Calculating Thrust for Rocket Weight & Altitude

In summary, the conversation was about calculating the amount of thrust needed to lift a rocket to a designated altitude. The main formula discussed was f=ma, with additional formulas for speed and distance. It was mentioned that these calculations can become complicated due to the changing mass of the rocket as it burns fuel. A good approximation can be made by considering only half the weight of the fuel. It was also recommended to check out NASA's website for tutorials on this subject.
  • #1
wolfspirit
33
1
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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  • #2
Newton's laws of motion. Start with f=ma, s=at and d=st. How complex of a scenario are you trying to analyze?
 
  • #3
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!
 
  • #4
'a' is acceleration not altitude :-)
 
  • #5
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.
 
  • #6
Thanks for that yes I can see how complicated it can get. I'll check out NASA'S website.
 

Related to Calculating Thrust for Rocket Weight & Altitude

1. How do you calculate the thrust needed for a rocket to reach a certain altitude?

To calculate the thrust needed for a rocket, you need to use the rocket equation, which takes into account the rocket's weight, the specific impulse of the rocket engine, and the change in velocity required to reach the desired altitude. This equation is: F = (m0 * ve) / (Isp * g), where F is the thrust, m0 is the initial mass of the rocket, ve is the exhaust velocity, Isp is the specific impulse, and g is the gravitational acceleration. By plugging in the appropriate values, you can calculate the thrust needed for a rocket to reach a specific altitude.

2. How does the weight of the rocket affect the thrust needed?

The weight of the rocket has a direct impact on the thrust needed. The heavier the rocket, the more thrust is required to overcome the force of gravity and lift the rocket off the ground. This is why rockets are designed to be as lightweight as possible, to minimize the amount of thrust needed and make the rocket more efficient.

3. What is the relationship between thrust, weight, and altitude?

The relationship between thrust, weight, and altitude is described by the rocket equation (F = (m0 * ve) / (Isp * g)). This equation shows that as the weight of the rocket increases, the amount of thrust needed to reach a certain altitude also increases. Additionally, as the desired altitude increases, the amount of thrust needed also increases.

4. How do you factor in atmospheric conditions when calculating thrust for rocket weight and altitude?

Atmospheric conditions, such as air density and wind, can affect the performance of a rocket and therefore must be taken into account when calculating thrust. These factors can impact the rocket's aerodynamics and the efficiency of its engines. Engineers use computer simulations and wind tunnel testing to determine the effects of atmospheric conditions on a rocket's flight and adjust the thrust calculations accordingly.

5. Can you use the same thrust calculation for all types of rockets?

No, the thrust calculation varies depending on the type of rocket being used. Different rockets have different engine designs, exhaust velocities, and specific impulses, which all affect the amount of thrust needed. The rocket equation can be adapted for different types of rockets, but the specific values for each variable will vary. It is important to use the correct values for the specific type of rocket being used in order to accurately calculate the thrust needed for a specific weight and altitude.

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