Paraffin wax is often used in (at least hypothetical) hybrid motors, mostly with N2O or HTP. Could it not, however, be used in a conventional configuration? Running at O/F of 12.4, 60 bar chamber pressure and 9.19 Ae/At, paraffin wax and ammonium nitrate achieve 2942.6m/s at sea level and 3211.5m/s in vac (using CEA). I don't know much about solid propulsion but I would assume that, being more volatile, it will melt/vaporise more readily and burn faster, but this could be useful (maybe a booster stage for ramjet propulsion). Why has this not been used before, or if it has, where? Somewhere colder maybe?

  • $\begingroup$ Is ammonium nitrate soluble in wax or otherwise able to produce a fine grain structure able to fully burn inside the motor? Suspect there are some mechanical/packaging issues here but would be good if there was a authoritive source. $\endgroup$ Sep 12, 2022 at 7:59
  • $\begingroup$ Using flourine as oxidator is only a theoretical option. It is so dangerous and toxic that there were no rockets built in series that used flourine. $\endgroup$
    – Uwe
    Sep 12, 2022 at 15:51
  • $\begingroup$ @Gremlin No, but you can increase its solubility in organic solvents via the use of chelating agents like polyethylene glycols; patents.google.com/patent/US3450582 discusses various possibilities. Ammonium nitrate is also frequently used in emulsions (i.e., dissolved in water & mixed with oil). As a solid, it's usually prilled: made into hollow granules, which are mixed with the fuel immediately prior to use, see en.wikipedia.org/wiki/ANFO Aluminium powder may also be used to boost it, but that's not so common, due to the expense. $\endgroup$
    – PM 2Ring
    Sep 13, 2022 at 7:52
  • $\begingroup$ Nitrous oxide is very soluble in oils & fats, I assume it's also relatively soluble in waxes. So I think it's possible to make a paraffin foam using N2O, perhaps incorporating chelated / emulsified NH4NO3. Of course, that would reduce its density, but I guess that's not an issue if the foam is produced inside the rocket, not stored as a foam in the tank. I have no idea whether foaming it would make it safer or more dangerous to handle. $\endgroup$
    – PM 2Ring
    Sep 13, 2022 at 8:03


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