FSDS artillery rounds - theoretical discussion

[Totoro]

What would it take to successfully field Fin Stabilized Discarding Sabot artillery rounds? Would such a round have enough perfomance advantages over conventional rounds that it finds its place in the battlefield in certain situations?

We use a regular 105mm round (or similar caliber) shape. We add a gradually narrowing tail section to it, streamline it into something of a waterdrop shape. We add fins for stability. In theory, we get much lower induced drag thus getting longer range. It ends up being somwhat heavier and aimately twice the length of regular 105mm round.

Now we need a sabot which will provide a flat section to the bottom of the round. Sabot is also bigger in caliber, made for 155mm tube. The whole thing is then used in 155mm howitzers.

Main question is: what kind of range increase can be expected of such an arrangement? over:
A) regular 105mm round fired from 45L caliber tube
b) regular 155mm round fired from 45L caliber tube

We assume that propellant cartridges are all standard for the given caliber.
Given how basebleed rounds offer up to 30% longer range, this would need to top that to be viable. Also, just how much space/weight does the gas generator take from a round? Does that make the round carry less explosive? How much less?

 

[weasel1962]

Re:

Deleted

 

[PlasmaKrab]

Lessee... elongated tear-drop rear section, stabilizing fins... keep it full-bore and you have discovered... the mortar shell!
I guess it was invented the other way round as a way to stabilize low-velocity cannonball, but nice try.

J/K, seriously now, why would you want to fin-stabilize something shot out of a rifled barrel? It would be both expensive (requires counter-rifling collars) and counter-productive.
And why create longer rounds when armored howitzers are always so crammed up and trailed ones are always too close to the ground? For an equal volume, the length penalty will always be the square of the caliber reduction, so I'm not sure it will even out favorably.
Besides, you'll probably only reduce the final effect of the warload (whichever) with a long, thin body.

Now what about a large, cylindrical, full-caliber base-bleed round with a terminal shockwave-breaking plasma spear? Except for "deliriously expensive", of course?

 

[Totoro]

Actually i forgot to mention that using smooth barells would be the way to go, as it'd increase the velocity of the round. Round itself would have to be intelligent enough to use the fins to stabilize itself and then use them to guide itself to the target, if one wants to employ expensive guidance. But that is actually beside the point.

Point is - how does one dramatically increase the range of a projectile without resorting to basebleed rounds or rocket assisted rounds? Lets not argue about why would one want that in the first place.

I came up with just two possibilities - either use self deploying wings on the round itself, which would mean a non ballistic trajectory, greatly lowered precision unless guided and longer time on target

OR increase speed while lowering the drag that a regular round would have at the given speed. This is where the firstmentioned proposition comes in.

I am aware that longer round is a potential problem which is in part why i'm not suggesting anything over 105mm caliber, but one also has to take the drag into account. Larger area gives larger drag. Not only that but at the speeds artillery is travelling, total drag is mostly comprised of drag induced by the vortexes in the back of the round. Yes, base bleed is designed to deal exactly with that but i am asking just how efficient that is. Could it be that instead of virtual, gas-made tail, a real, physical, carefully shaped tail section can lower the drag a lot more?

 

[PlasmaKrab]

Are you considering guided rounds or not? from the beginning you mention actuating fins. Or have I misunderstood something? If the round is to be guided at all, you can surely add any kind of gliding aid, provided it can stand the acceleration.

As to the length of the round, I think the problem is mainly in the length/diameter ratio, but for now, let's consider that room is not an issue. I'm still dubious about the way the round effect will be changed by the new shape (think size of the submunitions, and ignition and shockwave formation of a HE round). For most purposes, the more spherical you remain, the more useful room you get.

Maybe a spindle-shaped tail would be a compromise? I don't know what it would take to make it more efficient than a base bleed (unpractical length, hyper-accurate engineering, costly materials...).
Such a tail assembly (possibly finned) could be fitted inside a semi-sabot similar to that used for old APDS tank rounds.

Any idea about the actual amount of energy absorbed by the side drag, vortex drag and sonic shockwave? If you have formulas about those, you could have a more accurate picture on which parameters to tweak.

All in all, I like the rocket-assist concept enough. Looks like it gives over the BB the same kind of range advantage as the BB over standard. If you think about it, it is the ultimate evolution of the base bleed.

And frankly, I don't know wht more you can do further the a shell to give it better range, no.

 

[Big-E]

EM-Railgun is the only theoretical weapon that has the KE to make sabot rounds usefull. That's where the future of artillery is and the Navy get first wack at it.

 

[weasel1962]

Re:

Deleted

 

[Totoro]

Thank you all for your input. After some more thinking i have concluded that guided rounds would have to be used no matter what. When talking about 50-80 km ranges, it is obvious that precision of an unguided round over such distance would be unacceptable. And if one is going to use guided rounds, the relative cost increase of such a round would allow to use other systems too, like the mentioned self deployed wings.

It does seem that is, in the end, the best way to achieve range. Granted, it brings problems of its own, like longer travel time, bigger RCS for enemy anti-artillery radars, etc.

Sadly, I don't see a way to have both great range and decent precision over full distances while retaining cost not more than double that of a dumb round.

EM guns will be great but they too will be prohibitively expensive, with both the guided rounds and guns themselves being very pricey.