Operational Performace Comparison: Viper, Beagle, and Stubby

The F-35 compared with other modern jets.
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southerncross

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Unread post24 Sep 2019, 16:17

sprstdlyscottsmn wrote:The loft angle and loft logic have a huge impact on range. I based my missile model on the C5 and then increased range through lofting changes only.

Interesting, this sounds counter-intuitive but that is why we make calculations in the end. I will try to learn more about the issue. It is nevertheless relevant that the energy content of the missile is in principle not increased but just used more intelligently.
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botsing

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Unread post24 Sep 2019, 17:18

sprstdlyscottsmn wrote:The loft angle and loft logic have a huge impact on range. I based my missile model on the C5 and then increased range through lofting changes only.

With the AIM-120D version having the exact same motor as the C7 version I wonder if that also applies for the physical shape of the motor channel.

SpudmanWP had a very interesting post about that shape:

Image

viewtopic.php?p=308957#p308957

I think that is especially interesting when you combine those channel profiles with the different loft profiles.
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Unread post24 Sep 2019, 19:21

That's not something I can currently model. I use thrust profile 2 for everything except the Meteor where I was able to simulate throttling.
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botsing

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Unread post25 Sep 2019, 14:15

sprstdlyscottsmn wrote:That's not something I can currently model. I use thrust profile 2 for everything except the Meteor where I was able to simulate throttling.

Understandable.

My assumption would be that for range a rapid rise in speed to a less dense air level would be preferable, after that it should "coast" with the remaining thrust as long as possible to maintain it's speed and height.

It's too bad that in that image the thrust/time graph of each channel is compressed to fit, due to that we don't have the complete dataset to use in a model.
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Unread post25 Sep 2019, 14:39

Actually, I do model 5 as well as a dual pulse. Those offer phenomenal range with long slow burns in high altitude (long being 15-20s)
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Unread post25 Sep 2019, 16:37

sprstdlyscottsmn wrote:Actually, I do model 5 as well as a dual pulse. Those offer phenomenal range with long slow burns in high altitude (long being 15-20s)

Interesting! That one looked indeed like a favorite for long range.

And to avoid confusion, with dual pulse I assume you mean "dual-thrust" as in having a boost grain and a sustain grain?
SpudmanWP wrote:Terminology with rocket motors in not used consistently on the net (surprised?)

Previous generations of AMRAAMs had two different kinds of rocket fuel in them, boost and sustainer. When the missile is launched, it's the boost grain fuel that is burning. It burns quicker in order to get the missile up to speed. When the boost grain runs out, the sustainer fuel begins to burn. It burns slower in order to maintain the speed of the missile while it flies toward the intercept. There is no pause in the time that the boost runs out and the sustain starts.

An all-boost motor only uses one grain and is primarily used to get the highest speed possible. For the AMRAAM it is useful in the lofting flight profile as with the increase in speed comes a higher arc and thereby granting a longer range.

Some people use the term "Dual Pulse" interchangeably when talking about a motor with two grains and one where half the fuel is burned, the motor stops, then the motor can restart for the endgame engagement. The proper term for a boost/sustain classical motor is "Dual Thrust"

http://www.f-16.net/forum/viewtopic.php?p=308953#p308953
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Unread post25 Sep 2019, 17:10

Yes that is what I mean. Short time high thrust followed by long time low thrust.
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Unread post25 Sep 2019, 20:52

marsavian wrote:Yes Captor-M will be moved from side to side, up or down, but it will still spend less time in the vertical position than the fixed RBE2. Any Captor will be more stealthy than any RBE2 variant.


Well thats your opinion. According to Hornetfinn the rotation of the dish makes it a good reflector for radar waves. Even more than a untitled PESA/AESA Radar. This means roughly 1m2 RCS only from the rotating plate.
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Unread post26 Sep 2019, 08:31

swiss wrote:
marsavian wrote:Yes Captor-M will be moved from side to side, up or down, but it will still spend less time in the vertical position than the fixed RBE2. Any Captor will be more stealthy than any RBE2 variant.


Well thats your opinion. According to Hornetfinn the rotation of the dish makes it a good reflector for radar waves. Even more than a untitled PESA/AESA Radar. This means roughly 1m2 RCS only from the rotating plate.


Yes it does in most cases. When we compare fixed phased array antenna and mechanically scanned antenna, both will have pretty significant RCS perpendicular to the antenna (especially within +- few degrees). In RBE2 style radar that means that if the aircraft nose is pointed directly at enemy radar, it will have that increased RCS. If the nose is pointed off more than something like 5 degrees the RCS contribution from the antenna drops quickly and very significantly. With MSA radar like Captor-M the antenna moves from side to side and up and down constantly. This means there will be RCS spike when the antenna points towards an enemy radar. Becuase of the mechanical scanning, the antenna will have to point towards all the enemy radars within the scan volume, although only for a relatively short time. But if enemy radar is looking at that direction, it will get good returns from the MSA antenna. With RBE2 if the Rafale is flown so that the nose will not point directly towards any enemy radar, then the RBE2 antenna will not increase overall RCS that much. So I'd say that in most cases fixed RBE2 is better from RCS PoV than Captor-M MSA antenna.

Of course PESA/AESA antenna which is tilted is the best option for lower RCS. It will pretty much always point away from enemy radar and will not increase RCS much. Captor-E can be tilted away due to having repositioning mechanism for the antenna, so I'd say that is the better solution than either RBE2 or especially Captor-M.
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Unread post26 Sep 2019, 10:53

swiss wrote:
marsavian wrote:Yes Captor-M will be moved from side to side, up or down, but it will still spend less time in the vertical position than the fixed RBE2. Any Captor will be more stealthy than any RBE2 variant.


Well thats your opinion. According to Hornetfinn the rotation of the dish makes it a good reflector for radar waves. Even more than a untitled PESA/AESA Radar. This means roughly 1m2 RCS only from the rotating plate.


That's too high. How much time would a rotating plate be head-on remembering they cover a 120 degree rotating arc ? Probably a tenth to fifth (0.1-0.2 m2) of that is more appropriate in TWS mode.

p.s. Hornetfinn suggested 0.5 m2 for Captor-M

viewtopic.php?p=382015#p382015
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Unread post26 Sep 2019, 12:24

marsavian wrote:
swiss wrote:
marsavian wrote:Yes Captor-M will be moved from side to side, up or down, but it will still spend less time in the vertical position than the fixed RBE2. Any Captor will be more stealthy than any RBE2 variant.


Well thats your opinion. According to Hornetfinn the rotation of the dish makes it a good reflector for radar waves. Even more than a untitled PESA/AESA Radar. This means roughly 1m2 RCS only from the rotating plate.


That's too high. How much time would a rotating plate be head-on remembering they cover a 120 degree rotating arc ? Probably a tenth to fifth (0.1-0.2 m2) of that is more appropriate in TWS mode.

p.s. Hornetfinn suggested 0.5 m2 for Captor-M

viewtopic.php?p=382015#p382015


And in a another discussion 1 m2

Thanks for your explanation Hornetfinn.

hornetfinn wrote:MSA radar has big impact on RCS as it's a flat plate that needs to point directly towards target to detect it. It also needs to be rotated continually to search for targets which makes it pretty nice reflector for radar waves. With PESA or AESA it's possible to tilt the antenna so that it will direct most of the enemy radar waves away. Even when untilted, it will still still have much lower RCS from most angles than scanning MSA antenna as PESA or AESA antennas are not moving most of the time (even with repositioners). I'd say normal MSA antenna has RCS of roughly 1 square meter whereas PESA or AESA will be something like 0.01 square meters even without any stealth features.


So 0.5 to 1 m2
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Unread post26 Sep 2019, 13:22

So 0.5 to 1 m2


Not in rotating TWS mode head-on whereas that would be the RCS of the vertical RBE2 head-on. Captor has more stealth modes head-on.

p.s. do you have a link to that other discussion ?
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Unread post26 Sep 2019, 15:07

marsavian wrote:
p.s. do you have a link to that other discussion ?



Well this was a PM from Hornefinn in a discussion we had a view months a go. :wink:

marsavian wrote:Not in rotating TWS mode head-on whereas that would be the RCS of the vertical RBE2 head-on. Captor has more stealth modes head-on.


Do you have an official source for this stealth modes.
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Unread post27 Sep 2019, 03:45

APG-83 is 30% better than original APG-66v3
APG-68v9 is 33% better than APG-68v1
APG-68v1 has longer range than APG-66v3
So APG-83 has even shorter range than APG-68v9?
. The AN/APG-83 can simultaneously perform search, tracking and lock-on functions. For multiple targets, the detection range is increased by more than 30% compared with the original APG-66(V)3 radar.

https://airforcesmonthly.keypublishing. ... ight-test/
APG-68v9.png
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Unread post27 Sep 2019, 15:30

garrya wrote:APG-83 is 30% better than original APG-66v3
APG-68v9 is 33% better than APG-68v1
APG-68v1 has longer range than APG-66v3
So APG-83 has even shorter range than APG-68v9?
. The AN/APG-83 can simultaneously perform search, tracking and lock-on functions. For multiple targets, the detection range is increased by more than 30% compared with the original APG-66(V)3 radar.

https://airforcesmonthly.keypublishing. ... ight-test/
APG-68v9.png


The APG-66v2/v3 has a Range of roughly 90 km vs a 5 m2 Target.
https://www.forecastinternational.com/a ... _RECNO=326

This was the MLU upgrade for the European and Taiwan. Which should be close to the Block 50+ (APG-68v9)

When you look at Wiki etc, the range of the APG-68v9 is 105 km vs a 5 m2 Target.

https://en.wikipedia.org/wiki/AN/APG-68

This would concur with a Range of 80 km the for first APG-68.

So i would strongly assume the APG-83 has more Range then the latest APG-68. Espacly under jamming conditions.
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