The second stage of the propulsion system is used to boost the spacecraft from M
ID: 1344771 • Letter: T
Question
The second stage of the propulsion system is used to boost the spacecraft from Martian orbit into an interplanetary trajectory and return to Earth.
Knowing that the thrust generated by the second stage is 2755 N and the rocket exhaust velocity is 485 m/s; calculate the minimum amount of propellant needed to have a chance of returning to Earth. Assume that the thruster must be turned on for 2 minutes in order to reach the proper velocity.
Give your answer in kg.
Hint: First determine the burn rate of the propellant in kg/s and then use it to calculate the mass of propellant needed.
Explanation / Answer
use from the def of impulse
J = F* dt = m dV
so mass m = F* dt/dV
m = 2755 * 2*60/485
mass m = 681.65 kgs