Item — HN Reader

I'm guessing they're referring to the hypergolic propellants used on the Proton rocket? Which are, indeed, notoriously toxic.

In which case, they're not something SpaceX has shyed away from; they are indeed not used on the Falcon, but hypergols will power the SuperDraco engines on the Dragon 2.

When you need storable propellants (either for a launch escape system that needs to be ready to go at any time, or for ICBMs that can be kept in a launch-ready state), and a solid rocket won't do for whatever reason, there's just nothing else that will do the job.

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> When you need storable propellants (either for a launch escape system that needs to be ready to go at any time, or for ICBMs that can be kept in a launch-ready state), and a solid rocket won't do for whatever reason, there's just nothing else that will do the job.

That is, if you don't count Soyuz landing capsule, which carries about 30 kg of hydrogen peroxide and keeps that for up to 210 days flight before landing. And if you don't count Zarya spacecraft, which - never built, but was designed to use hydrogen peroxide for powered landing ( https://en.wikipedia.org/wiki/Zarya_(spacecraft) ), also after long flights. And Buran spaceplane, which used LOX and kerosine for maneuver engines able to word in a month-long flight. And Kliper spacecraft designs with propulsion on LOX and ethanol.

Even hydrogen can be made working after weeks of flight if you have large enough tanks - there was design of upper stage of N-1 with that. With Lockheed works on space tanker ( https://en.wikipedia.org/wiki/Advanced_Cryogenic_Evolved_Sta... ) the time range can be extended even more. I think we can leave those toxic propellants aside when we want.