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Date: Thu, 6 Jan 2000 10:58:45 -0000 From: "Stuart M" <divebimbo@li*.fr*.co*.uk*> Subject: XS News With all the recent talk about deco software I thought I'd pitch in and post an update on what has been happening with XS. First off, XS is still available free of charge at http://www.lizardland.freeserve.co.uk/download.html and I can be contacted at divebimbo@li*.fr*.co*.uk* Apologies to Gordon for posting self-serving mail, but XS is freeware (if you like then make a donation to DAN or DDRC) and I don't make a bean out of it. Nor do I care whether it is used for ARSE, DIR or otherwise, as long as no-one else is making any money off it either. XS NEW RELEASE The next version of XS is due for release at the start of next month. It is ready now but I can't be bothered uploading it until then 'cos I'll have to redesign the website and redo the manual too. Please don't ask me for the new version, it will be available from the website in a few weeks, and the current version will be available up to then. XS INCLUDED IN CAVE DIVING GROUP TRAINING MANUAL The UK Cave Diving Group (CDG) are planning a new edition of their training manual to replace the existing version. XS has been chosen by the CDG to be used for the decompression planning chapter and new features have been added at their request. I have a short article explaining how XS works in the CDG Newsletter 137 (April 2000). Nevertheless, the XS disclaimer still says don't use it for actual dive planning and that isn't about to change. ISOBARIC COUNTER-DIFFUSION The phenomenon of vestibular bends due to the above effect is rare and little known. Sheck Exley describes it in Caverns Measureless to Man where sudden fatalities have been caused by switching from high-He mixes to high-N2 mixes at depth, although he associates it with the change in density, and animal experiments have also demonstrated it. Recently, certain high-profile fatalaties have been associated (though never proven) with IBCD. I have to admit I know very little about it but at the request of the CDG XS can now check deco gas choices for gases which may lead to increased nitrogen ongassing rather than offgassing as would be expected. XS safety policy is to point out rather than intervene and it will now provide a warning where a gas has led to a noticeable rise in tissue N2 tension but will not actually do anything about it. Personally, I think the best plan is not to do stuff like switching to air on deep stops and to use more helium, but that's just me. QUICKER CONFIGURATION There is now a "Quick Configure" option where you choose the style of diving you are doing from a list and XS will adjust the operational settings accordingly (e.g. no-deco diving, mixed-gas, bail-outs, etc). REBREATHER FUNCTIONALITY The bug which affected shallow CC trimix stops with ppO2>1.0bar has been fixed. The user also has the choice of bailing out to open-circuit at any point in the deco schedule and can switch between CC Trimix, CC EAN and OC gases. The CCR setpoint can be set independant of the maximum ppO2 for open circuit setting (these were previously shared) and it is possible to change the set-point during deco. SURFACING %M-VALUES These figures show how close the gas pressures in the tissues come to their maximum allowed (m-value) at the end of the dive. These can be a good indicator of how safe (or unsafe) a dive can be, and they can also point to where a possible bubble may form. The %M for each tissue was displayed automatically at the end of each dive previously, but I don't know if anyone noticed that they were reading about 10% higher than they should have been. It looks like it is working properly now. SURFACE NOW FEATURE Ever wonder what would happen if you were to surface in the middle of your deco plan without completing it? XS has a "Surface Now" feature - it calculates the surfacing %M's (see above) to let you see what would happen if you swam straight to the surface, ignoring all your remaining stops. Generally a %M of about 85% or more in any tissue can lead to bubble formation, although where deep stops have been done WKPP divers have pushed more than 110%M without symptoms. The faster tissues also appear to be more tolerant of higher %M's too. This is just for illustration and emergency purposes - don't use it to cut chunks off your deco. Well, that's it. I'll upload it when I get the motivation. Liability blurb as before, don't dive on a dive plan generated by XS, it's for armchair diving only, blah, blah, blah. The new version of XS is just as likely to kill you as the old one. Any questions then please get in touch, as long as nobody asks me if it is Y2K compliant. If anyone (Adri?) fancies cross-posting this to Techdiver then feel free as I am no longer on it (life is too short :). Cheers, Stuart. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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