Q Branch outfitting Bond for the mission ahead. We always thought it brilliant how all the gadgetry and their function in these films was presented ahead of the fact. Then the audience sat back, in turn waiting for their deployment. Usually in the exact order that Q dished 'em out:
(YouTube Video)
We were always a bit drawn to the miniature underwater breathing device Q supplies to Bond:
(Internet Image)
One piece unit - small twin air cylinders and (we're guessing) some type of regulator valve
Q specs the breather as an approximate four minute, "last resort" air supply. Bond eventually employs the device three times, each a critical situation, throughout the remainder of the film.
Thought that we would have some fun and run thru some (rough) figures:
Those canisters appear about the size of a standard CO2 gas cylinder, as of the type used to power an air rifle or BB gun. So we searched on-line. We found that they come in various sizes of 8g, 12g and 16g (g = net weight of the CO2 gas in grams). Again, assuming the near size as of those on the breather, we split the difference at the 12g cylinder:
Cylinder pressure (max) was specified at 870psi (@ 70ºF)... say 60bar (P)
Cylinder volume, 14ml to 16ml... say 0.016L x 2 = 0.032L (V)
Atmospheric pressure (@ 1atm) = 1.013bar (B)
Cylinder capacity = [V x B] / P = [0.032 x 60] / 1.013 = 1.9 Liters (L) of air supply.
An average volume of breath of air, as we recall from our way-back-then diving course training, is around 0.5L.
So, 1.9L / 0.5L = 3.8 breaths... say 4 breaths of air.
Let's say that Bond, being the man that he is, is as efficient at diving as they come. As such, we're sure that we could categorize him within the 4 to 8 breaths-per-minute range of a master diver. Thus, in addition, he could surely hold his breath for at least a minute between breaths, and possibly two minutes (even when considering his 60-70 smoke per day non-filter Chesterfield habit). So, figuring four breaths of available air from the miniature breather, with a minute in between breaths, we would figure at least a realized four to possibly six minutes down time. This being in line with Q's theoretical four minute approximation.
All this with keeping in mind that these figures are based at surface pressure (1atm), e.g., escaping predator tiger sharks while trapped in the shallow depths of a luxury swimming pool. Doubling the depth to 10 meters (2atm) would specifically halve those numbers. Also, heavy physical exertion, e.g., hand-to-hand combat with enemy divers or out-maneauvering racing, hand grenade tossing speedboats, would drastically increase air consumption.
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Subsequent to completing our brief exercise we were surfing about on-line to acquire an image or two for inclusion herein, as well as to double check a few of our units and values. Along the way we happened across a divers forum site which included a post from an Australian fellow, tagged Fibonacci, who had previously done an almost identical, albeit more comprehensive breather analysis. Taken a few steps further, his study includes resting and working performance at depth. He also made use of available CO2 cylinder performance test data which allowed 'em run his analysis at higher pressures beyond the stated 60bar limit we found on line. With all results summarized in an excellent table format. We figured that we'd include a copy of his post:
(Internet Image)
This was a nice check of our figures. As you can see, make a few slight adjustments either way in the constants and variables and we're both spot on.
Another thing that we've found to have in common - we both need somethin' f*k'n better ta' do.
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