M109A6 test bed for XM907 ERCA

[Scott Kenny]

Oh, as stated repeatly... the distinction between tank & SPH needs fade. Tank utilization rates on the current Ukr front displays direct tank on tank incidences are rare whereas tank gun for indirect fire is prevalent.

They do different jobs, which require greatly different levels of protection.

 

[jsport]

They do different jobs, which require greatly different levels of protection.

havent been expressing complete fusion of roles but that SPHs need to have attributes such as heavier armor and APS, enhanced CROWS (some Paladins have), live track while the tanks need the FCS BLOS emphasis returned.

 

[Scott Kenny]

havent been expressing complete fusion of roles but that SPHs need to have attributes such as heavier armor and APS, enhanced CROWS (some Paladins have), live track while the tanks need the FCS BLOS emphasis returned.

APS, sure, you need defenses against things like Spike NLOS and drones.
Heavier armor, arguable, you can probably get away with a top attack capable APS.
Enhanced CROWS, only if you're expecting the bad guys to be sneaking infantry up to your arty. Unless you're getting a really fancy CROWS that can shoot down drones, then absolutely you need that CROWS.
Live track, the M109s just did a major refresh to use Bradley engines, suspension, and track.

Tanks have needed a 5km round for decades...

 

[Kat Tsun]

It is not. But one can always simply pick two MTA's with the Army and claim they will be forced to pick b/w one and the other and if it pans out that one does get cancelled we can claim we were right all along

Of course. No crystal ball is perfect. The problem is that neither are MTA's anymore.

Both are transitioning from MTA to Major Capability Acquisition, because they have failed to meet their initial timelines as of FY2025, and that is a bad sign for a program's health in general. MTA isn't supposed to be a pathway to spending more money, it's for things which might require more money than a small acquisition, but can be done rapidly by way of quick prototyping from arsenal to industry.

Neither ERCA nor LTAMDS could achieve this, so they're both up on the chopping block this year. It's not a huge leap in logic to assume that both are at risk for cancellation obviously, but given world knowledge developments since 2018, one is significantly less justifiable than the other when the Minsk II DMZ is no longer the standard by which guns are measured.

AGS and LOSAT weren't outright competing for contracts either, after all. If anything, they complemented each other. Because it's not about "competition" in a battlefield sense: it's about competition for the same pool of money, and the overall cost of a program versus the benefits it brings.

I feel ERCA's business case will be weaker now that the Minsk II DMZ is no longer the standard by which guns are judged, to say the least.

 

[bring_it_on]

Of course. No crystal ball is perfect.

Some of what you've mentioned is truly crystal ball stuff and completely divorced from reality.

 

[Kat Tsun]

Some of what you've mentioned is truly crystal ball stuff and completely divorced from reality.

Yeah, I idly speculate a lot? I was going to have a big post, but whatever. I guess we'll see next year, if ERCA survives to make MCA, I imagine it can make it to low rate production in a year or two's time from then.

They do different jobs, which require greatly different levels of protection.

Optimal SPH protection level is Bradley equivalent. How Pzh 2000 avoids dying in Ukraine: it can survive ~20-30 meter 155mm bursts.

havent been expressing complete fusion of roles but that SPHs need to have attributes such as heavier armor and APS, enhanced CROWS (some Paladins have), live track while the tanks need the FCS BLOS emphasis returned.

FCS NLOS-C was bad, it was just a 39-cal Crusader. A BLOS round for the 120mm is pointless, if you need indirect fire so badly just bring a 120mm mortar. It shoots further.

 

[MadRat]

Come on fella. This was about alternatives to ERCA and what it could be replaced with to not deviate from current 155mm options. The whole point of ERCA is to outrange a whole spectrum of rocket and tube artillery that is out in the real world today. The danger of ERCA is total cost of ownershio for the role. ERCA will not replace all 155mm tubes, its only a niche to mission kill threats to existing 155mm.

The argument is not about mortars. NLOS-C is M109A7 on a Bradley chassis, and ERCA is an extension of that. That was pretty daft to say a mortar has longer range than the M109 or a large tank round fired ballistically. Please stop. You are just plain being nonsensical rather than debating.

 

[Scott Kenny]

Optimal SPH protection level is Bradley equivalent. How Pzh 2000 avoids dying in Ukraine: it can survive ~20-30 meter 155mm bursts.

Exactly.

Optimal SPH protection is NOT Abrams/other MBT.

 

[Prophet141]

Come on fella. This was about alternatives to ERCA and what it could be replaced with to not deviate from current 155mm options. The whole point of ERCA is to outrange a whole spectrum of rocket and tube artillery that is out in the real world today. The danger of ERCA is total cost of ownershio for the role. ERCA will not replace all 155mm tubes, its only a niche to mission kill threats to existing 155mm.

The argument is not about mortars. NLOS-C is M109A7 on a Bradley chassis, and ERCA is an extension of that. That was pretty daft to say a mortar has longer range than the M109 or a large tank round fired ballistically. Please stop. You are just plain being nonsensical rather than debating.

So the ERCA is to normal tube artillery what SEAD with radiation homing missiles is to interdiction and strike aircraft?

 

[MadRat]

So the ERCA is to normal tube artillery what SEAD with radiation homing missiles is to interdiction and strike aircraft?

If counter-fire battery fits your answer. I'm not good with metaphors in that way.

The idea that ERCA would replace everything is outside the scope of the program. The proposed purposes to justify it are a bit dubious to me as the goal should be to use any of a spectrum of options which could be something from rocket-propelled SDB, to an MBT gun, ATACM variant, etc.

 

[Kat Tsun]

Exactly.

Optimal SPH protection is NOT Abrams/other MBT.

Just the vehicle that accompanies the M1 into battle.

That was pretty daft to say a mortar has longer range than (...) a large tank round fired ballistically. Please stop. You are just plain being nonsensical rather than debating.

...but it literally does.

An "indirect fire 120mm tank shell" is just a "bad 120mm mortar" for all intents and purposes. Mortars are useful because they can be zoned.

 

[MadRat]

Just the vehicle that accompanies the M1 into battle.



...but it literally does.

An "indirect fire 120mm tank shell" is just a "bad 120mm mortar" for all intents and purposes. Mortars are useful because they can be zoned.

I am not sure where you got the impression a 120mm mortar out ranged a 120mm gun. The gun has literally 3 times the range using a wide variety of options. It probably can loft a sabot round considerably further than 3x the mortar.

 

[Kat Tsun]

I am not sure where you got the impression a 120mm mortar out ranged a 120mm gun. The gun has literally 3 times the range using a wide variety of options. It probably can loft a sabot round considerably further than 3x the mortar.

Sabot rounds aren't "BLOS 120mm rounds"?

MRM's various contenders had a demonstrated range of something like 8-9 kilometers at Yuma from the M1A1's tank gun. This is broadly comparable to a 120mm mortar, except worse, because it's a low angle gun that can't fire in mountainous or urban terrain like a mortar can.

A 105mm howitzer like the L118 shoots even further and also zones.

 

[Firefinder]

A 120mm morter with RAP and PGK maxs out to 9.5km.

A 120mm gun with a muzzle velocity of 800 meters, read basically every 120mm tank gun, before including the ACTUAL artillery types like the naval 120mms and the russian 122mms.

When set at a 45 degree angle will punt a HE shell out to 20km with a decent degree of accuracy.

This includes the M256 gun of the M1. Which can, and has in combat, Yeet a High Explosive shell out to 18km with like 50 meter accuracy.

Its not often used cause of the inaccuracies of indirect fire and tanks often have better things to do. Which is why there no guidences shells for it either to keep crews from wasting ammo on it. But the M1 fire control computer does have an indirect setting, and both Ukraine and Russia are doing similar with all their T series.

Its not advertised either to keep people from getting confuse between being able to hit a tank size target at 4km from being able to hit a building size target at 18km. Basically only the crews and those who dig into the TMs know of it.

Or can do some simple math. And realize a gun that lobs a HEAT shell over 800 meters a second will out range a mortar that maxs out at less then 400 meters a second.

 

[Kat Tsun]

Yeah, America did that in Korea and Vietnam when there wasn't enough indirect fire happening, sure. It happens in any major war.

jsport is specifically referring to the various purpose-built BLOS rounds from the '90's and '00's, like MRM, as being a potential replacement for the M109A6 and M1 tank with a unified combat platform. I don't think these ever had ranges too much beyond around 10 to 12 km though? That's well within the capabilities of "advanced" (i.e. almost 40 years old) 120mm mortars like 2S31.

 

[Scott Kenny]

A 120mm morter with RAP and PGK maxs out to 9.5km.

A 120mm gun with a muzzle velocity of 800 meters, read basically every 120mm tank gun, before including the ACTUAL artillery types like the naval 120mms and the russian 122mms.

When set at a 45 degree angle will punt a HE shell out to 20km with a decent degree of accuracy.

This includes the M256 gun of the M1. Which can, and has in combat, Yeet a High Explosive shell out to 18km with like 50 meter accuracy.

And if your tanker has the FCS set to HEAT with a sabot loaded, will punt that sabot clear out of the range safety zones and into the high school gymnasium about 50km away (Yakima), or clear into France on a bad day (UK firing range, forget the name)

 

[MadRat]

2S31 is more rifled gun than mortar. And its vehicle-mounted with a limited capacity. It is not a true mortar. It has 'gun' in its description for a reason. And just to be clear, your current 155mm SPHs will easily outrange it. There is no need to keep moving all over the place as we are talking about being able to counter-fire in support of your forces. If you can get 120mm gun hits within 50 meters that sends a pretty strong message to the other guy that we can touch you and we know you are there. Will a tank gun match a 155mm artillery piece? Of course not. But it certainly is better than any mortar. And although Kat Tsun misdirects the argument towards a gun mortar, I am much more confident an M-1 is going to be better situated for hitting something 12-13 kilometers away. As a mortar, it is, a mortar. Because when used as a gun it may reach 13km but it doesn't fire the specialized goods that are going to do the real damage even out to 8km. The best effects come when using mortar ordnance. As a mortar.

 

[Firefinder]

And if your tanker has the FCS set to HEAT with a sabot loaded, will punt that sabot clear out of the range safety zones and into the high school gymnasium about 50km away (Yakima), or clear into France on a bad day (UK firing range, forget the name)

Not really.

While darts do hold their speed far better than the usual shells. They max out at less than 30km, cause once they hit a certain speed their stability goes the complete opposite direction direction and they basically shatter as they tumble.

And Test me, 50km is nothing for an Arty range. Which is the only time you will be setting the FCS to indirect mode. And the way the system is set up it would not put the gun at any angles where even darts will go more then 6km.

 

[Scott Kenny]

Not really.

While darts do hold their speed far better than the usual shells. They max out at less than 30km, cause once they hit a certain speed their stability goes the complete opposite direction direction and they basically shatter as they tumble.

And Test me, 50km is nothing for an Arty range. Which is the only time you will be setting the FCS to indirect mode. And the way the system is set up it would not put the gun at any angles where even darts will go more then 6km.

Guess I need to go find the news reports, then.

Because a tank at the Yakima range did manage to drop a sabot into the center of the high school gym that is not even on base. All because they had the switch set to HEAT not SABOT on a fairly long target.

 

[MadRat]

Early sabot rounds were not very long relative to width, but the modern ones are not exactly tumble prone.

 

[Kat Tsun]

2S31 is more rifled gun than mortar. And its vehicle-mounted with a limited capacity. It is not a true mortar. It has 'gun' in its description for a reason.

2S31 carries 70 120mm mortar rounds. It's almost double the M1 tank's ammo load. I don't know what a "true mortar" is. 2S31 can fire any 120mm Soviet mortar round, like how AMOS can fire any Western 120mm mortar round. It just has special mortar rounds for itself, too.

There is no need to keep moving all over the place as we are talking about being able to counter-fire in support of your forces. If you can get 120mm gun hits within 50 meters that sends a pretty strong message to the other guy that we can touch you and we know you are there.

You have a fair chance of even a 2S3 or M109 being able to escape at 50 meters from a 120mm HEAT or AMP burst.



Anything you're firing at with 10-20 kilometers is either going to be a very small howitzer, or a very large mortar, and not much else. It sends a message that you're missing the target and not very lethal, but it isn't going to make them stop. The D-30s will just fire back.

Of course not. But it certainly is better than any mortar.

That explains why every army in the world has replaced mortars with tanks? BLOS 120mm technology isn't new. It's been around for nearly 30 years now. Why has no one rapidly acquired it, but are busy rapidly acquiring more advanced howitzers and mortars instead?

I am much more confident an M-1 is going to be better situated for hitting something 12-13 kilometers away.

Have fun with fewer sabot or HEAT rounds if you're including BLOS shells in the natures of ammunition I guess. Why do you think the Army merged HE-OR-T, CAN, and HEAT-MP into the single AMP?

Because when used as a gun it may reach 13km but it doesn't fire the specialized goods that are going to do the real damage even out to 8km. The best effects come when using mortar ordnance. As a mortar.

...

Even bad mortars like the M120 have demonstrated delivery of PGM and cassette shells out to double digit kilometers.

https://apps.dtic.mil/sti/pdfs/ADA376461.pdf

Mortars will have a greater effect on target than any tank munition of the same caliber, because mortars have a greater proportion of explosive filler per projectile mass. They don't need to be particularly strongly constructed, unlike a tank round, because they are not subject to high accelerations. Mortars can be zoned, which means they can be fired at multiple angles with different burst charges, to achieve MRSI on a column of vehicles or counter battery.

Tanks can be used for indirect fire if you're desperate or if you have nothing better to do, which is dumb, but a valid use case. Tanks can't replace any extant indirect fire platform, though. Howitzers/mortars and tank guns/field guns are almost polar opposite requirements, really.

 

[Scott Kenny]

Have fun with fewer sabot or HEAT rounds if you're including BLOS shells in the natures of ammunition I guess. Why do you think the Army merged HE-OR-T, CAN, and HEAT-MP into the single AMP?

Which is an error on their part, IMO. HEAT and that HE-OR were the same physical round just with different fuzes installed, so putting a smart fuze that was hardened enough to work as an obstacle round is fine, but the canister does different things that are not directly replaceable by HE. Seriously, though, an Abrams holds 42 rounds. Most expected engagements, based on the NTC engagements, were 11-13 rounds. So it's not unreasonable to have 4x canister, 16x sabot, 16x AMP, and 6x BLOS. Or some variation of that mix.

 

[Kat Tsun]

Which is an error on their part, IMO. HEAT and that HE-OR were the same physical round just with different fuzes installed, so putting a smart fuze that was hardened enough to work as an obstacle round is fine, but the canister does different things that are not directly replaceable by HE. Seriously, though, an Abrams holds 42 rounds. Most expected engagements, based on the NTC engagements, were 11-13 rounds. So it's not unreasonable to have 4x canister, 16x sabot, 16x AMP, and 6x BLOS. Or some variation of that mix.

The AMP has a shrapnel/PFF combination body. There's a German round the Marines were looking at which is similar, called DM11, and AMP is possibly based on it. It is functionally more lethal than CAN, because it has a greater lethal range, even if it might not be as lethal at its optimal range or whatever.

NTC engagements don't represent reality, or at least a modern reality, but they may be based on Desert Storm experience. Ukraine War experience suggests ammo loads between 10 and 20 main gun rounds are adequate for tanks in combat for a single day. This is mostly because people are underloading the AZs, to reduce fire chances, but elimination of stuff like hull racks is becoming common as well.

KF51 and Leclerc both have autoloaders in their bustles. KF51 carries 20 rounds while Leclerc carries 22. Leclerc will soon lose the hull rack. AbramsX, I believe, has something like 34 rounds in its ribbon loader and is probably the highest density of all of them. It has a novel swinging arm, so that it can reach two layers deep, rather than the sort of single layer ram style ribbon loader of Leclerc. It may be less than that though, since GDLS has stated it doesn't use the M1-drop in specific Compact Autoloader, so either it's a development or maybe it's narrower or something.

Future tanks will just carry less ammo, if not because their bustles are crammed with machines, but because hull racks are being deleted.

Simply not a lot of room for more than two natures of ammo tbh. Naturally, howitzers and mortars are moving in the opposite direction, carrying more ammo. You need more rounds to prosecute an indirect fire engagement, after all, and there's an ever expanding list of natures of indirect fire rounds.

 

[Scott Kenny]

The AMP has a shrapnel/PFF combination body. There's a German round the Marines were looking at which is similar, called DM11, and AMP is possibly based on it. It is functionally more lethal than CAN, because it has a greater lethal range, even if it might not be as lethal at its optimal range or whatever.

Canister was the preferred mouseholing round in Iraq, that a tank could drop onto a building maybe 10m from where the grunts were stacked up. Yes, with grunts on the wrong side of the muzzle. And do it safely.

NTC engagements don't represent reality, or at least a modern reality, but they may be based on Desert Storm experience. Ukraine War experience suggests ammo loads between 10 and 20 main gun rounds are adequate for tanks in combat for a single day. This is mostly because people are underloading the AZs, to reduce fire chances, but elimination of stuff like hull racks is becoming common as well.

KF51 and Leclerc both have autoloaders in their bustles. KF51 carries 20 rounds while Leclerc carries 22. Leclerc will soon lose the hull rack. AbramsX, I believe, has something like 34 rounds in its ribbon loader and is probably the highest density of all of them. It has a novel swinging arm, so that it can reach two layers deep, rather than the sort of single layer ram style ribbon loader of Leclerc.

They should really go back to the TTB autoloader, 48 rounds stowed in 2 rings.

Simply not a lot of room for more than two natures of ammo tbh. Naturally, howitzers and mortars are moving in the opposite direction, carrying more ammo. You need more rounds to prosecute an indirect fire engagement, after all, and there's an ever expanding list of natures of indirect fire rounds.

And yet the 105mm in the M8 and M10 has IIRC 5 or 7 different settings in the FCS.

 

[Kat Tsun]

Canister was the preferred mouseholing round in Iraq, that a tank could drop onto a building maybe 10m from where the grunts were stacked up. Yes, with grunts on the wrong side of the muzzle. And do it safely.

XM919 will probably be able to do that.

They should really go back to the TTB autoloader, 48 rounds stowed in 2 rings.

It would ruin hulls if penetrated. M1 hulls are a limited resource since they haven't made any new ones lately. A turret can just be replaced.

And yet the 105mm in the M8 and M10 has IIRC 5 or 7 different settings in the FCS.

Stryker MGS only carried 18 rounds and M8 AGS only had 22, tbf.

I don't think anyone has said what M10 actually carries, but it's been suggested to be around 50 rounds, like the old M1. Presumably it may even use the old M1 or IPM1 ammo racks in the bustle, since it's a naked M1 turret, which would mean 44 rounds in the bustle.

 

[A Tentative Fleet Plan]

2S31 carries 70 120mm mortar rounds. It's almost double the M1 tank's ammo load. I don't know what a "true mortar" is. 2S31 can fire any 120mm Soviet mortar round, like how AMOS can fire any Western 120mm mortar round. It just has special mortar rounds for itself, too.

I was under the impression that the AMOS could fire Western 120mm ammunition for smoothbore Mortars, not the ammunition intended for the MO-120 RT?

 

[Kat Tsun]

I was under the impression that the AMOS could fire Western 120mm ammunition for smoothbore Mortars, not the ammunition intended for the MO-120 RT?

Yeah AMOS and NEMO are smoothbore. I think they need a little stub obturator attached to the mortar bomb but that's it.

I'm not sure enough NATO members, besides maybe France, Italy and Belgium, use the French F1 for it to be a problem.

 

[zen]

So just clarify for us mortals what driving band was used on L70 guns?

 

[Kat Tsun]

So just clarify for us mortals what driving band was used on L70 guns?

...because the L70 has a slower twist rate. A 1:46 to 1:27 progressive twist is a bit less demanding on copper drive bands. Pzh 2000 is a 1:20 twist, as is AS90, and most other 155mms tend to dwell around there, but I don't think any modern NATO howitzer is progressive twist.

 

[MadRat]

Just to be clear, if someone is reaching you from beyond 155mm range, where ERCA is a relavent option and today's 155mm is not, nowhere will a gun-mortar or BLOS round be the option. If they need to reach 50km then these are not an option so they are irrelevant word soup in this thread.

ERCA needs a businesss case to be built. Look at the other systems that can overlap this range. Otherwise the 2S31 and BLOS can be debated in a thread relevant to it. If the 120mm tank gun can reach these ranges, and ERCA will compete for this mission, then it is relevant as an exercise if ERCA can be justified.

 

[kqcke for you]

ERCA needs a businesss case to be built. Look at the other systems that can overlap this range. Otherwise the 2S31 and BLOS can be debated in a thread relevant to it. If the 120mm tank gun can reach these ranges, and ERCA will compete for this mission, then it is relevant as an exercise if ERCA can be justified.

Take 76mm Vulcano for the 120mm and hope for the best. Then you maybe achieve 2/3 of it and be happy because your Tank know can shoot far.

 

[Kat Tsun]

Take 76mm Vulcano for the 120mm and hope for the best. Then you maybe achieve 2/3 of it and be happy because your Tank know can shoot far.

You'd just use GMLRS fired from a HIMARS or something if you're being shot at by long range artillery.

HIMARS With RIG-360 for Strikes on Moving Targets: How It Will Work | Defense Express

Destroying moving targets with HIMARS from a 150 km distance becomes reality, moreover, it's thanks to the cheapest homing system in existence

en.defence-ua.com

If the developers succeed during live firings, GMLRS will get real-time radio guidance. In addition to the ability to destroy stationary objects matching the target data pre-programmed before the launch, it will be able to strike moving targets as well.

The biggest advantage though is that such a guidance system will be much cheaper than all the alternatives. For example, at present, the most affordable guidance system against moving targets is laser homing. The rocket is equipped with a homing head, and someone has to "illuminate" the target with a laser beam: either a UAV with a pointer or a soldier on the site. Both variants presume that the target is not too far, and the laser beam operator risks getting caught in the rocket's collateral damage.

Even if it moves it can be hit with RIG-360 integration. There's a lot of redundancy (this is good) in the whole deal.

Or just do what guys did in Desert Storm and drive the howitzers closer to the frontlines. America has fought extremely long range guns before, with M109A5s of all things, and was fine: https://en.wikipedia.org/wiki/Al-Fao

Granted, I don't think the Al-Faws were actually present, but the Army didn't know this.

 

[Scott Kenny]

Yeah AMOS and NEMO are smoothbore. I think they need a little stub obturator attached to the mortar bomb but that's it.

I'm not sure enough NATO members, besides maybe France, Italy and Belgium, use the French F1 for it to be a problem.

USMC bought the French rifle Mortar for some reason.

 

[Kat Tsun]

USMC bought the French rifle Mortar for some reason.

Yeah but they're a separate supply chain. The HERO requirements for Navy munitions make land rounds unsuitable.

 

[Firefinder]

One thing Im see people missing is how the Army is resetting itself up stucture wise. And how they doing it explains the ERCA role nicely.

With them going back to a Division set up.

Each division is slated to get 3-4 battalions worth of Arty under the current op order.

2-3 of those going to be the older L39s for general purposes roles. Light only getting theses thru.

And the final one to be an ERCA battalion for use as a gap filler slash commander sniper slash organic counter battery for the entire division much like how the 175 and 203s were used in the First Cold War.

While the MLRS will be returning to their higher level uses to be divided out to the units on an as needed basis. Or for near stragetic strikes.

Or just do what guys did in Desert Storm and drive the howitzers closer to the frontlines. America has fought extremely long range guns before, with M109A5s of all things, and was fine

Granted, I don't think the Al-Faws were actually present, but the Army didn't know this

The Faws never got used against US troops in either war.

Always was held back or got strike by air/mlrs before hand.

As is the Iraqis did use another gun that slightly out ranged the M109 that I forgot the name of.

And none of the Artillery Branch liked that.

Cue the last 30 years of the Artillery Branch pushing for longer range guns which the ERCA basically stems from.

Cause just because you can push up under fire to hand deliver a grenade to a bunker slot. Does not mean you like doing so.

And everyone agrees that uses a explosive yeeter, grenade launcher, rocket launcher, tank, B52 arc light strike...

Is far better for everyone who matters.

Thus the 70km range gun.

 

[MadRat]

Too bad they can't just sabot launch an elongated dart with a simplified electronic augmentor. You can drop your sabot shell and sustain with a slow-burn rocket stage. With computers like the Raspberry Pi being so cheap, they should be able to get quite a lot for less these days. You do not need a complete sensor suite in every round, just minor course correction thew first ten to fifteen kilometers, to get pretty precise terminal dives. The Germans and Swedes have been working on them for two decades, so might start by peeking at their stuff. While it may start out from a 155mm barrel, the actual delivery vehicle could be much less diameter and be plenty effective at 70km, if that is your true goal. The vast majority of your shells can be dumb shells still.

 

[Firefinder]

Too bad they can't just sabot launch an elongated dart with a simplified electronic augmentor. You can drop your sabot shell and sustain with a slow-burn rocket stage. With computers like the Raspberry Pi being so cheap, they should be able to get quite a lot for less these days. You do not need a complete sensor suite in every round, just minor course correction thew first ten to fifteen kilometers, to get pretty precise terminal dives. The Germans and Swedes have been working on them for two decades, so might start by peeking at their stuff. While it may start out from a 155mm barrel, the actual delivery vehicle could be much less diameter and be plenty effective at 70km, if that is your true goal. The vast majority of your shells can be dumb shells still.

The issues with the computers is not all the toys.

No.

Its the fact that they need to last upwards of 20 years without any issues going from -42 C to +60 C repeatedly while being able to work.

And that they need to withstand 20,000 Gees of Acceleration going both axillary and radially to survive being punted by nearly 30 pounds of explosives.

Which is not an easy or cheap ask for anything when combine.

 

[Kat Tsun]

Excalibur had a pretty girthy development period, mainly related to g-hardening the MEMS computers, IIRC.

 

[MadRat]

They had Copperhead figured out in the 80s literally using technology from the 70s. I have confidence its not the worst obstacle.

 

[jsport]

Some time back a USN research project started looking into propulsion & explosives being the same substance & structure w/next gen energetics. Throttleable munition propulsion also seems to still be moving. Munitions need to get smaller and resemble missiles until they are the one.

The Navy seeks the next generation of energetics for more potent weapons | Federal News Network

For the military, any advantage in weapons has a lot to do with energetics, the materials that explode and power projectiles. Recently the Navy awarded other transaction authority money to the…

federalnewsnetwork.com