Conservation of Momentum in Rocket Propulsion

In summary, the conversation discusses a problem involving a rocket with an initial mass M0 being accelerated by the expulsion of a partial mass dm at a constant velocity u. The question asks for the differential equation for the conservation of momentum and the terminal velocity when the final mass of the rocket is Me. Three different approaches using the conservation of momentum principle are provided, but the correct method is unclear and requires further physics insight to determine.
  • #1
VVS
91
0
Hi,

I really need clarification for this problem.

Homework Statement



A rocket with initial mass M0 is accelerated by expulsion of a partial mass dm of its mass m with a constant velocity u. Write down the differential equation corresponding to the conservation law of momentum for the velocity v(m) of the rocket and evaluate it under the condition v(m = M0) = v0. What is the terminal velocity when the final mass of the rocket is Me?

The Attempt at a Solution



I have attached three different approaches (all using the conservation of momentum principle) of mine in this pdf file.
But unfortunately I get three different results.
Please point out which approach is wrong.

thanks a lot
VVS
 

Attachments

  • Übung 2.3v3.pdf
    150.4 KB · Views: 193
Physics news on Phys.org
  • #2
What are your thoughts about the three methods? I think you can apply some physics insight to decide which is correct.
 
  • #3
I really can't tell. All three methods appear to be correct to me. I can't see what is wrong about any of the methods. But obviously because I get different answers something has to be incorrect, but I just can't tell what.
 

1. What is the conservation of moment in rocketry?

The conservation of moment, also known as the conservation of angular momentum, is the principle that states that the total moment of a system will remain constant unless acted upon by an external torque. In rocketry, this means that the total moment of the rocket and its fuel will remain constant throughout the flight, as long as there are no external forces acting on it.

2. How does the conservation of moment apply to rocket launches?

During a rocket launch, the conservation of moment is evident in the fact that the rocket's moment is constantly changing as it expels fuel and experiences external forces such as gravity and air resistance. However, the total moment of the system, which includes the rocket and its fuel, remains constant.

3. What is the significance of the conservation of moment in rocket design?

The conservation of moment is an important principle in rocket design because it helps engineers calculate the trajectory and stability of the rocket during flight. By understanding how the total moment of the system will be affected by different forces, engineers can design rockets that are more efficient and stable.

4. How does the conservation of moment affect the maneuverability of a rocket?

The conservation of moment has a direct impact on the maneuverability of a rocket. As the rocket expels fuel and changes its moment, it can rotate and change direction. However, the total moment of the system will remain constant, so the rocket's maneuverability is limited by this principle.

5. Can the conservation of moment be violated in rocketry?

No, the conservation of moment is a fundamental principle of physics and cannot be violated. In rocketry, external forces such as wind or turbulence may affect the trajectory and moment of a rocket, but the total moment of the system will always remain constant.

Similar threads

Rocket acceleration problem: confused about Newton's 2nd Law
    • Introductory Physics Homework Help
2
Replies
42
Views
3K
How Does Rocket Ejection Mass Affect Its Velocity in Space?
    • Introductory Physics Homework Help
Replies
1
Views
886
Distance between rocket and object
    • Introductory Physics Homework Help
Replies
30
Views
2K
I Deriving the relativistic rocket equation with exhaust efficiency
    • Classical Physics
Replies
1
Views
167
How do you solve the problem of a rocket with variable mass?
    • Calculus and Beyond Homework Help
Replies
4
Views
2K
I Meaning of the terms in the formula of the net external force
    • Mechanics
Replies
17
Views
942
Relativistic Rocket Equation
    • Introductory Physics Homework Help
Replies
2
Views
1K
B This rocket physics problem seems unrealistic
    • Classical Physics
Replies
17
Views
2K
Trouble with a Rocket Propulsion question (Variable Mass & Momentum)
    • Introductory Physics Homework Help
Replies
2
Views
1K
How to model a rocket equation from the derivative of momentum?
    • Aerospace Engineering
Replies
4
Views
2K

Hot Threads

Recent Insights

Back
Top