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The Project 1910 Kashalot ('Sperm Whale') Class deep-submergence submarine (NATO: UNIFORM Class) program was initiated in 1972 under the famous Malachite design bureau. Construction of the first boat starting in 1977 with the first of three boats entering service in the 1980s. Designed for special'ocean engineering' missions it was analogous to the US Navy’s NR-1 which had been built in the 1960s. The Russian boat was significantly larger however, at about twice the length which made it, on paper, a full-size submarine. Under the outer hull however it was in fact incredibly small, with an inner hull diameter of about 6m which allowed for two decks. The hull was split into two distinct sections with the unmanned reactor compartment and machinery room in the stern, with no direct access from the crew compartment.
Original artwork - CLICK for HIGH-RESOLUTION image.
Note: the midget submarine direct equivalent of the NR-1 was the project 1851 Nelma (NATO: X-RAY Class) which was built in parallel to Kashalot.
Main article on 
X-RAY Class
Both hulls are made of welded titanium which is corrosion resistant and much stronger than steel for a given hull thickness. On Kashalot this translates into an incredible 1000m (3,000ft) operating depth.
Photo: US Navy
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Project 1910 'Kashalot' boats
1. AS-13 Laid on the 'LAO' plant in Leningrad on 20th October 1977, launched on 25th November 1982. Joined the Soviet Navy 31st December 1986. In service with the Northern Fleet.
2. AS-15 Laid on the 'LAO' plant in Leningrad on 23rd February 1983, launched on 29th April 1988. Joined the Northern Fleet on 30th December 1991 (five days aftr the collapse of the USSR).
3. AS-33 Laid on the 'LAO' plant in Leningrad on 28th November 1988, launched on 23rd November 1993. Reportedly joined the Northern Fleet on 16th December 1994, but status unclear and possibly no delivered. Ceased 1998.
The start of construction of AS-13. Note the large flood holes in what appears to be a curved bottom section of the outer hull. Source oosif.ru
This close-up of the forward starboard thruster without the outer doors fitted (or retracted) clearly shows the universal joint at the bottom. The thrusters swing downwards on arms and can be steered to maintain a 'hovering' position above the seabed. The rubber acoustic tiles can be clearly seen thanks to the snow.
Specification
Displacement: 1,390 tons surfaced, 2,000 tons submerged
Length: 69 meters
Beam: 7 meters
Draught: 5.2 meters
Speed: reported as 30 knots submerged (likely much less!), 10 knots surfaced
Operating depth: 1,000 meters
Crew: 36
Armament: none
Photo by Vitaliy Kostrichenko, Oct 30th 2009
The operational Project 1910 boats are based at GUGI's secret based at Olenya Guba on the Murmansk Oblast. The hangar in the background covers more sensitive boats including the Project 10831 Losharik:
A) hangar, B) Project 1910 UNIFORM Class boat.*
Project 1910 (right) laid up in Severodvinsk, Arkhangelsk Oblast, Russia. The smaller boat on the left is a Project 1851 X-RAY class. This Project 1910 did not move from 2004 until 2014.
Project 1910 not present in 2016 but an X-RAY is (may not be the same X-RAY as at other times):
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