MISSION BRIEFING

Activity: Design Stabilizing Fins

Prep Time: 15 min

Activity Length: 60 min

Task: Create fins for a foam rocket that lands

downrange and follows a desired pathway.

By the end of this activity participants will 

• Know that fins can alter the stability of a rocket.

• Understand the relationship between a rocket’s

stability and its trajectory.

• Be able to improve rocket stability.

Materials

• 30-cm piece polyethylene

foam pipe insulation (1

piece per group)

• Foam food trays,

cardboard, or stiff poster

board

• Long tape measure and/

or rolling measure wheel

(used to indicate the

horizontal rocket range

and to measure distances

to where the rocket

landed)

• Launcher quadrant

template printed on

cardstock

• Rubber bands (size 64)

• Safety glasses

• Duct tape

• Scissors

• Meterstick

• Masking tape

• Zip ties

• Binder clip

• Pushpin

• 75-cm string

Safety

Remind participants that rockets should never be launched 

toward anyone. Safety glasses should be worn during launch.

Preparation 

Watch the “DIY Space: Build a foam rocket” video tutorial for 

instructions on building the rocket and conducting the activity.

SLS 

 

6

MISSION BRIEFING

Activity: Design Stabilizing Fins

Prep Time:

Activity Length:

Task: Create fins for a foam rocket that lands

downrange and follows a desired pathway.

15 min

60 min

NASA’s Space Launch System (SLS) will be 

the most powerful rocket NASA has ever 

built. When completed, SLS will enable 

astronauts to begin their journey to explore 

destinations far into the solar system. For 

more information on SLS, visit www.nasa.

gov/exploration/systems/sls/index.html.

MISSION GUIDANCE...

DO

• Keep a protractor nearby

to help participants with

launch angles.

• Allow participants to design

and	build	unique	fins.

MAYBE

• Create the launcher

ahead of time.

• Mark the launch pathway

ahead of time.

DON'T

• Give participants

templates	for	fins.

• Let participants launch

the rockets toward one

another.

Build It (Example illustrations below)

1. Using scissors, cut one 30-cm length of pipe foam for each

team.

2. Cut four equally spaced slits at one end of the tube. The slits

should be about 12 cm long. The fins will be mounted through

these slits.

3. Cut a 12-cm length piece of duct tape down the middle to

make two pieces. Place one piece over the other, sticky to

shiny side, to make the tape double strong.

4. Slip a rubber band over the tape and press the tape around

the nose end of the rocket (opposite the end with the slits).

5. Press the tape tightly and reinforce it with another length of

tape wrapped around the tube.
6. Cut fin pairs from the foam food tray or stiff cardboard. Refer to the fin diagram. Both fin pairs should be notched 

so that they can be slid together as shown in the diagram. Different fin shapes can be used, but they should still 

“nest” together.

7. Slide the nested fins into the slits cut in the tube. Close off the slits with a piece of duct tape wrapped around the 

foam tube. The rocket is finished.

Steps 1 and 2

30 cm

Step 3 Step 4

Step 5

Step 6

Step 7

Quick Tips and Tricks

• Some participants may struggle with “nesting fins.” Assist them with fins that nest/slide together.

• To ensure that vertical launch height is unchanging, place the bottom edge of the launcher on a table.

• Participants should measure two distances ONLY: downrange distance and distance off course.

7
Test It

1. Build the model rocket launcher (pattern included at the end of this activity).

2. Put a piece of string or tape on the ground in a straight line directly in front of the launcher. This line will be used to

measure the distance the rocket flew from the launcher and how far off course the rocket traveled.

3. Have participants launch the rockets at a specified angle using the rocket launcher.

A

B D

F

G

C

E

H

Meterstick

A. Launch site

B. Ideal or planned trajectory

C. End point of planned trajectory

D. Actual trajectory of launched

rocket

E. Point where rocket landed

F. Downrange distance traveled

G. Straight line from launch site

to point where rocket landed

H. Distance off course

4. After they have launched, participants will record the distance the rocket traveled (line segment F) and how far off

course the rocket went (line segment H).

Improve

1. Give each team additional supplies to redesign and build another set of fins. Ask them to consider the stability and

trajectory of their first set of launches and think of what improvements could be made to their fin design.

2. Discuss different variables that may impact their results, including the elasticity of the rubber band.

3. The goal is to increase the stability of their rocket, which is measured by how close they are to landing near the

tape measure or meterstick without a significant decrease in the range of their rocket or how far the rocket traveled

from the launch site.

4. Teams will repeat steps 4 to 6 of the rocket “Build It” procedure, conduct three launches, and then compare the

results of their redesigned fins with the results of their original design.

Extension

• Ask participants to add weight to their rockets by taping pencils to them. Give participants a limited number of

pencils they can use. Consider limiting where they can add the weight.

• Ask participants to consider the center of mass and investigate how it impacts rocket stability.

• Ask participants to measure the dimensions of each fin and use geometry to find the area. Gather data from the

entire class. Plot a graph comparing the area of a fin with the horizontal distance traveled by each rocket.

• For advanced participants, apply the rules of sine, cosine, or tangent to find angle CAE (in degrees) between the

planned path of travel and the actual path of travel for the rocket. By finding angle CAE, teams can compare results

across different fin designs, launch angles, and so forth.

• For advanced participants, capture video of the launch and use the open-source Tracker Video Analysis and

Modeling Tool (https://physlets.org/tracker) to collect data about position, velocity, or acceleration.

Challenge Questions

• How does a rocket’s stability affect trajectory?

• Why was it important to launch from different angles?

• How do you think the size, shape, weight, or location of fins on a rocket can affect its stability?

8
Launch Quadrant Pattern

(Actual size)

Fold on the dashed line. Lay fold on the upper edge of the meterstick and wrap paper around to the other side. The black dot of the protractor should be placed on the 60-cm mark of the stick. Tape the ends to hold the protractor in place.

Making the Launcher

1. Print the quadrant pattern on

cardstock paper.

2. Cut out the pattern and fold it on

the dashed line.

3. Tape the quadrant to the

meterstick so that the black dot

lies directly over the 60-cm mark

on the stick.

4. Press a pushpin into the black

dot.

5. Tie a string to the pushpin and

hang the binder clip on the end

of the string. The weight should

swing freely.

9

60 cm (24 in.)