CHAOS successfully launched as part of the stratospheric balloon mission BX35 on the 2nd October 2024. At the moment, we are in the middle of the data evaluation and the first results look very promising. In January, we have to submit our final results which will mark the end of CHAOS as part of BEXUS.
But Kiel University is not done yet. Currently, a new team of students is forming to apply to the next BEXUS cycle with the instrument SETH. So, CHAOS is passing on the torch. And fittingly, SETH is the Egyptian god of CHAOS…
You can find some photos from CHAOS’s launch campaign in Kiruna, Sweden below.
The heart of our experiment CHAOS is the Cherenkov detector. High energy particles travelling through this detector will create photons and because only few photons are created, a Photomultiplier Tube (PMT) is needed to detect them. This makes the use of High Voltages (HVs) necessary to operate the PMT and poses a security risk for our experiment. During the BEXUS balloon flight CHAOS will be exposed to low pressure environments. The combination of high voltages and low pressures can lead so-called corona discharges which could possibly harm the experiment. The easiest way to mitigate this risk is to place the experiment inside a pressure housing which ensures the same ambient pressure as on ground.
Here you can see the CHAOS pressure housing. It consists of an aluminum base plate on which a die-cast aluminum box is screwed. We use two additional U-profiles which press the box onto the base plate.
But we cannot simply put our pressure housing onto the BEXUS balloon. First, we have to prove that our design really works. This is why we performed several tests:
In a first step, we inflated our pressure housing with a tire inflator. Maybe not the most scientific way, but it worked. Sometimes scientists have to be creative. We were able to show that our pressure housing has no problems to withstand an additional pressure of 1.2 bar. During the BEXUS balloon flight the maximum pressure difference between the inside and outside of the pressure housing can be 1 bar.
But that was not enough. We decided to put our experiment in the vacuum chamber at our university to perform a professional vacuum test. For the test we placed a pressure sensor inside the pressure hosuing as seen in the following pictures:
The pressure housing was put in the vacuum chamber which was then evacuated to a pressure of 0.1 mbar. We left the pressure housing inside the vacuum chamber for a total of four days. The results can be seen in the following plot:
The red curve is the temperature inside the pressure housing and the blue curve the pressure. The big spikes in temperature and pressure are caused by the heating plate inside the vacuum chamber which we turned on for several hours. The measured pressure was corrected for the temperature using the ideal gas law. This is the green curve. We can see a linearly decreasing pressure. This leakage was expected because a perfectly airtight pressure housing is hard to build. But we only lost around 100 mbar in four days. This is totally acceptable because the BEXUS balloon flights only last several hours. To quantify our results, we performed a linear regression on our pressure measurements. This regression was then used to calculate a leakage rate of around Q = -0.003 mbar*l/s.
We are very happy with the results of our tests. Hopefully, they will convince the board of experts at our Critical Design Review (CDR) as well. The CDR will take place at ESTEC in the Netherlands in May. So, stay tuned and follow us on our journey!
This afternoon, the styrofoam boxes, which we ordered, arrived at our institute. We plan to place our experiment CHAOS inside one of these boxes for thermal control during the flight on the stratospheric BEXUS balloon. This approach was successully used by other BEXUS experiments from our Department before. These boxes were designed to transport and cool food and drinks, not to be flown on a stratospheric balloon. To test wether the styrofoam withstands the expected low pressure environments, we spontaneously decided to put it into our vacuum chamber and start a test. The styrofoam encapsulates tiny bubbles of air. In a low pressure environment this air wants to expand and can become critical if the syrofoam loses its structural integrity because of this expansions. Unfortunately, we could only place the lid of a box inside the chamber because of the size of the box.
The results of our test can be seen below. The plot shows the pressure of the backing pump (p2) and within the chamber (p1). We can see that we reached pressures of less than 0.01 mbar. This is three orders of magnitude below the expected pressure environment during the BEXUS flight. In the last picture we see the comparison of the tested styrofoam (top) with an untested lid (bottom). The tested lid shows some open pores, but the styrofoam kept its structural integrity. Therefore, we conclude that the styrofoam boxes are ready for flight.
CHAOS has successfully started into the year 2024. The next big milestone on our journey is the Preliminary Design Review (PDR) in Kiruna, Sweden at the beginning of February. At the PDR we will present the current status of our experiment design. But first, we have to hand in our first version of the SED (Students Experiment Documentation) at the end of January. This document includes all relevant information regarding our experiment. Currently, we are finalizing the design of CHAOS to include it in the SED and present it at the PDR. It is a lot of work but also a lot of fun. We have been told that it might be cold in Kiruna, but the polar lights make up for it. Therefore, the work will be definitely worth it. Stay tuned for more information on CHAOS and our journey to Sweden.
CHAOS has been selected for the 15th cycle of the BEXUS program! The next step of our journey will be the Preliminary Design Review (PDR) in February next year in Kiruna, Sweden, where we will be presenting the current status of our experiment. The final flight will take place next fall, also in the Esrange Space Center in Kiruna.
Thank you @germanaerospacecenter for selecting our experiment, we are very excited about this opportunity!
The selection workshop is over and we are on the train back to Kiel. We had two days with lots of new impressions and experiences at DLR in Bonn.
We arrived in Bonn on late Sunday evening. On Monday morning the workshop started with a general introduction to the BEXUS program. After that the invited teams presented their proposed experiments. Each team held a presentation of about 25 minutes followed by a discussion between the presenting team, the board of experts and the other teams. There were a total of three teams proposing an experiment for BEXUS and five teams proposing an instrument for the REXUS program. Our presentation of our proposed instrument CHAOS was the second talk of the day. Even though we were a little bit nervous, our talk went very well. The board of experts had some questions about our experiment design and scientific goals but we believe we could give satisfying answers. We were especially happy about the positive feedback which we got from the other applying teams. We ended the day with the other teams going out for burgers and visiting the Christmas market. Today the last three teams presented their experiments and we got some more information on what to expect from the BEXUS program and the further schedule. The workshop ended at noon with the board of experts starting to discuss which experiments they want to accept. The final decisions will be announced until 18th December. We had some time left before we had to catch our train, so we had lunch with the team SHAMA from STAR Dresden and in Cologne we took the chance for a picture at Cologne Cathedral.
One of the cool things during the workshop was meeting the other student teams. We were introduced to many promising experiments and it was especially interesting to see students from other fields than ours proposing ideas. We as physicists were forced to think outside the box. There were two teams focussing on the behaviour of liquids in microgravity which is particularily interesting for the fuel tanks of rockets and satellites. Another experiment wants to look at the effects of the conditions in the stratosphere on oxygen producing bacteria. But these are only a few examples.
The selection workshop was a lot of fun and we hope we get the chance to take the next steps in the BEXUS program. We are looking forward to potentially meeting the other teams again (Jay, I still owe you a drink). You can find more pictures and stories covering our journey on our instagram channel. There we will keep you updated on everything related to CHAOS, just as in this blog.
This Sunday afternoon we (namely Ava, Pierre and Hannes) started our journey to the selection workshop in Bonn. During the next two days we are going to meet the other candidates for the next BEXUS and REXUS cycles at the German Aerospace Center. It is planned that we hold a talk to present our proposed instrument CHAOS. After the selection workshop the final decision on which experiments can take part in BEXUS will be made by a board of experts and announced on 18th December. We did some last adjustments to our talk while sitting on the train and are looking forward to the selection workshop.
CHAOS has been selected to be presented at the selection workshop for the 15th BEXUS cycle from 27th November to 28th November 2023 in Bonn. We are happy about this great opportunity and will keep you updated. After the selection workshop the final decision on which experiments will have the chance to take part in BEXUS will be made.
In today’s meeting we discussed the final version of our Experiment Proposal for the upcoming BEXUS cycle. After some minor adjustments, we submitted our application to the DLR. Now, we are hoping for a positive response. If we are invited, we will attend the DLR Selection Workshop on November 27th and 28th. Stay tuned for further information on our instrument CHAOS.
