# 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 | ||

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Ev = Exhaust velocity (m/s) | Ev = Exhaust velocity (m/s) | ||

− | === Specific impulse === | + | ===Specific impulse=== |

ISP = Ev / 9,81 | ISP = Ev / 9,81 | ||

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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) | ||

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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 14:12, 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