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.