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Wooahhhh all. I think something got lost in the translation here.
No rockets are intended here. Just a little sea anchor like a
parachute.
the only high pressure air release would be to blow the folded up sea
anchor out of its
compartment.
And the high speed I refer to is about 6 knots and I will be 20 to 30 feet
of the bottom.
Just would feel better being able to stop when I need to. And this little
parachute seemed
like a good idea.
Dean
In a message dated 8/27/2008 1:07:11 P.M. Central Daylight Time,
ag@desertstar.com writes:
I
agree 100% with Jay's message and hence the "The following should be filed
under "insane" caveat.
Perhaps that should be changed to "ABSOLUTELY
INSANE". I was just trying to think of alternatives to those already
discussed and crossed off the list.
I can also not really imagine a
scenario where high speed at the bottom would be useful. A relatively
high speed (i.e powered) descent from the surface to near the bottom can be
nice if it can be accomplished safely and you are going deep
In response to
Jay (and no I am not really advocating the use of high pressure
retro-rockets...but in the interest of curiosity (which did kill some
cats):
Propulsion CAPABLE of high speed can be useful to fight
currents.
1) You really care about momentum, so you can trade off your
reaction mass with the velocity you expel it. Of course at this point
you may have to up-scale from scuba bottles, which is probably WAY more
dangerous than the risk of hitting something.
2) Didnt see that
mythbusters. If you have a gas compressed in tanks to a higher density
than water, you shouldn't loose any buoyancy (DONT TRY THIS), and was
thinking more about fast horizontal delta-v near the bottom, where a loss of
buoyancy is not the major concern.
3) if it was for absolute
emergencies then a stuck valve doesnt seem like a terrible price to pay.
Assuming there was a redundant system to blow ballast.
Also, some
shallow water wet subs can move pretty fast. But they dont have the mass
behind them that would make a collision as dangerous. Also some of
those bigger psubs may cause a pretty big mess at low velocity
collisions.
So maybe "PSUB momentum kills" ?
or really
"Operate in the envelope" is probably the correct message.
FWIW: Deep
Flight I has a max cruising speed of 12 Knots and a Min of 2 Knots. But
I think the idea is that it is super maneuverable rather than able to break,
and high speed is used primarily for descent. Still cant imagine12
Knots at the bottom...heck 2 knots seems fast. It does only weigh 3000
lbs...
-a
-----Original message-----
From: "Jay K.
Jeffries" bottomgun@mindspring.com
Date: Wed, 27 Aug 2008 16:35:32
-0700
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST]
Stopping Flaps
> While Andy's idea appears feasible on the surface,
there are some practical
> issues to consider:
>
> 1.
Air does not have a lot of mass so its reactive force would be
small
> in comparison to the 2+ tons of a typical PSUB;
>
>
2. As demonstrated on Myth Busters, dumping a lot of air
into the water
> in the direction of your downward trajectory will
actually cause you to have
> a loss of buoyancy and thus accelerate your
descent;
>
> 3. Dumping that much air (it is
going to take a LOT!) at one time will
> probably freeze up the valve
you are using (unless it is the VERY expensive
> Marrotta valves used
for big sub's ballast tank blow systems).
>
>
>
> Under most conditions found in typical PSUB operating areas, trying
to
> propel your PSUB at high speeds can be likened to driving in a
heavy rain.
> You can drive fast, out driving your visibility window,
and risk colliding
> with a car or something else before you slow down
to avoid the collision.
> Or you can slow down and drive within your
visibility window and be able to
> easily avoid obstacles. Your
PSUB weighs several tons and you do not have
> breaks like a car, trying
to stop a PSUB's inertia is like trying to break
> your car with your
foot out the door on the road. SONAR will help see
> things ahead
but your reaction speed and the maneuverability of your PSUB
> (stopping
or turning that inertia) will not help you. An issue here is a
>
thermocline can cause the SONAR beam to bend around an obstacle and you
may
> not see it until too late. Any high speed vehicle in the
water stays up off
> the bottom to avoid obstacles and this defeats what
the PSUB is trying to
> do, find things on the bottom. You need to
slow down if you are going to be
> near the bottom.
>
>
>
> It took years for many of the things learned
in the Technical Diving to
> permeate out through the old, hard core
deep wreck diving community in the
> NE United States. One of
those things was "Deep air kills!" Well, thought
> should be given
to "PSUB speed kills!" Other knowledgeable people have
> tried to
impart this fact to the list. Dean has put a lot of effort into
>
his PSUB to conquer this very trying environment found in the Great
Lakes
> and should be applauded for his efforts but care should be taken
in how PSUB
> speed is promoted.
>
>
>
> There are others that seem to periodically bring the same topics up
just to
> stir the pot. A healthy discussion of these subjects is
good but the
> concepts should be couched with notes of caution, not as
realities and
> proven technologies. In fact, usually when there
is a citation that appears
> that the subject is safe or feasible,
further investigation leads to hoary
> facts.
>
>
>
> Your resident naysayer,
>
> Jay
>
>
>
> Respectfully,
>
> Jay K.
Jeffries
>
> Andros Is., Bahamas
>
>
>
> Talk sense to a fool and he calls you foolish.
>
> - Euripides (484 BC - 406 BC)
>
>
>
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