Help with building a school rocket

In summary, this student is looking for advice on building a water rocket. They have gathered some information and are currently thinking about fuel options. They are also wondering if they need to worry about the rocket surviving the landing.
  • #1
StellarisVoid
13
4
Hello,
I attend a physics club at my school and now, we are building rockets until winter. I need some help because I really want to beat the GCSE students. We are in self chosen teams and the winner is who gets their rocket the highest(hopefully it will go high enough so we can't see it)
I have already gathered some information:
I should have a rounded nose for the rocket(decreased drag)
Centre of mass should be towards the tip (increase stability)
Placing fins at the bottom increases stability.

My current thoughts for fuel are:
Water
Vinegar and Baking soda.
Is there anything else I could use as a more powerful fuel? *I am in the UK so therefore, I cannot use solid fuel*

Should I 3d print the rocket, or at least attempt to? (most people will be using bottles so I hope I can do something different)
How do water rockets work? I can't wrap my head around how to push the water quickly.
What is the optimal fin shape?

Any other advice and things I should know? Help is greatly appreciated!
 
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  • #2
StellarisVoid said:
How do water rockets work? I can't wrap my head around how to push the water quickly.
What is the optimal fin shape?
Water rocket toys are inexpensive. Buy one to experiment with and to learn from. What is the optimum ratio of air volume to water volume?

1667411640884.png
 
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  • #3
StellarisVoid said:
We are in self chosen teams and the winner is who gets their rocket the highest(hopefully it will go high enough so we can't see it)
I have already gathered some information:
Sounds like a fun project. Hopefully the judges have a quantitative way to measure the height reached by each rocket.

Can you post the full text of the project/assignment/competition? It will help us to offer suggestions if we know all of the rules you are working under. Also, it sounds like you are not allowed to use combustion for propelling the rocket?

Can you post links or pictures to previous competitions? Thanks.
 
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  • #4
berkeman said:
Sounds like a fun project. Hopefully the judges have a quantitative way to measure the height reached by each rocket.

Can you post the full text of the project/assignment/competition? It will help us to offer suggestions if we know all of the rules you are working under. Also, it sounds like you are not allowed to use combustion for propelling the rocket?

Can you post links or pictures to previous competitions? Thanks.
This is just a competition the physics department organised and not an official competition.
Aim is to make our rockets travel as far up as possible.
Solid fuel is illegal in the UK which is sad:frown: otherwise I would've used "Rocket Candy".
 
  • #5
anorlunda said:
What is the optimum ratio of air volume to water volume?
I am not sure.
I am in Year 8 so I do not know much about rockets and how the aerodynamics work(sadly) so I was hoping to find out some stuff here.
 
  • #6
StellarisVoid said:
This is just a competition the physics department organised and not an official competition.
It's still important to understand the rules of the competition. For example, there are other ways to launch a rocket without propellant...

https://www.spinlaunch.com/#p1

1667412587369.png
 
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  • #7
berkeman said:
It's still important to understand the rules of the competition. For example, there are other ways to launch a rocket without propellant...

https://www.spinlaunch.com/#p1

View attachment 316598
I don't think that there are any particular rules apart from not using solid fuel and not to make anything too complicated as well as making sure we won't set the field on fire. Basic safety rules only seem to apply but I will check tomorrow.
Thanks for the link! I'll have a look at it.
 
  • #8
Other things to check:

** Does the rocket need to survive the landing? (may require a parachute system if your rocket gets high enough)

** Can part of the rocket/launch system stay on the ground after the launch, or does everything need to go up with the rocket system?

** How tall and how heavy can it be?

** Any bonus points for carrying a small WiFi camera along to send back video? :smile:
 
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  • #9
berkeman said:
** Does the rocket need to survive the landing? (may require a parachute system if your rocket gets high enough)
I don't think so because most people attending the club aren't too good at physics so the teachers aren't expecting much from us.
berkeman said:
** Can part of the rocket/launch system stay on the ground after the launch, or does everything need to go up with the rocket system?

** How tall and how heavy can it be?
I will check tomorrow, I too was wandering what size rocket am I allowed to make.
berkeman said:
** Any bonus points for carrying a small WiFi camera along to send back video? :smile:
That's a good idea! I will look into it.
Do you have any recommendations for a camera?
 
  • #10
StellarisVoid said:
I am in Year 8 so I do not know much about rockets and how the aerodynamics work(sadly) so I was hoping to find out some stuff here.
The way to find that out is to try it. In other words experment using the toy rocket.

There are also many Youtube videos of larger water rockets. You can learn from them.

It is hard for us to believe that there are not written instructions and rules for this competition.
 
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  • #11
StellarisVoid said:
Hello,
I attend a physics club at my school and now, we are building rockets until winter. I need some help because I really want to beat the GCSE students. We are in self chosen teams and the winner is who gets their rocket the highest(hopefully it will go high enough so we can't see it)
I have already gathered some information:
I should have a rounded nose for the rocket(decreased drag)
A pointed nose might be better.
StellarisVoid said:
Centre of mass should be towards the tip (increase stability)
This sounds wrong. CORRECTION: His statement is not wrong. Aerodynamically, it is correct. Furthermore, the fixed nozzle makes this correct even for the thrust force.
StellarisVoid said:
Placing fins at the bottom increases stability.

My current thoughts for fuel are:
Water
Standard, easy to load, and safe.
StellarisVoid said:
Vinegar and Baking soda.
Not sure how you can load this in.
StellarisVoid said:
Is there anything else I could use as a more powerful fuel? *I am in the UK so therefore, I cannot use solid fuel*

Should I 3d print the rocket, or at least attempt to? (most people will be using bottles so I hope I can do something different)
3d print is probably not strong enough. Try to get an aerodynamic bottle.
StellarisVoid said:
How do water rockets work? I can't wrap my head around how to push the water quickly.
Compressed air.
StellarisVoid said:
What is the optimal fin shape?

Any other advice and things I should know? Help is greatly appreciated!
 
Last edited:
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  • #12
By the way, hobbyists have quite a bit of success making water rockets out of 2 liter soda bottles.

You may be able to finish a soda bottle project and launch it before sunset today. Another team may want a year or two to design and build something that performs better. Does this competition have a specific deadline date? Is there any measure of merit other than how high the rocket goes? Do the physics teachers have a reliable way to measure how high the rockets go?

Edit: I think what I'm hinting at is that there are amateur rocket societies almost everywhere. Contacting them for advice, or assistance in running the competition might be a very smart thing to do.
 
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  • #14
berkeman said:
Hopefully the judges have a quantitative way to measure the height reached by each rocket.
Trig! It was practically invented for this!
 
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  • #15
FactChecker said:
This sounds wrong.
It's not. You want the center of gravity in front of the center of pressure.

That's why fins are on the bottom and not on the top.
StellarisVoid said:
Solid fuel is illegal in the UK which is sad
No it isn't. I can see several places that sell it.

It's entirely possible that your rules prohibit them, but that's why we asked you about them.
 
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  • #16
Vanadium 50 said:
It's not. You want the center of gravity in front of the center of pressure.
I've always wondered about that. Can you elaborate please? The helicopter is an obvious counterexample, but a helicopter is not a rocket...
 
  • #17
Vanadium 50 said:
It's not. You want the center of gravity in front of the center of pressure.
That's why fins are on the bottom and not on the top.
I stand corrected. Aerodynamically, that is clear. And for a fixed nozzle, I was (once again) misled by my intuition. (I forget what that error is called, but it is well known and I have made it here before.)

UPDATE: The intuition mistake that I am referring to is called the "pendulum rocket fallacy".
 
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  • #18
berkeman said:
a helicopter is not a rocket...
Exactly.

The thing is we are used to thinking "stable means weight on the bottom". But stable actually means "a small perturbation yields a restoring force (and restoring torque) in the opposite direction".

For a vase, you have two forces on it - gravity and the normal force. You want the center of gravity low so that the perturbing torque is minimized. In a rocket you have gravity and no normal force - instead of the normal force you hgave the sum of all the aerodynamic forces on it, The two axes about which these two torques operat are called the "center of gravity" and "center of pressure". Torque is the more relevant concept - we know the forces don't balance because the rocket zooms up.

Long story short, if the COP is behind the COG, a perturbing torque about the COG has as aerodynamic forces turning the rocket in the opposite direction - providing a restoring torque. Put it ahead and they are in the same direction, cwusing instability.
 
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  • #19
I checked at school today and there are no rules which is weird because health and safety? Furthermore, the physics teacher encouraged us to launch rockets at the PE Department and the school on the opposite side of the road:oldconfused:
Although I would love join a rocket club or something similar, I do not have one in my area and the nearest rocket club is about 50 miles away :(
 
  • #20
OK, then why not try for the KISS prize? (KISS=Keep It Simple Stupid). You may be able to build and launch it tomorrow. The main things you need are two 2 liter bottles and a bicycle pump.

 
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  • #21
anorlunda said:
OK, then why not try for the KISS prize? (KISS=Keep It Simple Stupid). You may be able to build and launch it tomorrow. The main things you need are two 2 liter bottles and a bicycle pump.


I use to do this as a kid and have seen the results of the bottle rupturing.
If it were me in the Youtube video, I'd have on safety glasses. Just sayin'
 
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  • #22
dlgoff said:
I use to do this as a kid and have seen the results of the bottle rupturing.
If it were me in the Youtube video, I'd have on safety glasses. Just sayin'
I was wondering about that. Good safety tip, Don!
 
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  • #23
anorlunda said:
OK, then why not try for the KISS prize? (KISS=Keep It Simple Stupid). You may be able to build and launch it tomorrow. The main things you need are two 2 liter bottles and a bicycle pump.


I might end up doing this. It would be quite funny bringing a whole 2m tall "launcher" into school.
 
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  • #24
Another question, in the video, the demonstrator removes a 'pin' to let the water out. Is this pin in the bottle or the pipe?
 

1. How do I design a rocket for a school project?

Designing a rocket for a school project involves several steps. First, research the basic principles of rocket design and the different components that make up a rocket. Then, determine the purpose and specifications of your rocket, such as its size, weight, and intended flight distance. Next, create a detailed design plan with diagrams and calculations. Finally, gather materials and assemble your rocket according to your design plan.

2. What materials do I need to build a school rocket?

The materials needed to build a school rocket will depend on your design and specifications. However, some common materials used in rocket construction include cardboard or foam for the body, balsa wood or plastic for the fins, a plastic or metal nose cone, and a motor or engine for propulsion. You may also need glue, tape, scissors, and other tools for assembly.

3. How do I ensure the safety of my school rocket?

Safety is a crucial aspect when building a school rocket. Make sure to follow all safety guidelines provided by your school or project supervisor. Use appropriate materials and tools, and always have adult supervision when handling potentially hazardous materials. Conduct test flights in a safe and open area, away from people and buildings. If your rocket uses a motor or engine, make sure to follow the manufacturer's instructions and safety precautions.

4. How can I make my school rocket fly higher?

There are several ways to increase the altitude of your school rocket. One way is to reduce the weight of the rocket by using lightweight materials and minimizing the number of components. Another way is to increase the thrust of the rocket by using a more powerful motor or engine. You can also experiment with different fin designs and placement to improve stability and aerodynamics. However, always make sure to follow safety guidelines and regulations when making modifications to your rocket.

5. Can I use a pre-made rocket kit for my school project?

Yes, you can use a pre-made rocket kit for your school project. These kits often come with all the necessary materials and instructions for assembly. However, keep in mind that using a pre-made kit may limit your creativity and learning experience compared to designing and building your rocket from scratch. If you do choose to use a kit, make sure to follow all instructions carefully and customize it to fit your project's requirements.

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