Our Phoenix engine firing

Our Propulsion Test Campaign in 2024

In May, the propulsion team of ASTRA achieved a very important milestone. The team successfully tested the propulsion system and fulfilled the requirements imposed by our system engineers for our future launch.

Our engineers at the Propulsion Test

I am Taro Tokita, currently the team lead of the propulsion team of ASTRA and I would like to tell you about the testing campaign of ASTRA’s new propulsion system. In simple terms, in the campaign we tested whether our engine works. As mentioned, the test was very successful and we were actually very efficient being able to hot fire twice on several days. But let’s start from the beginning!

Before we started with the actual hot fire testing though we had to pressure test our aluminium/CFRP (carbon fiber reinforced polymers) tank that the structures team of ASTRA made. Sadly, we experienced our biggest failure for the campaign here and the tank did not hold the required pressure of 90 bar (1.5 x). However, we were prepared for this situation and switched to the second tank that we brought which was made from steel and CFRP. This tank passed the test and so we could quickly continue our testing without longer hold ups.

Next, we characterized our injector plate with cold flow testing. These tests showed that our injector plate is kind of inefficient as it has a low discharge coefficient (this number describes the pressure drop that occurs when a fluid flows though the injector). As we realized later on this was actually better for us as this limited the oxidizer mass flow into the combustion chamber. Also, with these tests we leak proofed the setup and as there were no other anomalies we continued with the first hot fire test, a 2s burn!

For this first hot fire test everyone was nervous and slightly on edge. With all kinds of thoughts in our minds we assembled the test setup of the engine. After the last steps of sensor preparation were done, the team entered the control room to commence the filling operation of the tank. This was done via the ground systems in house built control unit. To our delight filling worked perfectly without any problems. Then, it was finally time to light the engine.

Countdown: 5, 4, 3, 2, 1, Ignition!

We saw the smoke from the Igniter exiting the nozzle. Then we saw how a lot of nitrous oxide exited the nozzle as well… For some reason, the fuel mixture did not catch on fire. This was confusing at first but after we took apart the motor, we realized that the problem was that one single Igniter did not produce enough heat to get the combustion reaction going. So this was an easy fix and we just used 2 Igniters. We assembled the system again and after the last steps of the setup we entered the control room hoping to see a flame this time.

Again, countdown:
5, 4, 3, 2, 1, Ignition!

Again, we saw the Igniters going off and then the engine fired and this was one of the most glorious moments of the campaign. We had no anomalies and no leaks, although the thrust generated was just slightly short of the target. By all accounts this was a near perfect result!

Our mascot Octavia after the test firing

The burn ended after 4s which is 2s more than what was planned. As we later found out, our main flow valve that controls the oxidizer flow into the chamber, cannot handle the liquid oxidizer flow and will only close as soon as the nitrous oxide changes to the gas phase. But now that we had proven that the engine works, we could continue testing and we directly went for a full duration test of 8s. We were able to replace the broken parts and the solid fuel grain and performed the next test on the same day. This test also showed no anomalies and therefore we could continue the campaign without any changes to the system. During the 3rd burn the nozzle partially eroded/melted so we replaced the nozzle with the second nozzle we brought. With the 3rd burn we also accumulated 2 similar thrust curves that we needed for one of the our launch requirements. Technically, we achieved our main goal.

With all subsequent tests we tried out different things. First, we included a Vortex plate that would mix the propellants in the chamber to increase efficiency. This worked very well for us and we also generated 2 similar thrust curves with this setup. This means that we could also fly with this setup at EUROC. Next, we also used a fuel grain that includes aluminium power. However, the powder was deposited in the outer most 2mm of the grain due to a centrifuge effect during the grain spinning process. Thus, this did not have a significant effect on the burn behaviour.

In the end we were able to perform 7 tests in 4 days, reached a peak thrust of over 7kN and fulfilled the requirements of our system. The next steps now are to evaluate all the data and to prepare for the launch at the end of this year.

I hope you enjoyed reading this blog entry and it gave you some insight about what is happening at ASTRA. Thank you for staying until the end, and don’t forget to expand your horizons!

For more information, pictures and videos: definitely check out our YouTube channel where a video about this testing campaign is published.

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The new board for 2024

It is simply in the nature of working on a big project like ours as a student in your spare time that your availability can change without you being able to prepare for it. This has been the case for two of our most current board members. As they no longer have the time to focus on ASTRA in between their studies, our CFO Arne Stemme and our secretary Frederic Bolgen are stepping down from their positions as of May. We would like to thank them for their great contribution to our project and wish them all the best in their future endeavours!

We are at least as happy to welcome our new board members! The position of CFO will be taken over by our former Deputy CEO, Kevin Matjeka (3rd from left). Having worked on our sponsor relations for the past year, he is very familiar with our financial situation and we are delighted to have him taking over our finances. The position of Deputy CEO will be taken over by our Propulsion Team Lead Taro Tokita (1st from right). As he is an integral part of our technical work, his expertise will be a great help in making more informed decisions on our board regarding all things technical. Finally, we also have some new blood on our board. Sara Nufal (3rd from right) joined the project management team just last December, working mainly with Kevin Matjeka on sponsorship and helping to organise our recent networking event with Starthaus Bremen. 

The new board starts it’s term at an exciting time: We are just starting to test the subsystems for our new rocket Phoenix for this year’s EuRoC 2024 competition. There is still a lot of work to be done and money to be raised in order to be able to compete.

So without further ado, let’s get to work and reach for the horizon!

Members of our team at EuRoC 2023

Our first attendance at EuRoC

Anyone who reads our website, talks to us, or receives a flyer from us knows directly: We want to reach outer space. We want to build a rocket that flies to 103.6 km, thus crossing the border to space. To achieve this, we are developing and building all the systems for a rocket which can achieve this lofty goal. 

But of course, safety is our top priority. That’s why it was clear to us from the very beginning that we would not simply launch our first rocket straight to 100 km. So what do we do? We decided to build a smaller rocket to test all of our systems and the design overall. This scaled down rocket would “only” reach an altitude of about 3 km, but will give us the opportunity to test technology and gain the experience we need to reach our final target. Accordingly, we are focused on building this smaller rocket KARMA. 

Over the last few months we have been working very hard to get closer and closer to this goal. We have completed many components, conducted countless tests of individual systems, and have also learned lots in the process. Then we applied to EuRoC 2023. EuRoC is a Europe-wide competition for student groups that build rockets. There you can launch different types of rockets to different target heights (3km and 9km). The rocket that most accurately reaches the designated target altitude wins the competition in its category 

After a long application period and a lot of preparation, a part of our team traveled to Portugal on October 7th – together with our 3m long rocket in our luggage. On site, many more tests were carried out and our rocket was fully assembled. Our engineers tried to implement as much feedback as possible in the short time and to improve and eliminate shortcomings in the rocket. Unfortunately, the time during the competition was not enough to change as much of the design as would have been necessary for a launch. Our launch was cancelled and our ASTRAnauts traveled back to Bremen. 

Of course, the trip to Portugal wasn’t for nothing. In the short time before and during EuRoC, we were able to make an incredible amount of progress in the development of our rocket. Through many tests we got a lot of opportunities to optimize details of our rocket. We will now collect the feedback we have received and take the time to incorporate it into our next design with one goal: to launch our rocket KARMA successfully in 2024!  

If you want to watch a short video about us at EuRoC, click here:

https://www.butenunbinnen.de/videos/studierende-bauen-rakete-100.html 

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ASTRA e.V. at Space Tech Expo 2022

The biggest exhibition for the space industry of Europe “SpaceTechExpo” took place in Bremen again in November 2022 and ASTRA e.V. got to be one of the exhibitors!
Every year this expo attracts exhibitors from the big players to small startups of the space industry who would like to present their ideas to an interested audience. This year was a special for members of space related student groups, because there was a group of booths at the SpaceTechExpo just for us!

Preparation for this event went smoother, because we already participated in 2021 and learned a lot from this. It was especially exciting displaying all of our new hardware protypes we were able to build in the last year. For the first time we had most of the final rocket parts to show to the public and this not only helped us getting more attention from curious persons, but also we got feedback and suggestions from some professionals or colleagues from other student groups.
Directly next to our booth there was the Dutch student group DARE and the Swiss student group ARIS as well presenting their projects. Talking with everybody at the SpaceTechExpo in person with the hardware directly next to us turned out to be very valuable! This lead to new testing opportunities e.g. for the drop test we got support from KST regarding this and from DARE with their wind tunnel.

In the end these three days were tightly packed for us at ASTRA e.V. with booth duty, B2B meetings and talking to other people at their booth. But it was absolutely worth the efforts!