Comment by perihelions | Hacker News Reader

Comment by perihelions | Hacker News Reader

That sus red smoke is nitrogen tetroxide [0], and the other fuel would be one of the hydrazine derivatives (I believe UDMH [1] here, given that the Twitter thread says this was a Long March 3B). It's exactly as poisonous as it looks.

[0] https://en.wikipedia.org/wiki/Dinitrogen_tetroxide

[1] https://en.wikipedia.org/wiki/Unsymmetrical_dimethylhydrazin...

edit: Oh yeah, those of you who are concerned about the toxic fumes from gas stoves (popular HN topic), this is exactly* that thing—except the stoves' are measured in micrograms and what you're watching in rocket disaster videos is multiple tonnes. One of these lands on your house, and you will not need to worry about long-term cancer risks ever again.

*(To be accurate, NO2 ⇌ N2O4 interconvert in dynamic equilibrium)

If you're interested in this sort of stuff, I cannot recommend the book Ignition enough. It's got the information density of a textbook, but it's filled with hilarious commentary and fascinating anecdotes.

https://library.sciencemadness.org/library/books/ignition.pd...

Ignition! is back in print, happily.

Not only that, it's half price! With free shipping!

Holiday promo at Rutgers University Press (I'm not affiliated with them, other than being a recent customer :)

https://www.rutgersuniversitypress.org/holiday-sale/

https://www.rutgersuniversitypress.org/ignition/978081359583...

Ignition! is the book that reconciled me with chemistry.

You might also enjoy Alchemy of Air.

Ordered, thank you!

I think we all would like to hear your story.

I bet it ends with a bang.

Well there’s an hour I’ll never get back. Had to close the tab or I’d be stuck for a few more hours!

Nicely uphill from the rice paddy this video was taken in, too. I'm sure that rice will be extra delicious as the rains wash the residues into the field.

WP about N-Nitrosodimethylamine, which apparently dimethylhydrazine is a precursor to "Contamination of drinking water with NDMA is of particular concern due to the minute concentrations at which it is harmful, the difficulty in detecting it at these concentrations, and to the difficulty in removing it from drinking water. It does not readily biodegrade, adsorb, or volatilize. As such, it cannot be removed by activated carbon and travels easily through soils. "

That's a real nightmare. Trace amounts of perchlorates (speaking of rocket chemicals) in water are attributed to some bad health effects, and the compounds you're talking about are so much worse.

SpaceX's Dragon capsule also carries hypergolics and they know not to mess around with the stuff, even trace residues are a concern when egressing astronauts and salvaging the capsule. There are similar stories from the Apollo era. Quite jarring that the Chinese program would knowingly and repeatedly douse civilian populations in them.

> *(To be accurate, NO2 ⇌ N2O4 interconvert in dynamic equilibrium)

... and isn't N02 red while N204 is clear? So, to be pedantic, the red they're seeing is N02?

Exactly!

> what you're watching in rocket disaster videos is multiple tonnes

But this one hardly had multiple tonnes,hadn't it? It was a spent side booster, so the most of the stuff had been burned before the separation, I think.

When you send a rocket to space, you want a margin for error. Usually this is couple percent for the first stage.

Given that the total weight of fuel at launch in this thing is couple hundred tonnes then yes, the margin for error can be multiple tonnes, but we will not know because the exact value will depend on the particulars of this launch.

if its hypergolic fuel you can be almost certain it was less than a few hundred pounds. "tonnes" of hypergolic fuel would be enough to level the hillside and send the iphone through your cranium.

most people cannot appreciate just how powerful hypergolic fuels really are. theres just no comparison, even when you see them IRL.

An example is the 2013 failure of a Proton-M at Baikonur, nearly full of propellant shortly after launch, carrying several hundred tons of hypergolics:

https://www.youtube.com/watch?v=rfuXUr-_Rns ("Proton M Rocket Explosion 02/07/2013")

https://www.youtube.com/watch?v=ycRVAcZC5R4 ("More Videos Of The Russian Proton M Launch Failure And Explosion With Three GLONASS Satellites")

(There's lots of different camera angles on YouTube; not sure which one to post).

Uh for the long march 3b boosters udmh / n2o2 is the primary propellant. That entire booster was full of it, so yes, it's liable to be a tonne or so left over (full propellant mass in the stage is double digit tonnes)

https://en.m.wikipedia.org/wiki/Long_March_3B

You don't need tonnes of it to be extremely toxic. The stench of it even from a properly burning engine is extremely nasty and sickening. I'm talking about the trace residue that you get from non-stoichiometric burning in the engine. Add to that all the excess added as guidance margin and whatever is trapped in the plumbings.

About 2% residuals is common in rocketry. This was probably 2-3 tonnes of propellant left int the tank when it impacted.

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