Stealth question - Reduction in RCS

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taog

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Unread post10 Jun 2019, 02:17

SpudmanWP wrote:
taog wrote:PS. what does "in a 40-deg. vertical fan" mean in the picture ?


It represents the space +20 and -20 degrees from the plane of travel.


Image

This picture represents a target's RCS measured from 360 deg. (or +180~-180 deg., horizon) and 0 deg. (vertical)

So "in a 40-deg. vertical fan" means +20 and -20 degrees (vertical) ?
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SpudmanWP

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Unread post10 Jun 2019, 04:04

Vertical (think donut), that's the way it seems.
"The early bird gets the worm but the second mouse gets the cheese."
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garrya

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Unread post10 Jun 2019, 04:11

taog wrote:PS. what does "in a 40-deg. vertical fan" mean in the picture ?

Like this, but vertically
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eloise

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Unread post10 Jun 2019, 07:47

taog wrote:Does there have any report or rumor mentioned the JSF RCS spec. earlier than that article (1999/2) ?

Great info, would you mind screenshot or cite the source?[/quote]
Just done it.[/quote]
I meant like this:
1.PNG
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taog

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Unread post10 Jun 2019, 07:52

eloise wrote:
taog wrote:Does there have any report or rumor mentioned the JSF RCS spec. earlier than that article (1999/2) ?

Great info, would you mind screenshot or cite the source?

Just done it.[/quote]
I meant like this:
1.PNG
[/quote]

:bang: wtf, it's my fault.

I can email it to you but i can not post it on the public forum.

If you want, give me your email address.
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disconnectedradical

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Unread post10 Jun 2019, 07:59

People are looking at JSF requirements in early 2000s. Who know what changed especially after program re-baseline.
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eloise

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Unread post10 Jun 2019, 08:04

taog wrote: :bang: wtf, it's my fault.
I can email it to you but i can not post it on the public forum.
If you want, give me your email address.

:mrgreen: please check your PM :mrgreen:
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taog

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Unread post10 Jun 2019, 08:21

disconnectedradical wrote:People are looking at JSF requirements in early 2000s. Who know what changed especially after program re-baseline.


JSF's RCS required i heard was mainly determined in JIRD-1 (1995) and JIRD-2 (1997). But it may also change in followed stage (Draft/Final JMS or even SDD phase). So do you have any information ? I am interested in the evolution of the JSF/F-35 RCS spec. changed.
Last edited by taog on 10 Jun 2019, 08:44, edited 1 time in total.
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taog

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Unread post10 Jun 2019, 08:38

This is the latest version (1997) I found on the internet for the detail of each JIRD. Although the released time of each stage in the picture is correct, i suspect some spec. may change.


Image
Last edited by taog on 10 Jun 2019, 10:54, edited 1 time in total.
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hornetfinn

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Unread post10 Jun 2019, 09:01

disconnectedradical wrote:People are looking at JSF requirements in early 2000s. Who know what changed especially after program re-baseline.


Exactly. I think they kept the RCS requirements lower than in F-22 because the whole idea was to make a relatively cheap fighter. I think it's entirely plausible and even probable (given later statements about ther respective stealth qualities) that they realized that it'd be possible to have lower RCS without significant cost increase. F-35 definitely has some changes from X-35 that gives better stealth qualities (like integrated canopy bow frame). There has been a lot of development in RAM and RAS which might also be quite a bit better than originally anticipated. There are also other possible reasons like improved manufacturing techniques and all kinds of small details.
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taog

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Unread post10 Jun 2019, 09:08

hornetfinn wrote:
disconnectedradical wrote:People are looking at JSF requirements in early 2000s. Who know what changed especially after program re-baseline.


Exactly. I think they kept the RCS requirements lower than in F-22 because the whole idea was to make a relatively cheap fighter. I think it's entirely plausible and even probable (given later statements about ther respective stealth qualities) that they realized that it'd be possible to have lower RCS without significant cost increase. F-35 definitely has some changes from X-35 that gives better stealth qualities (like integrated canopy bow frame). There has been a lot of development in RAM and RAS which might also be quite a bit better than originally anticipated. There are also other possible reasons like improved manufacturing techniques and all kinds of small details.


Actually in 2001, a report ("Lockheed Martin touts JSF stealth improvement", Aviation Week) said the F-35's RCS was lower than the -30 db requirement.

Image
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hornetfinn

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Unread post10 Jun 2019, 09:28

Thanks taog, nice find!

I think this is all about stealth technology maturation process. With F-35 there was immense amount of know-how and experience about stealth technology in US military industry and armed services (especially USAF). Also computer systems and software were powerful enough to do things that were impossible with F-22 for example. Same with manufacturing processes, which are often overlooked in the public. So they could develop very good characteristics for RCS while designing relatively low cost multi-role platform.
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optimist

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Unread post13 Jun 2019, 21:40

F-22 is lower in the targeting bands. The F-35 is lower in the search bands. I think it was chip who said it. I can't find the video. What happens after the MLU is unsaid.
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