How can I calculate the required thrust for my model rocket design?

In summary: Mentors exist to help with understanding safety and proper building techniques, but you need to look for them in person. Additionally, equations can be found on the internet, but they need to be verified before being used. If you are not part of a club or have a mentor, you will need to do more research on your own.
  • #1
uzt
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Hi, I am currently working on a Hybrid Rocket which uses fuel grain as 3-D printed ABS and oxidizer as N2O, but i need to calculate some basic parts such as required thrust to reach specific altitude. I want to calculate the required thrust to reach 1.5km for 10kg rocket with 7cm radius. It will launched 85 degrees vectircally. I want you to guys who is interseting model rockets, tell me which procedure should I follow, such that the given information about this rocket is enough to calculate the required thrust or not, do i need to calculate any other quantities to obtain required thrust or any other ideas to approach to this problem ?
Thank You,
 
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  • #2
You may well get some good answers here but I would expect that a model rocket forum is really where you should be looking. Ideal calculations are fine in the lab but you're talking about a practical situation where experience will tell you a lot in addition to a math model. For example, how much drag does your particular rocket shape have? Are there fins that add to the drag?

Also, you need to make some effort on your own. On this forum we don't spoon feed answers, we expect you to have shown some work of your own before we can jump in with help. Do you know any relevant equations to help towards your answer?
 
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  • #3
uzt said:
Hi, I am currently working on a Hybrid Rocket which uses fuel grain as 3-D printed ABS and oxidizer as N2O, but i need to calculate some basic parts such as required thrust to reach specific altitude. I want to calculate the required thrust to reach 1.5km for 10kg rocket with 7cm radius. It will launched 85 degrees vectircally. I want you to guys who is interseting model rockets, tell me which procedure should I follow, such that the given information about this rocket is enough to calculate the required thrust or not, do i need to calculate any other quantities to obtain required thrust or any other ideas to approach to this problem ?
Thank You,
Also, are you part of a rocketry club, or do you have an in-person Mentor to help you with this and make sure your work is safe?
 
  • #4
phinds said:
You may well get some good answers here but I would expect that a model rocket forum is really where you should be looking. Ideal calculations are fine in the lab but you're talking about a practical situation where experience will tell you a lot in addition to a math model. For example, how much drag does your particular rocket shape have? Are there fins that add to the drag?

Also, you need to make some effort on your own. On this forum we don't spoon feed answers, we expect you to have shown some work of your own before we can jump in with help. Do you know any relevant equations to help towards your answer?
Hi, thank you for your answer.
First of all, I tried to determine the regression rate of given propellent to obtain mass flow rate and then trying to obtain thrust from the formulation of;
T=m(dot)*Ve+(Pe-P0)*Ae, where m(dot) is mass flow rate, Ve= velocity at exit of the nozzle, Pe=Pressure at exit of the nozzle, P0=Free stream pressure, Ae=Area ratio of throat to exit.
But, then I realized that determination of the regression rate of the propellent is not easy. I faced several problems such that obtaining mass flow rate, and then I tried to calculate as projectile motion with the consederition of air resistance on particular body, but again I faced the problem which is coefficient of drag for this particular body. Then, I found a website which contains several equations about maximum altitude and velocity of model rockets. Here is the site
-> http://www.rocketmime.com/rockets/rckt_eqn.html#Theory
but, I do not know the formulas are true or not because there is some untitled variables which is not understandable at all.
So, my question is what should I do. Am I doing right or not? How can i calculate the mass flow rate or is it possible to calculate with these given information? Also, if you know any relevant books or articles about rocket propulsion, I am glad to hear.
 
  • #5
berkeman said:
Also, are you part of a rocketry club, or do you have an in-person Mentor to help you with this and make sure your work is safe?
I am not a part of a rocketry club or something. Just trying to build by my own with help of the book Fundamentals of Aerodynamics by John D. Anderson.
 
  • #6
uzt said:
I am not a part of a rocketry club or something. Just trying to build by my own with help of the book Fundamentals of Aerodynamics by John D. Anderson.

@berkeman 's question was more of a hint. Doing it on your own may expose you to risk of injury. Model rocketry with the help of a local club is safer and is recommended whenever possible.

Edit: @phinds ' post was also a hint to bring your questions to a rocketry forum. Discussing dangerous topics on PF is not allowed.
 

FAQ: How can I calculate the required thrust for my model rocket design?

What is a model rocket?

A model rocket is a small, scaled-down version of a real rocket that is designed and built by hobbyists for recreational use. It is powered by a rocket motor and can reach heights of up to a few hundred feet.

What materials are commonly used in model rocket design?

The most commonly used materials in model rocket design are lightweight plastics, such as balsa wood and cardboard, as well as lightweight metals like aluminum and titanium. These materials are chosen for their strength, durability, and low weight, which are all important factors in designing a successful model rocket.

How do you determine the stability of a model rocket?

The stability of a model rocket is determined by its center of gravity (CG) and its center of pressure (CP). The CG is the point at which the rocket's weight is evenly distributed, while the CP is the point at which the air pressure acting on the rocket is balanced. For a stable flight, the CG must be located in front of the CP.

What factors should be considered in choosing a rocket motor?

There are several factors to consider when choosing a rocket motor for your model rocket design, such as the rocket's weight, size, and desired altitude. Other factors include the type of motor (solid or liquid), the motor's thrust-to-weight ratio, and the motor's impulse (total energy output).

How can I improve the performance of my model rocket?

To improve the performance of your model rocket, you can make changes to its design, such as reducing its weight, increasing its aerodynamics, or choosing a more powerful motor. You can also experiment with different launch angles and altitudes to achieve better flight results. Regular maintenance and careful assembly can also contribute to better performance.

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