Planner: Bailout dive planning

[Robert Helling]

Willem,

> On 15. Jan 2019, at 09:16, Willem Ferguson <willemferguson at zoology.up.ac.za> wrote:
> 
> 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??

thank you for this suggestion. Just let me make sure, I understand it properly: The procedure you envision is that in PSCR mode (note that the planner does not do gas switches in CCR mode), the planner performs gas switches based on the depth recorded in the gas tables. But, in some way, each cylinder has a dive mode associated to it and when switching to that cylinder, the dive mode is changed accordingly?

Best
Robert
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