Of DAS, EOTS etc..

Cockpit, radar, helmet-mounted display, and other avionics
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Unread post09 May 2018, 16:46

I dunno Mixel, I'm not an aircraft cannon expert. Ever heard of Google? It's this really kewl thing of which you can ask it anything and it spits back answers atchya! :doh: (Sorry, just had to rib ya a bit.)

In short: 25x137 (GAU-12/A, GAU-22/A) appears to have roughly twice as much "pop" on a shell by shell basis compared to 20x102 (M61 Vulcan) and half as much "pop" compared to a 30x173 (GAU-8/A -- A-10).

25x137 appears to have no issue with 8mm - 12mm RHA plate at tactically significant ranges (out to 9000', perhaps? That's a LONG shot). 25x137 APEX also appears to be able to handle 20mm RHA plate @ 45° (not sure of the range) and 50mm RHA plate @ 0° (i.e. perpendicular impact). 20x102 seems to handle 8-12mm RHA OK. Not sure how it does with 20mm armor plate.

Am guessing this means M61 Vulcan may be getting a little long in the tooth for the newest armored personnel carriers, but that the GAU-22/A should not have an issue with them. GAU-22/A may be able to handle older tanks, dunno. I read somewhere that even the GAU-8/A may not be quite up to snuff against the very latest tanks. If true, then dropping to 25mm didn't lose much. On the other hand, maybe the 25x137 round may be able to disable an MBT from the side / rear top if it can disable the engine. I don't know how much armor tanks have there. They can't have 500mm of armor everywhere.

After googling a bit, my overall impression is that the GAU-22/A offers roughly comparable (perhaps slightly better?) performance to the M61 Vulcan. The 20mm Vulcan spits out roughly 81% more shells per second, so perhaps slightly better chance of getting a hit from more BBs. But each 25mm shell packs more wallop. So maybe a single 25mm will do in a fighter, whereas a single 20mm will only damage it (badly?). I can's speak to TOF (time of flight), range, or accuracy. Both the 20x102 shell (Vulcan) and 25x137 (GAU-22/A) have similar muzzle velocities. TOF to 1000' is probably negligibly different. The 25x137 *may* retain velocity better at longer ranges. But that's a swag on my part. On the other hand, one parameter I have seen discussed as an air-to-air gun factor is "throw weight" which is total mass a gun system can project in one second. The M61 spits out 100 100g 20mm shells a second for a total throw weight of 10kg. Using a Nammo PGU-47/U 25mm round (222g) for ammunition, a GAU-22/A will dispense 12.2kg per second. So a slight "throw weight" advantage to the GAU-22/A.

One web page, Modern Fighter Gun Effectiveness blah blah's on about a bunch of stuff, throwing out some numbers that I don't know how accurate or meaningful they are. However, they suggest the following:

30mm (30x173) == 2 x 25mm (25x137) == 4 x 20mm (20x102).

That is, the 30mm shell the A-10 fires is roughly twice as powerful as the 25mm shell the AV-8B / F-35 / AC-130 fires, which is roughly twice as powerful as the 20mm shell the M61 Vulcan (F-15, F-16, F/A-18, F-22) fires.

I am attaching below some Nammo PDF's I found. One I've seen before. The other appears to be the Nammo 2016 catalog. You can browse it for all sorts of munitions & projectiles. 25x137 APEX is on p. 89. 30x173 begin around p. 100. Happy surfing.

Some suggested Google search strings:

25mm apex armor penetration
armor penetration 20x102 25x137 30x173
20x102 25x137 30x173 compared
20x102 vs 25x137 vs 30x173

In my opinion, the F-35 possesses a gun system that is roughly equivalent to the M61 20mm cannon for air-to-air work, but offers roughly double the effectiveness in the air-to-ground role. A pilot with a good trigger finger will get 2-3 squirts with the -A model, and maybe 3-4 squirts with the -B and -C. The fat fingered pilot may only get 2 squirts out of each. However, comments by someone else in another thread a while back suggested the F-35 may be able to be programmed to fire precise round counts settable by the pilot via his gee whizzery flat panel display. The mental picture I have is that the pilot may be able to select a 10rd burst, or 20, or 30 etc. Combined with the JTAC wizardry being built in, it may be possible that the F-35 pilot can get / confirm target coordinates from the JTAC, and then have the aircraft fly a closed-system gunnery solution whereby the F-35 fires the gun with a commit authorization from the pilot. Then 10 or 20 or 30 rounds are precisely dispensed on the target. If true, IMO this would be an awesome CAS capability that no other aircraft possesses and could result in some truly special CAS abilities.
Found here: https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2014/armaments/Wed15439Sande.pdf
(2.44 MiB) Downloaded 24 times
Found via google here: https://www.nammo.com/globalassets/pdfs/ammobook/nammo_ammo-handbook_2016.pdf
(4.59 MiB) Downloaded 23 times
Take an F-16, add a dollop of A-7, a big gob of F-22, sprinkle on some AV-8B, stir well, then bake. What do you get? An F-35.
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Unread post09 May 2018, 16:57

I forgot to throw up this image I found here: http://warfaretech.blogspot.com/2014/03 ... annon.html

While this image is comparing APDS (armor piercing discarding sabot) performance between three different rounds used by cannons on APC's, I think it can give you a general, qualitative performance comparison between the 30x173 (A-10) and the 25x137 (F-35) rounds. This image suggests the 25mm gets you about 2/3 of the wallop of the 30mm.

Take an F-16, add a dollop of A-7, a big gob of F-22, sprinkle on some AV-8B, stir well, then bake. What do you get? An F-35.


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Unread post09 May 2018, 17:25

mixelflick wrote:How much more pop though?

Enough to punch a hole in a tank? Not questioning what you're saying, just curious..

Remember that the much vaunted DU rounds for the GAU-8 are a thing of the past. 25mm APEX is going to do better against armor than 30mm HE.

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Unread post09 May 2018, 22:26

stevedapirate wrote:
lrrpf52 wrote:
steve2267 wrote:I've been thinking about the same thing for A2A with the gun.

I suspect that guided bullets are going to have a range and ∆v problem when it comes to A2A. The AIM-9 can reach out ~20 miles compared to the GAU-22 or even GAU-8 that list ~4000 yards as the max range.

What I don't know is if that max range figure is due to dispersion or loss of bullet velocity.

Some high explosive rounds need sufficient impact velocity to initiate the fuze.

IIUC, some of the guided rounds that are being investigated can be command detonated via the datalink
so that could be less of an issue. For A2A, I tend to think the main utility of guided cannon rounds
would be in the C-UAS/counter-cruise missile role.

The company is also investing in advanced ammunition, such as programming 30mm rounds to be airburst rounds, which has great utility in countering unmanned aircraft systems, for example.

Orbital has a deployed a counter-UAS system with ground forces, but has ways to convert it to be used on ships or at sea ports.

And Orbital has also developed a way to guide small ammunition to hit even moving targets, Kahn noted.

The company took a 50-caliber round with precision guidance and hit moving targets in tests through the EXACTO program with the Defense Advanced Research Projects Agency several years back, Olson said.

Advanced ammunition has great utility for programs like the F-35, Kahn said, because instead of shooting 30 or 40 rounds to hit a target, a guided round can take out a target in one or two shots. An F-35 is limited to carrying roughly 200 rounds.





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Unread post11 May 2018, 21:32

I think that if you're going the route of guided gun ammunition you're probably going to want to go bigger but with a slower RoF. (Especially at $25k per shot!)

The GAU-8 has a max range of 1220 m where a 40mm Bofors has 10x the range and can reach out to 12,500 m. This should allow for a lot more flexibility in both A2A and A2G. With that kind of range you should be able to engage ground targets with guided gun fire from 40k ft. where manpads are a lot less problematic.


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Unread post12 May 2018, 01:31

If you go bigger it's more stress per round unless you bleed off significant energy in a recoilless system.

It's probably easier to integrate guided rockets into a small stealthily pod. How far can you reach with a 70mm-ish folding fin rocket?


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Unread post16 May 2018, 06:39

DoD FY2018 Rapid Innovation Fund

U.S. Special Operations Command (USSOCOM)
Requirement #: SOCOM-18-BAA-RIF-0001
Title: Guided 30MM Ammunition Capability
Military System or Acquisition Customer: Program Executive Office (PEO) – Fixed Wing
Description: Provide an enhanced accuracy, guided 30MM ammunition capability that is
compatible with current AC-130 W/J platforms’ Mk 44 Bushmaster II (GAU-23) automatic
cannon weapon systems. Deliver a 30MM round capable of receiving and responding to
externally provided post launch course corrections to accurately engage designated moving and
stationary ground targets, with guidance systems that are compatible with current Precision
Strike Package (PSP) on the AC-130 W/J aircraft configurations with little or no hardware
modifications. Proposed software modifications should lead to demonstrable capability by minor
additions to PSP software in about six months with full capability fitting in the annual PSP
software release cycle. The guided 30MM round target circular error probability (CEP) must be
predictable and provide considerable improved accuracy over standard unguided 30MM
ammunition. The guided 30MM round must operate within the operating envelope of the
AFSOC AC-130 W/J, altitudes (15,000 – 25,000’ MSL), ranges (1.0 - 10.0nm) and slant ranges
(2.5 – 3.0nm). Use of high fidelity modeling throughout development is encouraged to
determine the optimal munition configurations, characteristics and maximize the value of range,
ground, and flight testing. The initiative will conclude with a guided 30MM ammunition round
design, guidance and control system, and tracking system that has been demonstrated in a nearfinal
and realistic configuration.

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