There is only one known photograph of the experimental submarine, and few details are available about the rescue capsule. It is estimated to be about 40 feet in length and is built into the submarine as an integral part of the conning tower.

It is common knowledge among submariners that Soviet submarines have escape capsules, but little on the subject has been written in unclassified publications. American officers say United States submarines are not equipped with similar emergency devices because they take up too much space and the probability of a malfunction is too great. The United States Navy prefers to use submersibles for submarine rescue operations. Fire in Stern Compartment

The American official said the Soviet Navy had reconstructed events surrounding the submarine's loss and had made some details public in Tass dispatches and Krasnaya Zvezda, the Soviet military journal. The Soviet reports give this account:

A fire broke out in the stern compartment of the submarine while it was submerged. When compressed air lines ruptured and fed the fire, flames spread forward toward the compartment containing the submarine's nuclear reactor. Automatic damage control systems and the efforts of the crew failed to contain the flames, and after five hours, in danger of going down with all hands, the submarine was forced to surface.

Some crew members then abandoned ship in rubber rafts, but part of the crew including the captain stayed aboard fighting the fire and shutting down the submarine's nuclear reactors. The submarine's reactor engineer, who survived the sinking left the ship after the reactor was shut down.

When the submarine lost buoyancy and sank, five crewmen sealed themselves into the escape capsule, which was already partly flooded and filling with smoke. The capsule, which submarine experts believe was manually operated, apparently failed to separate from the submarine during the descent, but detached when the submarine reached the sea-bed and carried the five crewmen back to the surface. Sphere Eventually Sank