Scratch Golf Ball Rocket

On the other end of the size spectrum, trying to build the smallest rocket is a great way for children to learn rocket science.

 

Kids start with the assumption that a bare Estes rocket engine should go a long way, but it skips randomly through space bouncing all around you. Next thought: it needs fins and a nosecone. So, we add a nose cone and some fins to a motor, and it is still totally unstable (but now with a sharp point on it!).

 

You need a proper balance of weight and thrust vectors. A long rocket tube shifts the center of gravity forward, like a lever arm or see-saw. With a short rocket, you need a lot of nose weight to shift the balance point forward. So the shorter the rocket tube, the heavier the nose needs to be. My young son had the clever idea to tape a stray golf ball onto the nose of his 6” rocket made from the remains of others… and it flies perfectly straight every time. It also launches the golf ball at apogee instead of popping a chute…. So he can take on Big Bertha with his little rocket driver…

 

It’s Rocket Science redux! CP < CG

 

To be stable, the rocket’s CP (Center of Pressure) should be one or two body diameters behind the CG (Center of Gravity).

 

The fins are there to streamline the flow of air and provide a large surface area to help to keep the center of pressure below the center of mass of the rocket.

 

For more on stability, check out this page.

 

At high power launches, random dances, pinwheels, and landsharks are just big boy versions of the same experiments gone terribly wrong… =)

  • Dabbler 9y

    That's quite a payload! Hope someone yelled "Fore!" before launching this one!
  • Leino Olé 9y

    i wanna know which young boy was the 'clever' one....
    ?
    :)
    he deserves kudos!
  • Serena 9y

    oh! goody! .........evening bag size....;))...*
  • Erik Charlton 9y

    Next time you got'a try a launch with a "radar golf ball"...It might help with your recovery efforts =) Check this out --> www.golfsmith.com/ps/products/246863

    Thinking you could put gof balls in every rocket!
  • David Lindes 9y

    Thank you for the lesson! Very interesting.

    One question: Could you make something stable by putting an even bigger drag vector on, e.g. fins extending down, below the CP significantly, but with significant drag? (sorry, random thoughts of funny looking rockets are going through my brain right now. ;-)
  • Steve Jurvetson 9y

    Yes. larger fins, farther back will help, as will a longer rocket. You can conservatively think of the CP point as the half-way point the 2D side-silouette of the rocket (the cross-sectional area projection).
  • Slobodan Stupar 9y

    WOW!
  • Paul 8y

    Hi, I'm an admin for a group called Kids learning science, and we'd love to have your photo added to the group.


    --
    Found in a search. (?)
  • Steve Jurvetson 8y

    crimfants: Happy to. You might like Geekdad too. I blogged about it here.
  • Jeff Burns 8y

    Hi, I'm an admin for a group called The Boy Bedlam Review, and we'd love to have your photo added to the group.
  • Patron Saint PR 7y

    This image was used on the Annick Press LIVEBrary Blog You can view the post at this URL:
    annickpress.blogspot.com/2008/02/steven-elwood-diy-scienc...
    If you wish any changes to the attribution please notify us so that we may implement them. Thanks!
  • Pierdante Romei 7y

    wonderful idea!
  • stéphane giner 7y

    holy shit that's awesome.
    i always loved to play with powder and i'm going to build my rocket asap !!!!

    anyways, GREAT shot !
  • Steve Jurvetson 7y

    heh.... glad to see you're inspired.... here's a hint about how far the rabbit hole can go: Click on top video
  • John Shappell 6y

    Hi Steve, nice shot of the rocket.
    John...
  • Mike Pedersen 4y

    I'll betcha some golfers would like to launch their golf balls, instead of hitting them, but again, they should be looking for golf training aids to help them play better golf and not a rocket launcher. LOL.
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