smaller proton variants

[kerbiloid]

3 hours ago, wumpus said:

And as playing KSP will teach you: you can save a lot of energy if you can change your fuel into something with a lot more Isp.

In KSP I've changed all engines to UDMH+NTO usage.

[DDE]

4 hours ago, wumpus said:

The issue is "the dose makes the poison".  Dragons are a final stage that barely have any fuels, the Protons use in the first three stages (presumably anything using kerolox was inherited from another program.  Weird that they managed to reverse falcon/dragon).

But of course the definition of "rocket fuel" is something with vast amounts of thrust.  This invariably means practically explosive and often toxic.  While LO2 is *nasty* it will oxidize anything it can and will turn anything combustible into an explosive on contact it will also boil off rather quickly during a crash and simply go back to the atmosphere where it belongs.  Hydrogen is even less an issue and will boil faster (and presumably either become water vapor or completely leave the planet).  Kerosene might be pretty nasty, but it is sufficiently familiar to not cause a panic in the general population.

And as playing KSP will teach you: you can save a lot of energy if you can change your fuel into something with a lot more Isp.  This matters a lot with hydrogen and moreso if metastable solid hydrogen can be manufactured.  Even if it doesn't make sense to have the whole rocket use hydrolox, making the upper stages uses it makes your overall Isp nearly that of hydrogen (thanks to adding any stages above as "dead mass" in the rocket equation).

Heck, I've seen a NASA paper that suggests a liquid fluorine leak can be neutralized by a barrier of charcoal.