AIM-54 guidance

[renhanxue]

From everything that I read they never mentioned target RCS as a significant factor. Jammer/Signal ratio is maybe what you meant. The returns of a Tu-22 aren't "stronger" than the ones from a MiG-29 in that they have the same energy. You may get more returns from a Backfire but that will not effect burn-through range. And as the noise jammer only needs to be 50% the power of the radar he is jamming I'd guess it's very much possible to jam an AWG-9 at 10 miles with the power and cooling allocations you have in a Tu-22.

Well, you're right in practice. The RCS does matter, but from the radar equation it follows that while received power is proportional to the RCS, it is inversely proportional to R⁴ (where R is the range). Meanwhile, energy received from a jammer is inversely proportional to R² (since it doesn't have to bounce and come back - it's traveling only one way), and that's why the burn-through distance is a thing: energy received from the jammer falls off slower over range than energy received from echoes does.

 

Furthermore, range tends to be three orders of magnitude larger than RCS (from around 1 m² to around 100 m² for RCS and from about 1 to about 100 km for range). In other words, as far as jammer power output requirements go, if you want to hide yourself, range is vastly more important than RCS.

 

edit: to review the maths:

      Ps * G² * σ * λ² 
Pe =  ----------------
        (4π)³ * R⁴

Where:

Pe is the received power (in Watts)

Ps is the transmitted power (in Watts)

G is the antenna gain

σ is the RCS (in meters squared)

λ is the wavelength (in meters)

R is the range (in meters)

Edited May 11, 2016 by renhanxue

[Beamscanner]

From everything that I read they never mentioned target RCS as a significant factor. Jammer/Signal ratio is maybe what you meant. The returns of a Tu-22 aren't "stronger" than the ones from a MiG-29 in that they have the same energy. You may get more returns from a Backfire but that will not effect burn-through range. And as the noise jammer only needs to be 50% the power of the radar he is jamming I'd guess it's very much possible to jam an AWG-9 at 10 miles with the power and cooling allocations you have in a Tu-22.

 

The returns from a TU-22 are stronger then the returns from a MIG-29. The RCS of a TU-22 is significantly larger.. Thus it requires more power to mask the skin return from a TU-22 then a MIG-29.

 

As stated above, range is also a huge factor. It's much easier to have a 1/1 or better J/S ratio at longer distances because two way path loss(the radar signal) is inversely proportional to range to the 4th power (1/R^4) and one way path loss(the jammer) is only (1/R^2).

 

However, at closer ranges(like 10 miles) this loss is no longer significant enough to allow over a 1/1 J/S ratio. That is unless of course you have an extremely powerful jammer with high gain, and/or have an extremely small RCS (F-22 style).

Edited May 10, 2016 by Beamscanner

[Vitormouraa]

The returns from a TU-22 are stronger then the returns from a MIG-29. The RCS of a TU-22 is significantly larger.. Thus it requires more power to mask the skin return from a TU-22 then a MIG-29.

 

As stated above, range is also a huge factor. It's much easier to have a 1/1 or better J/S ratio at longer distances because two way path loss(the radar signal) is inversely proportional to range to the 4th power (1/R^4) and one way path loss(the jammer) is only (1/R^2).

 

However, at closer ranges(like 10 miles) this loss is no longer significant enough to allow over a 1/1 J/S ratio. That is unless of course you have an extremely powerful jammer with high gain, and/or have an extremely small RCS (F-22 style).

 

Beamscanner, what would happen if I lose the track while my AIM-54 still on SARH mode? Can I turn off the radar as well and it goes Active automatically?

[captain_dalan]

10 nm is the maximum usable range of the TCS for a fighters sized target. Bombers, transports and liners could be discerned and tracked from greater distances.

[Beamscanner]

Beamscanner, what would happen if I lose the track while my AIM-54 still on SARH mode? Can I turn off the radar as well and it goes Active automatically?

 

No sure, we dont have any hard data.

 

If you lose the target because its jamming you, the seeker will probably go to a HOJ mode.. But how it knows when to switch on its active seeker once in HOJ mode I dont know. The seeker can only be active for so long, turn it on too early and its a failed intercept. Perhaps for this reason it doesn't ever turn on and fly's passive PN into the jamming source..?

 

If you lose the target because he got into your doppler notch, or you got hooked on chaff, you better have had the TCS locked on him. That way you can slave the illumination beam onto the target anyway. But you'd have to be close for this, and you still wouldn't have any range information.

[ShuRugal]

No sure, we dont have any hard data.

 

If you lose the target because its jamming you, the seeker will probably go to a HOJ mode.. But how it knows when to switch on its active seeker once in HOJ mode I dont know. The seeker can only be active for so long, turn it on too early and its a failed intercept. Perhaps for this reason it doesn't ever turn on and fly's passive PN into the jamming source..?

.

 

Depending on how much room for computer hardware is in the missile, you could program the missile to gauge closure based on the increase in relative gain from when it entered HOJ mode. Since received signal is proportional to the square of range, when signal has doubled, range has decreased to 1/4 of last known value.

[MikeHunt]

Because videos...

 

 

 

 

 

 

I found the Iranian combat accounts on the F-14 to be very interesting.

Edited May 12, 2016 by MikeHunt

[GGTharos]

HoJ isn't what most people think it is. And if you want a 'range' count-down you can count down time-to-go from the last known good value. It's more realiable than measuring jammer power, which can easily vary.

 

Depending on how much room for computer hardware is in the missile, you could program the missile to gauge closure based on the increase in relative gain from when it entered HOJ mode. Since received signal is proportional to the square of range, when signal has doubled, range has decreased to 1/4 of last known value.

[Beamscanner]

HoJ isn't what most people think it is. And if you want a 'range' count-down you can count down time-to-go from the last known good value. It's more realiable than measuring jammer power, which can easily vary.

 

^Yeah I agree.

 

The jamming signal might change it's amplitude(depending on the jamming program) or the seeker might move out of the main beam of the jammer thus decrease the received power. So its not especially useful to try and determine range from the jammer's amplitude, because it may vary for reasons besides range decrease.

 

Most recent time to go makes sense.

Edited May 12, 2016 by Beamscanner

[Beamscanner]

here's an idea.

 

What if the terminal stage of guidance is activated by a pre determined depression angle on the received SARH reflection (or jamming source). We know that the AIM-54 does a pop up to high altitude, and maintains that altitude until it triggers it's terminal stage and dives down. Example: a downward angle on target of -45 degrees or an angular rate of change of 1 degree per second or more, trigger the terminal dive. No range data needed.

 

Sorry for the double post. I couldn't add these files to my previous post.

[GGTharos]

An interesting idea but I really don't believe it's in any way idea ... but I could be wrong.

The implementation of lofting algorithms that I have seen tends to reduce angle from boresight based on distance.

 

Of course, I'm pretty certain I haven't seen anywhere near to all the algos. :)

[lunaticfringe]

Not exactly sure where i read this (considering missile coding), but if memory serves each 54 was "color coded" before plane launch, in such a way that it corresponded to only one AWG9 "module"... I can't even recall the exact mechanism of beam recognition (it could be beam frequency, or something else similar to FOF).

 

Something to keep in mind is that the AWG-9 used frequency modulation as a technique to get around range ambiguity- subsequently, the ability to do this in a discrete fashion is already built into the system. Tie a specific modulation pattern to a missile as part of its tuning sequence, and invoke that modulation at the exact moment the TWS sweep should be looking in the airspace of a target needing update, and you just gave a specific missile its data. Meanwhile, the AWG-9 processes the return it sees just like any other pulse.

 

Depending on the bar/azimuth setting of the radar in TWS, there is essentially two possible timestamps for duration between sweeps. If the modulation is constructed with both a cue (to tell the missile to look) and a simple data package- such as modulation plus a secondary "off" modulation that somehow denotes range or a timestamp, you just gave actual range, or a component from which range can be computed using simple time, speed of light, and the weapon's own downrange travel and off-boresight shift to the target. Even an analog system of the day would be able to perform the computations just using its own speed (based on the specific launch/loft profile invoked at launch- of which there were several) and, generally speaking, not need the secondary part of the suggested modulation package- just the modulated ping to say "THAT GUY".

 

As far as the number of NPS thesis excerpts, DTIS/NTIS reports, and a few applicable NAVAIR documents, the -54A's datalink was very limited; with what I can ascertain, you're likely looking at simple changes in profile, designating active/HOJ, or perhaps updating the relative aspect indication to the weapon to something other than what it was told prior to launch (see: left RIO upright panel). When the AIM-54C became available, all sorts of magic happened with the DL in conjunction with the change to command inertial guidance.

 

Encoding target range from the carrier into the radar signal so the missile would decode it from a reflected signal just sounds overly complicated as I don't see what good would this range from the launching aircraft information do to the missile? The target may have changed course, velocity, etc. and the same goes for the launching aircraft.

 

You don't know what value would be found by a missile getting anything in the way of a range update as part of a reflected signal transmitted by it's launching aircraft at, accounting for atmospheric loss, 98% of the speed of light, because the target might have changed course and/or velocity in the time it took for...

 

...the most recent target pulse to be received...

...the AWG-15 to compute the apparent range...

...delay between bar/scan evolution (~6 seconds)...

...the AWG-9 to transmit the new modulated pulse...

...the pulse to reach the target aircraft and reflect...

...and the reflection to reach the missile in question?

 

Do you legitimately think a target is going to change these dynamics in an integral fashion in perhaps seven seconds to a point where the missile can't use it? A target moving at 500 knots hasn't moved a mile and a half in that time. And engagement dynamics being what they are, if they haven't gotten a shot warning or are otherwise occupied, the the aspect isn't making appreciable difference on the Doppler side of the house. Missile sees the return, adjusts for angle, and calculates new internal estimate of range.

 

The weapon doesn't specifically need that data, but in proportional navigation every little bit helps. And depending on the methodology it's trivial for the weapon to compute raw range from transmission, rather than its power.

[Dudikoff]

You don't know what value would be found by a missile getting anything in the way of a range update as part of a reflected signal transmitted by it's launching aircraft at, accounting for atmospheric loss, 98% of the speed of light, because the target might have changed course and/or velocity in the time it took for...

 

...the most recent target pulse to be received...

...the AWG-15 to compute the apparent range...

...delay between bar/scan evolution (~6 seconds)...

...the AWG-9 to transmit the new modulated pulse...

...the pulse to reach the target aircraft and reflect...

...and the reflection to reach the missile in question?

 

Do you legitimately think a target is going to change these dynamics in an integral fashion in perhaps seven seconds to a point where the missile can't use it?

 

I was talking about long range shots and the time needed by the lofting missile to get into the SARH range (inside which it can receive these reflections) which is much more than these 7 seconds.

Edited May 22, 2016 by Dudikoff

[punk]

The only reference I have ever came across was in a training or testing manual for ordies I think. I haven't the full title since it is an extract from somewhere.

 

"14313 CHAPTER 15 AIRCRAFT WEAPONS SYSTEMS The AIM-54 and AIM-7 missile fire control systems help to select, prepare, and launch AIM-54 and AIM-7 missiles. The AIM-54 is a long-range, semiactive, radar midcourse guided and active radar terminal guided missile. It operates in either the normal or boresight mode."

 

Don't know if that adds to your discussion or merely restates what you guys are arguing. Of course there is more than this regarding the AWG-9 system and such, but only general info. My understanding about its active terminal distance was around 10 miles or so.

 

<Salute>

Punk

[lunaticfringe]

I was talking about long range shots and the time needed by the lofting missile to get into the SARH range (inside which it can receive these reflections) which is much more than these 7 seconds.

 

Doesn't actually matter; the longer the range, the *less* the relative aspect change a target can make against the weapon.

[mherssens]

I came here to have an interesting read and I was not dissappointed at all. heh

 

I just like playing simulators because it's the next best thing to real flying. And I have been doing this for nearly 25 years. However, When I hear you guys talk, I am at a dead loss. You all use more terminology then NASA during a spacelaunch.

 

I guess that's how much you love DCS and Aerodynamics. It's truelly heartwarming to see you guys getting involved so much.

 

Sorry, I didn't mean to change the subject of the thread, but after 9 pages of not understanding anything, yet having a thrilling read, I just had to mention this.....for reasons.

[Chrinik]

Doesn't actually matter; the longer the range, the *less* the relative aspect change a target can make against the weapon.

 

Turning 90 or 180° away from the missile is turning 90 or 180° away from the missile, no matter how far it is away.

 

You were talking relative angular change, not aspect change.

Aspect can change quite dramatically quite quickly.

[lunaticfringe]

Turning 90 or 180° away from the missile is turning 90 or 180° away from the missile, no matter how far it is away.

 

You were talking relative angular change, not aspect change.

Aspect can change quite dramatically quite quickly.

 

This is true. I was in the middle of authoring an aspect training module for the board simulation I work on and it was stuck in mind.

[lunaticfringe]

Re: CW operation with embedded FM ranging.

 

One can be quite certain that the same technique applied with the AIM-7 is used between the AWG-9 and AIM-54 as described in both STT and TWS; all that changes is the rate of update.

[lunaticfringe]

The fight for data continues...

[D4n]

Ah so CNO office will reply to the request soon, good. Can't wait! :D

[lunaticfringe]

I *hope*, but my expectations aren't high. If rejected, I could go for an SBU (sensitive but unclassified) review, but that gets into MDR (mandatory declassification review) money territory at $55/hr, and they can get almost punitive depending on who you're dealing with, and still wind up with a mostly blank document.

[D4n]

Wait, 55 $ per hour? Who's gotta pay that then?!?!

[Vampyre]

Wait, 55 $ per hour? Who's gotta pay that then?!?!

 

The person requesting the information is.

[D4n]

Where is the price from? Is there a list on the internet with the prices?