Following the recent mishap with the Soyuz, Kazakhstan's deputy minister for defense and the aerospace industry said that about 22 tons of fuel (kerosene and liquid oxygen) were dumped/fell over the Kazakh countryside. Somewhat oddly, it seems to me, he noted that radiation in the area in question was at background level, which seems like a redundant but anxiety-provoking clarification, since why could there be any additional radiation anyway? Anyway, my question for those who might be in the know, is whether 22 tons of kerosene and oxygen seems like a potentially hazardous amount, also bearing in mind that this fuel was dumped as it was combusting at 47 kilometres into the air?

Here is the original report for Russian speakers:


UPD: Another report also alludes to 820 kilograms of nitric acid and what the Russians call heptyl. Oddly, this does not seem to be in the Kazakh media account, so the information presumably comes from Roscosmos rather than the Kazakhs.

  • $\begingroup$ Is your main question just "does this seem like a lot?" Do you mean is the quoted quantity correct? Or would you like to know what would have happened (did the LOX and kerosene all burn up together, or is there a big oil slick?) I think if you are only asking if it "seems like a lot" then that may not have a real objective answer. See if you can narrow down a little to what it is about this that is really capturing your interest. Oh, and Welcome to Space! $\endgroup$
    – uhoh
    Oct 18, 2018 at 8:35
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    $\begingroup$ Thank you! I have been lurking for ages! :) My question is whether this seems like a dangerous and potentially hazardous amount. That is a pretty subjective evaluation though, I guess, as you say. But given the height of dump, the likelihood of slicks is pretty nonexistent. But now I am more intrigued by the follow-up report (sketchily attributed, to say the least) of hundreds of kilos of nitric acid and heptyl also being detected. The Kazakh minister dismissed this saying, Soyuz doesn't use heptyl, so something is off. $\endgroup$
    – PeterL
    Oct 18, 2018 at 8:48
  • $\begingroup$ Okay that's great! It's best to now go back and edit the text of your question post itself, and refine the title so that this will show up in the right future searches by other readers. $\endgroup$
    – uhoh
    Oct 18, 2018 at 9:10
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    $\begingroup$ You can take this question (further) out of the space of opinions by phrasing it as "What are the dangers of..." $\endgroup$
    – user10509
    Oct 18, 2018 at 11:03
  • $\begingroup$ BTW, there have also been questions about fuel-dumping over on Aviation, and the common theme over on that site is: there is an awful lot of air in the atmosphere, those amounts are less-than-microscopically tiny in comparison. $\endgroup$ Oct 18, 2018 at 20:45

1 Answer 1


If you were close by it would be very bad to be around, but there is actually very little risk on this because these were dumped so high up. When the rocket broke up it was going moving quickly upward, so when it broke up these components would most likely have turned into aerosols, being dispersed in the atmosphere. I'm a bit fuzzy as to whether the rocket exploded or broke up, if it exploded a significant proportion of all these would be consumed anyway. Assuming it just broke up I'll look at each component separately:

  • Oxygen: A liquid oxygen dump near the surface would be very dangerous to those around because of the risk of explosion, but it will dissipate into the atmosphere. Adding oxygen to an oxygen-nitrogen atmosphere does not cause any risk
  • Nitric acid: again, not something you'd want to be close to, but again the components will dissipate and add to the other nitric acid in the atmosphere causing acid rain. A pollutant, sure, but not a real hazard, 820kg is a drop in the bucket
  • Heptyl: This is how Russians refer to UDMH, aka Hydrazine. Hydrazine is very toxic and dangerous for humans to be around, and Kazakhstan has had hydrazine rained down on it many times when rockets have failed. It's nasty but no human deaths have been attributed to it as a result due to the remoteness of the region. It does break down rapidly when exposed to oxygen, so how much will actually reach the surface from that far up is hard to calculate
  • Kerosene: kerosene is released into the environment already when it's burned as jet fuel (very similar chemically), lamp oil, heaters and when used as a solvent. The dispersal of a few tons of this in the upper atmosphere isn't awesome, but it's not a big deal either. There's lots of detail about human effects in this CDC report

None of this is healthy to be around, if a tank of the stuff survived the rocket's breakup and made it to Earth then it's a different story if it lands in a populated area. If it lands in the remote steppe, well, that's the best place for it to happen really, which is why they built a spaceport there in the first place.


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