CPD Workshops

Stomp Rockets

by Amy Collins January 9, 2019

This activity was created as part of a Gratnells What’s In My Tray CPD workshop for secondary science teachers and technicians to support practical work and delivery of the curriculum. It can be carried out as a stand-alone activity for students or combined with other activities from the session to form a STEM carousel.

You will need (per team of 4):

Kit for the launcher (sufficient to make one launcher):

  • 1 x Deep Gratnells tray with lid
  • 1 x Empty 2 litre bottle (e.g. coca cola bottle)
  • 1 x Roll of duct tape
  • 1 x 40cm piece of PVC pipe (½-inch diameter)
  • 1 x 1m piece of clear flexible vinyl tubing (½- inch inner diameter, 5/8-inch outer) to fit into the mouth of the bottle and over the end of the PVC pipe

Kit for the rockets (sufficient to make four rockets, one rocket per person):

  • 1 x shallow Gratnells (F1) tray with lid
  • 4 x A4 paper (use different coloured paper for each team)
  • 4 x A5 card (use same colour as paper)
  • 4 x 30cm piece of the same PVC pipe used for the launcher per person
  • 4 x scissors
  • 2 x roll sticky tape
  • 4 x felt tip pen
  • Optional extra equipment for decoration e.g. glitter glue, washi tape, paint.

Kit for measuring and targets (optional):

  • Long measuring tape or trundle wheel
  • Cones or flags to mark the distance travelled by the furthest rocket
  • A selection of different sized Gratnells trays to use as targets

Tip: If you plan to have multiple teams taking part in this challenge, multiply the kit by the number of teams, use two trays to store the equipment for each team and use different coloured paper and trays for each team. This helps to organise everything and differentiate the rockets.

This activity also works for individuals or smaller teams, just reduce the amount of equipment provided to make the rockets accordingly and increase the amount of time allocated to complete it.

Preparation:

  • Place the equipment for making the launcher into one deep Gratnells tray and put the lid on.
  • Place the equipment for making the rockets into one shallow Gratnells (F1) tray and put the lid on.
  • Repeat for each team.

What to do:

  • Approach the tray and lift the lid
  • Use the contents of the trays to make one launcher and four rockets (one rocket per person in the team).
  • The winning rocket will be the one that travels furthest so make sure your rockets are aerodynamic.
  • Mark each rocket clearly with your group’s name.

Tidy up time:

  • Once the time allocated to complete the activity has ended, put your completed rockets and launcher back into the deep tray. Put your equipment and unused materials back into the shallow tray. Everyone will launch their rockets together at the end of the session.

When all participants/teams have completed the activity, conduct the flight tests outside or in a large indoor space free of obstacles. Each team needs to decide on one team member to hold the launch pipe and load the rockets and another to do the stomping (using one foot only).  All teams should set up their launchers in a line facing the same way. All teams then load their first rocket on to the launch pipe, give a countdown “3, 2, 1 blast off!” and simultaneously launch the rockets by stomping on the bottles. Repeat the loading, countdown and launch for the other three rockets.

Measure or observe the longest distance travelled by the rockets. Winning team (furthest rocket) gets 5 points, next team 4 points and so on.

Optional extra bonus points for accuracy could be made available for landing a rocket in a tray. If you would like to do this, spread a selection of empty Gratnells trays across the landing area for the teams to aim at before launch commences.

Tip: Use the images below as a guide for how to make your rocket and launcher or have a look at our Build A Rocket video for some examples.

What is happening? (from the Exploratorium)

Stomp rockets work because of air pressure. You are creating a high-pressure region in the bottle by squashing the air inside into a much smaller space when you stomp on it. At the other end of the launcher, the air in the pipe and paper rocket are at normal pressure.  Air naturally wants to move from high pressure to low pressure. The moving air is what exerts a force on the rocket and launches it. Increasing that force will make your rocket go higher/further. The change in velocity is proportional to how much force you apply and the time during which the force is applied. The change in velocity is inversely proportional to the mass of the rocket. Therefore, lighter rockets tend to go further/higher.

To move through the air, a rocket has to push air aside. Things that are designed to travel quickly, such as sports cars and jets, are shaped to minimize the amount of air they push aside to move forward. Your paper rocket has been designed to move through the air efficiently, too. The V-shaped nose helps it cut through the air as it flies and the fins help stabilise it and move the rocket in a straight line.

If you tried two different-length paper tubes for your experiments, you may have noticed that the longer rocket flew further/higher than the shorter one. This is because a long rocket body has more distance (length of rocket) over which the force of the air from the PVC pipe is applied, which increases the amount of time during which the force is applied. As the air expands into the pipe and rocket, however, the force decreases, so there is an optimal length of rocket where force and time are maximized.

These variables – the force of the stomp, the length of time during which the force is applied to the rocket (which, in this case, translates to the length of the rocket), and the mass of the rocket – all affect how far the rocket flies.

Other things to try:

Ask yourselves the following questions

  • What happened to your rockets? Did all of them launch? If not, why not?
  • Which rocket designs went the furthest? Why?
  • Does it matter who stomps on the bottle?
  • Does the angle of the launch pipe effect distance travelled?
  • Does the length of the rocket (portrait or landscape rolling) effect the distance travelled?
  • Does the presence or absence or shape of fins on the rocket make a difference?
  • Does the angle of the rocket’s nose point make a difference?
  • What other variables could you change and how will you measure the effect?

Make a few more rockets to try out different designs, make predictions as to which will be the best and test them to see if they travel further. Use a tape measure or trundle wheel to record distance travelled during each test or place a labelled cone or flag where each rocket lands.

Health & Safety

As with all Gratnells Learning Rooms What’s In My Tray activities, you should carry out your own risk assessment prior to undertaking any of the activities or demonstrations. In particular, when launching your rockets, ensure you always launch away from other people and that nothing is obstructing the direction of travel.