# Difference between revisions of "Propulsion"

(3 intermediate revisions by the same user not shown) | |||

Line 7: | Line 7: | ||

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. | ||

− | + | P = F x ISP *9,81 / 2n or P= F x Ev /2n | |

− | + | where: | |

+ | |||

+ | P = power (Watts) | ||

F = Engine force (Newtons) | F = Engine force (Newtons) | ||

Line 15: | Line 17: | ||

ISP = Specific impulse (Seconds) | ISP = Specific impulse (Seconds) | ||

− | n = efficiency of | + | n = efficiency of engine, for an [[ion thruster]] this is between 0,2 and 0,8, for a [[Propellant|chemical rocket]], or [[Nuclear thermal propulsion|nuclear thermal rocket]], essentially 1. |

9,81 conversion factor | 9,81 conversion factor | ||

Line 37: | Line 39: | ||

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

− | ===Velocity=== | + | ===Velocity (Rocket equation)=== |

− | V = Ev x ln( | + | V = Ev x ln(M<sub>o</sub>/M<sub>f</sub>) |

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

Line 46: | Line 48: | ||

ln = natural logarithm | ln = natural logarithm | ||

− | + | M<sub>o</sub> = Initial mass of the ship (kg) | |

− | + | M<sub>f</sub> = 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. | 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. |

## Revision as of 10:39, 9 August 2019

## Contents

## Theory

### Propulsion equation

This is the equation that links the electrical power, the propulsive force and the ISP.

P = F x ISP *9,81 / 2n or P= F x Ev /2n

where:

P = power (Watts)

F = Engine force (Newtons)

ISP = Specific impulse (Seconds)

n = efficiency of engine, for an ion thruster this is between 0,2 and 0,8, for a chemical rocket, or nuclear thermal rocket, essentially 1.

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 (Rocket equation)

V = Ev x ln(M_{o}/M_{f})

Ev = Exhaust velocity (m/s)

V = ship final velocity (m/s)

ln = natural logarithm

M_{o} = Initial mass of the ship (kg)

M_{f} = 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.