Mystery explosion at Nenoksa test site: it’s probably not Burevestnik

Update September 2: If one believes CNBC’s story here then the cause of the incident was a failed recovery attempt of a prior Burevestnik missile test from 2018. In recovering the missile from the bottom of the bay something exploded under one of the vessels, which also damaged the missile’s reactor, leading to the radiation release. So there was no missile test, no reactor test, no launch, and equally there was no RTG or some other device responsible. I will leave the rest of the text below without updates so you can see my thought process, right or wrong, early on in this episode before much information was available.

I was going to stay away from this because there simply was not enough information to tell what happened, and the hot take factory had already run away with the story on the basis of close to nothing. Here is the most likely scenario as I see it. The explosion was not a missile launch test, and it was not Burevestnik, no matter how much arms control wonks want to think it was. It’s just unlikely based on the scant information available about the incident.

I have a different view from Jeffrey Lewis here. The notion that Russian Burevestnik program was in major trouble after moving from Novaya Zemlya test site is also probably incorrect. I think Lewis’ own commercial satellite imagery confirms the story that VNIIEF, the Russian nuclear research institute in charge of this work, basically tried to tell but couldn’t get out in time because people already piled in with speculation.

Jeffrey Lewis paid for this image
courtesy of Jeffrey Lewis and his institute who paid for this lovely image

They were testing the system on a platform at sea. According to some accounts the explosion blew the scientists into the water, which is why it took time for an accurate casualty count to come in as they were looking for their own people. It was not a missile launch, as such launches are easily detected by national technical means, and it was not on a rail launcher since we can clearly see one affixed on land at the test site. Why would they rail launch it from a platform at sea when they can fire it over the bay from the coast?

Update August 26: Looks like its not a RTG based on the isotopes detected, and instead a nuclear reactor. Also unlikely to have been a missile, and the initial explosion may have taken place underneath the platform rather than above it.

Let’s ask first order questions. Why did five leading researchers die? If it was a nuclear powered missile test why would they be near the missile? I know I’m always standing next to experimental missiles I’m testing, it’s the best way to see the explosion. If it was an experimental nuclear reactor (unshielded), why were they standing next to it at the time of the mishap? I know I always stand next to experimental nuclear reactors I’m testing. Typically when people stand around things, it is because they don’t expect them to explode or massively irradiate them.

The explosion was caused by a liquid fueled engine – why would there be a liquid fuel engine in Burevestnik? Subsonic cruise missiles have solid fuel as their boost phase. Ok here is the last question for Burevestnik theory enthusiasts. Imagine they are conducting a missile test on a small platform out at sea, and you believe that this is a missile powered by an unshielded reactor. I mean, kind of hard to shield a reactor on a relatively small cruise missile. In this theory Russia’s leading nuclear researchers are standing around an unshielded nuclear reactor on a barge, with the intent to turn it on. Forgive my skepticism.

I know you’re thinking, well maybe they lied about the platform and were testing it at the rail launcher site. So why were the scientists next to it then, and another question, why are there all these ships positioned in the flight path of the missile from the rail launcher? Wouldn’t the radiation from the reactor be a problem for them, the entire bay, maybe the towns?

Some in Russia have combined the two theories, suggesting that Burevestnik has a nuclear power component, but there is a separate liquid fueled engine for maneuverability. While interesting, its still unclear how either system actually powers Burevestnik and why a subsonic missile with maneuvering surfaces would remotely need liquid fueled thrusters or jets to maneuver. I’m raising this here to dismiss it because it doesn’t make much technical sense. We will get back to Burevestnik later.

VNIIEF’s statement, in classic Russian style, alluded to two types of projects without saying exactly what it was, a novel Radioisotope Thermoelectric Generator or a novel reactor type akin to U.S. Kilopower project. In my view they were indeed testing a novel Radioisotope Thermoelectric Generator with a liquid fuel engine combo. (That turned out untrue after it became clear that the different nuclides produced could only come from nuclear fission).

The idea being to use the RTG as a long term electrical heating solution to maintain thermostatic temperature inside the various components of a liquid fueled engine, either in a booster phase, or the canister itself, of a missile that needs to get up to speed very quickly from launch. Basically an atomic battery for a liquid fueled engine where the components have to be kept at a certain temperature in prolonged storage, otherwise the weapon has to be permanently connected to a power source. This is certainly not as sexy as a nuclear powered missile, but it’s much more probable as the real story behind what happened. That’s the story IZ eventually went with and (I believed it was closer to the truth than all the Burevestnik mania, but it turned out not to be a RTG)

RTG wikimedia
RTG design from wikimedia commons

Some of my musings on alternate explanations:

If we ask which secretive missile the Russian military is working on, that is principally for the Russian Navy, has most likely a high power liquid fuel engine – it’s could well be Tsirkon. Since Tsirkon has to be canister stored, and quickly sprint to a high velocity for its scramjet to work, most likely this missile could benefit from a RTG. It could be part of the canister storage system, or fall off as a booster. Some have also suggested Skif, a SLBM designed to be fired from the ocean seabed, even though that would violate a treaty banning such weapons. If its a liquid powered engine, then I’m skeptical on Skif and leaning towards Tsirkon, because the latter is likely to have a powerful liquid fueled engine/scramjet combo, and is actively being worked on whereas I’ve really not seen evidence of Skif being a thing. (it was none of these things either)

While we’re in the speculation business on RTG use, it might also be a maneuvering satellite. That sort of weapon could use a sustained power source, in space, and possibly have liquid fueled thrusters. Just working through the non-Burevestnik list here. If the radiation emitted sounds too high for a RTG, and I’m not an expert here so I don’t know how much radiation you get if you blow one up, I suppose it varies considerably depending on the type of material used and how much of it they were using. RTGs are fairly simple in design, but perhaps this RTG was novel and therefore more powerful.

Equally likely it was a novel nuclear power source, but again it begs the question as to the cause of an explosion, and why leading researchers would ever be standing around such a thing on a platform at sea. The obvious answer is they were setting up equipment, but I don’t see them testing an unshielded reactor off the coast of a town near Severodvinsk.

Now let’s imagine that the RTG story is a canard meant to distract us (which it turned out to be in retrospect). It could be a novel nuclear power source, but for what? Well, probably 10-20 different projects, at least those that I can think of. I’m not ruling out a component related to Burevestnik, but saying that something was tested with infrastructure associated with Burevestnik tests is like going to Kaputsin Yar and just guessing which missile was involved at a range testing 10 different missiles.

The scientists, the explosion and a source of radiation were all co-located which suggests they were working on something with explosive potential and a source of radiation. The radiation released seems quite small for a reactor, just my impression based on commentary from people who follow the nuclear side of things but perhaps too high for a typical RTG. So the circumstances  suggest it was something other than an unshielded reactor, involving an engine with liquid fuel propulsion, which should point us away from Burevestnik.

Moscow Times released a story from the hospital talking about exposure to Cesium 137 isotope, which while a byproduct of fission, is a source of gamma radiation. The thing is Cs-137 is total junk for power level and is basically one of the weakest isotope sources you can use for a RTG. Good PDF here with comparisons for those interested.

RTG isotopes 2RTG isotopes

So after initially leaning towards the RTG story, it seems that was a distraction and instead we are dealing with a nuclear reactor. There are several options for nuclear reactor tests with military applications at sea, from Poseidon torpedo to various types of ATGU’s, undersea atomic power stations, to of course our reactor for Burevestnik. However, to release these different isotopes it is likely that fission might have had to take place at the site, whereas in a missile the reactor would not turn on until after boost phase, which creates obvious problems since the explosion and material was released from the platform.

Back to Burevestnik

I wonder why people assume that Burevestnik is an open air flow reactor/ramject powered missile? Just because in 1960s U.S. project Pluto used this combination on a large supersonic missile does it make sense to assume that’s what Russia is working on as well? The U.S. tried to build 1957-1964, and it doesn’t make much sense that it is what Russia would try to build in 2019. Pluto was a large supersonic missile, with rocket boosters and multiple warheads designed as a supersonic low altitude missile (SLAM), while Burevestnik is a single warhead cruise missile shaped for subsonic or perhaps transonic flight. Its certainly not a mach 2 weapon.

project pluto
This is project Pluto in concept

Burevestnik clearly doesn’t look like a supersonic low altitude missile with those wing surfaces.

Burevestnik 2

this is burevestnik

Given Burevestnik appears to be a subsonic, or a transonic missile, not meant for supersonic flight and therefore not utilizing a ramjet which is better suited for mach 2+ it is probably not an open air flow system. Ramjets are highly inefficient at slower speeds and the wings on the missile don’t exactly look like a mach 2+ weapon. Burevestnik is going to have probably one of two propulsion types, direct air cycle or indirect air cycle. Direct air cycle just throws the air into the reactor and out the back. Highly radioactive. Indirect cycle is probably liquid metal cooled. Air makes contact with a heat exchanger that’s carrying the liquid metal from the reactor and goes out the back, much less radioactive. Of course maybe there is a nuclear power source just powering a turbojet and they’re not using the air for propulsion at all.

Also I don’t think its index is 9M730, although it was initially reported as such. There are still too many assumptions here about an experimental weapon without enough images or information, so in my view it is best to hold back on the guesswork.

Comments and feedback as always welcome. If you have alternative explanations please send them in. I do not know what it was, but there’s enough information to suggest that the hot take factory is wrong on this one.

6 thoughts on “Mystery explosion at Nenoksa test site: it’s probably not Burevestnik

  1. While there are some problems with the possibility of the explosion being Burevestnik, that alternative explanation has at least as much problems with it.

    First, I would like to point out that some of the issues pointed out here do have explosions. First is the presence of liquid fueled engine: No matter whether Burevestnik would use scramjet engine or something akin to GE J87 or its P&W competitor in ANP program, the thrust and cooling of a nuclear powered engine would rely on incoming airflow. Thus, you need either a very long takeoff roll or some other way get such a missile up to speed before the nuclear-powered system can generate enough thrust. So, launching it with a conventional rocket booster is an obvious solution. Burevestnik would almost certainly have a liquid or solid fuel engine to launch it. The launch videos that are available also support this as they appear to show a launch with conventional rocket booster.

    As for presence of the scientists near the explosion, that is really not a factor for or against it being Burevestnik. Sure, you don’t want to stand around Burevestnik being tested. But you don’t want to stand around Tsirkon of Skif being tested either. So, no matter what the system was it creates the same question: Why were those people around during the explosion. The only explanation I can think of is that the explosion didn’t happen during actual test but during a preparation for an upcoming test. And that applies equally no matter what system it is.

    Now, the RTG theory has some problems of its own. First is that while RTG could well be used for that kind of use, it is hard to think a reason why one would need a novel type of RTG for that purpose. The types of systems commonly used should work just a well. But even if it was a novel type of RTG, it could be easily tested separately or without fueled missile. The RTGs are extremely reliable as they have no moving parts. Why would there be a group of nuclear scientists present at such a test with fueled missile? A test with Tsirkon would far more likely have personnel from NPO Mashinostroyeniya present rather than from VNIIEF, wouldn’t it? Also, related is the presence of Serebryanka, for which is quite hard to find reason for if the source of radioactivity is from RTG. Finally, the radiation readings reported are difficult to explain with an RTG. For maximum efficiency, RTGs used alpha-active nuclides. This means that they radiate relatively small amounts of gamma radiation compared to their activity. And the types of radiation measurement systems used for measuring ambient radiation measure gamma, not alpha. Now, to get the reported dose rates in gamma radiation using nuclide that is primarily alpha-active, the release would have to been massive. The dose rates could be caused by reasonable release if it included nuclides that released high-energy gamma radiation, but the case if totally different if the release is alpha-active nuclides, such as those used in RTGs.

    Of course, all of the above questions would be explained if it indeed was some type of novel reactor power source. But if it was not used for Burevestnik, then what was it used for?


    • Thoughtful comment here, so let’s walk down the speculation road together, because I don’t believe alternative explanations can be weighed equally. The simple reason being is that the positive case for Burevestnik is weak, and the circumstances suggest it was something else. Also the linkage to Burevestnik exists entirely in the minds of people who want it to be that weapons program versus 10+ other things it could have been. That’s good enough for CNN but not good enough for analysis.

      – Cruise missiles are launched with solid boosters, especially subsonic ones. There is no reason to use a liquid fuel boost phase because its complicated, dangerous, and probably the last thing you want to add to a nuclear powered device.

      – I don’t know how Burevestnik’s reactor is cooled because I have not seen its design. I would guess its an indirect air cycle liquid metal cooled reactor, where the air makes contact with a heat exchanger, which is far less radioactive than doing a direct air cycle. I don’t think you need much speed to get that air going.

      – We have no evidence that it was a missile test, and all the evidence suggests it was a component test. There is also no proof that engineers from other design bureaus were not there, but for fun let’s turn this wonderful argument around. VNIIEF does not make missiles, only nuclear warheads and nuclear technology. So where pray tell were all the missile designers for Burevestnik’s alleged flight test? Quite likely there was no missile test at all. They were testing a nuclear power source, possibly connected to an engine or some other device.

      – Since the scientists, the explosion, and the source of radiation were all co-located it tells us that whatever it was, it was likely quite safer than an unshielded reactor and with an explosive chemical component. As such the circumstances of the test simply tilt us away from the Burevestnik missile theory and towards a component experiment theory, or some sort of nuclear power source. It is fascinating to read that nuclear power source + scientists must = Burevestnik as though there are not countless other nuclear power projects with military applications in Russia.

      – I am skeptical of your view that existing RTGs are good for X purpose or that nobody needs to test new RTGs together with new weapons/systems. You do not set requirements for Russia’s weapons programs. Under this logic, Burevestnik should not exist since its value added is somewhat dubious at best. Building a new RTG does not make sense for this purpose, but building a nuclear powered cruise missile totally makes sense?

      – Not sure its wise to speculate on how much gamma was actually released based on Russian sources since that story keeps changing. Which story do you believe? The 16x normal rate? the 20x normal rate? the 200x normal rate? So let me flip that and say, if it was a reactor why would the radiation die down within 1.5 hours of the release? Perhaps this is my own lack of nuclear knowledge here, but one can just as easily ask about the lack of radiation from a reactor explosion. In my view the gamma radiation released is inconsistent with a RTG unless the RTG was using a material that released more gamma radiation than you might typically expect. Let’s stop for a second, are we actually suggesting they were testing an unshielded reactor on a platform at sea? Because that’s what team Burevestnik thinks, and I believe there’s about a 0.0% chance of that being the explanation since they would not only irradiate themselves but also create a detectable radiation trail over their own bay.

      – It could all be explained by a novel nuclear power source, which is what VNIIEF also alluded to, akin to Kilopower project or a RTG design, which would not be used in Burevestnik. It could be used for at least a dozen or two dozen other applications that I can think of. From nuclear powered torpedoes and drones, to underwater atomic substations, sosus arrays, lasers, road mobile nuclear power stations, certain things in space.

      I would add that numerous journalists and experts, with diverse sources of information in Russia, have also all indicated that RTG is the most likely explanation followed by novel nuclear reactor for some application other than Burevestnik, and that there was no missile test. So there is a cluster of people with their own sources all of whom suggest it was some other military application.

      I think we should also consider that it could have been used to power a Terminator-style time machine to send Putin back into the 1980s in an effort to prevent the collapse of the Soviet Union. That theory is not much more speculative than the Burevestnik theory and could be similarly adjudicated via commercial satellite imagery 🙂


  2. Maybe the burevestnik engine is powered by isotope decay. I think for a subsonic cruise missile you need order MW power. This could be provided by 60 kg of cobalt 60. Including shielding to capture gamma energy and provide thermal reservoir, this would be few hundred kg. power transfer to the engine by a heat pump working with some liquid metal coolant.

    it may be far fetched but:
    – relatively easy to develop (you can substitute electric heating during much of development)
    – the incident would be a failure of the heat pump system – this releases only limited radioactivity as reported


  3. As it seems now, there *was* a Burevestnik reactor explosion, however during the recovery of a Burevestnik crashed in mid 2018.

    This would explain pretty much all the inconsistencies you mention above, including the (relatively) low and short-term radiation values: The amount of fission products accumulated in a reactor is *roughly* proportional to the energy previously released. In other words, Chernobyl released the fission products of about 200 days @ 3 GW (thermic). The burevestnik reactor *may* have operated a few hours before flying, maybe even much less (remember, the flying reactor can’t be shielded – thus probably a “new” reactor was used). And its power may be around 1 MW. From these facts I would expect the Burevestnik explosion to release about 10^6 times less fission products than Chernobyl.

    I think you have followed the wrong track (RTG), propagated by those trying to cover up the reactor explosion (remember the Japanese officials trying to negate the Fukushima meltdowns for about two months …). Fact is – every nuclear scientist (including the Sarov officials, btw) knows that a reactor blew up. The fission product detected are unambiguous. It might be wise to update your above statements accordingly.


    • No I followed the correct track, they were not testing a missile and they were not testing a reactor for the missile either – RTG was a reasonable early explanation at the time when there was limited information available most of which pointed against the initial ‘hot take’ stories. Well it turned out not to be a RTG, but at the time nobody knew anyway so I always enjoy the ‘in hind sight, based on no evidence, we were geniuses to have ventured a guess and gotten lucky.’

      Nuclear scientists didn’t know a reactor blew up and were just speculating. Later on it became clear the release came from a fission device, but even still we can deduce that likely the reactor did not blow up, but suffered damage that resulted in a rod/rods coming out. So all the people saying it was a missile test got it wrong, and the people saying it was a reactor test got it wrong, and the people claiming that a nuclear reactor blew up technically are also wrong.


  4. “(That turned out untrue after it became clear that the different nuclides produced could only come from nuclear fission).”

    So the RTG theory is completely incorrect based on the presence of short-lives fission fragments. (Unless it is a subcritical reactor RTG…)

    But I think we’re overlooking one possibility: that it was a low yield test of the Burevestnik “warhead”.

    A nuclear powered cruise missile needs no separately defined warhead; simply “re-configuring” the heat source (explosively) turns the missile into a nuclear bomb.

    A nuclear explosion could be created very easily by having the test missile run at low power on a static stand (generating a plethora of neutrons) and compressing the reactor with explosives (possibly with the addition of a reflector element).

    As for scientists being killed – do you really trust Russian government run “news” sources?

    Russia may have just violated both the CTBT and the older NTBT and claimed “oops, we had an accident…”.


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