Please anyone elaborate why hydrogen peroxide is not used as an oxidizer for main propulsion. I see that everyone agrees on this but from my point of view its a big flaw. I think that industry has seriously overlooked the potential of this compound and that future of cheep space flights lies in it's use.

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    $\begingroup$ Have you read the chapter "Peroxide, Always a Bridesmaid" in Clark's Ignition, which is referenced in the question you originally posted this as an answer to? $\endgroup$ – Organic Marble Feb 3 at 21:54
  • $\begingroup$ Peroxide is hella wet. No getting away from that, is there? $\endgroup$ – Starfish Prime Feb 3 at 22:09
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    $\begingroup$ Off course i did. Is it possible that all you guys refer to book which is written almost 5 decades ago? So many advances in chemistry of oxidizers, HTP stability, freezing point depression, hypergolic fuel combinations, high energy density fuels discovery, catalytic bed construction etc. This was all unknown to Ms John D. Clark back in 70s. $\endgroup$ – Silverback Feb 3 at 22:30
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    $\begingroup$ No, actually ever single one of those discoveries was not just known but was discussed by Mr. John D. Clark in his seminal work on rocket propulsion. $\endgroup$ – Anton Hengst Feb 4 at 0:58

HTP has been used as an oxidizer before. Kind of. See BLACK ARROW and the rest of the British keroxide. Turns out HTP by itself isn't a great oxidizer, but when you catalyze its decomposition into water and O2, you get lots of dry steam and hot O2, the latter of which is an excellent oxidizer. In fact, it's so hot, it's basically hypergolic.

Black Arrow launch

But there's major disadvantages.

  • Even though 95+% peroxide is perplexingly more stable than 35%, it's still got a shelf life of months at best (but recent work seems to be really turning up that number [Source]).

  • Your Isp is horrible due to all the water in your combustion chamber.

  • It's not much less toxic than other hypergols. Maybe it won't give you cancer, but you don't want to be breathing in the stuff in any volume much greater than 5%, much less 95%. It'll deeply burn through your skin in seconds.

  • It's not even that stable, and it likes to explosively decompose things. The longer it sits, the less stable it gets. An HTP torpedo aged, allowed a tiny bit of HTP through one of the cracks, catalyzed on copper, and killed an entire submarine.

  • Finally, it's notoriously sensitive to any contaminant in the propellant tank. Any scrap of organic material would induce an explosion during fueling.

That said, the biggest reason is simply the lack of research into it compared to other propellants. Initially, the disadvantages were too steep to justify working with it, and while HTP technology has improved, there's still a big knowledge gap between it and the comparatively predictable, well-behaved (if cancerous) IRFNA + MMA/Hydrazine/UDMH combinations.

Do go read that Ignition! chapter mentioned in the comments.

EDIT: I've looked into hydro-oxide engines before (HTP & LH2) and they are generally absolutely terrible. You gain all the disadvantages of hydrolox (massive LH2 tanks, big temperature difference between between fuel and oxidiser) and none of the advantages of its stellar ISP.

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    $\begingroup$ I'll give BLACK ARROW props at least for looking really cool at liftoff. No smoke! $\endgroup$ – Organic Marble Feb 4 at 2:53
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    $\begingroup$ Little known fact, it was actually Arthurian magic that miraculously lifted BLACK ARROW off the pad without any visible exhaust. SpaceX would later steal his name for their rockets, but true Brits know Merlin's just waiting to send a Londoner to space on wizardry alone. $\endgroup$ – Anton Hengst Feb 4 at 3:06
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    $\begingroup$ Technically, HTP has destroyed two submarines. HMS Sidon was destroyed loading HTP fuel into a torpedo, but had survivers. en.wikipedia.org/wiki/… $\endgroup$ – gwally Feb 4 at 17:47

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