Re: [FT] Some thinking on sensor and operational level games

Thomas Barclay wrote:

> Hi all
>
> Just thinking about sensors and a game at a
> higher level than the tabletop FT. By higher, I
> mean longer time and distance scale, with more
> hide and seek. Brian posted his ideas and I
> skimmed them, but I'm working on my own so I
> thought I'd quiz the list intelligentsia.

I think this was heavily assaulted in a previous thread on sensors that
evolved into an email discussion on Low-Probability-of-Interception
(LPI) radar and the problems of trying to quickly locate an object that
is light-seconds away with active sensors, between Derk Groeneveld and
myself.  The subject was Re:[FT] Flashes was: a couple of quick
replies.  We indulged in some technical speculations about what could be
done.

>
>
> Specifically:
> 1) At what range could one likely detect a
> starship with good passive sensors? By that, I
> mean optical (visible and not visible spectra)
> and other similar systems. Something that
> doesn't rely on "wazoo newtech".

Given that SETI has to remember where the Voyager probes are and using
1mu equal to 1000km but remembering those asteroids that sneak up on us,
somewhere between 450 (radius of the moon's orbit [approx.]) and several
hundred thousand (way past Jupiter).  Given that warships will try to
avoid detection, probably a good guess is 1000mu.  One of the primary
sensors for detection is infrared, near infrared, and microwaves,
because the ship will be radiating heat against the 5 kelvin background
radiation and the contrast between an object and its background is
proportional to the fourth power of the temperature difference.

>
>
> 2) How much does the answer to 1 depend on
> if the ship is thrusting?

It depends on the mechanism for the thrust, but if the thrust plume is
pointing at something, that something will be able to detect the inbound
from a long ways away.	For example, if a Bonaparte class is thrusting
directly away from a base, that base could probably detect the drive
plume at a distance of several light-hours.  The variation for other
angles would be specific to each class of ship, and could vary widely
between vessels of different sizes, with engines of the same power
output.

>
>
> 3) How much does the answer to 1 depend on
> if the ship has activated some kind of active
> sweep sensors or firecontrols?

The simple rule of thumb is that for equal receiver sensitivity, the
passive set can detect the transmissions of the active set at the square
of the active set's range.  So the active sensors of a pds (range of
6*10^6 meters) can be detected at 36 million mu, if the receiving set
knows what to look for.  Even if the passive set does not have
fore-knowledge of the pulse modulations and frequency hopping of the
active set, it will still detect the active emitter long before the
active emitter's receiver will detect a return echo.

>
>
> 4) How much does the answer to 1 depend on
> mass of the vessel?

All other things being equal, the larger vessel will be easier to detect
because it has less surface area per unit volume to radiate away heat,
so the hull surface will be at a higher temperature [see response to 1].

>
>
> 5) How much does the answer to 1 depend on
> EMCON levels employed? (is silent/black running
> of any use in space?)

Plenty, but it is harder to do [see responses to 1,2,3].  Ships will
have a hot and a cold side.  The cold side will be oriented towards the
likely direction of the opposition, and the hot side will be pointing
away.  The more ship's surface that made cold, the hotter the hot
surfaces must be.  It is likely that the simple expedient of making the
drive nozzles hot, and everything else cold is used, and an aweful lot
of time is spent coasting towards the target with off-axis thrust to
keep the vector pointing at the target.  Screaming in at high speed and
decelerating towards the target will let them know that you are coming
once you get to the turnover point.

Active sensors are only switched on when you know that the opposition
has found you, much like the active sonar of a sub.

>
>
> 6) I assume there are three phases to
> engaging an enemy:

Just like ASW.

>
>
> 1) gross detection - there's something out
> there, even if it is too far away to tell what or
> how many
> 2) fine detection - we can tell how many,
> perhaps what thrust, what mass, are any
> emitting
> 3) lock-on - we  have a fire control solution
>
> I assume passive sensors will generally take you
> through phase 1 and maybe phase 2, but you
> definitely need to "go active"
> (sensors/firecontrol) to get 3.

At 1000km per mu, the propogation delays of active sensors may actually
be too long to provide useful information, but it will help the passive
sensors.  At smaller scales (tens of km per mu), active sensors rule.

>
>
> 7) Does using active sensors increase your
> ranges for the first phase of detection? Or are
> they long enough that your pathetic amount of
> emitted energy just has no effect? I am sure
> active sensors would have some impact in the
> second stage, and obviously firecontrol is the
> third stage.

Only if your opponent is using them (IMHO).

>
>
> 8) How feasible are recce fighters or stealthed
> drones or missiles with sensors and a link back
> to the ship to extend your active or passive
> detection radius? Would communications with
> such a drone or fighter not become
> problematic beyond <insert arbitrary range>?
> Or if you had to suddenly manouvre in combat,
> thus breaking  your hard to detect presumably
> direct laser link?

At any significant range (about a light-second) the recce unit needs to
know how the ship will move, in advance, because the time to
re-establish the link will take at least as long as the propogation
delay IF the recce unit can detect the unit that is receiving its
transmissions.	However, a picket could detect inbound ships that have
just jumped into the system, FTL to the base and let the defending units
know where to jump to find the (hopefully) still disorganized and
scattered inbounds.

An attacking fleet that has just jumped into the system has the terrible
problem that there is no quiet way to let everybody know where everybody
else is.  They have to send out omnidirectional signals with a modicum
of power, or risk arriving at the battle in scattered penny packets
(this is the one good reason to use battleriders and tugs, the whole
squadron arrives in the same place, but you may as well spend the extra
9.1% to allow the battleriders to flee on their own).

Even though the pickets are spaced three or four light-hours apart, you
will still need dozens of them (another valid reason for campaigns to
have a lot of small ships).

>
>
> 9) If I have ECM or an area jammer, I assume
> that I'm making detection level 1 easier and
> detection levels 2 and 3 harder. Turning on the
> jammer systems would mean people would
> quickly discover something was emitting out
> there, but exactly where (more than a general
> few mu area) might be significantly more
> difficult to pin down than without the jammer.
> So you'd never use ECM or Jammers until such
> time as you thought the enemy already knew
> you were there (otherwise why give up your
> invisibility). Is this right? Or don't I get how real
> EW jammers/ECM  work?

You would use EW/ECM for different things, rather than concealing the
existence of a ship, you would obscure what the ship actually was.
Stingboats would pretend to be SDN's, the main battleline would try to
emulate a mass of stingboats.  Decoys would pretend to be ships and
ships would pretend to be decoys.  Ships would pretend to be heavily
damaged after being fired upon, maybe even detonating a nuke to fake
their destruction.

>
>
> This is just some starting points for my thinking.
> But any input from people with solid ideas or
> some sort of domain expertise (or a keen
> interest) would be worthwhile.
>
> Thomas.

Now I have to go back through the archive and see if I can find my quick