Cold War Targets: The Soviet HEN Class

The Soviets were our primary antagonists during the Cold War period,  and they developed and deployed a number of different submarine designs. These designs were based on a combination of factors, starting with available technology to build the boats. How they were to be employed, what targets they were designed to counter, etc.

The first generation of the Soviet Nuclear Submarine fleet was referred to in the West by the name HEN. This was a blending of the first letters of three classes of boats: Hotel, Echo, and November.

Each of the three classes had a different mission. The Hotel class were designed as Ballistic Missile Submarines,  or SSBN’s, known in the trade as “Boomers”.  Exho Class were SSGN’s used to counter US Carrier Battle Groups and carried anti-ship missiles. November class boats were fast attack, or SSN’s, armed with torpedoes and sent out to stalk other ships and submarines.

All three of these classes shared one common trait: Their nuclear power plant, and it is this that made them so dangerous for their crews, and those who supported them.  What made these boats so dangerous was that the nuclear power plant was a single-loop reactor system. We’ll talk for a minute about nuclear propulsion before proceeding.

Nuclear propulsion systems use a nuclear reactor to generate heat. That’s all it does: warm things up.  Pipes containing some form of fluid, either water, liquid sodium, liquid metal, etc, pass through the reactor and the fluid inside is heated. These pipes then pass through a heat exchanger which transfers the heat to other pipes containing water, and this water is super-heated to steam. That steam is then used to drive turbines which are either directly connected (through gears and transmissions) to the submarine’s drive shaft(s), or to electric generators which turn the shafts. Some steam is also bled off to run electric generators which provide what is known as “hotel power”. This is the electricity which runs the heating and cooling systems, lights, water pumps, etc.

Now, most systems are dual-loop, or higher. inthat there is one loop of fluid which runs through the reactor, the heat from that loop is transferred to another loop of fluid, and that latter possibly to a third. This prevents the radioactive fluid (which passed through the reactor) from contaminating the other fluids. After all, these have to pass through machinery (turbines) which must be maintained, etc.

What set apart the HEN class boats was that they used a SINGLE loop system. In other words, the liquid traveling through the reactor was turned to steam, and that steam flowed through the turbines, etc.  It caused no end of radiation problems for the engineering spaces, and was a danger to not just the crew, but shipyard workers who had to do maintenance and repairs.  As an aside, the infamous K-19, of “The Widowmaker” fame, was a HEN class boat, a Hotel SSBN.

Regardless, the three types of boats making up the HEN class are as follows:

HOTEL:  These were the first Soviet SSBN’s, and carried three SLBM’s in a special launch system behind the sail. These missiles were liquid fueld, a danger in and of itself, and the submarine was required to be surfaced in order to launch it’s missiles.  The missiles carried were the R-13 ( NATO SS-N-Sark) for the Hotel I class, and the R-21 (NATO SS-N-5 Serb) for the HOTEL II class.  The former had a range of ~350 NM. The latter had a new gas-ejection system which allowed the HOTEL-II to remain submerged to about 40 feet, and launch from there, plus had an increased range of ~750NM.

The relatively short range of both these missiles meant that these submarines had to come relatively close to the United States coastline, and could only threaten the coastal areas. Later advances by the Soviets would soon change that, however.

In total, 8 boats of the HOTEL class were produced. 7 of these were refitted and upgraded to the HOTEL II class starting in 1961, with work completed in 1963. In 1969, K-145 was further modified to a HOTEL III class, to be used as a test platform for the newer R-29 (NATO SS-N-8 Sawfly) which was installed on all later DELTA class SSBN’s.

The Hotel Class was based off of the Soviet NOVEMBER class SSN, with the basic sail design of the GOLF class added, including the missile compartment.  and had dual reactors driving twin shafts at ~20,000 HP. She displaced ~5500 tons submerged, and a speed (submerged) of 26 knots. She was, for the time,  a fairly noisy boat, and once detected, easy to track.  It was considered by many that, although she could theoretically hit a portion of the United States, that her real purpose was in threatening Europe, and major NATO bases and facilities.

I’ll write about the ECHO I & II class in the next episode.

Soviet Hotel K-19 at Sea

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7 Responses to “Cold War Targets: The Soviet HEN Class”

  1. 1 SCOTT the BADGER
    April 25, 2010 at 13:52

    Given Soviet QC, if a P-3 sank one, all the cod in the Atlantic Basin would glow in the dark. Given the reactor accidents that Hotels had, the P-3 wasn’t really needed, as they were self eliminating. Hard to say who was braver, the poor saps who had to serve ov them, or you guys who went out looking for them. I hear that the MIKE might be getting ready to leak from it’s reactor. And the MIKE was a much better sub than a HEN.

  2. 2 ClarkWard
    April 26, 2010 at 10:53

    Another problem with running a reactor/engineroom with only a primary is that as the coolant flashes to steam, it erodes away the cladding on the fuel elements, thus by design you produce contaminated steam. I’m sure that they made the cladding thicker to compensate for this (not!) but nonetheless, it gets eroded. Assisting this process is the fact that as the water flashes to steam, any non-volatile chemicals (used to maintain rx chemistry) get concentrated in small areas, resulting in wild variations in pH, exacerbating this problem.

    Sorry to get all reactor-nerdy on ya :) But I do love to be a submarining nerd.

    • April 26, 2010 at 13:45


      not a problem, shipmate! The idea here is to share what we know, and correct things we might be mistaken on.

      What you say is very true, and, in fact, it was material failure in the coolant pipes that led to the catastrophe on K-19. This class was loud anyways, due to the MCPs and other machinery that were 1st generation and not shock mounted. Ill get into that in my next post, either later today/night or tomorrow about the NOvembers.


  3. 4 virgil xenophon
    April 26, 2010 at 14:29

    Tim, as you may or may not know, I’ve been busy with other things (extended deep-water ocean sailing on the “Bounding Main”) so I’m just now over here catching up on your, as always, excellent posts, so forgive the absence. (BTW, I luuvvved your comment over at el tee Rajiv’s place about how to handle the toilet problem!Snerk,I ALSO carry a “master key” in the trunk of the car as part of my emergency kit–you just never know… :) )

    • April 26, 2010 at 14:38

      Great to see you back! I am envious, getting to sail the vasty deep with a fine woman, a good ship, and a stock of rum. Sigh…..

      Rajiv seems to me to be a great officer, with much potential. He writes well, and I can feel his frustration at times with how things are, versus how they ought to be. :)

  4. September 8, 2010 at 16:43

    Idaho National Laboratory’s Sodium-Cooled Fast Reactor is designed for management of high-level wastes and, in particular, management of plutonium and other actinides.


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