Re: Sensors

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On Tue, 29 May 2001, Ryan M Gill wrote:

> At 11:35 PM +0200 5/29/01, Derk Groeneveld wrote:
> >  > That assumes that targets are emmitting. A target at total
> >>  EMCON will presumably be relying on totally passive sensors.
> >>  Say a vessel (in space) moving ballistically and not
> >>  thrusting.
> >>
> >>  By relying on ESM systems you are looking at the various
> >>  fire control radars, navigation radars, long range
> >>  communications, search radar, weather scopes, data links,
> >>  Talk between ships radio, and other electronic garbage that
> >>  ships emmit.
> >
> >Yes. But so is any passive sensor.
> >
> 
> I'm not sure what you are saying here. Is it that Passives are like 
> the above ESM? I was essentially talking about Passives.

Okay, I thought you were commenting on ESM in specific. 

> >  > Further, just relying on passive sensors to recognize a
> >>  vessel will lead to funny incidents of "seeing" a harmless
> >>  tanker when in reality it is a CVA dressed up with the same
> >>  active emmissions.
> >
> >Then again, there's the same risk with active sensors. Also, you;'re
> >assuming everything CAN be disguised/masked (see below, engines
> discussion)
> 
> Ahh, but with actives and passives you'll have more information to 
> make your decision. Passives are using your eyes and ears in a dark 
> room. Active is using a little pen light to see a specific object. 
> (naturally you know this)

Of course a combination of the two is the most effective approach. No
argument there. 

But as for actives being a little pen light, well, I'm not sure I agree.
Active _tracking_ is a little pen light, but active search sensors are
more like a whopping wide beam.

> >Similarly, a sailing vessel can be given a nimitz-size reflection by
using
> >a simple retro-reflector...
> >
> 
> Reflection against what? Passives?  And from what aspect? (Space is 
> 3D, much harder to predict your aspect) It'll be hard to disguise a 
> sailing vessel from mm wave radar. A decent mm wave set can pick out 
> what style of rigging one would have.

Reflection would be against active sensors, of course.

Mmmm. I guess you can use mm radar in space at a lot longer ranges than
on
earth; on earth atmospheric dampening greatly limits mm waves. 

> The only thing I'd think that mm wave radar would have a hard time 
> with would be a very well done Q-ship. Besides, the whole principle 
> of mm-wave radar and its fine resolution is the basis for the ability 
> of Enhanced and Superior sensors to figure out what the current 
> status of a vessel is. ("Ok, his drives are down and geeze look at 
> that big hole in his port side weapons array, he's definately weak on 
> that side sir. His VLS system looks mostly popped too, so he's not 
> got much fight left in him...")

Sounds sensible.

> >Yes, but you're not going to do much ranging until you've acquired
the
> >target, meaning that EITHER passive sensors were good enough to
acquire
> >the target, OR you had to go active anyhow.
> 
> Ranging can be accomplished with passives too. 
> Inferometric/stadio-metric triangulation.
> I don't see needing Cepheid variables to figure out how far away that 
> Eurie BDN is...

I'm not familiar with Cepheid variables? As for 
triangulation, with the ranges involved with space combat, I doubt you
could do it with the sensors on one ship alone. I'm not familiar with
inferometric ranging, so I have no clue how that'd work for you ;)

> >Similar to modern passive sonar, where the noise can be related to
> >specific ships.
> >
> 
> I suspect that one would be able to tell what mass/drive power the 
> ship is by the Main drive/maneuvering drive efflux. Lots of charged 
> ions and you've got a big ship or a small ship using lots of power. 
> Figure out the Delta Vee and you've got the Mass and Drive Power at 
> that time Pegged. That closes your envelope of possible ships by a 
> large margin.

Also, the drives might have unique resonance frequencies etc? Sir, we've
seen this ship before, it's .... Then again, there might be a wartime
tuning of this frequency to a different one than peacetime?
  
Cheers,

  Derk
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