Text 22218, 193 rader
Skriven 2012-03-09 16:07:24 av HAP NEWSOM (1:123/140)
     Kommentar till en text av GLEN JAMIESON
Ärende: SILENT SERVICE 20309
============================
Gidday Glen!
-> 
->  ->  ->  -> My launcher used foot-pumped compressed air stored at 120
psi 
in 
->  ->  ->  -> spherical aluminium tank surrounding the quick-opening valve 
->  ->  ->  -> which allowed the pressure to be instantly dumped under the
->  ->  ->  -> dart, about 120mm diameter, which fired it out of the metre-
long
->  ->  ->  -> nylon barrel.  As the propelling air was expanded almost
down 
to
->  ->  ->  -> atmospheric pressure by the time the dart left the barrel, 
there 
->  ->  ->  -> practically no noise, which was one of the design 
requirements.
->  ->  ->  ->
->  ->  -> I think it was only about 2 minutes to pump up the tank.  Enough
->  ->  -> volume to expand it almost down to atmospheric pressure by the 
time
->  ->  -> the dart left the barrel.  Not much.  I was particularly proud
of
->  ->  ->
->  ->  HN> Two minutes is not bad at all!
->  -> 
->  -> I had the choice of any lightweight energy source to propel the
dart,
->  -> and after looking into the alternatives of springs, rubber bands and
->  -> blank .22 cartridges, decided on compressed air storage of the
->  -> operator's energy biscuits.
->  ->
->  HN> With that much weight, I'd have suspected
->  HN> a much more powerful launching system.
-> 
-> The dart plus camera only weighed about a pound, and the launcher,
-> about 4 pounds.  Minimum weight was one of the main aims, as
-> everything had to be carried by a soldier, sweating it out in Vietnam.
->
That is pretty light, Did it ever get into
use?
 
->  HN> You would want to get as much altitude 
->  HN> as possible for two reasons 1) more 
->  HN> photographic coverage and 2) better
->  HN> chances of remaining undetected both
->  HN> during flight and recovery.
-> 
-> The camera had to rise above the jungle, and unobtrusively photograph
-> any groups of enemy waiting in ambush.  Thus the silent launch and
-> landing arrangements.
->
Hoping of course that you have both a
clear launching site and retrieval 
location and the dart did not get 
stuck in a tree...then you'd still
have to process and print the film.
by which time the enemy may have 
eaten, camped and moved on.
  
->  ->  ->  -> A portion of that high pressure air was stored in a space 
within 
->  ->  ->  -> dart, and slowly leaked out through an adjustable needle 
valve.  
->  ->  ->  -> pre-set pressure, the remaining air was dumped into an 
actuator
->  ->  ->  -> released the camera "shutter".  This was usually set to
occur 
->  ->  ->  -> before apogee, while the dart was still rising vertically.
->  ->  ->  ->
->  ->  ->  HN> Sounds quite complicated!!
-> 
-> The design side was complicated, but it was simple to operate, as the
-> only variables were the direction to point the camera before launch,
-> and the pressure to pump it up to.
->
increased pressure would give increased altitude
as well yes?
 
->  ->  ->  -> To prevent the dart from rolling during its upward flight, I
->  ->  ->  -> vane with a tiny gyroscope, similar to that used by the US
-> 
->  -> Very likely, except that if I was designing the modern equivalent to
->  -> do that same function it would be a tiny, battery-powered, remotely
->  -> controlled drone aircraft carrying a digital camera.
->  ->
->  HN> As would I but it'd have to be a very
->  HN> small to remain undetected..I know that
->  HN> they have remote controlled blimps with
->  HN> digital cameras attached. I have seen
->  HN> them in use at the ballpark!!
-> 
-> Haha!  With electric propulsion, and a small size, the model aircraft
-> would make very little noise.  To make it even less noticeable, I
-> would shape it and paint it like a soaring eagle!!!
-> 
Yes, and instead of a digital 
camera a wifi webcam would do the 
job even better!
 
->  ->  ->  HN> BTW I have a new friend in Oz..she's
->  ->  ->  HN> a medic on a collins class sub out of HN> Sydney!
->  ->  -> I sympathise with her.  Those subs have been notorious for 
faults.
->  ->  HN> Boy are they ever! 
->  -> And now they are talking about replacements.  Suggestions that we
->  -> should buy US, Brit or French nuclear subs have been countered by
->  -> comments that they are all too big, and can't operate in shallow,
->  -> littoral waters.  Only smaller, non-nuclear submarines can go there.
->  -> Modern conventional craft built with air-independent propulsion and
->  -> lightweight lithium-ion batteries can operate for weeks without
->  -> surfacing.
->  -> 
->  HN> There is a lot of discussion in the 
->  HN> Submarine community on just that 
->  HN> subject. There is a powerful lobby
->  HN> in Aus that wants to build them
->  HN> domestically and an equally vocal 
->  HN> side that points out how poorly 
->  HN> that plan worked when it was last
->  HN> tried (Collins Class). There are 
-> 
-> They claim that we have learnt a lot of lessons from building the
-> Collins, and now we could do a better job.
->
As they say, "talk is cheap",
and your track record carries
a lot of weight.
 
->  HN> classes of smaller nuke boats that
->  HN> would be capable of working "inshore"
->  HN> just as well as "blue water". Many of
->  HN> the US boats spent more time in
->  HN> "shallow" ops than in deep ops! 
-> 
-> "Shallow" is relative.  According to what I have read of the
-> discussions, even the 5500t French Barracuda class, with 8.8 m beam is
-> considered too large to operate in littoral (brown) waters.  Only
-> smaller, non-nuclear subs fit this role.  They have to be capable of
-> operating at only 2 knots above an irregular seabed, or sit on the
-> bottom for extended periods.  They also have to be capable of long
-> distance travel, and be cheap enough for Australia to afford.  They
-> say a nuclear sub would cost as much as several conventional ones.
->
US nuclear attack subs have worked in littoral 
waters for years. However I would not recommend
them as a regular diet. I suppose it would also
depend on the river as well. Some are wide and 
deep enough that many boats could navigate 
them with out being detected. 
 
-> And, of course, above all else, politics comes into it.
-> 
No getting around that...which may mean
the OZ navy will be once again saddled
with a sub that it's difficult to even 
get a crew to man her. As it is the 
Collins class boats have a hard time
getting people to volunteer to crew them.

->  HN> However if it were ME making the
->  HN> purchase...I'd be looking at the
->  HN> Swedish boats..specifically the
->  HN> Gotland class boats, with air
->  HN> independent propulsion. There's
->  HN> not much of a need for huge 
->  HN> range and those dang boats are
->  HN> very VERY quiet!
-> 
-> Long range may not be needed in Sweden, but Australia is bigger, much
-> bigger.  And the Pacific Ocean is rather empty.
->
I said there's not much need for 
a huge range, not that the boats
are not capable of it. They run
significantly slower on the 
surface than submerged but can 
do a good 20 knots per hour when
running submerged. And they are 
still some of the most "undetectable"
boats in the water these days. 
And you're gonna have to make up
your mind mate...if you're gonna 
run them as brown water boats
or deep sea boats? The Gotlands
can do both, but they are not 
designed to be deep water boats
primarily. Provisions for the 
crew would be a bigger factor 
than the range of the boat itself.
chat with you soon!
hap
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