Is monopropellant/RCS hypergolic propellant?

[RandomRyan]

So, is RCS or monoprop or whatever you call it hypergolic?

propellants spontaneously ignite when they come into contact with each other.

[MinimumSky5]

As far as I'm aware, no, as only fuel mixtures are hypergolic, not individual fuels. Most Monopropellants (hydrazine, hydrogen peroxide for example) require a catalyst to decompose, and are actually quite stable at stp.

[Nibb31]

by definition, a monopropellant cannot be hypergolic.

[Hcube]

Hmmm technically you could have an instable propellant that would react with itself... Or say a racemic mixture with one isomer reacting with the other... Although its pretty much impossible.

[cfds]

The most common monopropellants, hydrazine and hydrogen peroxide, decompose exothermically when they come into contact with some catalyst. One can argue that monopropellant and catalyst react hypergolically, but a single compund cannot be hypergolic, as noted above.

[Chakat Firepaw]

There are some things that would be hypergolic monopropellants, (e.g. monoatomic hydrogen), they have this tendency to confuse "storage tank" for "bomb casing".

[Layereddiagram]

As everyone else is saying, KSP's monopropellant is probably decays once it's run over a catalyst. The only alternative that I'm aware of is a compressed gas thruster and hose things have TERRIBLE specific impulse.

[Nothalogh]

There are some things that would be hypergolic monopropellants, (e.g. monoatomic hydrogen), they have this tendency to confuse "storage tank" for "bomb casing".

Just looked into that, I guess Zubrin's NSWR is no longer the most insane design

[Kerbart]

I vaguely remember from John Clark's Ignition that there were actually some rocket fuel scientists who looked into that. I guess the fuel and oxidizer were not hypergolic at storage temperature. If I'm correct then he also stated that the idea was rapidly abandoned as it was, even for rocket scientist standards, pretty insane.

[Budgie]

I'd argue that monoprop + catalyst is not hypergolic, as the catalyst isn't actually used up, right?

[lajoswinkler]

Hypergolic reaction means that two or more substances react upon touching one another without heating up or spark at room temperature, and deliver enough energy to cause visible emission of light, therefore flame erupts.

If a substance AB touches a catalyst C that causes it to decompose violently into A and B, we could call it a hypergolic reaction, why not? It doesn't matter the catalyst is not chemically consumed - it still enters the reaction:

AB + C -> ABC -> A + B + C

or to summarize:

AB --C--> A + B

Catalysts aren't inert materials that magically cause the reaction to proceed. They are reactive, but simply aren't chemically consumed (they are wrecked physically, turning into powder, etc.).

AB is not hypergolic. C is not hypergolic. Their reaction is.

[Camacha]

by definition, a monopropellant cannot be hypergolic.

I thought so too, but apparently that is not totally true when looking at, for instance, hydrazine.