AIM-260 missile: the US Air Force and beyond-visual-range

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Corsair1963

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Unread post29 Oct 2019, 10:46

AIM-260 missile: the US Air Force and beyond-visual-range lethality

The US Air Force’s AIM-260 missile now in development offers marked improvements over the AIM-120, but, as Douglas Barrie explores, questions remain as to its end-game performance at extended ranges.


The United States military, and the US Air Force (USAF) in particular, invests in and places considerable store by superior technology to prevail against peer rivals. The USAF is also disinclined to allow its near allies to field capabilities it does not also have access to. In the air force’s slipstream, US industry is often first to market with advanced systems.

This makes the USAF’s apparent approach to its next generation of beyond-visual-range air-to-air missiles (AAMs) all the more intriguing.

AIM-260 missile

In 2022, the air force is planning to begin to field the Lockheed Martin AIM-260 Joint Advanced Tactical Missile (JATM) as a replacement for the Raytheon AIM-120 Advanced Medium-Range Air-to-Air Missile (AMRAAM). For almost 30 years the latter has been the Western benchmark for active-radar-guided missile performance.

The AIM-260 is the USAF’s priority AAM development, prompted at least in part by China’s increasingly capable AAM inventory. The People’s Liberation Army Air Force’s latest AAM to enter service, the PL-15, joined the inventory in 2018 and has a greater range than the AIM-120 family.

The AIM-260 undoubtedly offers marked improvements over the AIM-120, including in overall range. There remain questions, however, as to its maximum fly-out range and its end-game performance at extended ranges. The missile designer may have come up with a novel propulsion approach for the AIM-260 to address this, or perhaps there is an unseen development intended to provide a much longer-range engagement weapon. The USAF alternatively could rely on the tactical advantage of low-observable launch platforms, such as the F-22 and to a lesser extent the F-35, combined with the AIM-260’s performance to defeat aircraft with notionally longer-range missiles. Such an approach, however, will not work with the USAF’s ‘legacy’ fourth-generation fighters such as the F-15 and F-16.

Ramjet propulsion

The AIM-120 was replaced as the radar-guided AAM performance yardstick with the introduction into service in 2016 of the European Meteor extended-range AAM, developed by MBDA. The Meteor has greater range, and more importantly the missile remains powered during the final stage of a medium-to-long-range engagement. This is because the AIM-120 is powered by a solid rocket, while the Meteor uses a ramjet sustainer engine. While the AMRAAM has a greater peak velocity, the result of rapid acceleration likely to be more than Mach 4, the solid propellant burns out comparatively quickly even with a boost-sustain motor configuration when compared to a ramjet. The Meteor’s ramjet is thought to have fuel to operate for at least 60 seconds and a faster average speed.

All other things being equal, this gives the ramjet sustainer missile a far greater no-escape zone than a traditional solid-propellant missile. The no-escape zone is the volume of space in the front quadrant of the launch aircraft within which the target aircraft can be engaged irrespective of any evasive maneuver it might execute. The Meteor is described as having an operational range greater than 100 kilometers, and a 60 km no-escape zone. Alongside electronic countermeasures, defensive tactics include attempting to outrun and out maneuver the incoming missile by bleeding off its energy. In the case of a traditional solid-propellant missile, at medium range it is already coasting; the more it has to maneuver, the more energy it loses.

Despite almost 40 years of admittedly sometimes sporadic research and development into AAM ramjet propulsion, the USAF has not opted for this with the AIM-260. While the air force has not provided any detail of the propulsion for the AIM-260, it has said it does not use a ramjet. Air Force Brigadier-General Anthony Genatempo, the USAF program executive officer for weapons, has also previously told journalists that the missile does not use a ramjet. He also indicated the weapon would be no larger than the AIM-120.

Lockheed Martin may have adopted some form of boost-coast-boost configuration for the AIM-260 motor, possibly with a higher-energy propellant than previous generations of solid motors. Even so, it remains questionable whether this would provide a similar overall performance to a Meteor-class missile.

If it does, then the US has so far kept this propulsion development under wraps. If it does not, then the question that arises is whether the US has additional, as-yet classified, long-range AAM technology in the works.

This analysis originally featured on the IISS Military Balance+, the online database that provides indispensable information and analysis for users in government, the armed forces, the private sector, academia, the media and more. Customize, view, compare and download data instantly, anywhere, anytime. The Military Balance+ includes data on air-to-air missile holdings by type in armed forces worldwide.

https://www.iiss.org/blogs/military-bal ... nV00EKVxx8
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sferrin

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Unread post29 Oct 2019, 12:55

This article is getting a lot of traction for something that says exactly nothing new. :roll:
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Unread post29 Oct 2019, 22:41

What the author fails to consider is this- If the purpose of the AIM-260 is to address kinematic differences between the PL-15, etc... and the AIM-120 family, it's highly doubtful it has inferior performance. At the very minimum, it likely has at least parity performance with PL-15/Meteor class missiles.
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Unread post29 Oct 2019, 23:01

True. I guess it just raises the question of exactly HOW it manages to do that. With no ramjet and the same form factor as AMRAAM - where is the extra performance coming from?
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Unread post29 Oct 2019, 23:14

Spit balling some possibilities; higher specific impulse fuel, duel stage motor, increased rocket fuel payload through reduced warhead/guidance, high loft angle for long range shots.
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Unread post29 Oct 2019, 23:17

Writers seem to love to wave the magical "higher energy density propellant" phrase all the time. This phrase has only been used for what, the last decade? Physical limits tend to get in the way of neverending peformance increases. Raytheon is no newcomer to tactical missiles. If ATK (nee Northrop Grumman now) had a higher density propellant grain available that wouldn't bankrupt every wannabee ace fighter pilot out there, I'm pretty sure Raytheon would have already stuffed the AIM-120XYZ full of the stuff.

Since Lockheed Martin has done a lot of work with Hit-To-Kill missile tech with the Patriot Pac-3 and THAAD, I'm going out on a limb here and positing that this AIM-260 probably leverages
  1. reduced warhead weight (maybe even no warhead and simply go with HTK entirely?)
  2. multiple pulse motor (maybe a boost pulse, sustainer pulse, and possibly a terminal phase boost to regain energy at the very end)
  3. possibly a staged design -- though dropping a stage off over "friendly" or "neutral" territory may be problematic
  4. LM HTK tech using traverse mounted thruster motors ala PAC3/THAAD

    Image
  5. modest increase in fuselage diameter to permit
    • larger propellant mass loading
    • dual seeker technology -- AESA + IIR
  6. minimize aerodynamic control drag by using HTK attitude control technology (see SMSgtMac's blog post The Mysterious LM Cuda Missile


If LM did in fact create a CUDA missile.. AIM-260 could be a further development of that, OR, perhaps more simply, a booster design to get the CUDA to the hunting ground 100-200 km (nm?) distant.

Of course, if a higher energy density propellant is available, I'm sure LM would use it, all things (e.g. safety, reliability) being equal. But those sorts of gains would seem to be on the order of a few percent here, a few percent there.
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Unread post29 Oct 2019, 23:27

I forgot about true dual stage.
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Unread post30 Oct 2019, 00:16

Some compelling possibilities listed above. I'm not 100% sold on the HTK concept as I doubt it would be ideal when the target set includes LO/VLO targets with high end kinematic performance and heavy employment of EW/countermeasures. That said I wonder if the use of PAC3 style attitude control motors (ACMs) may allow for a reduction in the size of control surfaces which would in turn allow for a wider body.

I am also curious to see whether some sort of TVC control gets used. While I imagine this might add some weight(?), it would make closing to WVR with the F35 utterly suicidal out of the gate thanks to the ridiculous off-rail agility + cueing via AN/AAQ37.

I know Peregrine/CUDA are in the mix in this space but I'm not sure how much range you're actually going to get out of a weapon 2/3 the length of AIM9X, even if it does have a wider (5.5 vs ~7in?) motor/body. Increasing the number of AAM's carried internally is nice and all but 6 AIM260's strikes me as plenty for the overwhelming majority of A2A contingencies. A TVC AIM260 would be an absolute monster to deal with by comparison...
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Unread post30 Oct 2019, 01:27

LM has engineered / built / demonstrated some pretty nifty technologies including HTK Patriot PAC3, THAAD, and, if memory serves, they've had their hands in anti-ballisitc missile HTK kill vehicles.

If they have, in fact, built & demo'd CUDA, and it is a thrust vectoring, ACM'ing son-of-a-gun... then they may have all the pieces in place for the end-game kill vehicle. Not only that, but that same kill vehicle may easily be adaptable between anti-aircraft, anti-missile, perhaps even anti-ballistic-missile. The problem then becomes how do you get the kill vehicle to the hunting ground?

For WVR / near BVR, CUDA by itself may be all that is needed... Put two of them on the weps bay door(s) where a single AIM-120 currently sits. Put some sort of a modest boost stage that drops off, and now you have an AIM-120 replacement. Since weps weight is not really a huge issue with the F-35 (since you can carry two friggin 2k lb JDAMs), and since you can fit something approximately 14' long and roughly 24" in diameter into the weps bays... stick a big honkin' booster on the back of a CUDA (ala SM-2A), and now perhaps you have your vaunted ABM weapon.

Dunno about seekers, though. It would seem that a large fuselage body would be a boon to an AESA seeker. But maybe the future is in IIR and radar becomes less important if VLO continues to push boundaries.
Take an F-16, stir in A-7, dollop of F-117, gob of F-22, dash of F/A-18, sprinkle with AV-8B, stir well + bake. Whaddya get? F-35.

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