What's the status on the CUDA program

F-35 Armament, fuel tanks, internal and external hardpoints, loadouts, and other stores.
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weasel1962

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Unread post17 Oct 2018, 08:51

Thought the USAF already killed this. Although classed as medium range (for a 1.78m missile), its reach is maybe short enough to risk going into a WVR fight if armed with CUDA alone? If occupying only 1 F-35 bay to increase missile numbers (e.g. 6 CUDA) that would mean going with 2 (or 3 if the tri-pack works) AMRAAMs for a counter-air mission. interesting idea before the Chinese showed up with their x-long range PL-15/21s but I'd think F-22/35 pilots would rather go in with as many 120Ds as they can carry internally.
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element1loop

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Unread post17 Oct 2018, 08:58

hornetfinn wrote:Dual mode IIR + active radar would be great. It would be possible to use the radar only to measure range to target and use IIR seeker to track it continually. Then radar would be used just to "ping" the target from time to time which would be very difficult to detect and be considered as a threat. Of course the radar could also be used as main sensor in poor IR visibility conditions.


Agree, but have doubts about range being equivalent to AMRAAM, that all depends which model AMRAAM. Not D or C7 I'd say, it's length to diameter ratio is not ideal for low-drag, for its apparent size, and (conjectured) post boost weight. A smaller diameter would have been much better for an AMRAAM-like range (i.e. far less drag and energy loss in end-game with smaller diameter) which indicates to me that fire-and-forget BVR guidance needed more diameter so reduced range is the price and compromise required to get a deadlier missile. To my way of thinking this places CUDA in the short to medium range BVR missile, compared to D, but more deadly, with more of them.

Using SMSgt Mac's old analysis (from his blog pages on CUDA) I got a flight time to 143 km radius using 33-deg loft @ FL360 launch and Mach=1.03 against a 485 kt target, for flyout time of ~157 sec. A bandit doing 485 kts can travel 21.2 nm, or 39.2 km track-distance, in that 157 seconds, in any direction it pleases.

i.e. it becomes a bit of an ask, a true 'long-shot', for a little missile with a high-diameter drag for its stubby long-axis. More likely to be effective out to about 100 km radius. i.e. just right for F-35 stealth-fighting (as you described). But as I see it, from sim runs of AIM-9X BkII+ I've run the new 'winder being built specifically for the F-35 will be able to get very competitive BVR range to CUDA's.

So CUDA comes down to its "fire-and-forgettable-ness", its internal carriage and there being a few more of them. In those terms CUDA may be the right BVR missile for A2A role, in >2025 and keep improved AMRAAM for the true longer range shots. i.e.

4 x CUDA
2 x SLAMMER+
2 x AIM-9BKII+
Last edited by element1loop on 17 Oct 2018, 09:11, edited 1 time in total.
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wrightwing

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Unread post17 Oct 2018, 09:05

The selling point is being able to carry 12 AAMs internally, that can do HOBS WVR, or 100km BVR shots. Or some lesser amount plus LREW for long range shots.
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Unread post17 Oct 2018, 09:10

If its used in a self defence mode e.g. to take out an incoming missile, then maybe the range becomes less of an issue but makes more sense to take out the firer than the missile. 1.78m length missile to reach 100km? Unlikely to have significant energy for the distance but my guess is a lot less (more like 120A). Even an AIM-9X is 3m long.
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element1loop

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Unread post17 Oct 2018, 09:18

weasel1962 wrote:If its used in a self defence mode e.g. to take out an incoming missile, then maybe the range becomes less of an issue but makes more sense to take out the firer than the missile. 1.78m length missile to reach 100km? Unlikely to have significant energy for the distance but my guess is a lot less. Even an AIM-9X is 3m long.


Yes, the range numbers are out the window as soon as any target makes a first significant change of heading requiring a large flyout-to correction, and energy loss. 75 km may work in a proper fight.
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element1loop

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Unread post17 Oct 2018, 09:19

wrightwing wrote:The selling point is being able to carry 12 AAMs internally, that can do HOBS WVR, or 100km BVR shots. Or some lesser amount plus LREW for long range shots.


Selling point yes, but not likely in practice.
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Unread post17 Oct 2018, 09:48

AFAIK, smaller diameter than CUDA would not be much better for drag and it would mean much smaller amount of fuel and less space for seeker and other electronics. For example ESSM missile and Russian R-33/37 have pretty similar length to diameter ratio as CUDA. Even AIM-54 Phoenix was about similar and it had pretty respectable range. Sure AMRAAM sized weapon will have longer range than CUDA given same technological level. So it comes to whether longer range or larger numbers is seen as more important.
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Unread post17 Oct 2018, 10:27

Went back to check source of the CUDA = AMRAAM range back in 2012.

http://nacred26.rssing.com/chan-13533767/all_p1.html

We can reasonably conclude that the CUDA is a Medium Range Missile design, and approximate to the AMRAAM in range.....

I'm MOST certain that if I missed anything on this late night exercise, SOMEONE will let me know. Did I mention we're basing all this 'estimating' on a convention display model, vague comments, and a computer graphic?


Decent calculation but a significant range for variables. Assumes same efficiency of rocket motor etc. Would be interesting to see how the calculations would have been if applied to the AIM-9.
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element1loop

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Unread post17 Oct 2018, 10:53

hornetfinn wrote:AFAIK, smaller diameter than CUDA would not be much better for drag and it would mean much smaller amount of fuel and less space for seeker and other electronics.

Diameter impact to drag does make a large difference when the weight drops away with fuel burned. Resulting stored energy is lower and bleeds from drag faster. Thus R-33 and AIM-54 were meant for engaging bombers, heavies. AMRAAM overcomes the diameter drag via being longer for more fuel, and more stored energy after burn, to make drag work harder for longer to slow it down. Hence there's a range compromise in using a larger seeker and diameter for CUDA to produce a more deadly missile, but with a range-reduction as the cost.

Which is fine if the missile is also a "see-but-not-be-seen" design, and coming out of the F-35. I'm not saying the diameter impairs it as such, but there is a significant range penalty to a higher diameter with a smaller lighter missile.

The advantage it has is in having almost no warhead section and mass, so more fuel fraction. But less residual weight and stored energy once the fuel is gone (unless it can make a lot more steam from it), so loses that energy quicker, thus the more direct-attack hit-to-kill method it will apply. Even so, drag will affect it faster than it will the heavier AMRAAM, of same diameter, but AMRAAM relies on terminal AOA, but CUDA not as much (it wouldn't have the energy). It really comes down to how much smash a CUDA burn has, and how high it can reach, but the higher it goes the longer the flight time and the more energy falls short toward long range terminal phase (even with 1G assist). So larger diameter firstly limits the boost acceleration and final speed, then slows it earlier.
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Unread post17 Oct 2018, 12:23

element1loop wrote:The advantage it has is in having almost no warhead section and mass, so more fuel fraction. But less residual weight and stored energy once the fuel is gone (unless it can make a lot more steam from it), so loses that energy quicker, thus the more direct-attack hit-to-kill method it will apply. Even so, drag will affect it faster than it will the heavier AMRAAM, of same diameter, but AMRAAM relies on terminal AOA, but CUDA not as much (it wouldn't have the energy). It really comes down to how much smash a CUDA burn has, and how high it can reach, but the higher it goes the longer the flight time and the more energy falls short toward long range terminal phase (even with 1G assist). So larger diameter firstly limits the boost acceleration and final speed, then slows it earlier.


Not necessarily. For example VT1 missile used in Crotale NG AD system is also fairly stubby missile. Diameter is almost like in AMRAAM (16.5 cm or 6.5 inches), but it's significantly shorter than AIM-9 (2.35 m or about 80 percent of AIM-9 length). It accelerates to Mach 3.6+ (at low level) in about 2 seconds and reaches 8 km range in 10.3 seconds. It can also maneuver 35g up to 8 km range, so it retains speed and energy very well despite being stubby. It's somewhat similar design to CUDA in that it doesn't have own seeker (it's command guided missile) but does have pretty large warhead (between AIM-9 and AMRAAM) and is pretty stubby compared to AMRAAM.

Sure AMRAAM will have range/energy advantages compared to CUDA, but I'm not sure that smaller diameter CUDA would be better in anything than the proposed design. AMRAAM (or similar) is great for longer range but weapons load will be smaller. I think CUDA would be great complement for AMRAAM, but not replacement as longer range is sometimes preferable. I'd even go further and develop fatter AMRAAM for really long range shots against high value targets. It actually already exist in the form of ESSM or AMRAAM-ER (ESSM body with AMRAAM seeker). It has AMRAAM length, but much wider diameter (10 inches) and thus larger rocket motor with a lot more fuel and larger warhead. Ground launched it has 50 percent longer range and 70 percent higher altitude than AMRAAM (although don't know for sure what version is compared). It's not being developed for being compatible with fighter aircraft though.
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Unread post17 Oct 2018, 13:16

hornetfinn wrote: ... For example VT1 missile used in Crotale NG AD ... It accelerates to Mach 3.6+ (at low level) in about 2 seconds and reaches 8 km range in 10.3 seconds. It can also maneuver 35g up to 8 km range, so it retains speed and energy very well ...


That's a fairly good example of what I was pointing out, greater than Mach 3.6 impulse for only 8 kilometers. Short, stubby and light in high drag denser air doesn't go far. A lower diameter missile with the same fuel fraction, same start weight, same fin area, and same total weight after burn, will go much further than that 8 km. Take the hint from MANPADS design, if you want altitude and range then long and skinny for low drag to maximize available impulse, while minimizing energy loss from a small frontal x-section.

hornetfinn wrote: ... but I'm not sure that smaller diameter CUDA would be better in anything than the proposed design.


I'm not suggesting any change is necessary. I've no problem with that, but there's a range penalty involved which is IMO not consistent with a BVR missile that's equivalent to AMRAAM range performance. In all likelihood it may go 2/3rds that range, against heavy non-agile aircraft, and maybe half that against a fast agile fighter.

But if the sensor system requires higher diameter so be it, that trade-off may be a worth the compromise, to get a more lethal and independent missile (i.e. defeating VLO requires better sensors).
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Unread post17 Oct 2018, 13:51

Ok, now I understood better what you were saying. I think we basically agree here.

Just to note that VT1 missile in Crotale NG goes out to 15 km max (demonstrated performance) and 8 km is just typical engagement range. Twice heavier and longer/more slender AMRAAM used in NASAMS system is longer ranged, but the difference isn't that big either.
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Unread post17 Oct 2018, 15:47

hornetfinn wrote:I think we basically agree here.


Yup.
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Unread post17 Oct 2018, 18:47

weasel1962 wrote:If its used in a self defence mode e.g. to take out an incoming missile, then maybe the range becomes less of an issue but makes more sense to take out the firer than the missile. 1.78m length missile to reach 100km? Unlikely to have significant energy for the distance but my guess is a lot less (more like 120A). Even an AIM-9X is 3m long.

100km shots aren't likely, but the missile is credited with AIM-120C range. Instead of focusing on the exact numbers, consider the utility of of 12 BVR missiles, that have AIM-9X (or better) WVR performance as well. For longer range shots, there's the LREW which is also under development, and for self defense there's the MSDM. These 3 load out options, will greatly increase the A2A flexibility in the 2020s and onward.
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Unread post18 Oct 2018, 04:30

Would be interesting to see who actually credited the CUDA=AIM-120C range. I've noted credit of F-35A range as 3000+nm so different sources have different credibility as we (or some of us at least) are aware.

In the spirit of not focussing on actual numbers, I would suggest F-35 may not be the most ideal platform for MSDM due to the limited bay space. As an afterthought, I can see much greater benefit for legacies e.g. F-series especially with SDB styled quad-packed external loads. These would be flying into the 2040s (and later for other militaries) so the timeline is still useful and with a significant external market. I can see legacies performing tanker/AEW escort roles using MSDM to defend not only itself but also the value assets. That would include F-18 CAPs defending CVBGs against saturation ASMs. Basically flying "iron domes".

That would benefit from the greater AAM numbers and allow the F-35s to focus on more important air superiority roles.
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