On 21 Feb 2016 at 0:58, Richard Aiken wrote:

> Wikipedia states: "The Deep Submergence Rescue Vehicle (DSRV) is
> designed to rescue 24 people at a time at depths of up to 600 m (2000
> ft). Their maximum operating depth is 1500 m (5000 ft)."
>
> From what I can find with a casual google search, the presumed crush
> depth for modern American subs is (again according to Wikipedia)
> officially "in excess of 800 feet" but "probably actually twice that."
> Which would be about 1,600 feet, so it looks like the DSRV can handle
> whatever may be needful.
>
> Except . . . 
>
> I found a Federation of American Scientists paper which mentioned that
> the Soviet Alfa class had an estimated crush depth of *4000* feet.
> Since the Alfas were built with 1970s-era *Soviet* tech . . . one can
> not help but wonder how accurate that ~1,600 feet really might be, for
> the newest American subs. 

The question hasn't been "How deep can we make the crush depth" for decades. It's
been a combination of  "How deep does this sub need to go?" and "How much are we
willing to pay for a deeper diving sub?". Because the Alfas were intended to do what
amounted to high speed drive-bys they needed to be able to go extremely deep to avoid
counter attacks (also the deeper you go, the faster you can go before you start getting
cavitation on your props, and cavitation is extremely loud). The Alfas were
special-purpose boats, not standard attack subs, and were very expensive and
maintenance intensive.