Missile Dynamics - A discussion

[Alfa]

The lofting logic is indeed nuts.

When lofting a shot surely the nose needs to be elevated to fire the shot and shouldn't there be a cue so as the if the launch angle is not achieved the loft solution will not activate?

 

Yes I believe so - it sounds like lofting is implemented as a fixed feature for certain missiles.

 

Alfa, I am starting to think R-27ER burn time is possibly off, if not, Russians use some pretty fast burning rocket propellent... but also I can't believe R-27ER is just little longer range than 120's, I think it should be more, at least 20km more range... possibly this is cut due to shorter burn time.

 

Well its difficult to compare ranges based just on burn times - i.e. the R-27ER surely has a much bigger engine with more thrust, but is also a much bigger(more drag) and heavier missile.

 

But as I mentioned earlier, the burn time of the R-27ER itself looks very low compared with the other missiles - especially the R-77, which according to your findings has slightly longer burn time despite having a smaller single stage "boost-only" engine. Of course the R-77 is a later design and there could well be a difference in the propellant.

 

But then I read in another post(think it was frostie) that an R-27ER when launched straight at high altitude would "start to fall out of the sky" after some 60 km - thats clearly not right. According to manufacturer's data the 60 km corresponds quite well with their figures against a maneuvering target, but it should be able to achieve a range of some 100 km against a non-maneuvering target, which in turn means that "kinematic" range must be some way beyond that.

[Frostie]

But then I read in another post(think it was frostie) that an R-27ER when launched straight at high altitude would "start to fall out of the sky" after some 60 km - thats clearly not right. According to manufacturer's data the 60 km corresponds quite well with their figures against a maneuvering target, but it should be able to achieve a range of some 100 km against a non-maneuvering target, which in turn means that "kinematic" range must be some way beyond that.

Yes, this was tested on the current public version though.

http://forums.eagle.ru/showpost.php?p=1624500&postcount=681

[wilky510]

All of the test are done ix exact same conditions... flying at exact same speed, altitude and wings level and shots were taken at displayed Rmax, so yes, if you nose up and fire it will have bit more range added due to improved firing condition (to give it more range).

 

Also mind you I wasn't testing this in latest public version but latest testing build (obviously missiles are being worked on)

 

Alfa, I am starting to think R-27ER burn time is possibly off, if not, Russians use some pretty fast burning rocket propellent... but also I can't believe R-27ER is just little longer range than 120's, I think it should be more, at least 20km more range... possibly this is cut due to shorter burn time.

A little more range? It all depends on what version that's in the game, the C5 and up is supposed to have a much larger range than the earlier AIM-120C's. The problem is, this stuff is all classified. I'm sure the Russian stuff is even harder to find too.

 

 

And for the record, people saying it's porked on purpose. I highly doub't that, I'm sure it'll be fixed soon. Especially with every Russian flyer up in rise. You'll soon be outranging us, yet again.

[USAFMTL]

A Especially with every Russian flyer up in rise. You'll soon be outranging us, yet again.

 

But they are easier to spoof and avoid than the AIM-120C series. So its a good trade off.

[USAFMTL]

Hey Kuky I found this.

 

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%.

[IvanK]

Doesn't look too far off as far as ranges go - the only two things in your findings that look a little suspect IMO is the burn time of the R-27ER, for which only 9 sec sounds very low for a two-stage engine. The other is the lofting logic, which from your decription sounds porked.

 

Not AIM120 but AIM7 Loft logic and cueing.

 

[pepin1234]

Also we can see how the AIM-120 of our Sim make pipi over the physics. How come the 120 being a long and 150 kg missile can hit a close target 2 km away and the target is transversal direcction at 800 Km/H. The 120 of ED get over 3000 km/h at this time. I have to say ED should make more code about this feature. Our pilots dont need the AIM-9, because the 120 of ED have enough accuracy for hit a close target. Thats is absolutly wrong in the real life

[USAFMTL]

A. Our pilots dont need the AIM-9, because the 120 of ED have enough accuracy for hit a close target. Thats is absolutly wrong in the real life

 

Incorrect sir, the AIM-120 can engage anything from 2km, to 50/70km depending on the model. At that range mid course corrections are not need from the shooting aircraft and it goes right after the target on its own.

[pepin1234]

Incorrect sir, the AIM-120 can engage anything from 2km, to 50/70km depending on the model. At that range mid course corrections are not need from the shooting aircraft and it goes right after the target on its own.

 

 

I really dont bealive that.

 

First the missile have too much speed to be accuracy and get a high maneuverability.

 

And Second the Coca Cola is the best medicine to treat " anything " right?

 

Of course the affirmation is not logic and every missile have the best performance in certain phase but absolutly not at the first 2 or 3 km maybe even more far. So if ED and all the Beta Tester are so good to find the limitation of the R-27, they should know that too.

[Pilotasso]

Pepin do you have any concrete data other than belief?

[USAFMTL]

I really dont bealive that.

 

First the missile have too much speed to be accuracy and get a high maneuverability.

 

And Second the Coca Cola is the best medicine to treat " anything " right?

 

Of course the affirmation is not logic and every missile have the best performance in certain phase but absolutly not at the first 2 or 3 km maybe even more far. So if ED and all the Beta Tester are so good to find the limitation of the R-27, they should know that too.

 

20 years USAF, 4 years of that was missile maint. I was also AWACS and also did TDY's to the 83rd FWS for FOT&E on AMRAAM's.

[EtherealN]

First the missile have too much speed to be accuracy and get a high maneuverability.

 

The missile has to accelerate before it gets to speed.

[L0op8ack]

The missile has to accelerate before it gets to speed.

 

And,

if collision course was set up properly, there is no need for high maneuverability at all.

[Cali]

It's obvious he has no clue what he is talking about. All he had to do was look at a few internet sites and he would of found his answer. Another thing, it's pretty neat seeing the tactics used in real life in tacview format.

Edited December 10, 2012 by Cali

[pepin1234]

20 years USAF, 4 years of that was missile maint. I was also AWACS and also did TDY's to the 83rd FWS for FOT&E on AMRAAM's.

 

All that not say much about. When u see some TV programs about the US forces and when you hear some solders the say a lot of times the word " the Best " and " the best " and is not so simple like that. I invite you see some TV army programs about the Vietnam weapons and aircrafts war of the 70s. They were the best of the best... not really...

 

It's obvious he has no clue what he is talking about. All he had to do was look at a few internet sites and he would of found his answer. Another thing, it's pretty neat seeing the tactics used in real life in tacview format.

 

 

 

Are you saying INTERNET. No my friend some people here say all say internet is not true, but just when you talking about the good features of the R-27, of course.

[blahdy]

pepin: Please note that in real-life missiles do not behave like CoD:MW or Battlefield 3. 120C is not Mach 4 right out of the rail -- that answers your question wrt maneuverability at close range.

[USAFMTL]

All that not say much about. When u see some TV programs about the US forces and when you hear some solders the say a lot of times the word " the Best " and " the best " and is not so simple like that. I invite you see some TV army programs about the Vietnam weapons and aircrafts war of the 70s. They were the best of the best... not really...

 

Are you saying INTERNET. No my friend some people here say all say internet is not true, but just when you talking about the good features of the R-27, of course.

 

I'm not a TV program, I did my job for real. You're just ignorant.

[lunaticfringe]

All that not say much about.

 

Let's hear your credentials, then. Plus the data to support your claims- whether it be test shot video, RW commentary by individuals who have used/trained on, or maintained the system, or even a mathematical equation to back your premise.

 

The solution as presented within USAFMTL's comments are bound to the laws of physics, and the physics aren't lying. Further, he stated that Rmin turning performance is based on the version of Slammer being used, indicative of the control surface size.

 

I invite you see some TV army programs about the Vietnam weapons and aircrafts war of the 70s. They were the best of the best... not really...

 

Strawman argument: "I can't respond factually or with a logical example by which to reinforce my opinion, so I will throw a bunch of (junk) at the wall and see if it sticks".

 

In this case we have "let me show you television/book/magazine that shows US forces being harmed in combat without context"- those being ROE and tactics. There is simply no commentator on the planet stupid enough to make the remark that the hardware at the disposal of the USAF/USN/USMC was not better than their opposing counterpart; it was merely the methods by which they were used that caused losses. Further, one of those air arms stopped their losses all but overnight by adaptation of their methods to both the threat and their tools.

 

You'd know that if you had context. You'd also know that VPAF loss claims are about as worthless as used toilet paper for two facts:

 

1. they only recorded a combat loss to the enemy with the death/MIA of the *pilot*, not the airframe, and

 

2. their records have subsequently claimed no loss during engagements in which their was no opportunity of escape for the downed pilot, whether almost immediate collision into terra-firma, or an expanding fireball. At least one of these has been caught on film and was called a non-loss, which amps up the bull* meter.

 

So, since we've got your strawman argument out of the way, let's get back on subject and talk *missiles* with *facts*. Your move.

[Cali]

All that not say much about. When u see some TV programs about the US forces and when you hear some solders the say a lot of times the word " the Best " and " the best " and is not so simple like that. I invite you see some TV army programs about the Vietnam weapons and aircrafts war of the 70s. They were the best of the best... not really...

 

I do not understand what you said here. Look how many places say they have the best of this or that? What fighter is the best, who has the best tank, gun or what car is the best? Stats help out a lot, without them you really can't say much.

 

 

 

 

Are you saying INTERNET. No my friend some people here say all say internet is not true, but just when you talking about the good features of the R-27, of course.

 

Look at enough sites and you can get a very good guess on the range. You can't trust everything you read on the net, but some sites are pretty good. It seems like you didn't do any homework into this matter at all.

[Devilman]

R-27AE
Lengthft(m) 15.68(4.78)
Weight Ib (kg) 772(350.3)
Range mi (km) 50(80.5)

R-27EM
Lengthft(m) 15.66 (4.78)
Weight Ib (kg) 772(350.3)
Range mi (km) 50(80.5)

R-27RE
Lengthft(m) 15.68(4.78)
Weight Ib (kg) 772(350.3)
Range mi (km) 105.6(170)

R-27R
Length ft (m) 13.38 (4.08)
Weight Ib (kg) 558(253)
Range mi (km) 37.26 (60.0)

R-27T
Length ft (m) 12.46 (3.80)
Weight Ib (kg) 540(245)
Range mi (km) 12.4(20)

R-27TE
Lengthft(m) 14.75(4.5)
Weight Ib (kg) 560 (254)
Range mi (km) 25 (40.26)

R-73E
Lengthft(m) 9.51(2.90)
Weight Ib (kg) 230.3 (104.5)
Range mi (km) 24.8(40)

R-77(RVV-AE)
Lengthft(m) 11.81(3.60)
Weight Ib (kg) 385(175)
Range mi (km) 62.1(100)

R-60M
Length ft (m) 6.86(2.09)
Weight Ib (kg) 95.9(43.5)
Range mi (km) 4.97(8)

The wide variation in significant digits
in the original Russian data did not allow a
reasonable choice for a standard presentation.
In all cases, the metric data contains all
the significant digits that are available in the

Russian source material.....


[left]In rare cases, data in the text did not[/left]






[left]agree with the tabular data. The authors
made every effort to identify and correct
such discrepancies. However, some examples
remain. Usually, the differences are
small....[/left]

[Cali]

24 miles for a 73e? wow

[Devilman]

i think i would take more from the item r-27te at 25mi.

 

with the note's in the document stating some minor inacuracy's in translation, the assumption on the comparison of the 73 v 27-et would lead the conclusion is based on the seeker head.

 

that said the assumption is also the case on the 27em ae er with different range items for most.

 

the table data taken from a sukhoi book published in english 1996

[Groove]

In real life you would never tell your self this missile is bad so I pincer and wait, I know it will miss. You react different since you cant relay on your gathered intelligence as you can in games. That's why to emit this situation in a simulation you have to make missile deadly on both sides so the level of realism reaches in another point then just technical where the pilots learn how to exploit it after a while. ( or make the aim-120 not as effective in active state). That would not make the simulator less realistic rather the opposite.

 

This is proven to work in GI multiplayer campaign since the opponents don't know if they are fired upon by R or ER they have to take same defensive maneuvers as it would be ER.

 

Well, not 100 % true. In the 2nd Gulf War Allied Pilots being warned by their RWR that a SAM was launched at them tried to visually aquire that particular SAM. That way they could see if its guiding after them, and if it was not, they didnt evaded.

[GGTharos]

AIM-120's and R-77's, heck 7M/H's and R-27's that are modeled in game are not 70's missiles. Missile capability has been increasing, not decreasing. Are you going to judge the fuel efficiency and maintenance requirements of a car today by the standards of a 70's car?

 

But okay, you found some 'TV episodes where soldiers are saying this is the best' and 'Vietnam era missile things' ... and because of this we can ignore the opinion of USAMFTL, who works with these things for real, but his opinion 'doesn't say much'.

 

I think by this metric, your opinion is entirely worthless. There is simply no reason for the devs to consider anything that you suggest.

 

Is this your argument?

 

All that not say much about. When u see some TV programs about the US forces and when you hear some solders the say a lot of times the word " the Best " and " the best " and is not so simple like that. I invite you see some TV army programs about the Vietnam weapons and aircrafts war of the 70s. They were the best of the best... not really...

 

 

Are you saying INTERNET. No my friend some people here say all say internet is not true, but just when you talking about the good features of the R-27, of course.

Edited December 10, 2012 by GGTharos

[pepin1234]

AIM-120's and R-77's, heck 7M/H's and R-27's that are modeled in game are not 70's missiles. Missile capability has been increasing, not decreasing. Are you going to judge the fuel efficiency and maintenance requirements of a car today by the standards of a 70's car?

 

But okay, you found some 'TV episodes where soldiers are saying this is the best' and 'Vietnam era missile things' ... and because of this we can ignore the opinion of USAMFTL, who works with these things for real, but his opinion 'doesn't say much'.

 

I think by this metric, your opinion is entirely worthless. There is simply no reason for the devs to consider anything that you suggest.

 

Is this your argument?

 

What are you say about cars man?? USAMFTL say he was in the USAF and also the 120 can hit anything for 2 km, and I say the accuracy of the 120 must being not 100% because the missile can get the match 3,5 when approach the target in this phase. He was an USAF former saying his opinion, and I owner a SAMSUNG Galaxys, do you like know my opinion about wich one is better betwen the SAMSUNG and the Iphone?? That way I say the 120 should be downgraded in this phase, because right now is too much good and thats not possible at all.