[AR] Re: AW&ST Space Tourism Accident Impact.
- From: Timothy J Massey <tmassey@xxxxxxxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 7 Jan 2020 13:08:11 -0500
"John Stoffel" <john@xxxxxxxxxxx> wrote on 01/04/2020 02:50:36 PM:
"Keith" == Keith Henson <hkeithhenson@xxxxxxxxx> writes:
Keith> On Fri, Jan 3, 2020 at 9:18 AM Rick Maschek <dmarc-
noreply@xxxxxxxxxxxxx>
Keith> wrote:
I rock climbed and did mountaineering for 28 years and Search and
Rescue
for 16 years. Rescuing people and recovering bodies never seemed to
stop
people from wanting to continue.
Keith> Even more impressive is cave diving. Not sure what it is now,
Keith> but for a long time, the death rate among cave divers was about
Keith> 50% per year.
It was never *that* bad. At it's worst (1970's), it probably was in the
neighborhood of Everest attempts: a first-order estimate around 1:100
deaths. I'd actually buy something as high as 1:50, which might be the
source of the 50% recollection (from someone -- not Keith! -- who is bad
with math...). Which is terrible: that's about 100 times more dangerous
than recreational SCUBA.
It was the high (and increasing) level of deaths that forced the cave
diving community to create a series of protocols that are required of all
cave divers, primarily focused on six absolute and straightforward
requirements. To my understanding, there has been exactly one death in a
cave that was not attributable to breaking at least one of those
requirements (a cave-in blocked the exit).
Like any pursuit (certainly like rocketry), paying attention to lessons
from the past is vital. Accident analysis is a big part of cave diving
culture. Not as effectively as, say, aviation, but better than many.
There are forums for cave divers that look very similar to Arocket: lots
of noise from the peanut gallery (like me), but some truly expert
perspectives you can't get elsewhere, who have truly been there and done
that. We don't have "the obituary test" per se, but I've used that
concept more than once both with myself and others I've been talking to...
I have a good friend who cave dives in Mexico a couple of times a year
for a week at a time. He recently lost is long time instructor, but I
don't recall if it was heart attack, or a problem underwater. In any
case, it's damn terrifying, but I don't think it's 50% a year any
more... the gear and techniques have improved quite a bit. And my
buddy isn't pushing the limits at all down there.
Current rates are higher than that of recreational SCUBA, but for
properly-trained cave divers are not dramatically higher. Untrained
divers in caves are still a problem, unfortunately, and rebreather deaths,
on the other hand, have recently been at the level of ten times that of
recreational open-circuit SCUBA, and 2019 does not anecdotally seem to be
much different...
Three tanks: one in, one out, one spare.
Not quite: at *most* aggressive, we dive with fully-redundant gear and
the rule of thirds: one third of gas supply in, one third out, one for
contingencies. If your friend dives frequently in Mexico, he most likely
dives sidemount, which means that he has two completely independent tanks,
one along each side of his body. Other divers (such as myself) use two
interconnected but isolatable tanks mounted on our backs.
If gas volumes require, a diver may add a third tank (or more), but that's
not to add additional redundancy, but merely capacity: we're trained to
use the gas in those additional tanks in a redundant fashion, of course,
but it's not inherently more redundant (it's actually less: there's
simply more items to fail).
While I'm wasting everyone's time with off-topic nonsense, I'll throw in a
thank you: this is one of the most interesting and informative lists I
read. As a technical SCUBA diver, I do a bit of things with gasses
(including O2) at pressures up to 5000 PSI. The things I've learned
reading this list have been useful on more than one occasion. Thank you
for your advice and wisdom.
Tim Massey
(a lurking rocketry fan and recent TDI Full Cave diver)
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