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Comment by jjk166 | Hacker News Reader

1) Fuel spills happen as a regular part of working with fuels (leaking pipes, loose fittings, safety purges, general clumsiness, etc) not just rocket explosions.

2) Even if a rocket explodes in the air it is unlikely all of its propellant will completely burn up (fuels aren't mixed, the ratios are optimized for a specific combustion conditions, and there are multiple tanks, etc), and there are many failure modes besides "massive explosion"

3) Just because the main component of a fuel will boil off eventually doesn't mean chemicals added to the propellant or produced in side reactions will

4) Hypergolic just means chemicals spontaneously combust on contact with one another; it has nothing to do with environmental risk.

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> 3) Just because the main component of a fuel will boil off eventually doesn't mean chemicals added to the propellant or produced in side reactions will

What do you have in mind that exists in quantities large enough to make things "extremely toxic"?

> 4) Hypergolic just means chemicals spontaneously combust on contact with one another; it has nothing to do with environmental risk.

Nothing except if you look at the actual list of rocket fuels that get used.

> What do you have in mind that exists in quantities large enough to make things "extremely toxic"?

I don't know where you are quoting "extremely toxic" from but even small quantities of toxic chemicals can be cause for concern.

> Nothing except if you look at the actual list of rocket fuels that get used.

Just because a square's a rectangle doesn't make a rectangle a square. Hypergolics are toxic does not equal non-hypergolics are non-toxic. For example, hydrazine monopropellant.

> I don't know where you are quoting "extremely toxic" from but even small quantities of toxic chemicals can be cause for concern.

Look up a couple comments in the thread. "I was under the impression that regular use of rocket fuel made a lot of land extremely toxic."

And we can't just assume there are harmful additives in meaningful quantities.

> Just because a square's a rectangle doesn't make a rectangle a square. Hypergolics are toxic does not equal non-hypergolics are non-toxic. For example, hydrazine monopropellant.

Okay, technically it spontaneously decomposes upon contact with a catalyst. That's so close to the definition of hypergolic.

Also it was pretty clear what they were saying. You can nitpick the wording, but their underlying point is still valid. SpaceX isn't using toxic fuels.

> And we can't just assume there are harmful additives in meaningful quantities.

No one's assuming there are, but the onus is to prove that there aren't.

> Okay, technically it spontaneously decomposes upon contact with a catalyst. That's so close to the definition of hypergolic.

But that's not WHY it is toxic. A substance can be not only non-hypergolic, it could be completely non-flammable and still be toxic, like say Carbon Tetrachloride, which is why the parent comment that I was replying to saying "since it's not hypergolic, it's therefore not toxic" is wrong, which was the thing I was trying to correct. SpaceX isn't using toxic fuels, but not because they are not using hypergolic fuels.

> No one's assuming there are, but the onus is to prove that there aren't.

For an environmental assessment, yes. For someone casually arguing against the area becoming "extremely toxic" then we should need a reason to suspect large amounts of very bad additives.

> But that's not WHY it is toxic.

Yeah but nobody said that.

The post was giving reasons the area isn't being made toxic, and one of those reasons is because out of the list of normal rocket fuels only the hypergolic ones are terrible, and they're not using those fuels.

It's fine to point out that it's not directly because of hypergolic or not (though there are strong correlations based on how reactive things are), but it doesn't affect the actual point they were making. You made it sound like a rebuttal when it's not a rebuttal. At worst they worded it badly.

> 4) Hypergolic just means chemicals spontaneously combust on contact with one another; it has nothing to do with environmental risk.

Lmao, what are some hypergolic propellants that aren't toxic? They're insanely reactive by their very nature, that means they will react and fuck with anything that's alive. They're intrinsically incredibly toxic.

Just because hypergolics are toxic doesn't mean non-hypergolics are non-toxic, which was my point.

That being said, there are plenty of propellants used as part of hypergolic combinations that aren't toxic. For example, oxygen, used as part of the hypergolic ignition system for SpaceX's merlin engines.

Liquid oxygen as a hypergolic propellant? No. Rockets do not use liquid oxygen as a hypergolic propellant.

Merlin engines combine TEA-TEB with liquid oxygen to start the engines but do not use TEA-TEB as a propellant. TEA-TEB also spontaneously ignites with air; that shit is insane but you deliberately chose not to mention TEA-TEB because you know TEA-TEB would fuck you up (presuming you could even consume it without catching fire first!) Leaving out such a pertinent detail leaves it hard to believe you're not arguing in bad faith.

Why are we even talking about hypergolic propellants? Because a fear mongering comment upthread suggested that rocket propellants are extremely toxic. Scratch hyperbolic propellants off the list and what are you left with? Kerosene, methane, hydrogen, and oxygen. None of these present a significant toxicity threat, the worse of them is kerosene which can contaminate the soil and groundwater but all of the others vaporize harmlessly. So the fear monger was trying to cash in on the toxic reputation of hypergolic propellants to insinuate that Starship presents such a threat itself. This is complete nonsense, a bad faith argument that even a single minute of research can refute.

> Liquid oxygen as a hypergolic propellant? No. Rockets do not use liquid oxygen as a hypergolic propellant.

No, I said they use liquid oxygen as a propellant, and they use liquid oxygen as a hypergolic. The fact that this doesn't make LOX a hypergolic propellant is precisely my point.

> TEA-TEB also spontaneously ignites with air

> you know TEA-TEB would fuck you up

EXACTLY. Hypergolic is a property of the combination of chemicals, toxicity is a poroperty of a single chemical. Air is non toxic no matter what you combine it with. TEA-TEB is toxic no matter what you combine it with. Air being hypergolic with TEA-TEB does not suddenly make it toxic, nor does it suddenly make TEA-TEB non-toxic.

I'm not arguing in bad faith, you just are fundamentally misunderstanding what point I am trying to make, which again is that hypergolicity != toxicity. No more, no less.

> Scratch hyperbolic propellants off the list and what are you left with? Kerosene, methane, hydrogen, and oxygen.

You are repeating the misunderstanding about hypergolicity. Scratch propellants that can be used in hypergolic combinations off the list and you have nothing. Scratch hypergolic propallant COMBINATIONS off the list, and you still have non-hypergolic combinations of all those highly toxic propellants. Methane and oxygen are both non-toxic, but that has nothing to do with the fact that they need an ignition source to burn with one another.

"Now it is clear that anyone working with rocket fuels is outstandingly mad. I don’t mean garden-variety crazy or a merely raving lunatic. I mean a record-shattering exponent of far-out insanity.

There are, after all, some chemicals that explode shatteringly, some that flame ravenously, some that corrode hellishly, some that poison sneakily, and some that stink stenchily. As far as I know, though, only liquid rocket fuels have all these delightful properties combined into one delectable whole."

Isaac Asimov, from the leading words to John D. Clark's "Ignition!"

While technically true, in rocketry - where the term was born - "hypergolic" mostly mean "of hydrazine family", which are (almost all extremely) toxic.

So it's a moot point to talk about the fine print. What was meant is that SpaceX doesn't pollute the land with poisonous fuel of the Starship, and the one argument is that the fuel isn't poisonous to begin with.

(And I'd really like to know what kind of additive would be in liquid methane - medium cryogenic - which Musk hopes to keep adding on Mars and which is toxic.)

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