Difference between revisions of "Propulsion"

From Marspedia
Jump to: navigation, search
Line 51: Line 51:
  
 
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.
 
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
 

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.