Save image for better view. You are piloting a spacecraft whose total mass is 11

Question

Save image for better view.

You are piloting a spacecraft whose total mass is 1130 kg and attempting to dock with a space station in deep space. Assume for simplicity that the station is stationary, that your spacecraft is moving at 1.27 m/s toward the station, and that both are perfectly aligned for docking. Your spacecraft has a small retro-rocket at its front end to slow its approach, which can burn fuel at a rate of 1.51 kg/s and with an exhaust velocity of 113 m/s relative to the rocket. Assume that your spacecraft has only 30.9 kg of fuel left and sufficient distance for docking. What is the initial thrust exerted on your spacecraft by the retro-rocket? What is the thrust's direction (positive if in the direction of the velocity of the spacecraft, or negative if in the opposite direction to the velocity of the spacecraft.) Tries 0/25 For safety in docking, NASA allows a maximum docking speed of 0.0210 m/s. Assuming you fire the retro-rocket from time t = 0 in one sustained burst, how much fuel (in kilograms) has to be burned to slow your spacecraft to this speed relative to the space station? Do not enter unit. Tries 0/25 How long should you sustain the firing of the retro-rocket? Tries 0/25 If the space station's mass is 501000 kg (close to the value for the ISS), what is the final velocity of the station after the docking of your spacecraft, which arrives with a speed of 0.0210 m/s? Tries 0/25

Explanation / Answer

a) thrust = mass of fuel * velocity = -1.51*113 = -170.63

b) for spacecraft ...
initial mass = 1130 + 30.9 = 1160.9 kg
intial velocty = 1.27 m/sec

so initial momentum = 1160.9*1.27 = 1474.343 kg m/sec

Let the final mass of fuel be x...

so final mass = 1130+x
final velocity = 0.021 m/sec

so final momentum = (1130+x)*0.021 = 23.73 + 0.021x

change in momentum = 1474.343 - (23.73 + 0.021x) = 1450.613 - 0.021x

113*(30.9-x) = 1450.613 - 0.021x
3491.7 - 113x = 1450.613 - 0.021x
so... x = 18.066 kg..


so... amount of fuel = 30.9 - 18.066 = 12.834

c) time = amount of fuel spent / 1.51 = 12.834 / 1.51 = 8.4993 secs

d) final mass of spacecraft = 1130 + 18.066 = 1148.066 kg
1148.066*0.021 = ( 501000 + 1148.066) * v

so final velocity v = 4.80125 * 10^-5 m/sec

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.