Problem

You are piloting a spacecraft whose total mass is 1000 kg and attempting to dock with a sp...

You are piloting a spacecraft whose total mass is 1000 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 1.0 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 1.0 kg/s and with an exhaust velocity of 100 m/s relative to the rocket. Assume that your spacecraft has only 20 kg of fuel left and sufficient distance for docking.

a) What is the initial thrust exerted on your spacecraft by the retro-rocket? What is the thrusts direction?


b) For safety in docking, NASA allows a maximum docking speed of 0.02 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?


c) How long should you sustain the firing of the retro- rocket?


d) If the space station's mass is 500,000 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 0.02 m/s?

Step-by-Step Solution

Solution 1

RESEARCH:

(a)

The thrust of the retro-rocket can be measured as …… (1)

(b)

According to the ’s second law of motion, and use the kinematic equation of motion,

…… (2)

(c)

To determine time, use the kinematic equation of motion,and

(d)

According to the law of conservation of linear momentum,

And the final velocity of the station is after docking of your spacecraft is …… (3)

SIMPLIFY

(a)

Initial thrust exerted on space craft is,

(b)

Fuel burned is,

From the equation (2),

, from the ’s second law of motion,

Therefore

Therefore the required mass of the fuel has to be burned is

(c)

Time to sustain the firing of the retro-rocked is,

(d)

Final velocity of the space station after docking space craft is,

CALCULATE:

Given,

The mass of the spacecraft is

The speed of the space craft is

The rate of burning fuel is

The exhaust velocity is

The mass of the fuel left is

(a)

The initial thrust exerted on space craft by retro-rocket is

This thrust is opposite direction to the velocity of the spacecraft

(b)

The maximum docking speed is

The required mass of the fuel has to be burned is

(c)

The time taken to sustain the firing of the retro-rocket is

(d)

Mass of the spacecraft is

The velocity of the station after the docking of spacecraft, which arrives with a speed of

Therefore the

The final velocity of the station is after docking of your spacecraft is

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