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Author Topic: Lockheed Martin CUDA Air-to-Air Missile  (Read 65880 times)

Online sferrin

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #30 on: December 12, 2012, 05:19:03 am »
Active-radar homing has always had a bit of a medium range / dogfight mystique to it. Isn't this kind-of the point of ARH?

Speeed.

Because IR domes are physically weak, draggy and the performance of IR seekers drops with increasing missiles speed (turbulence and heating of the seeker dome are both problems) it is not a good choice for high speed missiles.

You mean like THAAD and HEDI?  ;)
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Online George Allegrezza

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #31 on: December 12, 2012, 08:25:14 am »
I think in each case the IR sensor is shielded for a portion of the flight, until the missile is above much of the atmosphere.

Offline SpudmanWP

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #32 on: December 12, 2012, 08:45:40 am »
NCADE might actually offer better range due to more % for fuel and 2nd stage being liquid fueled.

Take note that NCADE has an aerospike to protect the IIR seeker from friction heat.




http://i619.photobucket.com/albums/tt271/SpudmanWP/JDRADM/ncade1_zps67cc716a.jpg



http://i619.photobucket.com/albums/tt271/SpudmanWP/JDRADM/e7565783.jpg
« Last Edit: December 12, 2012, 08:56:32 am by SpudmanWP »
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Online sferrin

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #33 on: December 12, 2012, 09:34:12 am »
I think in each case the IR sensor is shielded for a portion of the flight, until the missile is above much of the atmosphere.

Both are endoatmospheric weapons.  The windows are cooled.
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Online George Allegrezza

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #34 on: December 12, 2012, 09:58:13 am »
Endo, schmendo. 


http://www.designation-systems.net/dusrm/app4/thaad.html


"In the terminal intercept phase, the KV is guided by an InSb staring FPA (Focal Plane Array) infrared seeker, whose window is protected in the initial flight phase by a clamshell protection shroud."





Online sferrin

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #35 on: December 12, 2012, 10:27:34 am »
Endo, schmendo. 


http://www.designation-systems.net/dusrm/app4/thaad.html


"In the terminal intercept phase, the KV is guided by an InSb staring FPA (Focal Plane Array) infrared seeker, whose window is protected in the initial flight phase by a clamshell protection shroud."
"DARPA Hard"  It ain't what it use to be.

Offline Void

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #36 on: December 12, 2012, 10:35:29 am »
George has it. Obviously, thinner atmosphere means less drag. NCADE has the advantage that the IR signature of it's intended target is gigantic.

Aerospikes work. But they have angle of attack limits, if the AOA is too high the shockwave will reattach to the dome and the temperature/pressure will rise even higher then what an unprotected dome would experience. Cooling is another option, but it severely distorts the wavefront. Side-mounted windows and faceted domes are more options.

Even when the seeker is protected there is still a loss of sensitivity from dome heating and distortion from turbulence. Radar by comparison is almost problem-free at very high supersonic and hypersonic speeds. Now, DARPA is currently working on the elaborate optics needed to correct the distortions produced by a low-drag ogive seeker dome and ALON promises much better material properties then current IR domes. Together they could make high-speed IR missile more practical, but that is in the indefinite future.

Online sferrin

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #37 on: December 12, 2012, 10:49:23 am »
George has it.

Yeah, not so much.  HEDI, AIT, and THAAD all use (or used) IR seekers at very high speeds within the atmosphere.  SM-2 Block III also as a secondary IR seeker (and SM-2 isn't a slouch in the speed department).
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Online George Allegrezza

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #38 on: December 12, 2012, 11:18:45 am »
Yes but remember those are all climbing out of the atmosphere, so the heating problem is a bit less challenging once they're in position for target acquisition.
« Last Edit: December 12, 2012, 11:41:52 am by George Allegrezza »

Offline Avimimus

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #39 on: December 12, 2012, 11:44:29 am »
Why not shroud the seeker and then dump the shroud during the last phase? Missile speeds during the terminal homing phase are lower than peak flight speeds and there isn't as much time for heat to build up. Of course, you'd need a command link and possibly a semi-active radar receiver for the BVR shots.

Anyway, I always thought the reason why IR was favoured for anti-satellite duties was due the fact that space provides a dark background with no atmospheric scatter. Acquisition ranges with IR at extreme altitudes easily outpace radar. Is this correct?

Offline SpudmanWP

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #40 on: December 12, 2012, 12:17:03 pm »
That is what NCADE and SDB2 do (discard shroud at the last moment).
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Online sferrin

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #41 on: December 12, 2012, 12:52:53 pm »
Why not shroud the seeker and then dump the shroud during the last phase?

That's exactly what THAAD does.  I read once that with the IIR windows it becomes a race between hitting the target and the window failing.  This was with things like HEDI and AIT where the heat loads on the windows were far higher than any AAM would see.
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Offline Void

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #42 on: December 13, 2012, 09:27:15 am »
George has it.

Yeah, not so much.  HEDI, AIT, and THAAD all use (or used) IR seekers at very high speeds within the atmosphere.  SM-2 Block III also as a secondary IR seeker (and SM-2 isn't a slouch in the speed department).

The SM-II has an infrared seeker. On the side.

Altitude is the key. Incredibly.

Here is a nice graph of the relation between Mach number, altitude, and the stress it puts on a dome:


And the relevant chart with the R' values for different kinds of IR dome materials:


And finally, the effect of dome heating on a hypothetical seekers SNR ratio:

Online sferrin

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #43 on: December 13, 2012, 09:46:32 am »
George has it.

Yeah, not so much.  HEDI, AIT, and THAAD all use (or used) IR seekers at very high speeds within the atmosphere.  SM-2 Block III also as a secondary IR seeker (and SM-2 isn't a slouch in the speed department).

The SM-II has an infrared seeker. On the side.

Altitude is the key. Incredibly.

So what are you implying, that they jettison the IIR seeker if the target is at low altitude?  ::)     Also HEDI was a low alititude ABM with an IR seeker (as was AIT) or do you think CUDA is going to be traveling faster than those did?  And that was 20+ years ago. 
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Offline Void

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Re: Lockheed Martin CUDA Air-to-Air Missile
« Reply #44 on: December 14, 2012, 12:30:32 pm »
So what are you implying, that they jettison the IIR seeker if the target is at low altitude?  ::)     Also HEDI was a low alititude ABM with an IR seeker (as was AIT) or do you think CUDA is going to be traveling faster than those did?  And that was 20+ years ago.

Cooled seeker. Different issue entirely.

Here is a good conference paper that talks about seeker options for the Endoatmospheric LEAP. I've quoted some relevant passages emphasis mine:


Quote from: Page 3
Hypersonic endoatmospheric operation presents significant issues for the use of EO seekers for end game guidance. Aero-optical (AO) effects, which are usually defined as boresight error (BSE), blur and jitter, are not expected to be as serious for an RF seeker. Figure 5 presents a top level description of the hypersonic flowfields surrounding a missile forebody and the effects on the target point spread function.


Quote from: Page 6
Hypersonic operation alsopresents significant performance issues for IR sensors. The shock and boundary layers distort incoming target signals, produce background radiance and elevate window temperatures (which increases background radiance).

Quote from: Page 6
Mitigation techniques range from the use of uncooled windows (trajectory shaping and minimizing exposure time) to active cooling. Active cooling is the most popular technique, but injecting
coolant into the airstream is a major contributor to AO effects
and has a large impact on vehicle size and weight (because of coolant storage and injection hardware).

And I said they don't work as well, not that they don't work at all.