TVC Model Rocket

Have you ever noticed that most model rockets have fins and most real ones don't?

The reason is real rockets use something called a Thrust Vector Control(TVC) system to stabilize and steer the rocket. The system essentially just aims the thrust of the rocket engines. It is actually possible to use this system at model scale and it results in the ability to create a more realistic flight pattern and, with much work, greatly increase capabilities(probably the most famous example is BPS Space's VTVL rockets).

This instructable is mostly geared towards those who want to do TVC but don't know how/where to start. In it I will introduce you to the necessary concepts and types of components necessary to make a rocket.

Note:

Access to a 3D Printer is incredibly useful for this project(it's close to impossible without one). If you don't have one, check your library; they often print things for (sort of) reasonable prices.

The frame is basically what everything else is suspended upon. It's pretty self explanatory.

The frame I made is based upon upon Delta Space Systems' frame setup. It is made up of some old fiberglass rods taken from a tent and 3D printed rings.

The Gimbal, directing the thrust of the rocket, is essentially the main difference between a normal model rocket and a TVC Rocket.

There are a TON of good, free designs out there and unless you happen to be incredibly good at CAD there probably isn't any reason to design your own. Just google "TVC Gimbal 3D Print" or something like that. As a side note, the gimbal I am using is, unluckily, not free but can be acquired on Delta Space Systems' Patreon page(No, I am not associated them).

Although different designs have some differences, most usually use two servos, one controlling the X axis and one controlling the Y axis.

The flight computer is the brain of the rocket. Its main job is to control the angle of the gimbal.

For the flight computer you will need some kind of microcontroller. I have a Teensy 4.1 which is an extremely powerful microcontroller just slightly more expensive than an Arduino Uno. It also has more pins than an Uno, is breadboardable and has a built in SD card slot which is extremely useful for datalogging.

You will also need an Inertial Measurement Unit(IMU). You really only need one with a gyro but an accelerometer and a magnetometer could be useful as well.

Unless you are planning on doing some kind of tethered flight(which sounds much more complicated than its worth) you will need a battery/batteries to power the flight computer and the servos.

Obviously, the flight computer is not going to do anything useful unless you program it.

You will need to integrate you gyro's readings and probably write a script that calibrates your gyro on the launchpad as the biases can change. You may also want to use something like a Kalman filter.

Then you will need to turn the data from the from the gyros into something useful. This is usually accomplished with a PID loop.

In order to be useful a PID loop need to be tuned. AEROVector is a model rocket simulator that I have found built specifically for TVC that is extremely useful for this. One thing to keep in mind though is that while the simulator can display the simulations in 3D it's actually only simulating them in two dimensions.

In addition you will need to determine how many degrees the gimbal moves the motor for every degree you move the attached servo(This can vary between the X and Y axis).

Thanks for checking out this project! Hopefully it has helped you understand TVC better.

In my first launch test I used to small a motor for my rocket(I set a weight lower than the final weight of the rocket in the simulator) and it only got a few inches of the ground. However, you can see the TVC system gimbaling the engine. So, while it wasn't spectacular success it also wasn't a total failure either.

Some last advice: if you ever get stuck on something(especially coding related), try using ChatGPT before you wander down endless forums; it's pretty good when it knows what you want.