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PropulsionHow do conventional rockets work? |
Density is the amount of space that a certain mass of material takes up. A dense material such as water is heavier than a less dense material such as gasoline for a certain size. A rocket which needs a certain mass of a fuel can use a smaller tank of a denser fuel rather than a bigger tank of a less dense fuel. The smaller tank will cost less to construct and be lighter than the large tank. However, there is a tradeoff by using a denser fuel like RP-1 or UDMH because they are lower performance fuels then LiH which produces a higher specific impulse.
| Propellant | Molar Mass | Specific Gravity |
| LiF | 38.0 | 1.43 |
| Hydrazine | 32.05 | 0.984 |
| LiH | 2.016 | 0.071 |
| MMH | 46.08 | 0.862 |
| Nitrogen Tetraoxide | 92.016 | 1.37 |
| LiO | 32 | 1.14 |
| RP-1 | ~175 | 0.58 |
| UDMH | 60.1 | 0.85 |
| Water | 18.02 | 1.00 |
How do we measure what fuels weigh?
