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Project name:BEXUS-ELFI
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The BEXUS-ELFI project follows on from the successful BEXUS-IMUFUSION project

Another team takes part in the European student competition REXUS/BEXUS 30/31

The REXUS/BEXUS programme

"The REXUS/BEXUS programme is realised under a bilateral Agency Agreement between the German Aerospace Center (DLR) and the Swedish National Space Agency (SNSA). The Swedish share of the payload has been made available to students from other European countries through the collaboration with the European Space Agency (ESA). Experts from DLR, SSC, ZARM and ESA provide technical support to the student teams throughout the project. EuroLaunch, the cooperation between the Esrange Space Centre of SSC and the Mobile Rocket Base (MORABA) of DLR, is responsible for the campaign management and operations of the launch vehicles." /DLR, ESA/

The team and the objectives of BEXUS-ELFI

The project team for the kick-off consultation

Full project team in 2021 (from top left):

  • Johanna Mohs, team leader until the end of 2020
  • Jonas Penzler, Mechanical Engineering
  • Lars Gebken, Automation and Electronics Development, Team Leader from 2021
  • Benedikt Streicher, Electrical Engineering
  • Florian Seegel, Computer Science
  • Jonas Jelonek, Automation and Electronics Development
  • Oliver Schröder, Computer Science
  • Jonas Stephan, Automation and Electronics Development
  • Prof Dr Matthias Viehmann, Senior Scientist
  • Prof. Dr Klaus-Peter Neitzke, Senior Scientist
  • David Bochmann, Computer Science

DLR and ESA have given the green light for the experiment's participation BEXUS-ELFI (Extremely Low Frequency and IMU)which will run from 2019 to 2022. Our students will be working alongside other high-ranking university and college teams from Germany and across Europe. ELFI focuses on the measurement of extremely low-frequency fields in the range up to 100 Hz. Of particular interest are the measurements around 7 Hz (Schumann frequency) and 16.7 Hz as well as 50 Hz and 60 Hz. The highlight was the flight of the stratospheric balloon in Esrange (northern Sweden, near Kiruna) in September 2021. Prof Viehmann and Prof Neitzke are once again supporting the team as senior scientists.

System structure of BEXUS-ELFI

csm_system_design_planned_web_f90c884cac
  • 1 - Gondola on the stratospheric balloon
    Cube shape, approx. 1 m edge length, contains the BEXUS-ELFI experiment and further
  • 2 - Main module BEXUS-ELFI
    Electronic module with amplifier, filter, controller, memory, sensors, communication, power supply
  • 3 - Coil as antenna on the scissor arm
    Scissor arm retracted during take-off, lowering of the antenna at a height of a few metres

Training week & Preliminary Design Review (PDR)

The BEXUS-ELFI team
Gondola with volume study
Presentation during the Preliminary Design Review (PDR)

At the beginning of February 2020, the BEXUS-ELFI student team from Nordhausen University of Applied Sciences accepted an invitation to a training week in northern Sweden, hosted by DLR, ZARM, ESA and SNSA. The Esrange Space Centre, which was the venue for this week, is located far north of the Arctic Circle. The local conditions were accordingly. At temperatures as low as -28 °C, the teams were able to gain an impression of the conditions their experiment will have to withstand later on.

During the week, events were held every day on the topics of mechanics, electronics, software development/programming, risk management and other project focal points. The aim was to optimally prepare the teams for the successful realisation of their experiments. A meeting was also held to discuss the design to date, including all technical solutions. Such a meeting is known as a Preliminary Design Review (PDR). Helpful hints and suggestions for changes were given in order to avoid potential problems and risks for all projects.

Critical Design Review (CDR)

Work in the LEDS university laboratory

The Critical Design Review (CDR) was scheduled for mid-May 2020. This involved checking whether the problems and risks identified in the PDR in February had been eliminated and possible improvements implemented. It was also checked whether the intended final design of the experiment met the requirements and had no further errors or problems. Any need for improvement had to be eliminated quickly.

Due to the coronavirus pandemic, it was unfortunately not possible to hold the CDR at the ESTEC (European Space Research and Technology Centre) near Amsterdam. Online video conferences took centre stage. Ultimately, the pandemic caused the launch to be postponed to 2021 and the launch team was expanded.

Thermal Vacuum Week (TV)

The Thermal Vacuum Week took place at ZARM in Bremen from 15/08/2021 to 20/08/2021. Two important tests were carried out: the thermal vacuum test and a mechanical load test. In the TV test, the electronics were tested up to a minimum temperature of -60 °C and a minimum pressure of 10 mbar. Under these extreme conditions, the electronics functioned as desired and measured values were recorded, saved and sent correctly. The mechanical load test of the device responsible for lowering the measuring coil on the scissor arm at an altitude of several metres revealed a need for optimisation. The original solution with the release of the scissor arm and its braking by a gas pressure damper was replaced by a geared motor with a cable winch. 

Campaign-Week Esrange

As part of Campaign Week from 24 September 2021 to 4 October 2021, the flights of the stratospheric balloons BEXUS 30 (with ELFI) and BEXUS 31 took place at the Esrange Space Center of the Swedish Space Corporation (SSC) in northern Sweden near Kiruna. After a short briefing and safety instruction by SSC staff, preparations for the launch could begin. Several system tests and flight capability analyses had to be carried out. The first test was the deployment test, in which the experiment, including the braincase, prime and antenna, was attached to the nacelle and the final test of the deployment mechanism for the antenna was carried out there. The extensive modification of the mechanics, which became necessary due to the tests during TV Week, could thus be tested in the final version in Esrange.

csm_team_representative_on_site_c9fd5e6bc2

The next test that the team and the experiment had to complete was the communication test, in which the connection between the Braincase and the ground station was configured and tested accordingly via E-Link, which is provided by the SSC. An interference test was also carried out to check whether the various experiments in the BEXUS 30 balloon's nacelle can work in parallel without problems or whether several experiments influence each other.

The final step before the launch was the Flight Compatibility Test (FCT). Here, the experiments were to work under flight conditions. For this purpose, all experiments were mounted on/in the gondola and the connection between the experiments and the ground stations was established. The nacelle was then picked up by the "Hercules" (launch vehicle) and transported to the launch pad, where the final check of the functions of all experiments was carried out.

After successfully passing all the tests, the BEXUS 30 balloon took off at 06:54 on 30 September 2021. The launch preparation and ascent can be seen under the following link. Filling of the balloon begins at 3:06:00 and it lifts off at 3:34:05.

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More Information

Key data of the BEXUS 30 flight

  • Start: 30.09.2021, 06:54 am, Esrange
  • Landing: 30/09/2021, 12:29 pm, Finland
  • Flight duration: 5 hours 35 minutes
  • Maximum flight altitude: 27.3 km
  • Minimum pressure: 16 mbar
  • Minimum temperature: -61 °C
  • Stored data volume of ELFI: 312 megabytes

After 5 hours and 35 minutes, the gondola landed in Finland. Contrary to expectations, the antenna and the mechanics with the scissor arm suffered comparatively little landing damage. The electronics remained completely intact and were able to record and store measurement data for some time after landing. The measurement data was stored with multiple redundancy on an SD card, USB stick and in the ground station.

View from the gondola of BEXUS 30 at an altitude of 27 km, Team BAMMSAT-ON-BEXUS

Link: linkedin.com/company/bammsat 

The data is currently being analysed. The project will be finalised in the form of a presentation of the results at an ESA symposium in 2022.

Links to current news about student activities

The following companies support the BEXUS-ELFI experiment:

  • Coroplast Fritz Müller GmbH & Co. KG Wuppertal
  • IMG Electronic & Power Systems GmbH Nordhausen
  • Dr Dietrich Müller GmbH Ahlhorn
  • Hermes Systeme GmbH Wildeshausen