grade eight?

[amalventano1 at tds.net (Allyn)]

> All this talk of fastener grades reminds me of the subsafe 
> program in the Navy.  The idea is that you want to keep the 
> water out of the people tank.
> 
> I was always told it was an incorrect grade of fastener on 
> the Thresher that failed allowing a large volume of water 
> into the switchgear (killing power) but reading about it 
> onlines tells me that it was an incorrectly brazed joint on a 
> main seawater valve.  Same effect.
> 
> I am sure that Al can correct me.  I was NOT a submariner.  I 
> would not be able to speak of such things intelligently 
> because I was a surface weenie (and consequently hete-- um 
> nevermind I won't say it.
> LOL)

It most likely started with the silver brazed joints, but ended with the then poor standard procedure of having a hair-trigger for
isolating the steam system (from the reactor), which cut off propulsion.  On a submarine, propulsion speed has a BIG influence on
the ability to 'drive' the ship shallow - even more than blowing the ballast tanks dry (which is risky when deep, as breaking the
surface at an uncontrolled angle can result in the ballast tanks partially re-filling with water).  Imagine a cup, upside down,
submerged in water, full of air.  For the equivalent visual, tilt the cup.

While the Thresher was a sad loss for the Navy, it caused _significant_ improvements in safety across the entire submarine fleet.
All joints are precision welded with matching material, tested, retested (radiography / ultrasonic).  Procedures were re-written
sith significantly greater flexibility (if absolutely necessary, we can boil the steam plant dry in order to propel the ship to the
surface and save the crew).  Safety systems were installed (there are now emergency stations that can remotely shut all major hull
openings of that compartment within seconds).  Heck, some boats can literally pressurize an entire compartment, so as long as the
(theoretically gaping) hole is low, the space will only fill to the level of that hole (though this only works at surface pressures,
so getting there is rather important (back to the steam plant comment above)).

Last comms from the Thresher:
"... minor difficulties, have positive up-angle, attempting to blow."
(5 minutes later)
"exceeding test depth ... nine hundred north". 
(1 minute later, the tracking ships sonar detected the implosion)

Al