Designing and Building a Self-Landing Rocket

Inspired by SpaceX's self-landing rockets, I decided to make my own - a rocket that deployed legs and landed upright. Here is a brief explanation for how this rocket will work: there will be two body tubes - an upper one (with leg holders and support struts) and a lower one (with fins, landing legs, and the on-board flight computer and electronics). After the rocket flies up, the two parts will be separated by the flight computer; the top part will come down with a parachute, while the bottom part will self-land using a motor that will be ignited by the flight computer. Here is a step-by-step breakdown of how I am making this rocket:

1. The three landing legs: They needed to be strong but lightweight. So, I went with wood and cut many holes into it. The legs are also 3 dimensional to provide more support and alleviate stress within the wood. There are a few other features (like notches and holes), whose purpose will be discussed later. 

2. The three landing leg holders: For most of the rocket's flight, the landing legs should be held next to the rocket; only at the very end should they deploy for the rocket to land. The leg holders are made out of wood to be strong, but have holes cut into them to be lightweight. They are also made to be aerodynamic because they will be sticking out the side of the rocket.

3. The support struts: Since there will be many holes cut into the rocket to fit all the wooden pieces, the body will become weaker. So, I made lightweight and aerodynamic wooden support struts:

4. I attached the support struts and leg holders to the upper tube of the rocket. I also attached a red tube coupler, which will hold the two parts of the rocket together until they are separated by the electronics in the bottom part.

5. Landing leg feet: The landing legs will have feet that spring out of the upper stage when the rocket needs to land. Here is a picture and video of the springing mechanism in action:

6. I attached the upper stage parachute to a hook in the red coupler, as well as the nose cone to the top of the rocket:

7. The fins: For this rocket, since I need access to the motor tube to make it suitable for self-landing, I first attached the fins and centering rings to the motor tube and then I will put all of that into the body tube later. I then attached a shock cord for a parachute to two metal hooks. The fins have holes in them because that is what the legs will pivot around when they are deployed.

8. Attaching the fin assembly to the rocket. Glue was put on the inside because if it was on the outside, that would increase drag on the rocket.

9. I attached the legs to the fins. The way they work is that there is a rubber band attached from a leg to a fin. When the upper stage is removed, that rubber band brings the leg into place. Once the leg is in place, to make sure it says there, there is a little wooden piece with a small rubber band. That piece slides into a nook in the leg and keeps the leg in place.

Here are two videos of the legs unfolding. The first video is up close, the second video is of all three legs unfolding at once.

Here is the completed rocket: