RE: [DS3] Dirtside Accelerator for Infantry

>>> <http://lists.firedrake.org/gzg/200110/msg00036.html>

> CS Renegade wrote:

>> Why is the proposed HEAT class restricted to missiles? Given the
>> relative figures surely HVC should fire HEAT rounds at long
>> range?

> From: ~ On Behalf Of Oerjan Ohlson
> Sent: 04 September 2004 20:16
> Subject: RE: [DS3] Dirtside Accelerator for Infantry

> Not if they want to hit moving targets at long range...

I wasn't implying a through-barrel missile system here, just an
ordinary HVC HEAT shell as opposed to one employing the simple KE
approach. My reading of the above was that a conventional KE round
fired at long range from an HVC would be rolling a D4 for effect,
whereas an HEAT round from the same gun would be rolling the same
number of D10 (and might also be argued to be exempt from APFC).

Moving targets? An evading target gets a secondary D8, but that
would apply regardless of the nature of the shell fired at it.
Is this a real-world consideration (i.e. only modern APFSDS has that
sort of range)?

>>>> [on the multiplied die concept] I'm having difficulty losing my
>>>> "weapon X beats armour x" & "armour X is proof against weapon
>>>>  x" wargamer's mentality, where X > x.
>>
>>> Hm? The *accelerator* allows armour X to be proof against weapon
>>> x and vice versa (for large enough values of X and small enough
>>> values of x); the *chits* don't (thanks to those "0" and "BOOM"
>>> chits). Why do you have to lose this particular mentality when
>>> you change *from* the chits *to* the accelerator...?
>
>> I think our problems centred around large-die low-calibre weapons
>> against strong armour that had the misfortune to roll low.
>> It just didn't seem right somehow, so I ran some test cases and
>> discovered that the chances worrying me were fairly low - for
>> example 1xD10 vs 3xD8 has a 15% chance of success whereas 2xD10
>> vs 4xD8 has a 25% chance of success, but would be expected to be
>> more lethal anyway. Under the chit system the worst a single chit
>> could do would be to damage an armour/3 target, but the chance of
>> two chits knocking out armour/3 rises to 28%.
>
> Question: why are you comparing Size/2 weapons vs. Armour/*4* in
> the Accelerator against Size/2 weapons vs. Armour/*3* under the
> chits...?

I managed to mangle my example. If all colours are valid, the chance
of two chits knocking out armour/4 is only 11% until the special
damage chits are factored in.

>> I realise I'm being blind to the possibility of a special chit
>> here, which may go some way to explaining my original reaction.

> Bingo :-/ With 16% of the chits being specials, the odds for
> drawing one or more are fairly high.
>
> Also, if you remove the "damage" results (including the specials)
> you'll need to replace them with something - otherwise you reduce
> the overall lethality of the weapons. When updating the
> Accelerator I chose to treat the "double damage" results
> (i.e. DAM+MOB, MOB+SD:T and SD:T+DAM) and "triple damage"
> (DAM+MOB+SD:T) as "destroyed" - at best such vehicles can fire at
> a DOWN1 FCS modifier but not move, or can move at half speed but
> not fire - either way they're pretty much out of the fight - and
> to treat "single damage" (DAM, MOB or SD:T) results as "worth"
> half a kill.

I'd agree with that interpretation of combined specials.

> Let's see how your examples look when evaluated in this way:
>
> D10 corresponds to "R&Y" validity, <snip illustrations>

So it does. I was still thinking of the original version that used
both D12 and D10 for full validity.

>>>> Am I correct in thinking that single opposed dice give a
>>>> flatter distribution than drawing N chits against a fixed
>>>> target total, when N > 2?
>>>
>>> Yes. This is why most "simple" DS-FMA systems (the ones that try
>>> to map weapon sizes/armour ratings directly to particular
>>> unmodified die types) tend to make all weapons very similar to
>>> each other, and why the Accelerator concept *doesn't* use just
>>> "single opposed dice" but "single opposed dice multiplied by the
>>> armour rating or weapon size" - the multiplication gets you away
>>> from those narrow distributions.
>>
>> But the distributions are still flat
>
> Sounds like you have a different definition of "flat" than I do,
> then. If you plot the Pkill and Pdamage for the various
> combinations of validity and weapon Size against target armour
> rating, the Accelerator gives curves that look quite similar to
> the ones you get from the chits - in fact, in many cases they're
> *more* curved than the chit ones.

If I draw one chit I get a variable set of outcomes based on the
relative frequency of chit values. If I draw two chits I get a
pyramid, skewed for the same reason. If I draw three or more chits
then I get a bell curve. Against that, multiplied or not, a single
polyhedral die can only give a flat distribution of equally likely
outcomes. Now we combine the results of two polyhedral dice; it
doesn't matter if they are added or subtracted, both count as a
combination for calculating probabilities. It does matter that they
are possibly of different geometries and may be multiplied by
different factors, but only for working out the values of all the
possible outcomes. I would expect the distribution to still be a
simple pyramid and a fairly even one at that, and the differing dice
and factors only serve to alter its shape.

Erm, I've just criticised the core FMA mechanic, haven't I? Oops,
didn't mean to do that.

>>> Weapon:\Target:	Militia 	Line		PA
>>> Militia/Line/APFC	53/36/22/10	28/16/07/02	11/06/03/01
>>> PA/APSW		79/58/37/16	60/37/18/05	38/21/09/02
>>> HEL etc.:		    10		    2		    1
>>> DFFG:		    37		    18		    9
>>> SLAM/3:		    16		    5		    2
>>> SLAM/4:		    22		    9		    4
>>> SLAM/5:		    29		    13		    7

>> There appears to be something I'm not aware of regards chit
>> validity when shooting at infantry - these aren't the figures I
>> would expect at all. <snip> Has [a correction been] published?

> ...the validity bit on p.36 directly contradicts the validity
> table on p.29, and when asked about it Mike Elliott stated that
> p.29 was correct and p.36 was wrong.

A bad dream is coming back to haunt me. I've a nasty suspicion that
when I first read DS2 I picked up on this and decided that pg 36
had to be correct because pg 29 made vehicle weapons ludicrously
ineffective when shooting at infantry. Still, there's no arguing
with the author's opinion. Amazing how the memory plays tricks,
isn't it?

>> Although I frequently arrange for both sides to field infantry,
>> they generally stay in the transports and are never effective
>> unless they can get to a worthwhile objective (such as a built-
>> up area) before the enemy appear. APCs are seen as big, fat,
>> undergunned targets.

> Sounds as if you need to use a lot more terrain! Infantry doesn't
> like wide-open plains; but if you play with terrain densities like
> those of northern Europe (where you're lucky to have a LOS of more
> than 1 mile, and the average LOS is IIRC about half that) they're
> a lot more useful.

One criticism normally levelled at my group's FT2 games is that we
use too small an area (typically 48 x 72mu, which is a squeeze even
for cinematic movement). Using a cm scale for DS2 we have an area
of 120x182 available, with games played sometimes down and sometimes
across the table. Open areas between obstacles are often in the
region of 50-80cm, and no-one goes thrashing through terrain because
it takes too long to get anywhere, so encounters generally will be
in the open bits. We could try a ridge down the middle of the
table...

>> Regards my "alternative" figures, I nearly didn't post them as
>> they were completely untried and did represent a departure
>> from the technology laid out by the quoted pages; for example,
>> all MDCs are described as small-calibre rapid-fire weapons
>> whereas I envision the larger class guns throwing projectiles no
>> smaller than those fired by comparable HVCs.

> The projectiles fired by HVCs at vehicles are sub-calibre KE
> rounds with large sabots, and the main reason the guns themselves
> are large-calibre is that the gas pressure needs as big as
> possible an area to push against to maximize the force on the
> projectile. With no gas pressure to worry about, MDCs can fire the
> same size of KE projectiles from a much smaller-calibre barrel -
> an MDC barrel designed to fire today's "120mm" KE rounds (fired
> from the HVC's 120mm ancestors) would need to be a little over 1"
> in diameter, plus slits in the barrel walls for the fins.

> (Note that DS2's description of HKPs is complete bunk - the
> weapons described by that blurb would find it extremely difficult
> to get up to even HVC performance...)

Doesn't DS2's HKP concept presume far higher barrel pressures? As to
why this might be better than sticking with the HVC design, the
weapon would be smaller and the ammunition would take up less space
and be less volatile. (The exotic HKP propellants might even be fed
from a tank rather than loaded as a cartridge or charge.) Do modern
MBTs still have hand-loaded rounds, and if so, how close to the
limits of manual handling are they? Wouldn't MBT design and
logistics both be easier if the round was just the penetrator and a
half-litre of skunkworks moonshine?

>> Possibly I'm just prejudiced by the number of models available
>> in the market with large-calibre guns looking for a role,

> Calibre only refers to the inner diameter of the barrel, and
> whereas an HVC barrel is essentially just a steel tube the MDC
> barrel is lined with a lot of equipment - magnets, electrical
> circuits, cooling gear etc. - which is likely to make it much
> thicker (i.e., with a larger *outer* diameter) than a HVC or
> RFAC of the same calibre.

True, but I like the idea of a gun that can fire a variety of
different rounds - AP, AT, GMS, LAD, mirror smoke, snapshot drone
reconnaissance... At some point in the range of mass driver weapons
the calibre has to go up, or there's no point in having mass driver
artillery.

>> and I'm certainly not sticking HVC on a hovertank.

> Because of the recoil? Then you shouldn't put big MDCs on them
> either - MDCs throw similarly-sized projectiles at significantly
> higher velocities, so their recoil is even worse than the HVCs'.

As the HKP is a development of the HVC, I'd view ground-effect and
then gravitic mobility as technological steps forward from wheeled
and track-laying systems. They aren't parallel developments and a
force will only utilise an earlier system if it is unable to buy /
build the latest equipment. An HVC just strikes me as an anachronism
on a hovertank.

>>> Note that since each shot can potentially kill multiple targets
>>
>> I recollect one of the innumerable "low vs high technology"
>> threads where there was a need to put down swarms of low-
>> technology "militia" before they overran the high-technology
>> forces. Logically, this is what APSWs were originally designed
>> to do, but they need to be able to eliminate multiple stands in
>> the time available.

> Nope. In this situation you need to buy more APSWs, not to make
> the few APSWs you already have über-powerful; there's a reason
> why vehicles in Vietnam and Palestine tended to have up to one
> MG per crew member other than the driver (and in a few extreme
> cases even he got one).

I've no objection to APSW (or similar weapons) being shifted to
very low effectiveness by the imposition of cover, but they should
be highly effective against infantry advancing over open ground.

>>> I'm a bit confused by the distinction between "cannister" and
>>> "flechette" here - today at least flechettes are usually used
>>> just in cannister ("beehive") rounds.
>>
>> I was under the vague impression that a cannister round flew its
>> fused distance then went bang, showering the immediate area
>> downrange with irregular-shaped fragments moving at the
>> cannister's velocity, whereas a flechette was a sabot round with
>> multiple darts spreading from the muzzle in a fairly tight
>> pattern

> There are two types of cannister <snip> - those which are
> essentially gigantic shotgun rounds and burst immediately after
> leaving the muzzle, and those which are burst open by a small
> bursting charge at a gunner-selected distance down-range; but
> both of them can contain either flechettes, relatively large
> "grapeshot" (usually spheres or cubes made of some heavy metal
> like tungsten) or a mix of the two. Irregular-shaped fragments
> are far more likely to come from standard HE shells.

Thanks for sorting out my understanding of these weapons; it's
been too long since I've looked at the relevant publications.

I would expect a cannister round that burst on leaving a
contemporary HVC to have a very limited range and thus only be
useful as a final defensive munition.

By contrast, a sabot-riding bundle of flechette darts leaving a
DS2 MDC would be travelling _very_ quickly, and given the same
cross-section / weight ratio of a full-sized rod the darts could
be expected to travel just as far.

>> A flechette dart wouldn't tumble

> They don't *tumble* much (except the first flip-over for the
> ~50% of the flechettes which are packed backwards in the round,
> both to use the available space more efficiently and to help
> disperse the swarm once the round bursts), but they *yaw* quite
> a lot which has similar effects.

>> and would therefore strike the target with greater penetration,

> Against soft armour (fabric), yes - often so much greater that it
> passes straight through leaving only a very narrow wound channel.
> Hard armour (metal or ceramic plates) is very good at stopping
> flechettes though, so PA would be essentially invulnerable to
> flechettes and many Line troops (e.g. NSL Armoured Infantry) would
> be mostly able to ignore them too.

So if my high-speed flechette isn't sufficient, what vehicular
weapon could be devised to defeat power armour? Given the above
table, all we have at the moment are APSWs and other PA, and I'm
a bit sceptical about anything less than an HMG ("class 0.5")
standing any chance at all. The APSW doesn't appear to be described
anywhere other than on pg 11, but I have always taken it to include
all the smaller-calibre MGs too.

>> I'm all in favour of giving powered armour a choice of weapons
>> so "AP" power armour would have a low-calibre weapon with a high
>> cyclic rate for dealing with unarmoured infantry. A more typical
>> PA would focus on knocking out vehicles or other powered armour.

> DS2 PA already *has* a choice of weapons: Basic "rifles" (what you
> you call "AP") drawing 3 chits in firefights and Close Assaults,
> GMS/L (focussing on knocking out vehicles but not much use against
> other PA), LAD (air-defence), and APSWs (heavier AP, increases the
> range to 12mu). The only infantry specialist type they can't
> really use is Assault, and that's only because Assault infantry
> are defined as drawing "3 chits" in Close Assaults rather than "1
> chit more than the corresponding Rifle type"...

I'd view powered armour as being short-changed in all of those
roles, though increasing their capabilities could rightly lead to
an increase in their points value. It depends on whether one
depicts power armour as a DARPA exoskeleton with a bit of armour,
a fully-pressurised suit of interlocking segments or the last
step before the DS2 Infantry Walker (i.e. close to a Dreampod 9
'Gear). Given the least of these options I'd still let power armour
take two of the above options and give them a better Close Assault
capability.

Nathan "building better worlds through superior firepower" Girdler