4 ms·
> In order to have a higher exhaust velocity the fuel temperature needs to be higher than chemical propulsion. Are you accounting for the fact that the NTR exh
by leereeves 4y ago
> In order to have a higher exhaust velocity the fuel temperature needs to be higher than chemical propulsion.
Are you accounting for the fact that the NTR exhaust (hydrogen) is lighter than chemical rocket exhaust?
At the same temperature, both propellants have the same average kinetic energy per molecule, so the hydrogen must be moving faster.
- mlindner 4y agoI wasn't accounting for it, but I assumed it wouldn't be significant. The efficiencies claimed are over 2x better than chemical rockets. You don't get that much just from changing gasses.
- Robotbeat 4y agoYes, you can. Hydrogen, for the same temperature, has a far higher speed of sound (which is close to the average speed of the gas molecules) than air or water vapor. This is why your voice is higher pitched when you breathe in helium (also a light gas like hydrogen). Basic kinetic gas theory stuff.
- perihelions 4y agoHuge difference between the molecular weight of H₂ (2) and its lightest combustion product OH (17).