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Original Message -----
Sent: Monday, August 03,
2009 4:44 AM
Subject: [PSUBS-MAILIST]
Escape from a PSUB
I
am behind on classes due to recent travel but here is a short reply to various
issues of submersible escape and rescue.
First
law of escape or rescue: KISS – Keep It Simple Stupid! The more
complicated a solution is the more likely your escape/rescue will fail.
By making a simple, well thought out pre-plan you have a much greater
likelihood of surviving in an emergency. The stress of being in trouble
and trying to get out of the sub will add all kinds of complications in an
emergency.
Many
of the issues posted here in the last few days have been covered extensively in
the past on this list and through one or more presentations at our annual
conferences. In these recent posts I note several misquotes and
perceptions that will not be practical for PSUBs.
Naval
submarines have many resources that are either not available and/or practical
for a PSUB. These large submarine have lots of stowage space (lithium
hydroxide for CO2 and bulky escape apparatus but not enough for
escape SCUBA tanks), a large segmented volume that allows escape to other
sealed areas which also provides a large reserve volume of breathable air and
capacity to hold a lot of CO2 before it reaches toxic levels.
This large volume (and mass) also lengthens the time before cold exposure
becomes an issue. These subs have multiple escape chambers designed with
2 hatches to the outside. The one used for escape allows a bubble to
remain in the top of the chamber that the escapees can use prior to ducking
down and escaping to the surface through a short angled tunnel. This
bubble feature has since been found to probably be detrimental to a fast
“press-down” to ambient outside pressure. These escape chambers have a
large apron around them that supports mating with a rescue submersible or bell
(the size of the apron makes this not feasible for most PSUBs). Finally
submarine operators are trained in the use of submarine escape apparatus, have
well thought out written procedures, and get a chance to practice in an escape
tower.
Throughout
the history of submarines and submersibles, in almost all cases, an individual
has a greater chance for survival through escape than if they were to await
rescue from the surface. And those that have been rescued from the
surface have been on the edge of expiration. Escape efforts should be
started as soon as possible due to deteriorating body temperature and
atmosphere quickly degrade both mental and physical capabilities of the
escapee. While ROVs are great tools underwater; finding one in sufficient
time of a size large enough to assist in rescue along with deploying it can
delay escape past the time that the escape can be conducted with any degree of
success. Last year’s hands-on exercise at the Conferences pointed out
many issues with trying to rig a PSUB for lifting to the surface in an
emergency.
When
discussing PSUB escape and rescue, most discussions focus on a submersible the
size of a K-350 as this is the most prevalent design and typical of the size of
many other subs. There is little excess room inside on one of these
submersibles to carry “extras” for rescue so great thought and lots of talk
with others experienced in escape/rescue. As noted by others, wetsuits
are probably not a good resource for PSUB escape. They can become
uncomfortable if worn throughout the sub’s dive and the cramped space does not
support storage and donning in an emergency. The issue of the suits buoyancy
is not a reality until the escapee nears the surface as the material is
severely compressed due to the pressure at depth (in 132 fsw, the closed
bubbles in a suit will be compressed to 1/5th their original size,
at 33 fsw ½ original size and thus decreasing buoyancy accordingly). A
fabric dry suit might be a consideration but may become uncomfortable in most
instances due to not being able to cool off easily.
The
rapid “press-down” to outside ambient pressure is completed quickly enough that
the toxicity of oxygen should not be an issue (divers for years made dives on
air to these depths for extended bottom times with not enough causalities to
impede others). The onset of O2 is usually gradual and has a
series of obvious symptoms that presage a seizure. While mixed gas could
be used, it is an un-needed added complications that will be expensive to
implement due to training and equipment.
While
many have taken note of my warning of an almost explosive release of the bubble
compressed in the sail when the hatch pops open, they have not focused on the
solutions that I have suggested. First the dogs to the hatch in the hatch
should be released. Sea pressure will keep it sealed until inside
pressure is equalized. Opening a valve to the outside will begin flooding
the sub and this can be expedited by opening a vent valve on the side of the
conning tower to vent the resulting compressed air. Some air will still
be trapped in the tower so the sub occupant(s) should start breathing from an
escape scuba cylinder prior to nearing equalization (a head strap attached to
the second stage of the regulator will be very helpful at this point and during
later escape efforts) and forcibly bracing themselves for the coming hatch
popping open and the outrush of trapped air that will try to carry them with
it. If they don’t, they can become snagged on projections within the sub
and/or knocked out by hitting objects in the sub or by the hatch swinging back
after popping open. Once things quickly settle down in the flooded sub,
they should pass their escape scuba cylinder (40 cf is a very good size) out
ahead of their exit. One hand should be above their head and one at their
waist (the one at their waist is to clear anything that they may become snagged
on while bailing out). The tank shouldn’t be strapped to them as they
will have much more difficulty getting out of the sub and a greater likelihood
for snagging on something they can’t reach. Occupants further back in a
PSUB do not have as good of odds for escape especially when it has not been
thought through and walked-thru ahead of time.
Once
outside of the PSUB, a buoyancy vest can be inflated to speed the escapee to
the surface. Some issues to keep in mind here: do not use an
auto-inflating vest as you will be pinned inside the sub when it floods (helo
crews learned this early on); it is going to take a lot of gas to inflate the
vest at depth…more than what is found in common CO2 cartridges; your
clothes are going to make it VERY hard to swim to the surface without
assistance; and if your tempatic membrane was ruptured during “press-down”,
your sense of balance will be way out of wack so up and down will be difficult
to discern in murky water.
I
have not went into all of the advantages to having a surface support vessel on
hand above you with crew that are knowledgably of your operations and
escape/procedures. When the escapee is headed to the surface, they should
keep a hand overhead to minimize the effects of coming up under the tender.
The
above recommendations are based upon my personal experience as a submariner
aboard US nuclear subs, training in an escape tower, many hasty exits from
sunken subs during explorations, reading every book and paper on the subject
that I could lay my hands on, building the escape simulator for a previous PSUB
conference, the preparation and presentation of several papers on the subject
at PSUB conferences, and discussions with many different PSUB owners.
Would
write more but have to get back to school work…check the archives.
R/Jay
Resepectfully,
Jay K.
Jeffries
Andros
Is., Bahamas
Save
the whales, collect the whole set.