[hoorayimhelping]

>If you can safely handle the dangerous fuels it's a much easier route to a liquid fueled rocket engine.

This kind of glosses over the whole hypergolic fuels are necessarily poisonous toxins that boil your skin if you touch them. To react with each other so quickly, they basically have to react with just about everything else as well - including human saliva, the liquid on eyeballs, and the liquid in your lungs.

This (extremely 60s styled) video is full of useful information about how dangerous hypergols are: https://www.youtube.com/watch?v=Zha9DyS-PPA

[helldritch]

In general, I would agree with you.

If you're dealing with umsymettrical-dimethylhydrazine and dinitrogen tetroxide, you're going to be in a world of pain trying to produce them, handle them and get them close enough to use in an engine without being so close that the fumes spontaneously ignite. Not to mention that the dinitrogen tetroxide boils at ambient temperatures, etc, etc.

Obviously, I was glossing over the danger (not something I do in real life when handling dangerous fuels, but probably something I do when writing a short comment on Hacker News) and anyone seeking to work on Rocket Engines needs to ensure that they consult with subject matter exports before, during and after any construction or launch preparations begin.

... With that disclaimer out of the way, in the grand scheme of dangerous fuel and oxidisers combinations, Kerosene and Hydrogen Peroxide are significantly safer to handle than traditionally used hypergolic mixtures:

- They are both liquids at ambient pressures and temperatures (don't underestimate the value of not needing highly pressurised canisters - above 2000psi in many cases - and cryogenic equipment, that's all mass you don't need to lift and failure states you don't need to control for)

- Storage and deployment of AVTUR (Aviation Turbine Fuels) is a well understood procedure with pre-certified canisters.

- Hydrogen Peroxide at sub-90%, and especially at sub 70%, purities is reasonably safe to store and handle, especially if you store it in an inhibited state and you're willing to have a suboptimal hypergolic reaction in return for a safer handling procedure.

- The pressures and temperatures created when reacting these two liquids together in a combustion chamber are extreme, but not so extreme as to be outside the remit of an amateur team.

This all doesn't mean that these are safe to handle - and failing to properly respect rocket fuel results in death for yourself and others - but it does mean that they're safer to handle.

In a perfect world I would manufacture solid state rocket propellants, but in addition to the negatives of not being throttle-able and being hard to early-terminate, manufacture of solid rocket motors is a criminal offence in the United Kingdom and getting an explosives certificate is a long, daunting task.

[jabl]

> in the grand scheme of dangerous fuel and oxidisers combinations, Kerosene and Hydrogen Peroxide are significantly safer to handle than traditionally used hypergolic mixtures:

Are they? AFAIU the propensity for HTP to exothermically decompose was the main reason why it was abandoned in favor of IRFNA/NTO. I mean, if you're switching to something as nasty as NTO or IRFNA for safety reasons, whatever you're switching from has to be pretty bad!

See also the Kursk submarine disaster.

> Hydrogen Peroxide at sub-90%, and especially at sub 70%, purities is reasonably safe to store and handle, especially if you store it in an inhibited state and you're willing to have a suboptimal hypergolic reaction in return for a safer handling procedure.

IIRC in Clark's Ignition the opposite was mentioned, namely that higher concentrations have better resistance to decomposition, presumably due to lower amounts of impurities which can get the decomposition reaction started.

[avmich]

> Are they? AFAIU the propensity for HTP to exothermically decompose was the main reason why it was abandoned in favor of IRFNA/NTO. I mean, if you're switching to something as nasty as NTO or IRFNA for safety reasons, whatever you're switching from has to be pretty bad!

I'm not sure the switch to IRFNA/NTO is for safety reasons. There is simplicity involved - you don't need catalyst with them. The components themselves are easier to get by and to store. They however have their own nasty properties regarding safety. Also historically nitric acid was initially used with turpentine, which is a hypergolic pair.

Here are some comments on safety.

https://yarchive.net/space/rocket/fuels/peroxide.html

[jabl]

> I'm not sure the switch to IRFNA/NTO is for safety reasons. There is simplicity involved - you don't need catalyst with them.

Yeah, good point, that's certainly an advantage.

> Here are some comments on safety.

> https://yarchive.net/space/rocket/fuels/peroxide.html

Coincidentally(?) those comments stop in the year 2000, when the Kursk put a dent in HTP enthusiasm. For a while at least.

Not that I have any good solution either. Seems all high performance liquid rocket fuels have some nasty downsides.

For small scale applications N2O + some light hydrocarbon like propane or ethane could be interesting. But that seems to be quite immature, so could be some showstoppers ahead in that path.

[baybal2]

> Hydrogen Peroxide at sub-90%, and especially at sub 70%, purities is reasonably safe to store and handle,

Union's space programme had uncounted casualties to something happening with H²O²

[skykooler]

Solid rocket fuel is scary in its own right, as well.

[adrianN]

Hydrogen peroxide and kerosene are not quite as dangerous as those in the video, I believe.

[beerandt]

Not as dangerous, sure. But...

Highly concentrated / "pure" HP is an entirely different animal than what you buy at the drug store. It absolutely is not something to be toyed with.

It may still safer to use than the "typical" hypergolics, but it isn't "safe."