For Those Interested in History: the Vital Statistics of the MIKE Class Soviet SSN, Lost 7 Apr 1989:

Turns Per Knot (TPK) at 70 rpm: 8.75 (eight knots; Russian source)

TPK at 250 rpm: 8.1 (30.6 knots) (submarine propellers designed to be most efficient at flank speed.)

Test Depth: 3350-feet; pressure-hull composition: titanium alloy

Estimated Collapse Depth: 4100-feet

Actual Collapse Depth: 5528-feet (on the sea floor); pressure: 2460 psi.

Failure occurred slightly above midline first compartment, starboard side only; the rest of the hull already flooded; bulkhead between first and second compartments may not have failed.)