometimes about how bandits will attempt to notch in close but will fail because of the distance. For a missiles or volley of missiles that dont even go active till they are 10nm out, the effect is exacerbated.

[Frostie]

That's not information' date=' that's bullshit. Lethal range is not a one parameter equation..[/quote']

Who said lethal range this is max range, would it help if I gave a non wiki link?

 

http://www.janes.com/article/37521/india-successfully-tests-home-grown-astra-aam

[Frostie]

Rtr for 120A is ~14nm at 20000'. Is it shorter if the bandit's at low altitude? No one who knows is talking, but at 9nm, that's well inside this Rtr AND the missile is going down-hill. This is not reflected in-game for any of the missiles.

Didn't say it's not an issue but some seem to think actives should be killing from 50nm away at sea level.

[TAW_Blaze]

Who said lethal range this is max range, would it help if I gave a non wiki link?

 

http://www.janes.com/article/37521/india-successfully-tests-home-grown-astra-aam

 

Perhaps?

 

Max range is lethal against a non maneuvering target isn't it.

 

Albeit that link doesn't say a lot more either. No launch speed specified, no target parameters either. This is far from open information.

[GGTharos]

Sure, and some thing ERs should do that. Anyway, yes, people expect a little too much and other accept too little.

 

Also that Astra article was interesting.

 

Didn't say it's not an issue but some seem to think actives should be killing from 50nm away at sea level.

[USARStarkey]

Are you sure you don't mean another sim which you're basing real life on.

From medium altitude and subsonic speed you're cutting the missiles balls.

 

quite sure. at 10nm IRL you are dead. This crap in DCS of dodging missiles in that close is nonsense. Sure anything is theoretically possible, but it is incredibility unlikely you would avoid a AMRAAM this close in IRL.

[GGTharos]

quite sure. at 10nm IRL you are dead.

 

No, you're not.

 

This crap in DCS of dodging missiles in that close is nonsense.

No, it isn't. 10nm is not close. In particular, a low-to-low shot is out of Rtr at that range for any of the playable missiles in the game with the possible exception of the AIM-7, and even that's up for debate.

 

Sure anything is theoretically possible, but it is incredibility unlikely you would avoid a AMRAAM this close in IRL.

It's been done RL, so, what exactly is it you're so certain of?