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Comment by perihelions | Hacker News Reader

Most deep-space probes use storable hypergolics (hydrazines + nitrogen tetroxide). Some of the crazy parts of this book actually came true!

(I don't intuitively understand how the JWST has $10 billion precision optics and hypercorrosive oxidizers right next to each other, and nothing bad happens. Engineering baffles me).

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Not just deep-space probes; Dragon, Orion, and I think Starliner all use hypergols. Plenty of satellites do as well, though I think there's a trend towards using various sorts of electric propulsion. Really, the big misprediction of the book (looking at chapter 13, "What Happens Next") is that it doesn't consider missiles (and some upper/deep-space stages) moving to solid propellant; but it's a book about liquid propellants, so I'm not too surprised.

Absolutely! I’m sure they analyzed for that, but backflow to the opposite direction of the nozzle is quite unintuitive but normal in rarefied flow, with propellant deposition next to the nozzle possible and documented [1]. Just because you point it away from the sensitive stuff does not mean it won’t get there and leave nasty traces.

[1] https://apps.dtic.mil/dtic/tr/fulltext/u2/a588174.pdf

The propellant tanks don’t leak, the combustion products aren’t corrosive.

Designing spacecraft is like “does this material ever outgas anything which might affect other parts? I guess we can’t use it” much less leaky propellant tanks.

> the combustion products aren’t corrosive

Nitpick: if the chemical combustion is perfectly efficient, there are no corrosive byproducts or remainder.

Nitnitpick: and we know it isn’t and the corrosive propellants will contaminate surfaces:

https://apps.dtic.mil/dtic/tr/fulltext/u2/a588174.pdf

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