MIM-72 Chaparral with head-on engagement capability

[Dilandu]

The major disadvantage of the MIM-72 Chaparral (initially) was its inability to engage jet aircraft head-on. The AIM-9D "Sidewinder", on which its missiles were based, could not lock on target from this aspect. While it wasn't a major disadvantage for a AAM, it was a big hindrance for SAM, since it basically means that Chaparral could engage enemy jets only in tail-chase conditions. Which seriously limited its engagement range.

So I thought about two possible solutions:

* SARH Chaparral - to equip the M54 mount with a small range-only radar, paired with optical sight (like AN/VPS-2, used on M163 VADS self-propelled Vulcan guns), tuned to work with semi-active seekers of AIM-9C missiles. By reducing radar to ranging only, and providing manual tracking with the optical sight, we would avoid the complex problems of locking on low-altitude target (which plagued Mauler SAM) - and still we would get the capability of making head-on engagements. AIM-9C should be compatible enough with standard launch rails, used on Chaparral.

* Laser Chaparral - a bit more... extravagant idea. By 1968, the laser-guided BOLT series bombs were already used in Vietnam. So, what if we equip Chaparral mount with the AVQ-9 "Pave Light" (Zot Box) laser desginator, paired with optical sight - and create a derivative of AIM-9D missile, with infrared sensor in seeker replaced with laser-detecting photocell? By aiming optical sight on target, operator would "paint" it with laser beam, and laser-seeking AIM-9 missile could engage it head-on.

So... what's your opinion?

 

[Elan Vital]

The major disadvantage of the MIM-72 Chaparral (initially) was its inability to engage jet aircraft head-on. The AIM-9D "Sidewinder", on which its missiles were based, could not lock on target from this aspect. While it wasn't a major disadvantage for a AAM, it was a big hindrance for SAM, since it basically means that Chaparral could engage enemy jets only in tail-chase conditions. Which seriously limited its engagement range.

So I thought about two possible solutions:

* SARH Chaparral - to equip the M54 mount with a small range-only radar, paired with optical sight (like AN/VPS-2, used on M163 VADS self-propelled Vulcan guns), tuned to work with semi-active seekers of AIM-9C missiles. By reducing radar to ranging only, and providing manual tracking with the optical sight, we would avoid the complex problems of locking on low-altitude target (which plagued Mauler SAM) - and still we would get the capability of making head-on engagements. AIM-9C should be compatible enough with standard launch rails, used on Chaparral.

* Laser Chaparral - a bit more... extravagant idea. By 1968, the laser-guided BOLT series bombs were already used in Vietnam. So, what if we equip Chaparral mount with the AVQ-9 "Pave Light" (Zot Box) laser desginator, paired with optical sight - and create a derivative of AIM-9D missile, with infrared sensor in seeker replaced with laser-detecting photocell? By aiming optical sight on target, operator would "paint" it with laser beam, and laser-seeking AIM-9 missile could engage it head-on.

So... what's your opinion?

Or alternatively you could use the guidance method the Soviets used for Strela-1 and Strela-10, or finally Rapier/Roland's SACLOS method.

I'm afraid lasers would be a difficult to get right early, even for ATGMs this technology wasn't going to be ready until 1974 or so.

 

[tomo pauk]

So... what's your opinion?

Adopt the AIM-9C SARH sidewinder, obviously together with the fire-control radar from the F-8 Cusader.
Copying the guidance system from the SA-9 is also an option (there was a number of these missiles captured and available for the West).
Later (late 1970s), go with the -9L, that is an all-aspect IR homing missile.

SACLOS and MACLOS hould also be easy to implement for the AIM-9.

 

[Dilandu]

Or alternatively you could use the guidance method the Soviets used for Strela-1 and Strela-10, or finally Rapier/Roland's SACLOS method.

This would require development of completely new missile. Which is clearly outside of Chaparral project scale.

I'm afraid lasers would be a difficult to get right early, even for ATGMs this technology wasn't going to be ready until 1974 or so.

But the laser-guided bombs were used from 1968. And I'm not talking about ATGM's, but refitted AAM - with the replacement of IR-sensor in her seeker by laser-detecting photocell.

Adopt the AIM-9C SARH sidewinder, obviously together with the fire-control radar from the F-8 Cusader.

It would be far too costly, and I'm not sure that fire control radar from F-8 would be able to handle ground clutter. Most likely it wouldn't. And for low-altitude defense, it's important.

 

[tomo pauk]

It would be far too costly, and I'm not sure that fire control radar from F-8 would be able to handle ground clutter. Most likely it wouldn't. And for low-altitude defense, it's important.

Americans have the money.
Radar 'stolen' from the F-8 will be pointing out upwards, ie. towards the sky, not downwards towards the earth.

BTW - is any suggestion from the posts #2 and #3 valid from your perspective?

 

[Dilandu]

Americans have the money.

Problem is, that Chaparral was envisioned of low-cost fast-into-service solution. So while Americans have the money, US army didn't have exactly much to spend on it.

Radar 'stolen' from the F-8 will be pointing out upwards, ie. towards the sky, not downwards towards the earth.

Er, no. The Chaparral - as well as Mauler - was designed first and foremost for low-altitude interceptions. I.e. when radar beam moves at low angle, close to surface, and faced serious ground clutter.

BTW - is any suggestion from the posts #2 and #3 valid from your perspective?

Exactly which suggestions? To develope a command guidance for Sidewinder? It would require near-complete rebuild of the whole missile, a new autopilot and guidance system.

 

[tomo pauk]

Exactly which suggestions?

Never mind - just something I need to keep in mind when you ask for people's opinions next time.

 

[Dilandu]

Never mind - just something I need to keep in mind when you ask for people's opinions next time.

I'm not sure I understood you. Your suggestion were:

Adopt the AIM-9C SARH sidewinder, obviously together with the fire-control radar from the F-8 Cusader.

As I pointed out, F-8 FC radar would not work due to ground clutter.

Copying the guidance system from the SA-9 is also an option (there was a number of these missiles captured and available for the West).

It's plainly impossible, because SA-9 went into service nearly the same time as Chaparral.

SACLOS and MACLOS hould also be easy to implement for the AIM-9.

No, they wouldn't. They would require complete rebuild of the whole missile, most problematic would be putting a gyro autopilot on it (since the existing rollerons & balanced rudders configuration would not be able to handle command guidance).

 

[tomo pauk]

I'm not sure I understood you.

Let me explain.
Step 1: you make your points and ask fellow forum members for their opinions/suggestions/feeback
Step 2: several suggestions are made
Step 3: you dismiss the suggestions

My conclusion: in further debates, I'll avoid making any suggestions to you.

 

[pathology_doc]

ith optical sight (like AN/VPS-2, used on M163 VADS self-propelled Vulcan guns), tuned to work with semi-active seekers of AIM-9C missiles. By reducing radar to ranging only, and providing manual tracking with the optical sight, we would avoid the complex problems of locking on low-altitude target (which plagued Mauler SAM)

If the tracking radar can't lock on, what are the chances that the -9C seeker head will be able to do so?

It might work better at sea, where the target has no elevated terrain to pop up from or hide behind, and you can mount a bigger, more powerful radar with better signal processing and target tracking capability and more raw power on a larger, essentially fixed platform

 

[Dilandu]

My conclusion: in further debates, I'll avoid making any suggestions to you.

You conclusions are rather... weird. Why are you taking dismission of your suggestion personally? I put enough arguments to demonstrate why I think they wouldn't work. I though it is called "discussion", when sides exchange arguments and counter-arguments.

If the tracking radar can't lock on, what are the chances that the -9C seeker head will be able to do so?

That's why I propose to NOT use tracking radar, but the much simpler, narrow-beam ranging radar, aimed by optical sight. I.e. radar is used as designator and ranging device only; no attempt to actually track the target. The same idea was used on self-propelled Vulcan gun (small ranging radar, paired with optical sight, with no tracking capability), and as far as I know, it worked fine on it.

Essentially my idea is NOT to use the radar to search or lock on the target. It would be done by optical sight (well, it's Chaparral, after all... it's really rather primitive. Originally it was supposed to use turret from WW2-era M45 Quadmount). The radar would work only as illuminator for missile seekers.

 

[tomo pauk]

You conclusions are rather... weird. Why are you taking dismission of your suggestion personally? I put enough arguments to demonstrate why I think they wouldn't work. I though it is called "discussion", when sides exchange arguments and counter-arguments.

You have also dismissed Elan Vital's suggestions.

 

[Dilandu]

You have also dismissed Elan Vital's suggestions.

Yes, because again, I pointed out that completely rebuilding the homing missile into command guided one would be very costly and complex. I really doubt it could be done with 1960s Sidewinder at all; it would require a proper roll gyro to precisely stabilize the missile (so the missile and command station would agree about "up-down, left-right" directions) and a whole point of Sidewinder was basically to NOT install the gyro autopilot (that's why rollerons were implemented).

You may disagree with my logic, but you must agree that I do not just dismiss the ideas without explanation.

 

[pathology_doc]

The radar would work only as illuminator for missile seekers.

That's the question I'm asking - could the missile actually do the job and home successfully under conditions you're arguing the search-tracking radar cannot reliably track?

 

[Dilandu]

That's the question I'm asking - could the missile actually do the job and home successfully under conditions you're arguing the search-tracking radar cannot reliably track?

Just found the engagement envelopes:

 

[Hood]

By 1974 the MIM-72C had an all-aspect capability with the AN/DAW-1 guidance section using the new M817 directional doppler fuze which predated the AIM-9L by three years (which used an AN/DSQ-29 solid-state guidance section, new InSb seeker and the DSU-15/B AOTD laser proximity fuze.

So you have an interim issue for six years. It does show though that there were multiple ways to get all-aspect capability. I hate hand waving things into existence earlier than historical, but I wonder how far forward you could push the development of MIM-72C, 1968 might be pushing it but it doesn't feel like an insurmountable obstacle for an IR-guided missile by that that.

A modified AIM-9C with AN/VPS-2 sounds reasonable. Production ended in 1967 but a SARH MIM-72 would give that Motorola production line a new lease of life. Only 1,000 9Cs were made though (seems pretty low rate production over a decade), so not sure if they could ramp up production or not. One would hope so.
Commonality with M163 helps too.

 

[pathology_doc]

That's the question I'm asking - could the missile actually do the job and home successfully under conditions you're arguing the search-tracking radar cannot reliably track?

Just found the engagement envelopes:

View attachment 691830

I assume this is looking down on the engagement from above and represents one half of the forward aspect?
Very nice; where did you find it?

 

[Elan Vital]

By 1974 the MIM-72C had an all-aspect capability with the AN/DAW-1 guidance section using the new M817 directional doppler fuze which predated the AIM-9L by three years (which used an AN/DSQ-29 solid-state guidance section, new InSb seeker and the DSU-15/B AOTD laser proximity fuze.

So you have an interim issue for six years. It does show though that there were multiple ways to get all-aspect capability. I hate hand waving things into existence earlier than historical, but I wonder how far forward you could push the development of MIM-72C, 1968 might be pushing it but it doesn't feel like an insurmountable obstacle for an IR-guided missile by that that.

A modified AIM-9C with AN/VPS-2 sounds reasonable. Production ended in 1967 but a SARH MIM-72 would give that Motorola production line a new lease of life. Only 1,000 9Cs were made though (seems pretty low rate production over a decade), so not sure if they could ramp up production or not. One would hope so.
Commonality with M163 helps too.

While testing of MIM-72C started in 1974, if I recall it only entered service in 1978.

While not in the spirit of the thread, introducing variants of the Sidewinder better than the D (E, F, G or H) in the interim period could already be a decent improvement.

 

[Dilandu]

I assume this is looking down on the engagement from above and represents one half of the forward aspect?
Very nice; where did you find it?

From "Pilot's handbook for Sidewinder 1C (AIM-9C and AIM-9D) air-to-air guided missiles".

 

[Pioneer]

For my 50¢ worth, if I may, I'd opt for the incorporation of the M121 smokeless motor as soon as possible.
I'd also opt for a launch booster motor to improve the inherent air-launched Sidewinder design to have a much superior reaction time on launch.

Regards
Pioneer

 

[Scott Kenny]

It would be far too costly, and I'm not sure that fire control radar from F-8 would be able to handle ground clutter. Most likely it wouldn't. And for low-altitude defense, it's important.

You only need the illuminator circuits and antenna, as on the USN's Basic Point Defense Missile System, not the full AN/APQ-84 or -94 radar. As long as the operator can keep the turret pointed within the same clockface as the threat, the missile will guide. Nothing on the ground will have enough doppler shift compared to the aircraft.

 

[overscan (PaulMM)]

You only need the illuminator circuits and antenna, as on the USN's Basic Point Defense Missile System, not the full AN/APQ-84 or -94 radar. As long as the operator can keep the turret pointed within the same clockface as the threat, the missile will guide. Nothing on the ground will have enough doppler shift compared to the aircraft.

Which would highly relevant if the said radars were pulse-doppler. As they weren't, ground clutter is a big issue if there are mountains or hills or tall buildings or trees in the area.

 

[Scott Kenny]

Which would highly relevant if the said radars were pulse-doppler. As they weren't, ground clutter is a big issue if there are mountains or hills or tall buildings or trees in the area.

This is strictly the Continuous Wave Illumination part of the radar, which as I understand SARH tracking uses the doppler shift of the incoming to track.

 

[overscan (PaulMM)]

This is strictly the Continuous Wave Illumination part of the radar, which as I understand SARH tracking uses the doppler shift of the incoming to track.

It doesn't use CW. AIM-9C had a conical scan pulse seeker, not a CW seeker.

 

[Scott Kenny]

It doesn't use CW. AIM-9C had a conical scan pulse seeker, not a CW seeker.

Ah, my bad. Must have just been Sparrows and Standards, then.

 

[R_K_M]

Red Top achieved limited all aspect capabilities in '64. It was kind of shit and twice the size of an AIM-9, but if you accept the size you can probably make a pretty decent seeker by '69. BGT apparently also had an all-aspect seeker available in the early/mid 70s (Viper/ALASCA), thought that was ultimately cancelled in favor of the AIM-9L.

Point being: build a bigger missile and fund partner projects.

 

[Dilandu]

It doesn't use CW. AIM-9C had a conical scan pulse seeker, not a CW seeker.

If I recall correctly, AN/VPS-2 is a pulse-Doppler radar?

Point being: build a bigger missile and fund partner projects.

Problem is, that it's far outside of Chaparral project scope. Which (at least initially) boiled down to "let's took the old WW2-era Quadmounts, replace machineguns with spare launchers for AIM-9, and put it all on M113"

 

[R_K_M]

Red Top would be more expensive and potentially reduce the amount of missiles ready to fire (though it is not inconceivable that you would still be able to mount 4 of them), but it was already available and would not delay the program.

If you spread out the development cost for new all-aspect Red Top variants between US/UK and potential users like DE/IT the whole thing wouldn't even be particularly expensive.

 

[Scott Kenny]

If I recall correctly, AN/VPS-2 is a pulse-Doppler radar?

Pretty sure the F-8 used an AN/APQ-94.