Talk:Hypergolic propellant

Untitled

Surely that should be Aniline-Nitric acid, not Hydrazine-aniline? PML.

"... the trend in ICBMs has been to move toward solid fuel boosters."

Oh man, this sounds almost sarcastic to me. There are trends in ICBMs, really? What's hot this year, haha.

Not funny. -- .~.

Article talks about "hyperbolic" engine. That's probably incorrect, but someone who actually knows should make the edit.

4th Paragraph

The fourth paragraph opens with the sentence: "They are less likely to explode when starting." But the previous sentence refers to both Solid Fuels and Hypergolic Fuels - so which is less likely to explode? I assume Solid Fueled rockets because the article implies they're more stable, but I'm not a rocket scientist.

The article for hard start seems to focus on hypergolic fuels, so I would assume that they are more likely to explode than solid fuels. Solid propellants should not explode if the nozzle opening is sufficiently large to prevent a buildup of pressure inside the engine. I suppose a hypergolic engine could explode if the components were mixed too quickly, in the wrong proportions, etc. I am not going to make any changes until we can get a source. --71.227.190.111 00:45, 16 July 2006 (UTC)

I think you misread the article. Hard start is particularly an issue with non hypergolic liquid fuels, as in addition to the fuel and oxidiser entering the chamber, ignition and associated timing is required. Ignition failure or delay is the normal cause of a hard start. Hypergolic fuels self ignite on mixing, so the ignition step is not required/not as critical.The specific inclusion of hypergolic fueled systems in the hard start article is, I believe, because although a hard start is less likely with a hypergolic fuelled rocket motor, it is by no means impossible. So my understanding is that in order of risk of startup is liquid fuel non hypergolic - hypergolic - solid fuel.

Solid fuel rockets are essentially uncontrollable and fixed thrust, so lack flexibility. Liquid fuelled rockets can provide variable thrust, can to get higher specific impulse, and in some cases handling is easier than for hypergolic fuels. On the pad ignition is easier to control. Thus a common set up is solid booster/liquid fuelled first stage, with hypergolic upper stage(s) where ignition is required in flight. The Shuttle main engines are liquid fuelled, but the orbital manoeuvring system is hypergolic.

(Fair use image removed by bot) Serious hard start --Shoka 23:03, 24 October 2007 (UTC)

Linking to disambiguation pages

Perhaps the disambiguation page was created after this, but I'm so tired of articles linking to disambiguation pages, when it clearly should be linked to an article. Anyway, I linked MMH properly, and not to a disambiguation page.

HTP / kerosene

Why isn't this a "true" hypergolic? In an article on rocketry, the crucial factor making hypergolic propellants of interest is their simple and reliable ignition, without the need for separate igniters and the risk of hard starts. Although the British HTP / kerosene engines did use a prior catalytic decomposition, they had all the engineering benefits of being hypergolic engines (just look at their reliablilty record, compared to their contemporaries). In a purely chemical context, the question of whether cold HTP + kerosene is hypergolic is indeed arguable, their place in rocketry seems secure. Andy Dingley (talk) 13:13, 28 April 2008 (UTC)

hypergolic means the two propellants spontaenously chemically ignite on contact. Kerosene and H2O2 do not. DonPMitchell (talk) 19:12, 3 November 2008 (UTC)

Kerosene and _hot_ HTP (from the prior catalytic decomposition) are hypergolic though. Andy Dingley (talk) 10:01, 4 November 2008 (UTC)

Etymology?

Does anyone know anything about the etymology of the term "hypergolic".? 95.89.154.146 (talk) 02:05, 8 May 2009 (UTC)

hyper + ergein ("lots of work = energy"). So hyperergolic. Say that quickly ten times and you will have reduced it to hypergolic. 2A01:CB0C:CD:D800:ED8F:60EF:8209:7153 (talk) 15:35, 11 April 2021 (UTC)

Correct usage

Strictly speaking it's the propellant combination that's hypergolic, not the propellants themselves. I've restored a sentence that stated that the term "hypergolic propellant" is commonly used, even though that's not strictly correct. John added a cn tag to this, but the title of the article itself presumes that it is in common use. If we don't want to state that, then we should perhaps rename the article to just "Hypergolic". Martijn Meijering (talk) 16:48, 23 October 2010 (UTC)

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Hypergolicity vs pyrophoricity

This is very poorly explained currently by the relevant articles. The current text makes it sound like the two are unrelated (or even mutually exclusive) phenomena, when (at least in my understanding), pyrophoricity is a special case of hypergolicity (a pyrophoric substance is hypergolic with room-temperature air).

Is my understanding about the relationship between the two phenomena correct? Or is there some technical reason to treat "pyrophoric" as distinct from "hypergolic with air"? This needs to be elaborated in the relevant articles. --NetRolller 3D 13:08, 1 March 2018 (UTC)

Your conclusion is logically plausible, although logic isn't popular hereabouts as it's too close to WP:OR / WP:SYNTH and it's preferred to use the commonly used terminology, as evidenced by WP:RS. It's not unusual for a situation like this to be "true but unhelpful". Workers within the field needing to distinguish between hypergols and pyrophores find it more useful to regard the terms as disjoint, rather than hypergolic being a hypernym of pyrophoric. It's just not helpful to have to qualify "hypergolic" every time as "hypergolic with air" or else "hypergolic, but not with air". So the term isn't used for materials which are pyrophoric with air, unless it's in a more specific context. Many hypergolic compounds are also pyrophoric, but these behaviours are regarded separately. TEA is pyrophoric, and is used as TEA-TEB as a rocket engine starting fluid (and why Falcon Heavy's central core wasn't recovered). As they're pyrophoric, they have to be stored carefully and pyrophoric behaviours are definitely not wanted. For Falcon Heavy it seems as if some oxygen ingress into the ground-side storage system had already reacted with some of the igniter liquid, reducing its potency. The central core ignited, but didn't reach full thrust as expected and so the on-board computer aborted the attempt to recover it.

The main concrete distinction is the time issue. Owing to their different fields, "pyrophoric" is usually a term from the safety field and "hypergolic" from rocketry, a material is seen as pyrophoric if it will react with air (eventually), but a useful hypergolic must react immediately to be useful. So a slow-reacting material can be dangerously pyrophoric and hard to store or handle, yet not counted as hypergolic because it's unreliably slow.

Finally there's the issue that a single material can be pyrophoric (the air is implicit), but hypergols really refer to a combination of materials. So a hypergolic mixture might be a hypergol, but just the one component of it isn't regarded as such. Some mixtures have a relatively benign alcohol fuel and then nitric acid. Neither component is considered hypergolic alone.

I wouldn't rewrite it extensively as you might be thinking. It would become confusing, as this is really a terminology question rather than an ontological one. At most, write a footnote and keep it out of the main article flow. I'm more concerned about phrases like, " They are therefore sometimes called storable liquid propellants." when this isn't their defining characteristic (and there are some storables which are non-hypergolic, such as kerosene+IRFNA). NASA isn't immune either, with leads like "Hypergolic fluids are toxic liquids that react spontaneously and violently when they contact each other." when it's hard to thing of such an energetic combination that isn't toxic, and anything that's immediately on fire is considered harmful too, but again it's not their defining characteristic. Andy Dingley (talk) 15:52, 1 March 2018 (UTC)

I'm not proposing replacing "pyrophoric" altogether, but rather getting rid of claims like something that's "pyrophoric, but not hypergolic" (especially annoying in case of TEA-TEB, with the Falcon 9 apparently relying on the hypergolicity of TEA-TEB with LOX for in-space restarts). I would also like to add something like "Substances that are hypergolic with air at room temperature are said to be pyrophoric", but right now it sounds like this is somehow explicitly excluded from the definition of hypergolicity. And yes, I'm aware of the use of "hypergolic" in certain circles as a strict synonym for "hydrazine-based" (see also: liquid methane is certainly cryogenic, but is it "cryogenic"? Not according to those who strangely reserve that term for LH2), but this is kind of a misuse of the term, and it's probably not how the article should define it. --NetRolller 3D 11:26, 6 March 2018 (UTC)

References

I'm no expert, but it feels like the confusion might have come from the use of two pyrophoric substances together. The mixture is not hypergolic, only more pyrophoric if I understand it correctly. I edited the related technology paragraph to make this a little clearer. Amphioxi (talk) 23:21, 14 October 2020 (UTC)

Rolls Royce RZ2 Mk3

Just for interest the RZ2 MK3 engines used on Blue Streak used a hypergolic starter. This was put in place By the RR representative just before the floor beneath the engine chambers was removed. The starter wires lashing about as the main engines ran up at -4secs was a problem, bearing in mind the nickel tubes of which the engine chambers were formed, were not overly strong.Drg40 (talk) 19:11, 8 July 2019 (UTC)

New info and changes

Hello all, I have gone and changed some names around and added further historical context based mostly around Clark's book

I have also deleted the first citation needed section in the "history" section as I could not find any evidence of this and Clark lists Walter specifically as the first to stumble upon hypergolicity

I am fairly new to Wikipedia, so review and help would be appreciated, please let me know if I messed anything up.

Thanks all! Mameyn (talk) 19:48, 14 September 2021 (UTC)