Calculating Thrust for Rocket Weight & Altitude

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Discussion Overview

The discussion revolves around calculating the thrust required for a rocket based on its weight and the desired altitude. Participants explore the principles of physics involved in rocket propulsion, particularly in the context of model rockets.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant inquires about the formula for calculating the necessary thrust for a rocket to achieve a certain weight and altitude.
  • Another participant references Newton's laws of motion, suggesting starting with the equations f=ma, s=at, and d=st, and questions the complexity of the scenario being analyzed.
  • A participant clarifies that they are considering a model rocket and seeks confirmation on the meanings of the variables in the equations, mistakenly interpreting 'a' as altitude instead of acceleration.
  • One participant corrects the misunderstanding regarding the variable 'a', emphasizing that it represents acceleration.
  • Another participant notes the complexity of calculations due to the changing mass of the rocket as it burns fuel, suggesting that thrust remains constant while mass decreases, leading to increased acceleration.
  • This participant proposes that a good approximation for thrust calculations could involve considering half the weight of the fuel, as the rocket starts with full fuel and ends with none.
  • A later reply mentions resources available on NASA's website for further learning.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and complexity regarding thrust calculations, with no consensus reached on a specific formula or method for determining thrust for model rockets.

Contextual Notes

Participants acknowledge the complications arising from the changing mass of the rocket during flight and the assumptions involved in approximating thrust requirements.

Who May Find This Useful

Individuals interested in model rocketry, physics students, and those exploring basic principles of motion and propulsion may find this discussion relevant.

wolfspirit
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This is my first posting - I don't know whether its on the right section but I have a question
is there a formula to work out
how much thrust you need to get a certain weight of rocket up in the air, also for the rockets altitude?
Thanks
 
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Newton's laws of motion. Start with f=ma, s=at and d=st. How complex of a scenario are you trying to analyze?
 
Thank you. As for how complex - not very. I'm just thinking about making a model rocket and i wanted to work out how much thrust i will need to get it to a designated altitude.
Can you please just confirm what the letters mean. (f=ma, s=at and d=st) Am I right in thinking they are f=force, m=mass, a = altitude, s=speed, t=time d=distance?
Thanks again!
 
'a' is acceleration not altitude :-)
 
Unfortunately, these calculations can get quite compluicated, as the "m" keeps changing. As your rocket burns fuel, it becomes lighter, yet the thrust "f" remains the same. So, same thrust with less mass means greater acceleration.

I think (and I hope someone will correct me if I'm wrong here) you can get a fairly good approximation if you figure in only half the weight of the fuel. Since the rocket starts off lifting all pof the fuel and ends up with none, half would be the mean average of the fuel mass.

Also, if you go on NASA's website (NASA.Gov), you can find some pretty cool tutorials.
 
Thanks for that yes I can see how complicated it can get. I'll check out NASA'S website.
 

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