zaf88:
why doesnt the prism allow you to change setpoints on the fly, what is the positive b enefit of this?
Zaf, the idea behind the automatic setpoint change is that the diver can't forget it. Simple as that, it's a safety measure. If you read Howard Hall's Rebreather Blunders (available at Rebreathers Worldwide and at his own website) you'll see he forgot to do so on his Biomarine and ended up in chamber due to it and a few other mistakes. Divers can forget, especially when loaded with tasks other than flying the rig.
On the initial prototypes the setpoint was both adjustable and manually switched. Even then switching was forgotten a couple of times, so the idea and the manually adjustable setpoint controls were thrown out. Pete showed me the controls, and Steve Millard has a picture of them in his Prism article, still available on NW Design's website.
and about third party testing, which method is more stingent, the navy protocol or CE's?
They are simply different protocols, at least when the NAVY uses their own.
Some of the tests are like, setpoint control accuracy, WOB & hydrostatic differences, scrubber duration and such, also both the protocol and the requirered results may differ.
The NAVY also requires testing that are application specific to the use of their rebreathers like magnetic signature and the like that would not make a difference to a civilian diver.
When CE on the other hand takes materials into consideration, they require recycleability rather than a low magnetic signature, a bright color for visibility etc.
Both are thorough test regimen have their pros and cons, and passing one doesn't mean you'll pass the other. A MK15/16 wouldn't pass the WOB/HD requirements of CE, while the Inspiration didn't even get to manned testing because it failed the loop gas analysis.
Yet those rigs are used successfully for their intended purposes.
lastly, when you travel with your prism, are catalina 19's readily available at most destinations or do you have to take your tanks with you?
Depends on where you go, really. Many if not most RB divers seek out locations where they can get gas, tanks and absorbant as needed. If not they either haul it along or send it ahead. 'silent running' here on the board travels quite a bit with his Prism and made a couple of posts in that regard. Jeff Bozanic published an article on his Bikini trip, available on the web, and explains the logistics to use a CCR there.
Plenty of poular destinations have at least one shop who supports rebreathers and can supply the needed consumables and tanks.
If you do need to bring your own tanks they'll have to be inspected so the valve needs to be removed. Also, the Prism can take the smaller and lighter two liter tanks if weight/size is an issue.