Today, we have an experiement for you!

Rocket Stability 

Rocket stability is an important issue for rocket scientists. The success of a space launch depends upon “pinpoint” accuracy. Stability means making sure the rocket follows a smooth path in flight. If it wobbles, the ride will be rough and extra fuel will be burned to get back on course. If it tumbles, it’s time to push the destruct button! An unstable rocket is dangerous.

Luckily (for astronauts!) it is relatively easy to ensure stability when traveling through the atmosphere if two things are kept in mind. These two things are center of mass (COM) and center of pressure (COP).

The COM is the balance point of a rocket. Try balancing a pencil or ruler on your finger. If the pencil or ruler rests horizontally, the COM is directly over your finger. If the COM is to the right of your finger, the stick will tip to the right. If to the left of your finger, the stick will tip to the left.

An object, tossed into the air, rotates around its COM. Rockets also try to rotate around their COM while in flight. If this rotation is allowed to happen, the rocket becomes unstable. This is where COP comes to the rescue.

Now COP is a little more complicated but it is also a balance point. It is the balance point of the air pressure applied to the rocket by air molecules striking it as it flies through the air.

For a stable rocket, the COP is located to the rear of the rocket and the COM to the front.

Watch a real life rocket launch here!

Your task

Having learnt about the COP and COM, watch this  video about paper rockets. If you have the resources at home, you could try to make one! You will need: paper, sellotape and a straw.

After you watch the video, answer the question below…

What do you think will happen if you change the length of the rocket or the number of fins? 

17 comments on “Science-Rockets!

  1. I think the more fins you have, the more stability the rocket has but if you put too many fins the rocket will become to heaven and not fly high.
    If you change the length of the rocket, also if you make a bigger rocket it will increase in weight making it go through the air slower than a lighter one.

  2. Jeanne Yr 6 says:

    I think if you change the number of fins either the rocket wont be as stable if take some away. However if you add fins the rocket will go straighter and more stable.

  3. If you make the rocket longer, it will be heavier and you’ll need more fuel to make it fly. The more fins you have the more stable the rocket will fly but if you have too many, it may be hard to avoid things or change direction.

  4. If you add more fins to the rocket, I think that they will make the rocket heavy causing it to fly lower than it should.If you change the length of the rocket,like the fins,it will be too heavy and won’t be able to go as high as other rockets.

  5. Jade year6 says:

    I think the more fins you put the more balance the rocket will get therefore put to many it will b even more stable so will do even quicker I think about 3 fins is a good amount.
    If you put less fins the rocket will not be so stable and will wobble.

    If you change the length of the rocket to make it more thinner and streamline it will be quicker.though if you make thicker s jada said it will be heavier and not go that’s fast.

  6. I think that if you add more fins it will become a more stable so it will but if there are too many the weight of it will slow it down and eventually go back to the ground. Also If there are too many fins all over the place near to the aerodynamic point of the rocket it won’t give it space when going up. If we change the length of the rocket it will have more space for fins which will make the rocket stable.

  7. Good Morning Miss Gorick and Mrs Healy,
    I think that the more fins you have the more stability the rocket would have so it wouldn’t just wonk around twisting and turning a bit like Jada said; it would make the rocket fly in a straight line. In my view i think the smaller and lighter the rocket is with more fins would be quick and slick and it wouldn’t take as long as a rocket with not many fins and a very long body of the rocket.

  8. Good morning to you and a good April the 1st of the first of April to all.

    Rockets are simple vehicles. They’re are transporter in the shape of a cylinder, with a circle based pyramid on top. Changing length of the rocket would change the speed, but it depends on how ou change it. There would be either effect: an effect where when you stretch it out, you have to stretch or shrink the entire rocket. The bigger the rocket is the slower it’ll go, the smaller, the faster. Changing size of the rocket wouldn’t effect it that much, it would only change the speed (if what I believe is correct).

    Adding more fins can change a bit to. The fins purpose is to keep the rocket on course, without them it’d be hard, and the rocket won’t be able to stabilise. It is crucial for fins to be placed correctly to, and if you have so many, it would be hard to find the right places for all of them. They have to be put symmetrical to help the rocket stay on course. Like changing the size of the rocket, adding fins will effect the speed, in this case, the rocket will move slower, but smoother.

    This is what I think would happen. I also think that people have another way of seeing these things. I wonder what those other ways are?

    – Your guy, Ethan. ?

  9. Making a rocket longer would make it heavier and more difficult to control because it’s more area to manage.
    On a rocket fins are used to stabilise. Stabilisers are also used to control the rocket’s direction. More fins would result in better stability.

  10. I think that if there are more fins the rocket will be more stable, but it would make it heavy, and so it will fly low. I also think that if you make the rocket bigger in length the rocket might not be stable on one end and then collapse, or it will make it too heavy. I did the experiment and I found out that the more fins there are the more stable the rocket, but it was heavier and it won’t fly high or fly a long way.

  11. ?(●'◡'●)paloma says:

    Hello everyone ,

    I think that the more fins there are the more stable the rocket is. It would fly around like crazy. It would stay normal like Jada and Elly said it would fly in a straight line and it would be quick and slime!?‍?

  12. By adding more fins will make the rocket heavier and that will cause more fuel to be added but the lighter it is the better.

  13. Morning tatoes☺️,

    I think that the rocket will become unbalanced if you add more fins to one side and it will be to heavy and will not go as far and as fast as other rockets.

  14. Laetitia says:

    If you made the rocket longer and thinner, it would increase the chances of the rocket flying straight and the more fins, the more stable the rocket would be. Although if you put on too many fins they will weigh the rocket down and the rocket will crash.

  15. Miss Gorick says:

    Afternoon all! You have all made interesting predictions and I agree with you that if the rocket has fins, it should be more balanced 🙂

    The thought of travelling into space makes me feel scared! What do you all think?

  16. I would be more excited to go into space, because I could end up making a big discovery, and I know my fellow crew mates would have me back all the time.

  17. Laetitia says:

    I would feel scared too if I was being fired into space floating about inside a giant metal cylinder for a week or 2.

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