4 ms·

Regarding hypergols, I love the fact that you are absolutely correct that they’re mostly relegated to places where you _need_ autoignition these days, but then

Regarding hypergols, I love the fact that you are absolutely correct that they’re mostly relegated to places where you _need_ autoignition these days, but then you look at the Proton rocket family... https://en.wikipedia.org/wiki/Proton_(rocket_family) https://en.wikipedia.org/wiki/Proton_(rocket_family)

catalogia 6y ago
If it ain't broke, don't fix it. Titan IIs are no longer around, but they too were used into the 21st century.
- jabl 6y ago
  Not broken, but better choices are available. Many early space rockets were outgrowths of military ballistic missile programs, where hypergolics were favoured due to storability, as being able to launch on a moment's notice was critical. But for launching satellites or humans into orbit, that's not a particularly relevant consideration. On the downside, hypergolics are expensive, and their toxicity makes handling them more expensive still. Meanwhile, cryogenic technology has developed and is today affordable and reliable. Heck, even amateur efforts like Copenhagen Suborbitals are using LOX.
jabl 6y ago
I should have made it clearer that I was writing about trends, not absolutes. So yes, hypergolic powered rockets are still around, but mostly they are old designs on the way out. The Proton family you mention was on the drawing board before the book was published, and is to be replaced by the kerolox powered Angara family. Similarly, the Chinese hypergolic Long March 2/3 families are old designs in the process of being replaced by the kerolox powered Long March 5/6/7 families.
- jkachmar 6y ago
  Ha, TIL! I’m not too familiar with the Long March family but that does make sense. More random engine nerdery: - It’s really exciting to see all of the development going into full-flow combustion metholox engines these days; BE-4 and Raptor have been incredible projects to follow. - The Rocketdyne F-1 is still the most impressive rocket engine to me, although the RS-25 is a very close second. Watching videos of the Apollo launches and seeing those things in action is absolutely awe-inspiring.
  - jabl 6y ago
    Yes, the staged combustion methalox engines under development are interesting. Though there's value in keeping it simple too. Gas generator engines got us to the moon and back. And if the goal is routine travel to Mars, I think we really need nuclear propulsion. And yeah, F1 is really impressive. Heck, the entire Apollo program was an astounding achievement in so many ways. Though the geek in me is disappointed that kerolox engines produce so much soot that you can't see the Mach diamonds..

catalogia 6y ago

If it ain't broke, don't fix it. Titan IIs are no longer around, but they too were used into the 21st century.

jabl 6y ago
Not broken, but better choices are available. Many early space rockets were outgrowths of military ballistic missile programs, where hypergolics were favoured due to storability, as being able to launch on a moment's notice was critical. But for launching satellites or humans into orbit, that's not a particularly relevant consideration. On the downside, hypergolics are expensive, and their toxicity makes handling them more expensive still. Meanwhile, cryogenic technology has developed and is today affordable and reliable. Heck, even amateur efforts like Copenhagen Suborbitals are using LOX.

jabl 6y ago

I should have made it clearer that I was writing about trends, not absolutes. So yes, hypergolic powered rockets are still around, but mostly they are old designs on the way out. The Proton family you mention was on the drawing board before the book was published, and is to be replaced by the kerolox powered Angara family. Similarly, the Chinese hypergolic Long March 2/3 families are old designs in the process of being replaced by the kerolox powered Long March 5/6/7 families.

jkachmar 6y ago
Ha, TIL! I’m not too familiar with the Long March family but that does make sense. More random engine nerdery: - It’s really exciting to see all of the development going into full-flow combustion metholox engines these days; BE-4 and Raptor have been incredible projects to follow. - The Rocketdyne F-1 is still the most impressive rocket engine to me, although the RS-25 is a very close second. Watching videos of the Apollo launches and seeing those things in action is absolutely awe-inspiring.
- jabl 6y ago
  Yes, the staged combustion methalox engines under development are interesting. Though there's value in keeping it simple too. Gas generator engines got us to the moon and back. And if the goal is routine travel to Mars, I think we really need nuclear propulsion. And yeah, F1 is really impressive. Heck, the entire Apollo program was an astounding achievement in so many ways. Though the geek in me is disappointed that kerolox engines produce so much soot that you can't see the Mach diamonds..