Difference between revisions of "Propulsion"
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[[Category:Propulsion]] | [[Category:Propulsion]] | ||
| − | == Theory == | + | ==Theory== |
| − | === Propulsion equation === | + | ===Propulsion equation=== |
This is the equation that links the electrical power, the propulsive force and the ISP. | This is the equation that links the electrical power, the propulsive force and the ISP. | ||
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F = Engine force (Newtons) | F = Engine force (Newtons) | ||
| − | |||
| − | + | ISP = Specific impulse (Seconds) | |
n = efficiency of electric engine | n = efficiency of electric engine | ||
| Line 22: | Line 21: | ||
Ev = Exhaust velocity (m/s) | Ev = Exhaust velocity (m/s) | ||
| − | === Specific impulse === | + | ===Specific impulse=== |
ISP = Ev / 9,81 | ISP = Ev / 9,81 | ||
| Line 29: | Line 28: | ||
Ev = Exhaust velocity (m/s) | Ev = Exhaust velocity (m/s) | ||
| − | === Fuel consumption === | + | ===Fuel consumption=== |
m = F/Ev | m = F/Ev | ||
| + | |||
m = Fuel consumption (kg/s) | m = Fuel consumption (kg/s) | ||
| Line 37: | Line 37: | ||
Ev = Exhaust velocity (m/s) | Ev = Exhaust velocity (m/s) | ||
| − | === Velocity === | + | ===Velocity=== |
V = Ev x ln(Mo/Mf) | V = Ev x ln(Mo/Mf) | ||
Revision as of 13:12, 12 May 2019
Theory
Propulsion equation
This is the equation that links the electrical power, the propulsive force and the ISP.
Pe = F x ISP *9,81 / 2n or Pe = F x Ev /2n
Pe = electric power (Watts)
F = Engine force (Newtons)
ISP = Specific impulse (Seconds)
n = efficiency of electric engine
9,81 conversion factor
Ev = Exhaust velocity (m/s)
Specific impulse
ISP = Ev / 9,81
ISP = Specific impulse (Seconds)
Ev = Exhaust velocity (m/s)
Fuel consumption
m = F/Ev
m = Fuel consumption (kg/s)
F = Force (Newtons)
Ev = Exhaust velocity (m/s)
Velocity
V = Ev x ln(Mo/Mf)
Ev = Exhaust velocity (m/s)
V = ship final velocity (m/s)
ln = natural logarithm
Mo = Initial mass of the ship (kg)
Mf = Final mass of the ship (kg)
The propulsive force is the force the engines produce to push the ship. This is factor of the available electrical energy, the engine efficiency and the propulsive system ISP and ejection velocity.
For the Enterprise: Available electrical energy = 2,5 GWe ISP = 5000 Efficiency (n) = 80% Thrust = 2 500 000 000 W x 2 x 0,8 / (5000*9,81) = 84 000 N = 8 300 kg = 8,3 Tons
