Tullibee was an alternate design optimized for anti-submarine warfare, much smaller and slower than the Threshers and with a quiet turbo-electric propulsion system.

[4] Although they used the same HY-80 steel (yield strength 80,000 psi (550 MPa)) as the Skipjacks, the Threshers' pressure hulls were made using an improved design that extended test depth to 1,300 ft (400 m).

It was determined that the source of this noise, called blade-rate, was the blades of the screw vibrating when they hit the wake of the sail and control surfaces.

This made available the required large space in the bow for the BQQ-2 (BQQ-5 as modernized from the late 1970s) sonar sphere, a new and powerful low-frequency detection sensor.

As a result, the SUBSAFE program was instituted to correct design flaws and introduce strict manufacturing and construction quality control in critical systems.

The seawater and main ballast systems of future classes (Sturgeon-class SSNs and Benjamin Franklin-class SSBNs) were redesigned, and some Threshers and other submarines were rebuilt to SUBSAFE standards.

Joints in any equipment carrying seawater must be welded (not brazed), and every hull penetration larger than a specified size can be quickly shut by a remote hydraulic mechanism.

Although counter-rotating propellers produced impressive gains in speed on the experimental Albacore, in Jack the results were disappointing because of the difficulty in sealing the shaft.

[citation needed] The gaps in the hull number sequence were taken by the unique Tullibee, and the George Washington, Ethan Allen, and Lafayette-class fleet ballistic missile submarine classes.