A four-man team in South Africa recently broke an amateur rocketry record by launching a homemade rocket to ten kilometers’ altitude. Two of the members are father and son: Mark de Bruyn and David de Bruyn. We asked them about their experience and what led to them breaking the record. They also shared with us their thoughts about how to go about pursuing amateur rocketry.
What is Cape Rocketry, and how did you come to break the altitude record?
David: Cape Rocketry was formed recently to formalize our group and its goals. We had set our sights on the 10-kilometer mark for a few years as a milestone altitude because reaching it would mean surpassing the previous record of 9.5 kilometers set by a group from Gauteng called SARA (South African Rocketry Association).
We have been working towards building a rocket capable of reaching 10 kilometers but only started the project in earnest six months before the launch.
To achieve this, there were a few “enablers” which had to be in place, after which it was a matter of putting it all together. The most important was the propellant, which required years of work to perfect. Once we had a good formulation, it was fairly straight forward to produce enough propellant for our 10-kilometer rocket. Another important factor was the ability to accurately model aerodynamic performance and simulate design options such as propellant geometry. Of course, measuring the altitude reached and retrieving the rocket required advanced electronics, which I have developed over time and now export.
Combining all of the above gave us the tools we needed to reach the 10-kilometer goal and in so doing break the African record.
Mark: This small group was formed from a loose association that the four members have had for a few years. We had done launches together before but then decided that we had the capability of perhaps breaking the 10-kilometer barrier. We decided to pool our efforts and found that we could work really well together. The 10-kilometer challenge was set more than 10 years ago and we have attended a number of launches where this was attempted. David and I were also at the launch of the previous record height set by SARA (South African Rocketry Association).
There have been launches in the past where it was considered that the rocket could have gone higher than 10 kilometers, but none of these heights were ever confirmed and I think in most cases, the rockets were not retrieved. One of the goals of the 10-kilometer challenge, as I think it is with all of these launches around the world, is that the rocket must descend under a parachute, it must be recovered intact, and its altitude must be confirmed from more than one source.
Although we had a pretty good idea of the propellant characteristics we did a few static tests of smaller motors with similar design ratios before finalizing the 10-kilometer motor.
Because of the height, we needed to get clearance from the Civil Aviation Authority and also arrange a suitable launch site. This had to be done a few months in advance.
The rocket is fully reusable and after cleaning, it can be fitted with some new “O” rings and a few other items, reloaded with propellant and new ejection charges, and then be launched again. If we do launch it again, we will probably change a few things on it just for the sake of trying something different.
What are your plans going forward?
David: We are working on a new design to reach 20 kilometers. This will bring with it a new set of challenges. One such challenge is airframe materials. Reaching higher requires more propellant and therefore larger rockets. Standard aluminum pipes are no longer available and nozzles can also no longer be machined from single graphite billets. This is what the team will be focusing on in the near future.
Mark: Although the normal thing would be to do a two-stage rocket, as that will get us to a much higher altitude very quickly, we will probably stick to single-stage designs for a while. We are starting to work on new materials and techniques for a rocket to go higher. We may, for instance, try to use carbon fiber composites for the casing and fins. We are constantly working on different propellant formulations and we can match the propellant with the other parameters.
The nice thing about rocketry is that there are so many different things that need to be investigated and it’s a hands-on way to do science.
Where did your interest in rocketry come from, and what advice do you have for people with similar interests?
David: I got started when we assembled a kit rocket from Experilab, which my mom had bought for us a few years prior. We took it out one night when we were looking for something to do. That was over a decade ago. Building a rocket requires a multitude of disciplines and that is what I really enjoy. There is an endless amount to learn and that has kept me interested ever since!
My primary advice is to stay safe! A good way to avoid unnecessary risks and have a good chance of success is to buy a rocket kit, just like we did. In South Africa, you can buy kits from Aerospace Research.
Mark: Like most youngsters, I became interested in rockets in the 1960’s with the space race, but we couldn’t get the rocket kits that were available in the USA. Very much later on, we assembled a kit rocket we bought from Experilab and this got us hooked.
There are a lot of websites dedicated to hobby and high-powered rocketry. I would say start small and keep on learning and analyzing. Always use good common sense and be careful. The website David gave is probably the way to start, but also read up as much as you can. A very good website is Nakka Rocketry. This activity is very popular in the USA and there are dedicated groups all around the world.