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Is Rocket Grade Hydrogen Peroxide and Liquid Hydrogen a hypergolic propellant combination? I recall, seeing the combination somewhere on the www, however I couldn't retrace the source where I saw it.

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As far as I know the answer is no.

The autoignition temperature of Hydrogen is 536 °C according to Wikipedia.

Although this temperature could vary with pressure, I am also unaware of LOX/LH2 being hypergolic, hence adding water to the mixture (you asked about hydrogen peroxide) should not make things that much easier.

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  • $\begingroup$ It's possible that the hydrogen would catalyze the decomposition of the peroxide, which produces oxygen and steam at something not far from that autoignition temperature. $\endgroup$ – Steve Linton Jan 11 at 13:47
  • $\begingroup$ @SteveLinton You could add some other catalyst as well to start the combustion, but if a certain amount of transferred heat needs to be given for the reaction to start, I'd argue that by definition it would not qualify as an hypergolic mixture. $\endgroup$ – Mefitico Jan 11 at 14:48
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    $\begingroup$ I'm not sure what you mean by tranferred heat, If you run peroxide over a catalyst, it releases enough energy to heat itself to about 600C, so if you then added some hydrogen it would very possibly auto-ignite with the oxygen in the decomposition products, so you wouldn't need an additional igniter. $\endgroup$ – Steve Linton Jan 11 at 14:59
  • $\begingroup$ To clarify: A combustion essentially sustains itself by producing enough heat to activate more of the same chemical reaction, causing a chain effect, but it requires ignition to begin. Hypergolic implies spontaneuous combustion, so the activation energy should be around the available energy of the involved particles. You make a fair point that by heating one element and then mixing you technically did not use an external ignition, but I believe this is somewhat a borderline case. I'm also unaware of this being technically feasible. $\endgroup$ – Mefitico Jan 11 at 15:06

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