Active vs Passive

From: "Brian Quirt" <baqrt@mta.ca>

> Most of this post I can agree with, but I'm not sure about faster

It's the difference between trying to aim a rifle at a target about 60 metres

In a message dated 4/13/00 10:12:14 AM Central Daylight Time,
> aebrain@dynamite.com.au writes:

<<
It's the difference between trying to aim a rifle at a target about 60
 metres
 away via a TV camera with a 4/10 second time delay, and aiming it via
 listening
to the noise the target makes while wearing a blindfold.
 The data from the TV is twice as old as the sound (which takes 2/10 of
a
 second
to travel the distance), but considerably better for targetting purposes.
> [quoted text omitted]

Besides you aren't stand in full view jumping up and down, waving your arms
and shouting into a bull horn "HERE I AM BULLY-BULLY! Come RUN OVER
ME!".
Active sensors are like fighting a knife fight in pitch black - sure you

might catch him in the flashlight beam - but he sure as hell will see
the beam AND its source.

> Alan and Carmel Brain wrote:

I would simply note that both of the above examples relied on passive sensors.
I also think that stealth to the point that "we don't know if anything's
there" is essentially impossible, because you simply CAN'T hide your waste
heat (except by running your ship at a 3K ambient temperature, but that would
probably degrade your combat effectiveness). I simply don't think that it's
possible to hide yourself effectively in a space battlefield. Sure, if you're
far enough away it's essentially impossible to HIT you, but it's still going
to be obvious that you're THERE. As to what distance is far enough, it depends
on your
maneuverability, your cross-sectional area, and the speed of weapons
fire (sensors are assumed to be speed-of-light, if faster sensors exist
things will change).

> I also think that stealth to the point that

I think you underestimate just how big space is. Scanning all of visible space
and then subtracting out all background noise would be very, very difficult.

Also, only using passive sensors, it would be almost impossible to determine
range without significant transverse movement by either the target or the
detector.

Also, if you assume superconductors (and I think we have to in a space game)
it would be fairly easy to sheild a ship so it would only emit EM radiation
(light, heat, etc.) in one direction (say to the rear). It would be very
difficult to detect such a ship with passive sensors (except perhaps with a
mass detector).

This is a fair analogy.

I would chnage it to fignting under moonlight rather than pitch black. An area
with a lot of solar flares or other sporatic radiation may be like a cloudy
night. An area in deep space, far from radiation sources may be like a clear
night. Hiding in a solar flare or magnetosphere of a planet may be like a
moonless night.

The flashlight would give you better definition (better 3D perception
especially at long range) and more information (such as color) about what is
around you. But you have to shine it on the target for it to be effective.

Your opponent, however will be able to see both what you are shining the beam
on and the origin of the flashlight.

Another good analogy would be sonar.

You could tell that another ship is out there. You may even be able to gain
some information on the opponent due to reflection of ambiant radiation
(sound) or emitions from the target. You may also be able to get a location,
course, and/or speed of the opponent depending on  how long you
listened, if your possition changes, if the target's possition changes, and if
you are using multiple sensors that enable you to triangulate. The ability to
do this would depend on how good your equipment is, how much time you have to
collect and sort data, how strong a signal you are getting from the target
(ie. how poor his stealth is), and how good your crew is. If you have a
database of profiles, you may even be able to determine the type of ship.

However, to get the best lock on the target you project a STRONG signal (ping)
that is still strong after it reflects off your target. This way you, to a
large extent, determine how strong a signal the target is providing. However,
you have also just provided an even stronger signal for your target's
targeting.

I think that you are arguing against yourself.

If space is so large that you would not be able to pick a ship out from the
background noise, then it is too big to know where to point your active
sensors. You have to have some idea of where to scan in order to ping the
target with your sensors.

The above assumes directional active sensors. If you have omnidirectional
active sensors, the power output to ping something at 52,000km (52tu) would be
enormous. The background noise would only add to the problem.

I do agree with your comment about range. Unless you or your opponenet are
moving a significant amount, it would be difficult to determine range using
passive sensors. This is why the closer you are to an object the easier it
should be to deterine details.

I will have to think more about the superconductors for uni-directional
heat dispersion. Some random thoughts: Superconductors conduct two ways.
Ambient solar radiation will heat the side of the spacecraft facing the
system's star greater than the background. You can't duct this with
superconductors without the superconductors heating and defeating the purpose
of using them to direct the heat. If you trail them into space to allow them
to radiate the heat away, you have a glowing arrow pointing to your ship. If
you keep them close to your ship, the heat will reflect off you your hull. In
space, you have to rely on straight radiation (as there are not enough matter
to help take away the heat in the way that air or water does on earth). The
superconductor radiates heat at all points evenly, so it radiates the same
amount of heat inside the ship as outside. If hit by radiation (solar or
weapon) it would conduct the energy back inside the craft.

I saw a show reciently about the Hubble telescope and the repairs on it. When
the astronaut was in the shadow of the Hubble, it was extreemly cold. When on
the Sun side of the Hubble, it was extreemly hot.

-----
Brian Bell bkb@beol.net
http://members.xoom.com/rlyehable/ft/
-----

> -----Original Message-----
[snip]
> >

> On 13-Apr-00 at 13:05, Bell, Brian K (Brian_Bell@dscc.dla.mil) wrote:

> Superconductors conduct two ways. Ambient solar radiation will heat

Sure you can. You refrigerate the outside of the ship, you take the heat from
the refrigeration process and dump it into your unidirectional superconducting
wire, which would glow read hot (assuming it didn't stop superconducting.)

Of course, if you want to be directional you have to trail the wire inside a
cone such that only radiation directed in the preferred direction escapes.

It doesn't sound very efficiant to me and I find it hard to believe something
like this would be used, but it could be done. We do
it now with heat exchangers, its just that the air/ground is a bit
better at siphoning off the waste heat.

In a message dated 4/13/00 12:01:42 PM Central Daylight Time,
> Brian_Bell@dscc.dla.mil writes:

<<
I do agree with your comment about range. Unless you or your opponenet are
moving a significant amount, it would be difficult to determine range using
passive sensors. This is why the closer you are to an object the easier it
should be to deterine details.
> [quoted text omitted]

I think the best model available for sci-fi sensors (active and passive)
is modern day submarine warfare. No, the first detection by passive sensors

gives one a HUGE possible range reading, but the submarine can alter
course -
triangulate the target's passive signature and work out a firing solution over
time. I think that is what would happen in space combat.

In a message dated 4/13/00 12:01:42 PM Central Daylight Time,
> Brian_Bell@dscc.dla.mil writes:

<< Superconductors conduct two ways. Ambient solar radiation will heat the
side of the spacecraft facing the system's star greater than the background.
You can't duct this with superconductors without the superconductors heating
and defeating the purpose of using them to direct the heat. If you trail them
into space to allow them to radiate the heat away, you have a glowing arrow
pointing to your ship. >>

In space there is nothing to conduct the heat. Superconductors and heat sinks
could funnel the heat away from the potentially engaged side of your vessel
and into space on the opposite side - the bulk of the ship itself would
mask that heat release, would it not?

Popeye said:
I think the best model available for sci-fi sensors (active and passive)
is modern day submarine warfare. No, the first detection by passive sensors

gives one a HUGE possible range reading, but the submarine can alter course
-
triangulate the target's passive signature and work out a firing solution over
time. I think that is what would happen in space combat.

Why bother? There's no water to interfere with your comm, so just send a
message laser to your corvettes on either flank and get them to triangulate.

> On 13-Apr-00 at 14:52, Chris DeBoe (ChrisD@jubileetech.com) wrote:

Corvettes? Corvettes? We don't need no stinking corvettes.

In a message dated 4/13/00 1:52:35 PM Central Daylight Time,
> ChrisD@jubileetech.com writes:

<<
Why bother? There's no water to interfere with your comm, so just send a
message laser to your corvettes on either flank and get them to triangulate.

> [quoted text omitted]

I was assuming a single ship or sensor picket trying to pin point a
bogey -
sorry if I was not clear.

I said:
> Why bother? There's no water to interfere with your comm, so just

Popeyes replied: I was assuming a single ship or sensor picket trying to pin
point a
bogey -
sorry if I was not clear.

Oh, you were clear--my point was, it's worth it to spend 30 points or
whatever so you can triangulate NOW and without burning thrust. CTs and SCs
weren't originally designed to be missile bait.

In a message dated 4/13/00 2:18:56 PM Central Daylight Time,
> ChrisD@jubileetech.com writes:

<<
 Oh, you were clear--my point was, it's worth it to spend 30 points or
whatever so you can triangulate NOW and without burning thrust. CTs and SCs
weren't originally designed to be missile bait.

> [quoted text omitted]

Absolutely they were designed as patrol and picket platforms so why not use
them as such!

> Popeyesays@aol.com wrote:

Yes, that would work (somewhat), although how are you going to be sure which
side is safe to radiate on? If you're wrong, you've just become VERY visible.
Also, doing this requires extra power (heat sinks are NOT
super-efficient), which therefore means you have to radiate more heat,
which means....

I'm just not sure it would be worth the effort.

> Popeyesays@aol.com wrote:

I can agree with this, but with one caveat. Given only a slight advance
over present-day technology, the detection range will be VASTLY greater
than the weapons range (even for a non-thrusting ship), therefore you'll
probably have an excellent position/velocity track LONG before you get
within weapons range (of course, weapons range with projectiles against
ballistic targets is essentially infinite, but if you start manuvering to
avoid being hit you've just announced your presence to anyone else within
about 50 AU).

> It doesn't sound very efficiant to me and I find it

Theoretically, you could also have a heat storage unit, which would absorb
heat for a period of time and then release it all at once (or over a short
period of time). This would allow you to control when you radiate heat (and
any other em radiation). Hopefully you'd find the oppertunity to discharge the
radiation when out of view (or to direct it behind you.

This next is purely speculative, but since the heat we're talking about is
really just low frequency em radiation, it should be possible (with
superconductors and similarly wonderous technology) to convert the heat energy
into a more useful form of energy (like say a laser).

In a message dated 4/13/00 2:34:33 PM Central Daylight Time,
baqrt@mta.ca writes:

<<
I can agree with this, but with one caveat. Given only a slight advance
 over present-day technology, the detection range will be VASTLY greater
 than the weapons range (even for a non-thrusting ship), therefore
you'll
 probably have an excellent position/velocity track LONG before you get
within weapons range (of course, weapons range with projectiles against
ballistic targets is essentially infinite, but if you start manuvering to
avoid being hit you've just announced your presence to anyone else within
about 50 AU).
> [quoted text omitted]

absolutely - lying doggoe with life support and sensors on auxilliary
and waste heat confined as much as you can stand to the inside of the ship
would probably make a picket ship a hell! Much like a U Boat running silent in

thickened air and sweltering heat from the bodies within.

In a message dated 4/13/00 2:32:48 PM Central Daylight Time,
baqrt@mta.ca writes:

<< Yes, that would work (somewhat), although how are you going to be sure
which side is safe to radiate on? If you're wrong, you've just become VERY
visible. Also, doing this requires extra power (heat sinks are NOT
 super-efficient), which therefore means you have to radiate more heat,
which means....

I'm just not sure it would be worth the effort.
> [quoted text omitted]

The point is do you radiate any heat at all into space - space hasno air
to
heat byradiation. At best to a sensor youwould be a pinprick - a hot one

determined only if you can read the surface temprature of the hull - the

waste heat would be read perhaps in em emiissions but would be a lot less
noticeable than neutrino or particle emission, sensor or communicator
emission - running under EMCON you would just be a lump of metallic
composition indistinguishable from a planetoid - until you add thrust
and
start to maneuver THEN you stand out like a sore thumb from delta-vee
analysis and perhaps a drive plume.

> opeyesays@aol.com wrote:

That sounds like an excellent analogy. Adding to that is that your trajectory
is ABSOLUTELY predictable. Given that (since they don't have
to carry life-support), you could probably get railgun shells down to
(roughly) ambient temperature, it's also the case that you may not get a
chance to see the shot that kills you (if your position/trajectory are
known (but you don't know it), and you're keeping your engines off to (try
and) avoid detection, there isn't really any maximum range at which a kinetic
energy weapon can hit you, and unless you go active you probably won't detect
it approaching).
        Of course, defending ships probably wouldn't have to do this -
having a fixed installation doing the detection work would probably give you
even better results. Assuming that ships can't just jump in on top of the
planet, there's essentially no way for a fleet to remain hidden after it's
jumped in (assuming the energy from the jump doesn't give it away
immediately). If they manuver, they've been spotted, and if they don't all you
have to do is put some debris in their path....

> Popeyesays@aol.com wrote:

I'm going to respectfully disagree with a lot of this. Neutrinos are
INCREDIBLY hard to detect. We can only detect a few, and that's with a STAR
providing the output. Detecting neutrinos from a REACTOR would be almost
impossible. As to temperature difference, current sensors can detect a
difference of a few Kelvins from ambient (given what ambient is, that means
that, with current technology, we could detect a
ship-sized object out at least as far as Jupiter if it were any hotter
than about -200 centigrade). As for indistinguishable from a planetoid,
again, ignoring the 200-or-so-degree difference, yes. I'm not all that
sure that that difference can be ignored.

Let's figure out how you can detect an FT ship.

PASSIVE

First of all, the Doubletalk generators. This means: Neutrino detection Warp
signature Disturbances in the Force
  etc

Then, the PSB methods: Occulting background radiation (ie you detect something
that's a little blacker than space)
  EM (usually Infra-Red) Radiation from Hull
EM Radiation(Visible and Up) from Drive exhaust
  Particle emission (though signal/noise would be very low)
Reflection of natural sources of radiation (ie Stars nearby) Very energetic EM
from weapons firing. Moderately energetic EM from active sensors. Forward Mass
detector (relatively low range)

ACTIVE

Doubletalk Generators: Tricorder readings Hyperspace Radar Precognition etc

PSB: Reflected EM that could be any frequency with wavelength smaller than
twice the length of the target. Reflected particles?

Active methods could include bistatic Radars/Lidars where the
easily-detectable emitters are physically separated by a large
distance from the undetectable receivers.

Virtually all of these have some form of counter: from "baffled jets"
to Radar Absorbent material, dumping heat via a tight-beam laser,
etc. And its complicated by the fact that empty space isn't: You may be able
to detect several thousand objects, one of which is a hostile, the others
innoffensive chunks of rock, ice etc.

One thing that is not easily hidden is course and velocity changes. Also, If
penetrating an enemy system, you can reasonably expect that

One problem with EMCON, though--don't fusion piles produce neutrinos?
(I
seem to remember something of the sort from a physics --or was that
astronomy?--class years ago.)

Which means nothing but low-tech power sources (or VERY high tech ones).
And that could make maneuver kind of difficult (if you are assuming
anti-grav drives or high-power ion or plasma jets or something like
that).
Hmm--it does suggest a cool scenario with some special house rules
though:

A low-tech force using chemical rockets for propulsion (advanced ones,
of course, but still limited thrust duration due to fuel requirements) facing
off against a super-high-tech force (which, having been trained in
fighting
other super-high-tech forces doesn't recognize the threat in time) using
fusion piles for power and some high-tech propulsion.  Result?  Some
very stealthy ships that are easy to destroy but very hard to find fighting
very fast, hard to destroy ships that stand out like strobelights in a dark
room. Might be fun...

Rob

[quoted original message omitted]

> One problem with EMCON, though--don't fusion piles produce

Thanks for bringing this up.

Forward Power Station (Alarishi Empire) is pleased to provide antimatter power
systems to a select clientele [FSE and IF need not apply. ESU terms, COD and
that does mean "cash" as in "hard currency"and lots of it]. Plentiful power
with low emissions, an unmatched safety record [no one else is building
antimatter ship drives, but why dwell on details like that?], superb field
support [you blew it up again? okay, we'll send someone to run
it for you--that's salary, expenses, per diem and bonuses, of
course], all at a reasonable price [cheaper than, say, a
dreadnought--the guys who stay here have salaries, expenses, per
diems, and bonuses too].

> "Robert W. Hofrichter" wrote:
(I
> seem to remember something of the sort from a physics --or was that

Yes, they do. I recall some calculations (done for a
Traveller-based
game, from the designer's notes, url at
<http://www.grognard.com/info/brillanc.txt>), that essentially found
that for a hydrogen fusion reaction, a neutrino detector will detect, on
average, 10^-21 neutrinos/second (per ton of detector per watt of the
fusion plant). Thus, given a 1,000,000 ton detector (10,000 TMF) and a
100,000MW power plant (VERY large), on average one neutrino would be detected
every 26 minutes. Just TRY and build up a sensor track from that much
information..... You'd be better to detect the heat which such a plant will
have as a byproduct. Again, with current technology (although I've
unfortunately
lost this url), a ship-based infrared telescope could probably detect a
working fusion plant millions of km away simply from waste heat (yes, you
could probably store the heat somewhere, but the effort of keeping the
temperature of the outer hull more than 200 degrees lower than the inside (so
that the people on board don't freeze) seems essentially impossible).

> A low-tech force using chemical rockets for propulsion (advanced ones,
facing
> off against a super-high-tech force (which, having been trained in
using
> fusion piles for power and some high-tech propulsion. Result? Some

Well, the difficulty is that chemical rockets put out a LOT of energy, much of
it visible (and CERTAINLY detectable by telescopes). Hell, if your drive uses
reaction mass, and provides 0.1g or more of thrust, it could probably be
detected at least a billion km away. Of course, the more efficient your drive,
the higher its exhaust temperature, the easier it is to detect, but ANY ship
using it's drive is going to stand out like a strobelight. Of course, your
drive may not use reaction mass (although I'm not inclined to assume
reactionless drives), but even so you'll need SOME source of power.
Essentially, I don't think that effective combat range will even APPROACH
10,000,000 km by 2183 (see the above url for information on trying to focus
lasers at MUCH lower distances), but I also don't see how you can AVOID
detecting a ship at
that range if you're trying at all. Yes, ECM/ECCM/etc. will be useful
when you're already fighting (hitting someone at long range, even with
speed-of-light weapons, isn't easy), but I think that it'll be fairly
obvious WHERE the ships are (or, at least, were x seconds ago, thanks to the
lightspeed delay).

> Popeyesays@aol.com wrote:

> The point is do you radiate any heat at all into space - space hasno

You don't need air to heat in order to radiate heat. Heat is just another
wavelength band of EM radiation like visible light, UV, radio
waves, X-rays etc. It propagates just fine in vacuum...

Regards,

The real questions are:

Will technology advance far enough to enable you to cloak your emmissions to
match the background radiation? Difficult, but not impossible.

and

Will technology advance far enough that a single ship (or group of ships)
using passive sensors can scan the entire sky and then crunch all the data it
gathered in a reasonable time frame (say minutes or an hour)? Again,
difficult, but not impossible.

I'd say current technology is completely incapable of either. And it's just
your personal take on which has advanced further in the game you're playing.

Also, with the invention of long range mass detectors (ala Honor Harrington),
the issue becomes moot.

From: "Adrian Reen-Shuler" <saltpeanuts73@yahoo.com>

> The real questions are:

> Alan and Carmel Brain wrote:

I like your list, but I'd add on one passive method: drive flares (ie you
light up your drive, you're putting out a LOT of energy (after all, it's
changing your course), and that's probably fairly detectable. Otherwise, I
think this list is an excellent base point.

I had an idea for EW,

    If you use the fire control center as a ECM/ECCM emitter reciever
during a round, the firing unit subtracting thenumber of comitted FCS's from
the number the defender comits.

The target gets a bonus shield level(s) if the value is positive in its favor.

Systems used this way would not be available for firing at ships.

I had an idea for EW,

    If you use the fire control center as a ECM/ECCM emitter reciever
during a round, the firing unit subtracting thenumber of comitted FCS's from
the number the defender comits.

The target gets a bonus shield level(s) if the value is positive in its favor.

Systems used this way would not be available for firing at ships.

From: "Brian Quirt" <baqrt@mta.ca>

> > EM Radiation(Visible and Up) from Drive exhaust

> I like your list, but I'd add on one passive method: drive flares (ie

Covered in the above.

> Brian Quirt wrote:

There was a long thread on rec.arts.sf.science which basically agreed with
you.
        There was a lot of high-powered math thrown around,
and heavy physics, but there it was.

Go to Deja.com and look for a thread called He Who Radiates is Lost

> "Robert W. Hofrichter" wrote:
(I
> seem to remember something of the sort from a physics --or was that

I'm not trying to make fun of you, but I do find your terminology amusing. I
believe that it either betrays your age or the age of the materials you have
been reading.

Specifically, "pile" is a rather obsolete term for a nuclear reactor. It came
from the original prototype reactor, which was literally a pile of graphite
bricks with uranium slugs and cadmium damper rods threaded through it. They
don't build them that way any more.

Fusion reactors have not been created yet, but they are likely to include
reaction chambers either shaped like donuts or spheres. So they might be
called a "fusion torus" or a "fusion ball", or something like that.

But your original statement is correct, fusion reactors produce neutrinos.

> Hmm--it does suggest a cool scenario with some special house rules
facing
> off against a super-high-tech force (which, having been trained in
using
> fusion piles for power and some high-tech propulsion. Result? Some

Interesting scenario. There was something vaguely related to this in David
Mace's novel NIGHTFLIER. In that novel, ships could always be detected when
they used their propulsion systems. This precluded surprise. You might not be
able to see a ship running silent, but you could always calculate its current
position, based on the data from when it changed its vector.

In the novel, a breakthrough occured. It was a crude prototype of an artifical
gravity drive. The main point was that it could change a ship's vector WITHOUT
any betraying thermal emissions.

> Brian Quirt wrote:

> Brian Quirt wrote:

I actually went and looked this up a few days ago (remembering reading the
thread). I had planned on posting the URL, but my connection was so aweful
that it made it painful to type. Note: this is not the same thread that Nyrath
is talking about, his is probably better.

Here's the one I found:
http://x39.deja.com/[ST_rn=ps]/viewthread.xp?AN=313068792&search=thread&
svcclass=dnserver&ST=PS&CONTEXT=955733588.1856897036&HIT_CONTEXT=9557335