Propellants: Difference between revisions
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=Propellants= | =Propellants= | ||
Here are some links: [http://www.thespacerace.com/forum/index.php?topic=2583.0 tables and info]. Wikipedia's [https://en.wikipedia.org/wiki/Liquid_rocket_propellants#Bipropellants table]. Another [http://www.braeunig.us/space/propel.htm table]. | |||
==Fuels== | ==Fuels== | ||
* RP-1, storable, not dangerous, available?, moderately cheap, density: 806 kg/ | * RP-1, storable, not dangerous, available?, moderately cheap, density: 806 kg/m<sup>3</sup> | ||
* E85, storable, not dangerous, readily available, cheap, density: 780 kg/ | * E85, storable, not dangerous, readily available, cheap, density: 780 kg/m<sup>3</sup> | ||
* | * LH<sub>2</sub>, cryogenic, not dangerous, requires specific storage and permit?, quite expensive, density: 71 kg/m<sup>3</sup> | ||
* | * Ethanol, storable, not dangerous, readily available, cheap, density at 92.5%: 800 kg/m<sup>3</sup> | ||
==Oxidizers== | ==Oxidizers== | ||
* [https://en.wikipedia.org/wiki/Liquid_oxygen LOX], cryogenic, explosive, requires cryogenic storage, cheap, density: 1141 kg/ | 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. | ||
* [https://en.wikipedia.org/wiki/Nitrous_oxide#Rocket_motors Nitrous oxide] (N<sub>2</sub>O), refrigerated liquid (boiling at -88.5°C), non-toxic, density: 1223 kg/ | |||
* [https://en.wikipedia.org/wiki/Hydrogen_peroxide Hydrogen peroxide], pressurized, | * [https://en.wikipedia.org/wiki/Liquid_oxygen LOX], cryogenic, explosive, requires cryogenic storage, cheap, density: 1141 kg/m<sup>3</sup> at 92.2K and 1 atm, 974.42 kg/m<sup>3</sup> at 120K and 10bar | ||
* [https://en.wikipedia.org/wiki/Nitrous_oxide#Rocket_motors Nitrous oxide] (N<sub>2</sub>O), refrigerated liquid (boiling at -88.5°C) or self pressurizing (vapour pressure at 20°C is ~50.1 bar), but critical temperature is at 36.4°C, non-toxic, quite expensive, density: 1223 kg/m<sup>3</sup> at -88.5°C, 750 kg/m<sup>3</sup> at 20°C, changes dramatically with temperature | |||
* [https://en.wikipedia.org/wiki/Hydrogen_peroxide Hydrogen peroxide], pressurized, self-decomposes explosively, expensive to have it manufactured at a high concentration, density: 1450 kg/m<sup>3</sup> (pure) | |||
* [https://en.wikipedia.org/wiki/Nitrogen_tetroxide Nitrogen tetroxide] (N<sub>2</sub>O<sub>4</sub>), storable, highly toxic, density: 1443 kg/m<sup>3</sup> at 21°C. | |||
==Mixes== | ==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 T<sub>c</sub>/M, combustion temperature / molecular mass, is a good indicator of the exhaust speed, as explained [http://www.thespacerace.com/forum/index.php?topic=2583.msg17485#msg17485 here]. | |||
{| border="1" class="wikitable" | {| border="1" class="wikitable" | ||
!Oxidizer | !Oxidizer | ||
!Fuel | !Fuel | ||
!I<sub>sp</sub> ( | !I<sub>sp</sub> (sea lvl) | ||
!I<sub>sp</sub> (vacuum) | !max I<sub>sp</sub> (vacuum) | ||
!Stoichiometric | !Stoichiometric | ||
!Combustion temp. | !T<sub>c</sub> Combustion temp. (K) | ||
!Average density | !Average density (kg/l) | ||
|- | |- | ||
|rowspan="4"|LOX | |rowspan="4"|LOX | ||
|LH<sub>2</sub> | |LH<sub>2</sub> | ||
| | |381 (r=5.0) | ||
|455 | |455 | ||
|8 | |8 | ||
| | |3304 | ||
| | |0.32 | ||
|- | |- | ||
|RP-1 | |RP-1 | ||
| | |289 (r=2.29) | ||
| | |353 | ||
|2.56 | |2.56 | ||
| | |3526 | ||
| | |1.02 | ||
|- | |- | ||
|E85 | |E85 | ||
| Line 44: | Line 51: | ||
|? | |? | ||
|2.26 | |2.26 | ||
| | |around 3360 | ||
| | |around 1 | ||
|- | |- | ||
|Ethanol | |Ethanol 95% | ||
| | |277 | ||
|? | |? | ||
|2.19 | |2.19 | ||
| | |3314 | ||
| | |0.97 | ||
|} | |} | ||
Revision as of 00:17, 6 November 2012
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, 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 temperature is at 36.4°C, 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 |
