AIM-54 Phoenix performance

[Stratos]

Would a AWACS or a early warning radar station detect a Phoenix launch?

[captain_dalan]

Would a AWACS or a early warning radar station detect a Phoenix launch?

Ouch, we had a long discussion on this one and GGT made some very good and detailed points. Maybe he can point you out to the thread?

 

(Short answer - and least satisfactory..... depends)

[Stratos]

Ouch, we had a long discussion on this one and GGT made some very good and detailed points. Maybe he can point you out to the thread?

 

(Short answer - and least satisfactory..... depends)

 

Will like to read such discussion, hope someone can find the post.

[Pilum]

Attached is a track with an AI controlled F-14 launching an AIM-54C at an AI controlled Tu-95 at a distance of 180 Km. The track shows the missile accelerating to an astounding TAS= 6700 Km/h (M=6.3) and it is only lofted to an apogee of 20 Km altitude at which point it has a speed of M=5.4. It then decends towards the target and slams into the Bear at M=3.5!

 

This type of missile performance is more in line with what you would have expected to come of the rails on an X-wing scrambled from Tatooine rather than a missile launched from a Tomcat and my guess is that an Admiral in the USN would have given his right arm to get his hands on this type of hypersonic missile. :smilewink:

 

Attached is also what I think is a more realistic AIM-54C performance estimate, now based on the new impulse estimate of 91728 lbs for the Mk47 rocket motor as per data based on post #15. Note that this scenario is very optimistic even though launch range is 169 Km not 180 Km since the missile has a modest M=1.3 at impact and any manouvering by the target would defeat the missile.

 

I have tried to come as close as possible to the launch scenario in the DCS track in the attached C++ simulation but as can be seen, a more realistic estimate of the AIM-54C performance is nowhere close to the current performance in DCS.

 

Looks like the Phoenix flight model needs some major tweaking.

F14A long range AIM54 Tu95 kill.trk

Edited March 28, 2015 by Pilum

[GGTharos]

Yup, that looks more realistic.

 

NASA expects 8 sec at M5 when the missile is launched (on an arcing trajectory, I don't want to call it lofting) at M2 and 50000', and 50 sec at M4.

 

I think your loft trajectory is not what a missile would do, but that's just a slightly educated guess that might be wrong. Basically, I expect the dice angle at the end to maintain the target maybe 5-10 deg below the missile flight path with a smooth transition to pure in altitude at say maybe 10km, then lead when closer.

[Pilum]

Yup, that looks more realistic.

 

NASA expects 8 sec at M5 when the missile is launched (on an arcing trajectory, I don't want to call it lofting) at M2 and 50000', and 50 sec at M4.

 

I think your loft trajectory is not what a missile would do, but that's just a slightly educated guess that might be wrong. Basically, I expect the dice angle at the end to maintain the target maybe 5-10 deg below the missile flight path with a smooth transition to pure in altitude at say maybe 10km, then lead when closer.

 

Why don't you think the missile would fly like I modeled? I think the way it flies now would be pretty efficient: First, get up as fast as possible into thin air to reduce air resistance, so go for 45 deg loft. In this phase no need for lift, i.e fly at 0 deg aoa to reduce drag even further. Then when at apogee, start flying at best "glide ratio" to extend flight further than when going 0 g load factor all the way. In fact, I can get the missile to fly even further by increasing aoa at apogee, e.g flying at 0.9 g load factor, but then it's much slower when it comes down to do the intercept.

 

So what would in your opinion be a more efficient efficient flight path than the one I run now? Maybe I could model it and see how that would compare?

[GGTharos]

You need to optimize for the intercept, not just range. Reducing look-down is beneficial, especially for a missile with older technology; certainly 120's don't fly like this, nor do Nike's.

 

There's some sort of compromise between range optimization, time-to-target and geometry. That's why.

 

I think the initial loft to altitude (30-45deg) is fine, but I believe the missile will 'cruise' at an altitude until it is time to dive at an angle that will optimize intercept geometry, not necessarily glide (but since you're already going down-hill, it's still very beneficial).

 

Like I said, stick the target a certain amount of degrees under the horizon, then reduce this number of degrees as you get closer to reduce maneuvering is the target attempts a last second jink.

 

So what would in your opinion be a more efficient efficient flight path than the one I run now? Maybe I could model it and see how that would compare?

[Pilum]

You need to optimize for the intercept, not just range. Reducing look-down is beneficial, especially for a missile with older technology; certainly 120's don't fly like this, nor do Nike's.

 

There's some sort of compromise between range optimization, time-to-target and geometry. That's why.

 

I think the initial loft to altitude (30-45deg) is fine, but I believe the missile will 'cruise' at an altitude until it is time to dive at an angle that will optimize intercept geometry, not necessarily glide (but since you're already going down-hill, it's still very beneficial).

 

Like I said, stick the target a certain amount of degrees under the horizon, then reduce this number of degrees as you get closer to reduce maneuvering is the target attempts a last second jink.

 

I actually tried extending the range by a more cruise like flight: In this case the missile transitions to 0.9 load factor at apogee and it does fly longer: 175 Km as compared to the 135 Km in the scenario the figure in post #29 depicts so it flies longer but the flight time is very long: 273 s and it is basically out of energy only doing M=0.9. Read somewhere that the battery time on the Phoenix was in the order of 200 s but not sure about that.

 

In addition, I agree about the intercept: The scenario modeled in #29 is purely theoretical for max range and for a more lethal shot the missile needs to have more energy when it comes down. Say, the Tomcat was to launch at 136 Km instead, then the missile would hit the target 132 s later at a respectable 1985 Km/h or M=1.84 after flying 110 km.

Edited March 28, 2015 by Pilum

[turkeydriver]

The AIm-54 should use info from the radar and its own avionics to determine the best profile. The longest range shot would use that drastic climbout and arc to achieve highest speed and range but I'm not sure about the final leg dropping to attain the target at 10-15 degrees below the missile and then co-altitude. I'd think of it as an inverse SAM that would drop down using pulse to keep the beam from being effective. Under 10 miles you would have a near 90 degree reflection from the huge planform(bomber) of the target and have the best return. If you're co-altitude the best signal return comes from the engine face if viewable, the mounting bulkhead for the radar dish, and the cockpit installations(seat, HUD, pilot). Regardless of the head on returns, they would be smaller than a return of the entire planform from directly above and only benefit a Doppler radar lock. During fighter intercepts, this is the most typical type of engagement, so fighter weapons and tactics are focused on using this to the best benefit. The AIM-54 definitely uses co-altitude during min distance shots -up to 10 miles, and low-altitude cruise missile engagement. I don't know if the AWG-9 and onboard AIM-54 avionics tell the missile to engage a fighter differently than a bomber during the end-game. I'd say the different profiles is bogus, but the AIM-54C AFAIK engages low-altitude cruise missiles with a unique flight profile, just like the long range engagement is unique. I'm betting getting any type of accurate answer is not possible at this time.

[GGTharos]

There's more than one paper out there describing optimal trajectories at least based on geometry.

 

As for 'diving under' the target, never heard of a single AAM/SAM doing anything like that, and I can already think of at least two good reasons as to why not. Incidentally, reflection from top or bottom will be greatest, because tennis court.

[turkeydriver]

There's more than one paper out there describing optimal trajectories at least based on geometry.

 

As for 'diving under' the target, never heard of a single AAM/SAM doing anything like that, and I can already think of at least two good reasons as to why not. Incidentally, reflection from top or bottom will be greatest, because tennis court.

 

not diving under- I'm meant a "reverse SAM" because it dives from above instead of climbing from below. Of course they'll both calculate lead pursuit to get the kill, but both profiles offer a large radar target for a pulse based system.

[Pilum]

The AIm-54 should use info from the radar and its own avionics to determine the best profile. The longest range shot would use that drastic climbout and arc to achieve highest speed and range but I'm not sure about the final leg dropping to attain the target at 10-15 degrees below the missile and then co-altitude. I'd think of it as an inverse SAM that would drop down using pulse to keep the beam from being effective. Under 10 miles you would have a near 90 degree reflection from the huge planform(bomber) of the target and have the best return. If you're co-altitude the best signal return comes from the engine face if viewable, the mounting bulkhead for the radar dish, and the cockpit installations(seat, HUD, pilot). Regardless of the head on returns, they would be smaller than a return of the entire planform from directly above and only benefit a Doppler radar lock. During fighter intercepts, this is the most typical type of engagement, so fighter weapons and tactics are focused on using this to the best benefit. The AIM-54 definitely uses co-altitude during min distance shots -up to 10 miles, and low-altitude cruise missile engagement. I don't know if the AWG-9 and onboard AIM-54 avionics tell the missile to engage a fighter differently than a bomber during the end-game. I'd say the different profiles is bogus, but the AIM-54C AFAIK engages low-altitude cruise missiles with a unique flight profile, just like the long range engagement is unique. I'm betting getting any type of accurate answer is not possible at this time.

 

Ok, that the missile would have different flight profiles for different ranges makse sense: No need to loft if the shot is closer ranged since the burn time of the engine is 27 s there is plenty of energy to allow a high speed proportinal navigation intercept in the horizontal plane as well. So it sounds logical that the fire control system in the AWG-9 radar would most likely then have some kind of grading of the commanded flight profile from a horizontal shot at close range to a high loft at extreme ranges. OTOH I guess the AIM-7 would be used unless the longer legs of the Phoenix is needed and what's close for the Phoenix might mean quite long for the AIM-7.

 

About the guidance in the end phase the idea that the missile would dive down early and not attack from above sounds interesting. I guess it makes sense in a way since it makes it easier for the on-board radar to aquire the target with more clear sky as background instead of major ground clutter. However, if the AWG-9 radar is able to maintain lock all the way then the missile radar should have both range and doppler info making it easier for the on-board missile radar to lock-on since both the range- and velocity gates in the missile know in which bins to expect the target given that this should be extractable from combining the radar measured range and speed with ditto from the missile INS. OTOH given the small aperture of the missile radar antenna the main- and sidelobe clutter may be troublesome so maybe the missile really needs to dive down to be closer to co-altitude to the target. Guess it also depends on the type of target? A Tu-95 should give quite a heft return but I guess it's different if the target is a fighter and in addition, I wonder if it really was in the AWG-9's capability to lock up a figther sized target at 120-180 km?

 

Anyway, the main thing I wanted to point out is that the kinematic FM of the Phoenix in DCS right now seems to be way too optimistic and since the Mig's R-3R is AFAIK scheduled to be adjusted (see link below) then the Phoenix FM will also need some TLC. Just to improve the Phoenix's kinematics would be a step in the right direction but too also get the long range guidance closer to IRL behaviour would of course be icing on the cake.

 

http://forums.eagle.ru/showpost.php?p=2308197&postcount=1

[captain_dalan]

A Tu-95 should give quite a heft return but I guess it's different if the target is a fighter and in addition, I wonder if it really was in the AWG-9's capability to lock up a figther sized target at 120-180 km?

 

At that range, who knows.... even detection would be tricky, let alone a soft lock.

[Stratos]

Anyone found the PHoenix detected by AWACS post?

[GGTharos]

Why are you asking? What do you actually want to know?

[Stratos]

Why are you asking? What do you actually want to know?

 

If a Phoenix launch can be detected by an AWACS or a EW ground station.

[Paradox]

If it can be detected and tracked by radar then yeah it can.

 

A missile that shape and size ought to have a sufficient RCS to be detected by AWACS.

 

I couldn't speculate as to what range it could be detected at.

[GGTharos]

Right, I mean why do you want to know that? What is the question you actually want to answer (or what is it you want to assume based on the answer?) :)

 

If a Phoenix launch can be detected by an AWACS or a EW ground station.

[Stratos]

Right, I mean why do you want to know that? What is the question you actually want to answer (or what is it you want to assume based on the answer?) :)

 

If SOVIET AWACS and/or Early Warning ground station can detect such launches and help friendly fighters to avoid the missile is my real doubt.

[GGTharos]

No, they can't. That's why you have an on-board RWR.

[Stratos]

No, they can't. That's why you have an on-board RWR.

 

So, AWACS will not detect a Phoenix launch?

[GGTharos]

It'll detect a launch against itself (technically, if you are watching for video separation you can detect the launch, but no one does this when they've got to watch multiple targets at once - you could see it when you're STT on a contact, so SAM operators could see eg. missile or bomb separation from an aircraft but they couldn't track it after - you won't know what was launched and what it's aimed at anyway).

 

They'll detect the F-14 though ... then again, so will your RWR when the time comes.

Edited March 31, 2015 by GGTharos

[Stratos]

It'll detect a launch against itself.

 

The question is, can a A-50 track a AIM-54 from launch during all it's flight?

[GGTharos]

Not very likely. Even if they did, they can't/won't do anything about it, they have other things to do ... this is why there's an RWR onboard your aircraft.

 

The question is, can a A-50 track a AIM-54 from launch during all it's flight?

[Stratos]

Not very likely. Even if they did, they can't/won't do anything about it, they have other things to do ... this is why there's an RWR onboard your aircraft.

 

Pretty hard for me to read it properly in russian fighters. :(

 

Thanks for the info!