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Home » How to build a rocket (on the basis of STR-07 “Florent”)

How to build a rocket (on the basis of STR-07 “Florent”)

You may have heard the phrase “It’s not rocket science!” before, which implies that a certain topic is not difficult to understand. As it turns out, in theory, building rockets is a lot easier than you might think and can be broken down into a few key challenges. So launching a rocket is easy, and rocket science’s bad reputation is a product of people’s tendency to exaggerate and totally undeserved? Well…

Below, I will try to explain the five basic challenges one has to face when building an experimental rocket. Note that these are usually addressed simultaneously and not in below outlined order. Please also keep in mind that in reality things might be a bit more complex than described in this article.


1) Body

Firstly, you have to design and build a light and durable body for your rocket, taking into account aerodynamic stability and the expected stress on your structural elements, as well as the dimensions of the components that you are planning to fit into the corpus later on.

STR-07 was built with emphasis on lightweight materials and durability. Its body is manufactured out of fibre glass and carbon fibre, the four fins are 3D-printed and laminated with layers of fibre glass.[space_20]

2) Electronics

Even small rockets contain much more electronic components than you might expect, providing you with a way of communicating with your rocket on the launchpad, and during and after the flight.

Among other components STR-07 “Florent” houses our own Space Team FMS 3.2, an “Altimax Simply Altimeter” and an “XBee” radio module. When in “flight mode” the on-board FMS (“Flight Management System”) detects in which state the rocket is by means of various sensors and triggers certain actions like the separation during descend. The rocket’s sensors included a gyroscope, accelerometers (high G & low G), a 9DOF sensor and sensors for temperature & air pressure. We adapted the “pyroless recovery system” (PRS) and made it “igniter compatible” – now we can arm the system independently from our FMS. The two PRS-channels are designed redundantly, each of them now has its own control board and power supply.[space_20]

3) Propulsion

This step is crucial: You have to find an engine that is suitable for your rocket and securely fit it into your rocket. Additionally, it is absolutely necessary to think of a safe and simple way of arming and igniting the engine.

STR-07 was propelled by a “Cesaroni Pro75 L800-P” on its maiden flight, which carried the rocket to a height of around 3 kilometres.[space_20]

4) Recovery

Accomplishing a safe recovery of your rocket and retrieving it without any damage is actually more difficult than outsiders might expect. There are several different approaches, we at “TU Wien Space Team” like to use a recovery system that separates the rocket into two parts after the rocket has reached its apogee and slows it down with two parachutes to approximately 5 m/s.

A reliable separation and recovery is the key for the reusability of our rockets. In the case of STR-07 this step soon turned out to be the biggest challenge that our team had to face: During our extensive testing routines some concerns over the reliability of our CO2-powered “pyroless separation mechanism” arose, so we adapted our arming procedure and our checklist. We decided to focus our efforts on the perfection of the separation mechanism and managed to pass all technical inspections and exams. We successfully demonstrated the separation of our rocket in three consecutive test runs and successfully simulated the whole flight on the ground in front of the jury (“vol simulé”).[space_20]

5) Launch

Once you have managed to build a safe and reliable rocket you are ready for the final step: Finding a suitable launch opportunity and launching your rocket. One thing to keep in mind: Obviously, you need a ramp/platform that is compatible with your rocket.

STR-07 got a “Go for launch” from the jury of “Planéte Sciences”, the organisation in charge of C’Space, in the morning of July 19th 2017. In the afternoon of the same day our rocket took off, disappeared into the clouds and reached an altitude of 3 kilometres according to the data we received from the rocket. Nevertheless, it soon turned out that something had gone wrong: The rocket and its two parachutes were nowhere to be seen. After a futile search for our rocket and some calculations we had to face the frustrating reality: STR07 was gone. Our rocket’s recovery system had not worked according to plan. There is only a slim chance that our rocket will ever be found.



We have learned our lesson and are already working on an improved version of STR-07 “Florent”. We consider some parts of this project very successful, despite us not being able to recover our rocket: We were able to gain lots of expertise in manufacturing and lightweight rocket design, as well as in general problem solving and trouble shooting. In addition, we managed to recruit new young and enthusiastic Space Team members and get them interested in our fascinating field.

On this occasion we would like to thank all our sponsors. Without their brilliant support we would have had a very hard time realising our ambitious project. In particular, in the name of the whole Space Team, we want to give a big THANK YOU to the following sponsors:

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TU Wien Rektorat
Airbus Operations GmbH


Berndorf AG
Modelshop Vienna


Liros GmbH
Texas Instruments
Ing. Prägler GmbH