Dirtside Question: Zero or low G combat

Has anyone out there come up with a set of rules for zero or low g combat for
Dirtside? I'm thinking about running a Dirtside table at the Cold Wars
convention and am considering a scenario set on Mars. Any ideas or links

would be appreciated:)

> Has anyone out there come up with a set of rules for zero or low g
the Cold Wars convention and am considering a scenario set on Mars.
> Any ideas or links would be appreciated :)

I don't remember the value of the gravitation on Mars, but I wouldn't call it
zero or low g. So I wouldn't change the rules much.

If you are thinking about an un-terraformed Mars, the thin athmosphere
would be the main difference to an Earth-type planet. Some suggestions:
- use only power-armoured infantry
- if you use 'normal' infantry treat them as being under gas attack
- reduce aircraft capabilities (less payload, higher vulnerability or
cost), ditto for hovercraft.
- Increase DFFG range due to thinner athmosphere
- Increase HVC/MDC range due to lower gravity
- Better terrain performance for grav-vehicles due to lower gravity
- Appropriate terrain - no water features or vegetation
- sandy areas create dust cloud (treat as smoke screen) if crossed by
hovercraft

Greetings Karl Heinz

G'day guys,

> If you are thinking about an un-terraformed Mars, the thin athmosphere

They'd also be pretty cold unless they were very well rugged up so they may
actually find it harder to get around (not that their BMF is huge to start
with).

> - reduce aircraft capabilities (less payload, higher vulnerability or

First up, is the atmosphere thick enough for aircraft to work OK? I don't know
that much about aircraft, but I assumed that the reason people suggested the
use of airships on Mars (something picked up upon by Kim Stanley Robinson in
his Mars trilogy) was that the atmosphere wasn't thick enough for more
conventional aircraft. Secondly (just to show my complete ignorance), with a
lower gravity wouldn't the aircraft (whatever they ended up being) be able to
carry more as they don't have to fight their own mass as much??

> - Appropriate terrain - no water features or vegetation

Make things steep and sharp, the way you'd imagine the world looks before
erosion, and then multiply everything by 10x size wise;)

Cheers

Beth

I did a scenario set on the Moon (vacuum, low gravity, closer horizon)
called Moonbase Xi (http://www.ftsr.org/ds2/scenarios/moonbasexi.html).

To answer beth's question, yes and no. Aircraft would need much greater lift
area (without increasing weight) or would need much larger engines
(but then they would be more of controlled low-altitude rockets). And
yes and no. If you could get the same lift from the same mass, the carring
capacity would be increased. If you have to increase the mass to get
sufficient lift (of the same mass), then no it would carry less mass (as some
of the mass that would have been carried is used to provide lift).

-----
Brian Bell bkb@beol.net
http://www.ftsr.org/ds2/
-----

> -----Original Message-----

> Stanley Robinson in his Mars trilogy) was that the atmosphere wasn't

> KH Ranitzsch wrote:

> I don't remember the value of the gravitation on Mars, but I wouldn't

Our on-list astronomers should be able to give a better value, but
assuming that Mars is homogenous - which I believe is rather inaccurate
- the gravitic acceleration on the Mars surface is just under 0.4g. Not
zero g, but certainly lots less than we have here.

> If you are thinking about an un-terraformed Mars, the thin

> cost), ditto for hovercraft.

Increase the Close and Medium range bands somewhat due to reduced gravity and
air resistance, but wouldn't the maximum possible ranges get *shorter* since
the horizon is closer? (Mars's radius is just over half that of Earth.)

> - Better terrain performance for grav-vehicles due to lower gravity

...unless of course the grav effect is a repellant force like the one
between two equal-sign electric charges, in which case grav vehicles
get the same terrain performance (reduced lift exactly cancels reduced *need*
for lift) but risk having their forward velocity reduced (reduced air
resistance doesn't offset reduced propulsive force).

> - Appropriate terrain - no water features or vegetation

Sandy areas on Earth tend to create dust clouds if crossed by any
vehicle which isn't grav or high-flying VTOL/aerospace... the rules
don't take that into account much though :-/

Later,

> Oerjan Ohlson wrote:
Not
> zero g, but certainly lots less than we have here.

It's a bummer that one of my colleagues who specialized in Mars research
recently moved to another project, but if you really want the data, I'll be
happy to track her down and see what figures she has in her books.

[...]
> > - Increase DFFG range due to thinner athmosphere

Without doing the math I don't recall that it would be *that* noticeable, at
least on an SGII or DSII scale (then again, I guess that depends on
your DSII scale ;-)

> > - Appropriate terrain - no water features or vegetation

Maybe because the time scale for the sand/dust cloud to be around is
less than what a single DSII turn is? (I don't have my DSII rules with
me, so I'm just popping this off the top of my head :-)

M 'resident star guy, climber, and mainly lurker these days :-(' k

> > >I don't remember the value of the gravitation on Mars, but I
Not
> > zero g, but certainly lots less than we have here.

.37g, IIRC, but that's by memory.

> It's a bummer that one of my colleagues who specialized in Mars

Max range in DS is what, 60"? So Mars would (off the cuff, not even BOTE) have
about 48" horizon. Gillett's book on building planets has the formula but it's
at home.

Thanks for all of the responses:)

Here is what I'm considering for my Mars battle:

1. Shorter horizion (the 48" suggestion sounds about right). Longer range
bands. I'm going to play test that one and go for what 'feels' right. 2. Only
specialized GEVs (slow ones maybe?) 3. I'm using the background from William
R. Forstchen's Star Voyager Academy
series (actually, Prometheus)- all fighters on Mars (that were
mentioned)
were space fighters- that shouldn't change anything I think.
4. I would think that the lower gravity would allow infantry to move a bit
faster- say 1/3d faster.
5. The background mentioned above has no powered infantry in it. I'm assuming
that the infantry in the background are space suited infanty. Maybe the bulky
suits would counteract #4??? 6. Terrain is going to be primarly some rocky
ridge lines, sand dunes, rough rocky areas, and a dug in SAM site (the mission
is to destroy the SAMs)
7. Forces-
USMC (United Space Military Command- United Nations)

4-6 platoons of Space-to-ground marine assault troops (Veterans armed
with standard assault weapons, IVARs, GMSL, and APSWS)

1 platoon of LAV (wheeled or hover light armored vehicles- size 2 or 3
with light weapons and carrying a squad of infantry each)

1 squadron of Glen class fighters (a large aerospace fighter with missiles and
HELs)

2 USMC Space Force Frigates to provide Ortillery support (Not too heavy gun
wise, but some support punch for the USMC)

CFF (Colonial Free Forces)

1-4 platoons of militia (average to low quality troops with militia
weapons)

1 platoon of regular CFF infantry (similar to USMC marines)

1 SAM battery (2 fixed launchers, a couple of troop bunkers with a few fire
teams manning them, and a few teams with LADs)

I don't have a set point value in mind, but that should be the ball park. I
want some rules that will lend some realism, but won't make the scenario too
unbalanced.

Thanks!

> Indy wrote:

> Increase the Close and Medium range bands somewhat due to >>reduced

In the usual scale (1" = 100 meters), 60" is essentially the distance to the
horizon from the turret of an MBT standing on a flat plain on Earth. (DSII
doesn't give any range bonus if the MBT is standing on the only hill on that
plain though <g>) Double the curvature of the surface, and you should get a
quite noticable decrease in max range (at
least for line-of-sight weapons).

It wouldn't matter much in SGII, that's true <g>

> Sandy areas on Earth tend to create dust clouds if crossed by any

Hopefully yes, but it depends a bit on how many vehicles you have :-/
It'd take longer to settle in lower-gravity environments, certainly.

Later,

Actually, I think it would force them to move slower if anything, but it would
greatly increase endurance. However the military would use up that extra
capacity by giving the units more crap to carry around. Veteran units would
have the savvy to leave most of it behind.

Horizon is SQRT(height above ground * planetary radius). Martian radius is
3400km, gravity is.38.

Is that formula correct? Using it, the average turret height of a AFV would be
5.5m (6378000m earth radius, * 5.5m, sqrt = 5923 close to 60" or 6km). I did
not think that AFVs were that tall (that's almost a 2 story building)

Anyway using this formula, distance to horizon on Mars would be 4324, or 43"
(using the 5.5m AFV height and the formula below).

It's pretty much correct if you work from mathematical first principles. I
think the exact formula should be

SQRT (height above ground * planetary radius + (height above ground)^2)

but the extra (height above ground)^2 is so small it makes little difference
to the answer unless you're a long way above the surface.

Tony

> "Bell, Brian K" wrote:

> Is that formula correct? Using it, the average turret height of a AFV

5.5m tall? I'm not the most metric guy around (hey, I'm an American), but
that isn't too far off. My M-1A1 from the old army days was a pretty
tall machine (despite the low profile it presents). I could stand next to the

track and only my head and chest (or shoulders- memory kinda fades with
age;) were above the track.... and I am 6'1" tall... a meter and some change
in the metric system. The turrent was easily another 5 or so feet taller than
me... and you can add another foot to that because of the TC's position. I
believe that is pretty close to 4 or 5 meters, so that guess shouldn't too far
off.

And before you say it, the Bradley IFV was almost as tall as the Abrams...

> Is that formula correct? Using it, the average turret height of a AFV

6'1" is damn near two metres. Also, when determining if you can see something
over the horizon, you have to calculate the distance from you to the horizon,
and the distance of the target to its horizon, and then sum the two together.
In the extreme, all you have is two commanders looking at each other and
arcing shots over the horizon. So a 60" earth horizon is quite a good choice
for all but two groups of infantry looking at each other.

Cheers,

> Scott Case wrote:

> Is that formula correct? Using it, the average turret height of a AFV

Um, yes it is. At least if more than 100% counts as "too far off" :-/

> My M-1A1 from the old army days was a pretty tall machine (despite

An M1A1 is under 3 meters tall (2.80 IIRC, but I don't have exact
figures at home :-( ).

> I could stand next to the track and only my head and chest (or

"Some change" in this case is almost another meter, which explains why
you're a factor 2 off :-/

Regards,

One of the things this discussion seems to have missed (unless I am forgetting
an email or so in here) is that the 60" LOS that we are talking about is
really LOF (line of fire). The rule setting this up on page 4 even defines the
LOS pretty clearly as "...the maximum aquisition

range of any sensor system in play (one very good reason for this is...the
recommended groundscale, is actually not far off being horizon
distance on a roughly Earth-sized world...)."

In a nutshell, we are not only dealing with visibility issues. I know it

would be hard to account for, but how much would the sensors be effected

by a shorter horizon? If it is neglible, could you reasonably run a
battle on a smaller world - Mars - or a moon without making significant
adjustments to range?

> Tony Christney wrote:

> Is that formula correct? Using it, the average turret height of a

> but that isn't too far off. My M-1A1 from the old army days was a

> tall... a meter and some change in the metric system. The turrent was

> easily another 5 or so feet taller than me... and you can add another

> foot to that because of the TC's position. I believe that is pretty

G'day Noel,

> In a nutshell, we are not only dealing with visibility issues.

If they can "see" through or around the curvature of the planet then not a
lot, the question then becomes what happens to the round if you still fire at
the longer ranges? I guess missiles would go with the curvature, but wouldn't
lasers etc just keep going (ignoring deflections off the atmosphere) straight
off the planet (and so the horizon becomes the effective upper range anyway)?

Cheers

Beth