Propellants

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Propellants

Here are some links: tables and info. Wikipedia's table. Another table.

Fuels

  • RP-1, storable, not dangerous, available?, moderately cheap, density: 806 kg/m3
  • E85, storable, not dangerous, readily available, cheap, density: 780 kg/m3
  • LH2, cryogenic, not dangerous, requires specific storage and permit?, quite expensive, density: 71 kg/m3
  • Ethanol, storable, not dangerous, readily available, cheap, density at 92.5%: 800 kg/m3

Oxidizers

Besides the cryogenic issue, LOX is probably the safest oxidizer. Others may be storable at nearly ambient temperature, or under pressure, but they are less stable, subject to explosion or toxic, and more expensive. In a cold country, Nitrous oxide can be a good alternative, but if temperature is around 20°C its density is too low and tanks require a large spare volume. Nitrous oxide is at least 20 times more expensive than LOX too.

  • LOX (internal link), cryogenic, explosive, requires cryogenic storage, cheap, density: 1141 kg/m3 at 92.2K and 1 atm, 974.42 kg/m3 at 120K and 10bar
  • Nitrous oxide (N2O), refrigerated liquid (boiling at -88.5°C) or self pressurizing (vapour pressure at 20°C is ~50.1 bar), but critical point is 36.4°C and 72.45 bar, non-toxic, quite expensive, density: 1223 kg/m3 at -88.5°C, 750 kg/m3 at 20°C, changes dramatically with temperature
  • Hydrogen peroxide, pressurized, self-decomposes explosively, expensive to have it manufactured at a high concentration, density: 1450 kg/m3 (pure)
  • Nitrogen tetroxide (N2O4), storable, highly toxic, density: 1443 kg/m3 at 21°C.

Mixes

The stoichiometric ratio is not the optimal ratio for rocket applications. The density and exhaust speeds are more important than maximum temperature. In particular, the ratio Tc/M, combustion temperature / molecular mass, is a good indicator of the exhaust speed, as explained here.

Oxidizer Fuel Isp (sea lvl) max Isp (vacuum) Stoichiometric Tc Combustion temp. (K) Average density (kg/l)
LOX LH2 381 (r=5.0) 455 8 3304 0.32
RP-1 289 (r=2.29) 353 2.56 3526 1.02
E85 ? ? 2.26 around 3360 around 1
Ethanol 95% 277 ? 2.19 3314 0.97