Alan,
When you wrote about how a ship could be detected using passive systems, you
had weapons fire, hull heat, drive emissions. Nowhere did I see leakage from
comms - either by using an omni-directional transmission or by having a
poorly targetted or poorly focused point-to-point link. I assume you
meant that to be in the list. Poor EMCON (esp from comms) would have to be one
of the easier to detect mistakes (because comm signals tend to look
man-made
and be fairly distinguishable from local radiations... in most cases
anyway....).
This whole debate was nicely summed up by the comments made that for every
sensor, their is a jammer or countermeasure and therefore the only question is
which you believe has advanced further. And what kind of game you want to
play.
Some of us like aircraft carrier WW2 style battles with large numbers of
fighters and attack-boats, others prefer Jutland style WWI gun battles
between battle lines, and others prefer the sub-hunt metaphor for space
combat. The truth is, space combat may be any of these (or more likely, all of
these in some degree) and only by freezing a snapshot can we tell which
it is - for as time passes, undoubtedly progress will change the flavor.
There may be periods where sensors are so good and fighters so bad that it
looks like WWI cruiser/DN duels, there would be a time where fighters
have improved to the point where it resembles Carrier Combat, and there could
come a time where masking technologies render it once again like sub warfare.
It's just up to each of us to decide which flavor he or she likes and to run
with it.
> From what I can see, the official "mainstream" version is likely to
That just makes business sense. But each of the camps mentioned above (and
others not thought of yet) can make their own suggestions and we all benefit
from the discourse.
PS - I think I have to question Oerjan on his comments on the radioation
of
heat/IR. Though I agree with the physics he is suggesting (that energy
is a
wave-particle duality and one can emit without having air to conduct the
heat), I can only conclude this emission is very inefficient because the Space
Shuttle engineers had to put quite a bit of thought into how to dispose of
waste heat. They actually eject material (essentially jetisoning the heat with
the mass of coolant). So obviously the radiation of
IR/heat
energy isn't sufficient without such additional methods - at least as it
pertains to keeping the shuttle a nice, habitable vehicle. Now, whether this
means the radiation is insufficient for detection (since something IS radiated
despite the vacuum outside) remains a topic for debate.
> Thomas.Barclay wrote:
> PS - I think I have to question Oerjan on his comments on the
Conduction and convection are much more efficient mechanisms for transporting
heat than radiation is, certainly. However, radiation is
what's most readily available to spaceships :-/
> So obviously the radiation of IR/heat energy isn't sufficient without
The problem here is that the shuttle is out in space for a week at a
time or so. FT warships tend to stay out for much longer periods - how
much "bunker mass" would they need just to stay cool? How have the various
space stations handled the excess heat problem?
> Now, whether this means the radiation is insufficient for detection
Any IR sensor (sight, goggles, binoculars, whatever) detect IR radiation,
rather than convection or conduction. (OK, they can see heat
being convected away from a warm body - but they see the IR radiation
being radiated from the warm air or fluid doing the convection... and
as for heat *conduction*, well - if the sensor has to physically touch
its target in order to detect it, it probably isn't that much use in deep
space <g>)
Regards,
> Oerjan Ohlson wrote:
Also, you have to consider the relative temperature of the surroundings. The
average temperature of the Earth is 16 degrees, which means that radiation
won't do that much for you. Radiation is also of course proportional to
surface area (which may explain part of the
shuttle's problem. Another part of it may be re-entry - the shuttle was
specifically designed to be well-INSULATED so that heat can't get in
during re-entry, and this might have the effect of making it hard to get
heat OUT when in orbit)
> >So obviously the radiation of IR/heat energy isn't sufficient without
Mostly through heat radiation. The difficulty here is all the different plans
for suppressing heat radiation. If just keeping your crew from boiling
requires you to dump a LOT of heat, it's much harder to suppress your
emmission.
> >Now, whether this means the radiation is insufficient for detection
Definitely. The other (semi)-missing factor here is relative
temperature. On the Earth, there isn't THAT much of a temperature
differential, so you need to have a pretty high differential to detect
anything. In space, though, things are different. The background is MUCH
cooler (a random patch of sky is probably going to be within shouting distance
of absolute zero), and a ship hull just CAN'T be kept at that temperature very
well (or, at least, I wouldn't really want to try to design a ship where the
outer hull is more than 250 degrees centigrade cooler than the inner hull).
Current technology is well able to detect a
few degrees divergence from background (not via earth-based telescopes,
of course), and I see no reason to suppose that future technology will be any
LESS capable.
From: "Thomas.Barclay" <Thomas.Barclay@cbu.xwavesolutions.com>
> When you wrote about how a ship could be detected using passive
> On 15-Apr-00 at 19:21, Brian Quirt (baqrt@mta.ca) wrote:
> The background is MUCH
This is one I would like verified by someone knowledgeble about astronomy,
just because a gas is thin doesn't mean the temperature is low.
> On 15-Apr-00 at 19:21, Brian Quirt (baqrt@mta.ca) wrote:
Roger
> This is one I would like verified by someone knowledgeble about
I'd also think a random patch of sky might contain stars, which are kinda
hot...
> On 15-Apr-00 at 19:21, Brian Quirt (baqrt@mta.ca) wrote:
I was looking around the internet, trying to find some kind of information on
detecting objects in space and ran across this link, which puts it about
2.73 K or around -270 C.
http://image.gsfc.nasa.gov/poetry/ask/a11121.html
The site in general has all kinds of neat information.
> Definitely. The other (semi)-missing factor here is relative
I was trying to set up a spreadsheet to see what kind of heat transfer you
would get using different temperature differences between an inner hull at say
25 C and the outer hull, and a space temperature
of -270 C. What I was wondering is what are the sizes of some of the
ships? Since the heat transfer depends on surface area.
Right now I am using a cylinder 100m long with a 20 m diameter, and you hit a
kilowatt around a 175 degree difference in hull temps with around 58 kW at no
temperature difference. These are pretty approximate numbers because radiation
is ungodly complex, at least to me.