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Make a Model Rocket Land Vertically

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Abstract

Companies like SpaceX and Blue Origin are dramatically lowering the cost of space flight by designing reusable rocket boosters that land back on Earth. Getting a rocket to land vertically without any damage - and without using a parachute to slow it down - is quite a tricky physics problem! In this project you will modify your own model rocket so it can land vertically.

Summary

Areas of Science
Space Exploration
Physics
Difficulty
Method
Engineering Design Process
Time Required
Average (6-10 days)
Prerequisites

None

Material Availability

Model rocket kit required, see materials list for details

Cost
Low ($20 - $50)
Safety

Follow the National Association of Rocketry's Model Rocket Safety Code when doing this project.

Credits
Ben Finio, PhD, Science Buddies

Thanks to Blue Origin and Ken Hess for help developing this project.

Science Buddies is committed to creating content authored by scientists and educators. Learn more about our process and how we use AI.
https://www.youtube.com/watch?v=L_ISHsPX5pk

Objective

Modify a model rocket so it can land vertically.

Introduction

You might have seen a rocket launch on TV or online, but have you ever seen a rocket land? Check out this video of Blue Origin's New Shepard NS-25 flight and read about Science Buddies founder Ken Hess's experience on the flight here. Skip ahead to about 1:28 (one hour and twenty-eight minutes) in the video to see the booster land after separating from the crew capsule, which lands on its own. Figure 1 shows the booster after a safe touchdown.

Blue Origin NS-25 booster after touchdownImage Credit: Blue Origin
Figure 1. The NS-25's booster after a safe landing.

Getting a rocket to land vertically without falling over is quite challenging. Since it does not have parachutes, engineers use the rocket's engine to slow it down so it does not crash into the ground. The rocket uses an automatic computer control system to steer using fins. These fins adjust the aerodynamic forces acting on the rocket and help keep it upright. Landing the rocket upright so it can be reused, instead of letting it crash or burn up in the atmosphere, makes the cost of space flight much cheaper since you do not need a completely new rocket for each launch. 

Some model rocket enthusiasts have reproduced SpaceX and Blue Origin-style vertical landings. This requires large, expensive model rockets and a lot of experience. However, you can still demonstrate vertical landings using smaller (and much cheaper) beginner-level model rockets. To do so, first you need to understand a little bit of rocket science!

For the initial upward phase of a model rocket's flight, it is important for the rocket to be stable. This means that the rocket will fly relatively straight, or nose-first, and not turn sideways and crash (potentially into a crowd of onlookers). A rocket's stability depends on the relative locations of two things. The first is the center of mass (also called the center of gravity). This is the average location of the rocket's weight. In reality, a rocket's mass is distributed throughout the entire rocket, and gravity pulls down on each part of the mass. However, in physics, we can treat the weight as a single equivalent force that acts through the center of mass (Figure 2).

Diagram showing a model rocket's weight acting downward through its center of massImage Credit: Ben Finio / Science Buddies
Figure 2. A model rocket's weight acting downward through its center of mass (COM).

The other is the rocket's center of pressure. Air pressure acts along the entire surface of the rocket. However, just like with the rocket's weight, we can treat this distributed pressure like it is a force acting on a single equivalent point. We usually break up aerodynamic forces into two components: drag (which acts opposite the direction of motion) and lift (which acts perpendicular to the direction of motion). Note that since model rockets fly up, lift acts sideways (unlike an airplane that flies horizontally with the lift force acting up), as shown in Figure 3.

Lift and drag forces acting on a model rocket's center of pressureImage Credit: Ben Finio / Science Buddies
Figure 3. Lift and drag forces acting on the center of pressure (COP).
https://www.youtube.com/watch?v=k_1-fmQCjWo

How do the center of mass (COM) and center of pressure (COP) determine whether a rocket's flight is stable? For stable upward flight, the center of pressure must be below the center of mass. That way, when the rocket tilts away from the direction of motion, it experiences a restoring force (technically a restoring torque - a torque is a "twist" resulting from a force acting about a rotation point) that pushes it back in the correct direction (Figure 4). If the center of pressure is above the center of mass, then the resulting aerodynamic force is destabilizing - it will continue to push the rocket farther off course.

Diagram showing stable and unstable model rocket COM and COP locations during ascending flightImage Credit: Ben Finio / Science Buddies
Figure 4. When the center of pressure is below the center of mass during ascending flight, the rocket is stable (left). When the center of pressure is above the center of mass during ascending flight, the rocket is unstable (right).

So, that covers the first part of a rocket's upward flight. The center of pressure should be below the center of mass, which keeps the rocket flying with its nose pointed upward and its tail pointed downward. Normally, at apogee (the highest point of a flight), a model rocket's nose cone will pop off (but remain attached to the rocket's body with a rubber band), and a parachute will deploy. The entire rocket assembly then falls back to Earth, slowed down by the parachute. 

However, what if you want to model the flight of a reusable rocket, where the crew capsule (represented by the nose cone) separates and lands with parachutes, but the rocket descends vertically on its own without a parachute? You do not want the rocket to come down nose-first, like a lawn dart - you want it to remain upright and come down tail-first. This means that for a stable descent, you need to reverse the relative locations of the center of pressure and center of mass - the center of pressure should now be above the center of mass (Figure 5).

Diagram showing stable and unstable COM and COP locations for model rocket descending flightImage Credit: Ben Finio / Science Buddies
Figure 5. When the center of pressure is below the center of mass during descending flight, the rocket is unstable (left). When the center of pressure is above the center of mass during descending flight, the rocket is stable (right).

How can you change a model rocket's center of mass and center of pressure mid-flight? A rocket's mass is always changing because the engine gets lighter as it burns fuel. This removes mass from the back of the rocket, shifting the center of mass toward the front. Ejecting the nose cone removes both mass and surface area from the front of the rocket, shifting both the center of mass and center of pressure toward the back. You can also change a rocket's center of pressure using deployable ring or wedge fins like those used on the New Shepard vehicle. This project's procedure will show you how to reverse the aerodynamic stability of a basic model rocket using a ring fin that is exposed after the nose cone deploys, but there are many more things you can try. Can you get your rocket to land vertically?

Terms and Concepts

Questions

Bibliography

Materials and Equipment

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Experimental Procedure

Download PDF of Procedure
This project follows the Engineering Design Process. Confirm with your teacher if this is acceptable for your project, and review the steps before you begin.

If you have never launched a model rocket before, read a beginner's guide like this New to model rocketry? page before you proceed. In this project, you will start by assembling your model rocket according to the instructions that came with it. You will conduct a "string twirl test" to assess the model rocket's aerodynamic stability. You will then modify your rocket to see if you can make it fly tail-first after the nose cone has ejected and the engine has burned out. Optionally, you can conduct a live launch of your modified rocket if you follow proper safety precautions.

  1. Carefully follow the instructions that came with your model rocket kit to assemble your rocket, but do not attach the launch lug yet. The launch lug is the tiny tube glued on to the the rocket body that slides onto the launch rod. It is easier to find the center of mass and conduct stability tests when the launch lug is not attached yet (the launch lug is light enough that it should not significantly affect the center of mass). Figure 6 shows an example completed rocket.
estes alpha III model rocketImage Credit: Ben Finio / Science Buddies
Figure 6. An Estes Alpha III model rocket, assembled according to the instructions included in the kit.
  1. Put a new engine in the rocket. The engines are heavy, so it is important to include them when finding the center of mass.
  2. Balance the rocket horizontally on your fingertip to find the approximate location of the center of mass. Watch the video at the top of this page for a demonstration.
  3. Cut a piece of string about one meter long. Snugly tie one end of the string around the body of the rocket where you located the center of mass.
  4. Try to balance the rocket by hanging it from the string as shown in Figure 7. It can be difficult to get the rocket to balance perfectly, but do the best you can. Slide the string back and forth in small increments to adjust the balance if needed (this is why it is easier to do this step before the launch lug is attached since it can get in the way of sliding the string). Once you have gotten the string as close as possible to the center of mass, use a small piece of tape to hold it in place so it does not slide around.
String balance technique to find a model rocket's center of massImage Credit: Ben Finio / Science Buddies
Figure 7. Model rocket balanced while hanging from a string tied to its center of mass.
  1. Go outside to an area free from obstruction where you can twirl the rocket around without hitting anything. 
  2. Spin the rocket around and watch it closely. There are two ways to do this. Either way, make sure you spin the rocket fast enough that it does not drag on the ground.
    1. Keep your feet still and twirl the string over your head. The disadvantage of this approach is that you can only see the rocket when it passes in front of you, but the advantage is that you will not get dizzy!
    2. Hold on to the string and spin your entire body in circles. The advantage here is that you get a clear view of the rocket the entire time, but it might be hard to do this without getting dizzy! With this method, you can even hold a phone or camera in one hand and take a video of your rocket that you can analyze later. Figure 8 shows a screenshot from such a video. 
rocket string twirl test for aerodynamic stabilityImage Credit: Ben Finio / Science Buddies
Figure 8. A rocket being twirled around on a string tied to its center of mass. The rocket flies nose-first (from left to right in the image), indicating that it is aerodynamically stable. 
  1. Did your rocket fly nose-first? If so, it is aerodynamically stable - the center of pressure is behind the center of mass. This should be the case for a beginner rocket kit if you followed the instructions properly. If your rocket was not stable (it flew tail-first or flopped around):
    1. Double-check to make sure the string did not move around and is still tied to the center of mass.
    2. Try adding weight to the nose cone, for example by packing modeling clay inside it, to move the center of mass forward.
    3. Try using bigger fins to move the center of pressure backward. 
  2. For the next step you will need a used engine. You can do this by conducting a launch (following the instructions in your rocket kit and the NAR safety guidelines), or, with adult supervision, igniting an engine that is clamped into a very heavy vise (Figure 9).
An estes A8-3 model rocket engine clamped into a heavy viseImage Credit: Ben Finio / Science Buddies
Figure 9. An Estes A8-3 engine firing while clamped into a heavy vise.
  1. Swap out the unused engine in your rocket for the used engine.
  2. Remove the nose cone from your rocket. Cut the shock cord (the rubber band connecting the nose cone to the body), but leave the parachute attached to the nose cone. You should now be left with the main body of the rocket and a used engine, simulating what would happen after the engine has burned out and the nose cone has ejected. 
  3. Find the rocket's new center of mass by sliding the string as you did in step 5. Tape the string to its new location. 
  4. Repeat the spin test from step 7. Does your rocket flutter around, or is it aerodynamically stable? If it is stable, in which direction? Does it fly nose-first or tail-first? Remember that your goal is for the rocket to come down tail-first during descent. 
  5. Now for the most challenging part of this project: modify your rocket body so that it flies tail-first and is stable during the spin test. To do this, you will need to shift the center of upward so it is above the center of mass when the rocket is vertical. One approach to do this is to use smaller fins on the tail of the rocket (Figure 10) and add a ring fin around the top of the rocket's body (Figure 11). Figure 12 shows the completed rocket body.
Original size model rocket fins and modified smaller finsImage Credit: Ben Finio / Science Buddies
Figure 10. The original plastic fins on an Estes Alpha III rocket (left) and fins that have been trimmed down using scissors (right). The fins on the right show some damage from landing on a hard surface.

Ring fin made from cardboard tube attached to model rocketImage Credit: Ben Finio / Science Buddies
Figure 11. A ring fin made from a cardboard tube. The fin is attached to the rocket's body using two small paper spacers and glue. Take care to attach your ring fin symmetrically to the rocket's body, so the gap is even the entire way around.

Rocket modified for vertical descent with a ring fin and smaller tail finsImage Credit: Ben Finio / Science Buddies
Figure 12. Rocket modified for vertical descent with a ring fin and smaller tail fins. 
  1. Repeat the spin test with your modified rocket body. Does it fly tail-first now? If not, how can you continue to adjust your design?
  2. Remember that your rocket still needs to fly nose-first on the way up.
    1. Repack the parachute, put the nose cone back on, and swap the new engine back in.
    2. Relocate the center of mass. 
    3. Repeat the spin test. Does your rocket fly nose-first? If not, how can you modify the design so the center of pressure is below the center of mass during the initial phase of flight?
    4. One possible method is to modify the shape of the nose cone as shown in Figure 13. This shape blocks air from passing through the ring fin while the nose cone is attached, so air does not pass through the ring fin until the nose cone separates. You can also try adding modeling clay to the nose cone if you have not already, so the rocket's center of mass will shift more when the nose cone separates. 
A model rocket nose cone with a modified shape to adapt to a ring finImage Credit: Ben Finio / Science Buddies
Figure 13. Modified nose cone. A paper cone glued to the nose cone blocks air from entering the ring fin while the nose cone is attached.
  1. Repeat the spin test with your modified nose cone. Remember to relocate the center of mass if needed. Is the rocket stable in the forward direction now? 
  2. Double-check to make sure your rocket is still stable in both configurations. Remember to remove the nose cone and swap out the new/used engines as needed. Can you make any further changes to your rocket to improve its stability in both directions?
  3. Optional: conduct a live launch of your rocket. Some important safety guidelines:
    1. Only try this approach with small, lightweight, "beginner" level rockets. Larger rockets are more likely to cause injury or property damage if they crash-land.
    2. NAR safety guidelines require that all rockets have a recovery system such as streamers or a parachute. Since your parachute is now attached to your nose cone but the nose cone is no longer attached to the rocket's body, you must add a separate recovery system to your rocket. You can do this by attaching one or more streamers to the inside of the rocket's body tube. They should allow you to demonstrate vertical landing without affecting the rocket as much as a parachute. Read this guide to learn how to make and attach a streamer to your rocket.
    3. Conduct your launch on a soft surface like a grassy field, not a hard surface like a parking lot. Landing vertically on a hard surface may damage your rocket's fins and make it harder to reuse. 
    4. Make sure your modifications do not make it difficult for your rocket to slide smoothly along the launch rod. For example, you may need to cut or poke a hole in your modified nose cone so it fits over the launch rod. 
  4. If you have not attached the launch lug yet, make sure to glue it on and wait for the glue to dry before you proceed. 
  5. If possible, get a few volunteers to help you film your launch. That will make it easier to analyze the footage later to see if your rocket stayed upright during descent. If you have mutliple volunteers, get them to film with different zoom levels. One person can film a wide-angle shot, which makes the rocket more likely to remain in the frame, but smaller and harder to see. Another person can try zooming in and tracking the rocket, although it will be more difficult to keep the fast-moving rocket in-frame. 
  6. How does your rocket behave during a live launch? 
    1. Does it fly straight during the initial powered flight?
    2. Does the nose cone separate properly? Does the parachute deploy?
    3. Does the rocket body remain vertical as it falls, with the tail pointed toward the ground?
    4. Are there any differences between a real launch and the string-twirl test?
    5. Can you make any further improvements to your design based on your observations during a live launch?
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Global Goals

The United Nations Sustainable Development Goals (UNSDGs) are a blueprint to achieve a better and more sustainable future for all.

This project explores topics key to Industry, Innovation and Infrastructure: Build resilient infrastructure, promote sustainable industrialization and foster innovation.

Variations

  • For an advanced rocketry project, can you build a rocket with more features used by real reusable rockets, such as:
    • Active stability control with fins and/or thrust-vectoring
    • Deployable landing gear
    • An engine that fires again to slow the rocket before landing

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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Finio, Ben. "Make a Model Rocket Land Vertically." Science Buddies, 25 Sep. 2025, https://www.sciencebuddies.org/science-fair-projects/project-ideas/SpaceEx_p046/space-exploration/vertical-landing-rocket. Accessed 18 June 2026.

APA Style

Finio, B. (2025, September 25). Make a Model Rocket Land Vertically. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/SpaceEx_p046/space-exploration/vertical-landing-rocket


Last edit date: 2025-09-25

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