max range of the an/apg81 and AESA

Cockpit, radar, helmet-mounted display, and other avionics
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playloud

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Unread post10 Oct 2016, 17:56

What kind of price difference would we be talking about for an APG-81 with GaN vs GaA?
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hornetfinn

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Unread post11 Oct 2016, 09:25

playloud wrote:What kind of price difference would we be talking about for an APG-81 with GaN vs GaA?


This question is impossible to answer without knowing what the exact purpose and goal is. For example is the point getting maximum range performance which would mean quite a bit higher number of modules and would mean basically totally new antenna assembly and possibly other significant changes. That would be pretty expensive, likely something like 2-3 times the current unit cost. If the idea was to switch GaAs modules to GaN, it would be less costly, but still more expensive (currently, but changing quickly). If the idea was to have current performance level at lower power consumption and heat generation along with even higher reliability, it might actually be significantly cheaper. This is because much less modules would be needed with GaN and GaN can be used with less to no packaging, less cooling and prime power.

Another thing is that GaN cost has gone down quickly and seem to continue to do so as processes are improved and production is increased massively. I think it's time for fighter radars to move to GaN in about 10 years as right now GaAs is more than good enough and we can get a lot of other improvements to radar systems by then and not just the move from GaAs to GaN. I'm sure F-35 will receive GaN radar antenna at some point, probably in 2025-2030 timeframe.
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spazsinbad

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Unread post13 Oct 2016, 13:16

Sweden’s SAAB sweetens deal for Gripen jet
13 Oct 2016 DINAKAR PERI

"In an aggressive push to capture a share in India’s fighter aircraft market, Swedish aerospace major SAAB has offered its latest radar technology [GaN] as part of the Gripen fighter package...

...Explaining the developments in Advanced Electronically Scanned Array (AESA) radar, Lars Tossman, vice-president & Head of Communications of SAAB said that they were the first company to develop an AESA radar with Gallium Nitride which, he said, significantly enhances its efficiency and performance over the current AESA radars...."

Source: http://www.thehindu.com/news/national/s ... 212340.ece
RAN FAA A4G Skyhawk 1970s: https://www.faaaa.asn.au/spazsinbad-a4g/ AND https://www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/
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bring_it_on

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Unread post14 Nov 2016, 15:07

playloud wrote:What kind of price difference would we be talking about for an APG-81 with GaN vs GaA?


You would have to talk to industry insiders to try to find out the industrial cost of switching materials over to GaN and deliver the sort of scale the JSF as a program demands. I mean, we aren't talking about a couple of dozen radars a year here. That cost imho is a lot more significant than the actual unit cost of the hardware itself since the latter can be used to offset other cost down the road through higher up times, longer life, and less costly upgrades down the road.

At some stage the cost associated with creating that capacity may be more than justified by higher performance, and/or lower cost on account of other programs creating the broader capacity for you. However, unless there is a performance deficiency that can only be overcome by making an investment there are probably far better areas to invest the finite FOD resources than switching over to GaN radar. I agree a decade from now the equation may change but for now there are a lot of capability enhancements that will consume the mult-billion dollar follow on development program.
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spazsinbad

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Unread post12 Aug 2017, 18:50

Just a 50 second video about the APG-81 F-35 AESA radar: https://twitter.com/i/videos/tweet/896383342203023360
RAN FAA A4G Skyhawk 1970s: https://www.faaaa.asn.au/spazsinbad-a4g/ AND https://www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/
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doge

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Unread post21 Sep 2017, 21:04

"2010 Falcon 9 rocket & 2012 NASA's ATREX five rockets" is still in my heart...

APG-81andDAS.jpg


So I made this. (It's not so accurate, though... :oops: )

APG-81 range forecast.jpg


Would you choose what number(1,2,3,4,5,6)? (or Between what number and what number?)
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white_lightning35

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Unread post22 Sep 2017, 00:44

I would choose 1 probably. The upper ranges just don't seem right though due to the radar horizon. I can't see a fighter tracking something from 500km, much less 3400.
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hornetfinn

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Unread post22 Sep 2017, 09:01

AFAIK, the Falcon 9 rocket was not detected and tracked by AN/APG-81 but rather with EODAS only. I don't think it's possible to track such a long distance target with fighter sized radar within near future, no matter how large the RCS is. It also shows that against very hot targets emitting huge amount of thermal energy, IR system can easily outrange radar. It would be interesting to see how EOTS sees such a distant target.

I also think that those 5 NASA ATREX rockets were a lot closer than 1300 km. They were launched from Wallops Island and looking at the map and comparing it to that video it would seem the range is something like 100 to 200 km. Still very impressive range against such a small rocket. Terrier Malemute sounding rocket used is about similar size as large SAMs and has pretty similar launch properties. This is of course not really surprising given the origin of that rocket. I found it very impressive that AN/APG-81 tracked the very small and incredidbly fast second stage until and after the burnout. AFAIK; these rockets have top speed of something like Mach 12 or so. So, we can be pretty sure that any S-300/400 or similar launch will be detected by EODAS very far away and if within AN/APG-81 cone, will be tracked by the radar also. Of course there is EOTS also, which can look for it...

Another very impressive thing about EODAS was that it continuously tracked the burned out first stage to plummet to the ground. While definitely very hot after burnout, it should've been quite well cooled after heading to the ground for about a minute. We are also talking about object that is about the size of a regular air-dropped bomb.
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Dragon029

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Unread post22 Sep 2017, 09:36

hornetfinn wrote:AFAIK, the Falcon 9 rocket was not detected and tracked by AN/APG-81 but rather with EODAS only.

That appears to be correct. My estimate is that it's around 100km away (I did some perspective tracing off Google Earth):

https://www.youtube.com/watch?v=qF29GBSpRF4


One of the rockets launched that night was a Terrior Orion, which is about 10.7m long, 36cm in diameter at the rocket motor and around 1500kg with a payload. A Falcon 9 is about 47.7m long, 370cm in diameter and over 400,000kg.
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doge

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Unread post22 Sep 2017, 12:02

oh...I did not know that... :oops:
white_lightning35 wrote:

hornetfinn wrote:

Dragon029 wrote:

I'm sorry to have caused trouble...! :oops: :oops: And thank you very much for teaching me carefully!



Just in case,
I'll leave things that I modified and subdivided...
APG-81 range forecast2.jpg
Last edited by doge on 23 Sep 2017, 07:55, edited 1 time in total.
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sunstersun

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Unread post22 Sep 2017, 17:28

would be kinda weird if they didn't upgrade to GAN.
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glennwhitten

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Unread post25 Sep 2017, 06:08

One of the posters on the video stated that the image was a digitally processed combination of SAR and DAS data. Sensor fusion?
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hornetfinn

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Unread post25 Sep 2017, 13:12

sunstersun wrote:would be kinda weird if they didn't upgrade to GAN.


That will happen without doubt, but will take some time. Currently GaN is used only in ground radars only but no doubt fighter radars will get GaN modules. But it's not easy thing to do and requires a lot of development work and money to achieve. It's not just that we take out GaAs modules and put new shiny GaN modules in their place. A lot of other things need to be redesigned and replaced and all this is not easy or cheap.
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hornetfinn

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Unread post25 Sep 2017, 13:36

glennwhitten wrote:One of the posters on the video stated that the image was a digitally processed combination of SAR and DAS data. Sensor fusion?


I doubt there is SAR used in those videos, but sensor fusion probably is. I think the video is EODAS imagery with virtual HUD symbology for sensor tracks. It seems like DAS and AN/APG-81 are working together to track the target. It seems like at first one sensor gets a track, then both sensors begin to track the target separately and then symbology quickly changes to single track.
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stealthflanker

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Unread post24 Nov 2017, 21:44

Hmm i wonder if we can work from the cooling capacity to predict maximum average power and then range. It appears for me at least, to work better than just guessing how much power emitted by the TRM.

Im curious if there is anything related to JSF cooling capacity made public ?

Theoritical limit for GaN power electronics is 300 Watt in X-band. However with liquid cooling (155 Kw/sqm) The possible emitted power could be emitted by the TRM would be 105.8 Watt peak and 24 Watt Average power (25% duty cycle, X-band. A-class Amplifier)

With 1676 modules it would be 177 Kilowatt Peak and 44.3 Kilowatt average power. Thing is of course whether the aircraft can carry that 155 Kw/sqm cooling capacity.
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