4 ms·

HTPB, unburnt ammonium perchlorate, aluminum powder. https://en.wikipedia.org/wiki/Hydroxyl-terminated_polybutadiene https://en.wikipedia.org/wiki/Hydroxyl-ter

• ridgeguy 9y ago
  And the combustion products include lots of water and hydrogen chloride, which combine to form hydrochloric acid. The gritty aluminum oxide (another combustion product) is probably a pretty good particulate sponge for holding acid as it cools below HCl's condensation point.
  • alex_hitchins 9y ago
    Thanks both for the reply. Is the Aluminimum oxide forming part of a thermite style reaction then?
    • Taniwha 9y ago
      only to the extend that the Al powder in the motor is burning in the O2 released from the perchlorate, it'[s not an exchange like a traditional thermite Essentially they add Al because it burns well and has a high mass which ups the mass of the exhaust gasses and as a result gives you more thrust
    • tropo 9y ago
      Somewhat yes. Iron oxide is included, but considered a catalyst. The rubbery plastic binder is a fuel. The Aluminum is a high-energy fuel. The "ammonium" part of ammonium perchlorate is a fuel, and the "perchlorate" part is an oxidizer. The amount of aluminum is limited to prevent the temperature from getting too high and because it makes low-energy exhaust particles. Good exhaust particles are low-mass gasses with few degrees of freedom in the molecular shape. Aluminum oxide forms solid particles consisting of many atoms stuck together, which is pretty useless.