On 05.08.2014, at 09:10, Joakim Bygdell <[email protected]> wrote:
Hi,
> Planner:
> Changing GF values by typing in a new value hangs subsurface if "last stop at
> 6m" is checked.
I did not realize this before, but indeed you can choose combinations of
settings that make deco impossible (i.e. take infinitely long): Let’s assume
for simplicity that you are breathing air and try to deco at 6m. Then by
waiting as long as you want, the inert gas saturation in all your body
compartments will approach that of the inhaled gas (i.e. 1.6bar x 80% = 1.28bar
of N2) and by choosing small enough GFhigh that can be too much to surface.
Indeed some experimentation showed that GFhigh=34% seems to be the boundary
case. Choosing a lower value of GFhigh results in subsurface trying forever to
wait long enough to be allowed to surface.
What shall we do about this?
1) Nothing. We consider it a user error.
2) Not allow setting GFhigh to values below 35% if “last stop at 6m” is
selected (GFhigh=1% still allows to surface with the saturation at 3m, so the
problem is only with decoing at 6m). In fact, I don’t think values below 50%
are reasonable anyway.
3) Always ascent after 48h of deco (the Buehlmann model is not supposed to be
extrapolated to such long times anyway)
4) Always ascent to 3m after 48h of deco (which then eventually brings us to
the surface as argued above)
5) Do 3) or 4) with a statement in the notes that this is what happened (new
translatable string, hurray!)
6) Throw an error message and refuse to plan deco (again a new string).
Let me know what you want and I will implement it.
Best
Robert
--
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Robert C. Helling Elite Master Course Theoretical and Mathematical Physics
Scientific Coordinator
Ludwig Maximilians Universitaet Muenchen, Dept. Physik
Phone: +49 89 2180-4523 Theresienstr. 39, rm. B339
http://www.atdotde.de
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