> One point which was pretty much conceeded (and
That is, assuming you're using a reaction drive based on chemical rockets. A
reasonable assumption in some cases (Vector movement, relatively low ranges),
not in others (any Cinematic).
There are 2 different problems regarding what we usually call "detection".
There's 'Detection' and 'Identification'. Thus using a reasonable radar, we
may be able to 'Detect' pretty much everything of reasonable size within the
volume of interest.
But 'Identification' - sorting out which objects are harmless chunks of
rock, and which are planetbusters, is something else entirely.
Useful Identification clues:
Any EM emissions higher than background, including weapons, active sensors,
communications, waste heat, exhaust. In the case of weapons, active sensors
and exhaust, these are likely to be very useful in Detecting the object in the
first place.
Any Gravitational anomalies, ie densities lower or higher than they have any
right to be. This can be judged by either some form of mass detector, or more
likely the behaviour of the object with respect to the solar wind, or
radiation pressure.
Any anomalous reflectivity of EM from the background, such as a silver ship, a
facetted ship with extreme lobes etc, different reflectivity to differnt
wavelengths, or most particularly the absorbtion spectrum: what material is
the surface made from?
But the real kicker here is its Kinetic motion. In general, harmless objects
do not change their course from a ballistic trajectory, and those that do (as
the result of elastic collisions or outgassing) leave unmistakeable traces,
and do not alter their motion much. (OK, in collisions they can, but in a
predictable way, unlike outgassing)
Some things can be easily Identified: ships that fire, ships whose comms you
intercept (though even there, it's possible that an el-cheapo robot
drone could
mimic a real ship). Others are more difficult - is that "shiny" object a
piece of debris from aprevious battle, or a frigate? Or even a large piece of
tinfoil dropped to get your attention while the real ship is elsewhere? A
quick pulse
from a laser might help find out - if the object recoils, it's low mass
(or a real ship using a reactionless drive that's attempting to make you think
that), if its return spectrum shows a composition of silica with a bit of
nickel and iron, it's an asteroid (or a ship with a cammo net). But if it
emits a Terrawatt beam, or suddenly pulls a 6g acceleration, you know it's not
natural. In the former case, it's a ship, in the latter a ship or decoy.
As regards waste heat - a coolant laser should do the job of taking the
radiated temperature down to reasonable levels. Remember that if anything is
"of interest" it's probably relatively close to an unshielded fusion reactor,
ie a Star, so will heat up accordingly.
What this means for FT is that depending on your exact PSB, we could go from
> aebrain@dynamite.com.au wrote:
Well, pretty much assuming you're using a reaction drive at all (ANY reaction
drive is going to be detectable, at least if it's causing any discernible
acceleration...and what's the point in having it on if it's not moving you
anywhere?) As for reactionless drives, that one I can't swallow. I am willing
to grant that there may be a way to make an FTL drive without violating any
natural laws (especially if it involves leaving the universe for awhile).
However, I don't believe that you CAN make a reactionless drive that doesn't
violate conservation of energy, momentum, angular momentum, etc.
> There are 2 different problems regarding what we usually call
Agreed, but I can't see that as being much of a problem at TACTICAL ranges,
only at strategic ranges (for the record, i consider anything within 1e6 km to
be 'tactical ranges' (even though I do NOT believe that there are any
reasonable weapons with engagement ranges anywhere NEAR that), and 'strategic
ranges' is considerably farther away. From Earth,
say, 'strategic ranges' is sort-of 'nearest planet' (unless the target
is manuvering, in which case it's on the order of 2-3e9 km).
> Useful Identification clues:
Definitely. You thrust, you're spotted (if you keep it up for any length of
time, which you have to in order to change your course by any significant
amount).
> Any Gravitational anomalies, ie densities lower or higher than they
I don't see these as being all that useful. I think the useful range on mass
detectors is likely to be fairly short (but I haven't seen any calculations
either way, so it's just a thought). As for solar
wind/radiation pressure, it's only really noticible on things DESIGNED
to catch it, and given how quickly it drops off with distance from the sun, I
can't see it as being useful (if you have the resolution to detect that, you
can read the numbers off the hull anyway).
> Any anomalous reflectivity of EM from the background, such as a silver
Reflectivity is a good measure. So is black body temperature (ie if it's
different from the measured temperature, or peaks in a different region of the
infrared). Another thing is for those ships with 'directional radiators.'
Because a radiator's efficiency as a radiator drops off fairly rapidly as you
make it directional, a radiator that
only radiates through (say) a 60-degree cone is likely to be as big as
(or bigger than) the rest of the ship. Of course, this is also VERY close to
the breakeven point (the point at which your radiator absorbs as much heat as
it radiates, thus becoming useless).
> But the real kicker here is its Kinetic motion. In general, harmless
And, in general, massive objects don't collide very much (if they were
going to, they probably already have). ANY non-ballistic object is going
to draw attention to itself, and keeping your fleet ballistic VASTLY reduces
what you can DO with it (especially if there aren't any interesting targets in
your immediate trajectory after your last jump).
> Some things can be easily Identified: ships that fire, ships whose
object a
> piece of debris from aprevious battle, or a frigate? Or even a large
Well, if it accelerates at all, you can likely determine thrust (from exhaust,
see above for 'reactionless drives'), and acceleration, which gives you a
pretty good idea of mass (yes, you can defeat that by making your decoys as
heavy as your ships, but in that case why not just build more ships). As for
the 'shiny object' if it's moving on a trajectory towards something important,
it may be dangerous so burn it. If it isn't, don't do anything until it
accelerates. After all, unless it's heading right at you (in which case it's a
danger WHATEVER it is), an object per say isn't all that dangerous to you.
> As regards waste heat - a coolant laser should do the job of taking
First, what IS a "coolant laser?" I've never encountered that term, and I have
NO idea what it could be. Second, yes, blackbody temperature has to be taken
into account, but an inhabited ship CAN'T be a blackbody (not even close,
because of the crew), and THAT can be detected.
> What this means for FT is that depending on your exact PSB, we could
Agreed, as long as 'up close and personal' is 'a million km or
so.'
Now, all you have to do is imagine weapons that can DO something at that
range....
From: "Brian Quirt" <baqrt@mta.ca>
> First, what IS a "coolant laser?" I've never encountered that term,
http://www.optitemp.com/optitemp.htm
Shows them in use as Water coolers (!)
http://www.colorado.edu/physics/2000/bec/lascool1.html
has data about using lasers to produce subzero Kelvin (WHAT!) temperatures
> Alan and Carmel Brain wrote:
temperatures
> but that's about individual atoms and bosons.
Actually, from the information provided, it looks like the lasers have to be
EXTERNAL to the closed system, which would make this slightly more difficult
to use. It also seems that, in accordance with thermodynamics, the power you
would have to put into cooling the atoms would itself generate enough waste
heat to counterbalance the cooling effect (note that this doesn't keep the
system from cooling atoms (or water), it just seems that everything OUTSIDE
the area being cooled would end up hotter). I didn't see anything in either to
suggest otherwise (and
neither water-cooling nor bose-einstein condensation require reducing
the heat level of the entire system, any more than refrigerators reduce the
overall temperature of your house).