Planner: Bailout dive planning

Willem Ferguson willemferguson at zoology.up.ac.za
Tue Jan 15 00:16:54 PST 2019


Robert,

Your last patch for a button that enables bailout planning greatly 
improves the user experience. I have one question. Frequently in CCR 
diving the last part of deco is performed using bailout. In semiclosed 
rereathers, a significant part of the ascent is often performed in OC 
mode (=bailout) because remaining on the loop extends the deco time 
significantly and can also affect PO2 unfavourably. In eCCR dives, the 
oxygen part of the deco is often done off the loop because the 2 litre 
oxygen cylinder does not contain enough oxygen for the deco (this last 
point is a technicality from the planning point of view, not a 
substantive issue).

When planning a dive and there is planned bailout, it is currently 
difficult do this sort of planning. For instance, let us take a normoxic 
trimix SCR dive for which the last two stages of decompression is using 
EAN50 and oxygen. To plan for deco off the loop (=bailout) for EAN50 and 
oxygen, the only way that I can see is to do the planning without 
bailout, record all the depths and time durations of ascent that comes 
from this plan, then enter, in the dive planner points table, all the 
additional segments during ascent up to the point where the bailout to 
EAN50 is performed. The planner will then compute the remaining bailout 
part of the dive plan.

In multideco, this is not a problem because there is a separate list of 
OC cylinders that one can select, and when a cylinder is marked as OC, 
then the appropriate bailout (=off-loop) calculations are done.

Within Subsurface, I propose that, in the available gases table, an 
additional "Use" is created: bailout. Technically the "Use" of OC-gas is 
not valid in CCR dives, but that is another different issue). The 
categories would then be: OC-gas, unused and bailout. When the planner 
calculates an ascent profile and a cylinder is marked as "bailout" then 
the calculations are modified appropriately. I think the change to the 
UI to do this is trivial: the real work comes in including this in the 
deco algorithm.

I hope my argument is understandable??

Kind regards,

willem




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