Consider a cargo vehicle that will travel back and forth between the moon and LEO that is propelled by an electric propulsion system on a slow spiral trajectory. Assume that the characteristic velocity change (?v) for this mission is ?v=6,800 m/s. The propellant and electric efficiencies are ?u=0.85 and ?e=0.9, respectively. Assume a power plant specific mass of ?=40x10-3 kg/W and an average power level of P = 10,000 W. The final useful system mass at the destination is to be mf=8,000 kg. Calculate and plot the following:
a) The mission time versus the exhaust velocity. (Plot this. Use 5,000 m/s < Ue < 50,000 m/s range for your plot)
b) The useful final-to-initial mass ratio versus the exhaust velocity. (Plot this!)
c) The initial mass of the tug at an exhaust velocity of 20,000 m/s.
d) The propellant mass required at an exhaust velocity of 20,000 m/s.
e) The mass of the power plant.