I'm working on a scenario inspired by a recent report I heard on NPR about the
ocean of Europa... it's still in the embryonic stages of development.
Anyway, I need some help that I'm hoping some listers might be able to
provide:
No. 1 Is there any naturally occurring element that can block radar? Is there
any elemnet hypothesized or
in hard sci-fi literature that can do this?
Essentially what I'm looking for is something that can refract radar and
prevent accurate readings.
No. 2 Will an abnormally loud aquatic environment prevent the effective use of
sonar?
Thanks in advance for any help you can provide.
In a message dated 2/24/00 2:39:13 PM Central Standard Time,
> kevinbalentine@yahoo.com writes:
<< Anyway, I need some help that I'm hoping some listers might be able to
provide:
No. 1 Is there any naturally occurring element that can block radar? Is there
any elemnet hypothesized or
in hard sci-fi literature that can do this?
Essentially what I'm looking for is something that can refract radar and
prevent accurate readings.
No. 2 Will an abnormally loud aquatic environment prevent the effective use of
sonar?
Thanks in advance for any help you can provide. >>
1) Any thick natural surface will stop radar cold as it reflects the
beam -
rock, trees, wooden walls - sufficent distance of thick vegetation any
substance through whihc the beam will not pass is a "naturally occuring"
anti-radar device
If you mean purposefully used artificial substance we have chaff today -
which is a thin strip of mylar - preferably cut to the same physical
length as the wave length of the radar which sends back HUGE echoes to the
receiver effectively making any definition of possible targets impossible.
Background sound must be filtered out of passive sonar detection systems,
computers and the human ear are very good at doing this, but both require time
to evaluate the data. Echoes from active sonar are alos bollixed fairly
easily, though not always effectively, by bubble bursts and noise makers,
botto echoes and the like.
> On Thu, 24 Feb 2000 12:38:26 -0800 (PST), Cleats Balentine writes:
Sure. Lots of dirt. Hills are good at blocking an amazing range of EM
radiation. Do you want something smaller? steel blocks radar fairly well I
seem to remember. Mostly because it reflects it like crazy, so you get a good
return on the steel, but not on anything behind it. Really, radar penetrates
things fairly poorly, so just about anything will block and reflect it.
Now, if you want to absorb the radar so you get no returns, its a little
harder. I believe water absorbs radar pretty well, as do some new plastics and
such.
> No. 2 Will an abnormally loud aquatic environment
Maybe. There are two general forms of sonar detection, active and passive.
Passive is just listening for sounds that sound unnatural. If the background
is loud and random, but there is still a repeating man made sound in there,
you may well be able to find it, if the random sampling isn't so much higher
amplitude that the man made sound is reduced to noise.
Active sonar is where you send out a loud "ping" and listen for the echos. If
the background is loud enough, it might be hard to hear the ping when it comes
back, but in general you should be able to tune the frequency of the ping so
that you can listen to a very tight frequency range and eliminate most of the
noise.
Does that help?
The information I'm getting is helping... especially when it comes to the
sonar question.
About the radar, I'm looking for some (potential) natural occurring
atmospheric disturbance that could prevent the use of radar.
For instance, our intrepid explorers have just entered an unknown atmosphere
and discover that, for some reason, their radar doesn't function properly. Is
there even the remote possibility that could happen?
> --- Matthew Seidl <seidl@vex.cs.colorado.edu> wrote:
> On Thu, 24 Feb 2000 13:35:39 -0800 (PST), Cleats Balentine writes:
I'm guessing here, as my phyics and wave-mechanics classes were a LONG
time ago, but there are definitly some things that would play heck with radar.
1) Dust storms, or anything that gets solid particles up into the air.
Especially ones that are very reflective to radar. Too many bounces.
2) I'd guess that some complex molecules, especially organic plastics, could
absorb the radar. So go for a soupy jungle atmosphere and say that there's so
much of this stuff in the air it really degrades the signal. Maybe the organic
soup even LIKES the radar. Yummm. Energy.:)
3) Radar is mostly useless in things like forests, so go for world trees. A la
the Hyperion books. A world covered with tree's a mile high. Withen the
forest, the trees would make radar mostly useless.
Now that's exactly what I'm looking for... I can almost *taste* that soupy
atmosphere now.
Thanks for all the input guys.
> --- Matthew Seidl <seidl@vex.cs.colorado.edu> wrote:
G'day,
> No. 2 Will an abnormally loud aquatic environment
Massive chemical or temperature shifts inside the water column - they
act as a barrier and you've got #@% of getting a correct return. I've seen
guys track a single zooplankter (about 0.5mm) through the water column not a
problem and then bang hit the thermocline and they wouldn't be able to find a
whale even if it was sitting there waving at them! The problem would be
exascerbated if your pycnocline (density break-point) was either large
or there were multiplte ones betwen water masses with different chemical
make-ups similarly with haloclines (salinity based break-points).
Biological swarms (even things as small as femtoplankton which is 0.00000001 m
in diameter) can through it out if congregrating in huge
numbers in a bloom or what-not. This kinda problem is why there are
still so many marine charts on Earth that have 'island' or 'shoals' marked on
them where there are none - the mapper was hitting either a
thermo/pycno/halocline or a group of fish.
Hope that helps
Beth
> On Thu, 24 Feb 2000 15:13:23 -0800 (PST), Cleats Balentine writes:
Just remember that this is getting pretty out there. I could swing some PSB
for this, but I'm not sure I could swing solid scientific BS for it. I'll let
the more expert people on the list give that a try.:) Computer questions, I
can answer. Advanced materials science and biology are more out of my league.
How about very violent and frequent electrical storms? Or dust storms carrying
high volumes of highly ferrous particles? or lot of mountains
around with a lot of iron in them - there are places on earth where the
mountains are so full of iron, radar and radio communications are very
hindered. I'm no expert, but these are my thoughts...
> The information I'm getting is helping ... especially
Sure. A high level of atmospheric ionization could do that. Atmospheric
turbulence with large temperature gradients could, as well, depending on the
radar frequencies in use. For example, in the vicinity of a volcano or other
*large* geothermal feature on an otherwise cold planet.
- Sam