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Re: (TFT) New File on Dwarves on Rick's web pages.

As this discussion goes on, I have to admit I'm no scientist and am not fam
iliar with the issues from that perspective.  What I WAS, however, was
 an infantryman and platoon sniper.  As such, I routinely got to work 
with night vision equipment, including both IR scopes and "starlight" scope
s.  They provide different kinds of information, and they need to be v
iewed differently, each possessing its own advantages and disadvantages.�� But one thing neither of them required was for me to carry a compact nu
clear power plant with me to power them.  Furthermore, they were robus
t -- meaning that an ignorant and clumsy infantryman, carrying 60 lbs of ge
ar in a pitch-black night in the middle of a forest could use them without 
too much risk of destroying them or killing himself in the process.  (
I also used starlight type scopes later on when I flew helicopters for the 
Air Force, though of course there was considerably less likelihood of me dr
opping them under those conditions.)
In short, the issue of cryogenics and power limits really never came up for
 those of us using them in the field -- and this was in the late 70's and e
arly-to-mid 80's.  Yes, some of them needed batteries, but not a car b
attery or anything silly like that.  We could (and did) attach them to
 our helmets, or use them as scopes on our rifles, depending on the model a
nd the situation.  The only really annoying thing I remember was that 
they were heavy enough (being soldier-proofed mechanical equipment) that yo
u needed to sling some counter-weights on the back of your helmet to offset
 the neck strain (especially when flying helicopters with them) -- which me
ant a couple of rolls of quarters in a velcro pouch attached to the back of
 your helmet.  The modern ones I've seen our people using in Afghanist
an and Iraq seem to be a lot more streamlined and light-weight than ours we
re.  Obviously, counterweights would not be required if they were a bi
ological component of the creature using them.
The bottom line, this is not something that cannot be conceived of or is to
o hard to do, and it is not something that is impossible for biological cre
atures to do, given that several creatures seem to "see." at least partiall
y, in the IR spectrum.  Indeed, a reasonably well equipped modern infa
ntryman would do quite well in a "dungeon" environment (if he could avoid f
reaking out when a hideous creature jumped out at him (or "her," these days
 too, I guess) from some side passage), especially since modern camouflage 
"paint" (or "makeup," if you prefer) for the soldiers to use is actually IR
 suppressing (just as the battle dress uniforms are) precisely to overcome 
enemy IR scopes and the like.  If they weren't in common use, the Arme
d Forces never would have gone to the trouble and expense to do any of that
.  And they wouldn't be in common use if they were all that hard to cr
eate or operate, or required something like a refrigeration plant to work.

      From: "Tapley, Mark" <mtapley@swri.edu>
 To: "tft@brainiac.com" <tft@brainiac.com> 
 Sent: Sunday, February 7, 2016 3:25 PM
 Subject: Re: (TFT) New File on Dwarves on Rick's web pages.

On Feb 7, 2016, at 8:58 AM, TFT Digest <tft-owner@brainiac.com> wrote:

> The thing I don't like about 'infravision' is how does it work when the
> dwarf him or her self is generating heat.  The sensors (the eyes) wo
> drown out the signal with their own emissions.  (I suppose it could 
> in the very near infrared, but then it wouldn't be much use as a night 
> vision ability.)  The D&D infravision, only made sense to me as a 
> magical effect.

    I had the same worry - when working on a design for an i
nfrared telescope spacecraft. But, it actually can work. 

    First, the optics are emitting infrared energy isotropic
ally (in all directions), wheras they are *focussing* down to a point incom
ing incoming energy from the target over a large solid angle (as seen by th
e target). Bigger optics (compared to the size of the detector) can concent
rate on the detector more energy from the one direction of the target than 
they are emitting in that specific direction. 
    Second, many emitters emit preferentially at a few speci
fic wavelengths which stand out against their normal black-body curve, and 
if the target emphasizes some wavelengths that are different from the optic
s, that can provide enough of a relative advantage for the detector to disc
riminate them. 
    Finally, even if the optics are overwhelming the target 
at a given frequency and for the given focussing, if the detector can still
 resolve the *difference* in intensity caused by target emissions, it can s
till form an image. (That is, the detector sees the small additions caused 
by the presence of the target compared to what it sees when looking at a co
ld, empty background).

    All this is theoretical, but night-vision (IR) goggles a
nd IR telescopes and sidewinders (the snakes, not the missiles) are effecti
ve, and some of them work well without cryogenic detectors. It is also true
 that the more sensitive ones, particularly as you go down into far IR wave
lengths, do use cryogenics, but remember that radio (and microwave, of cour
se, is just far far far IR) receivers are usually not cryogenic. So clearly
, there are techniques that will be effective even in the presence of detec
tor-generated heat.

               ��             - Mark
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