Visiting the drop tower of the University of Bremen

Deutsche Version


Welcome to the drop tower of the University of Bremen! 😉 Obviously this pencil is only a model of the tower. Many thanks for this remarkable present!


I had another great opportunity to visit a fantastic facility of the German science and technology community. It is a honour to report about this visit for you – as always. I hope that I can share a part of my own enthusiasm and excitement with you.


The drop tower Bremen in the twilight of the evening before the actual day of my visit.


This time I was visiting the science and space city Bremen in the North of Germany. The visited facility is the drop tower – the best drop tower of the world. The tower is the main research facility of the ZARM. ZARM stands for ‚Zentrum für Angewandte Raumfahrttechnologie und Mikrogravitation‘. That is German and means ‚Centre for applied space technology and microgravity‘. Additionally, there exists a centrifuge system at ZARM for hypergravity research. This also sounds quite interesting, doesn’t it? I hope to report about this during a future visit. 🙂



Here I am at the upper end of the drop tube at 119 meters above the ground. The red cone is closing the drop tube. The structure of the tower (white) is not directly connected with the tube. This helps to avoid that wind can disturb the drop experiments.


What is the purpose of such a drop tower? You may guess that something is dropped here – and that is absolutely correct. Here at this drop tower things are released for a free fall of 110 meters. This free fall takes about 4.7 seconds. That is fine, but may not sound too interesting at the first moment. But consider that during this free fall the falling item is in the condition of weightlessness (or more correct: microgravity). You know that mircogravity is a condition that you can find on board of the International Space Station ISS or any satellite orbiting Earth. These are also in the condition of free fall. Due to their large velocity they always miss the Earth and therefore microgravity is contained.


At the lower end of the drop tube with a length of 110 meters. You can see the system for lifting the experiments to the top of the drop tube.


Here in the tower the dropped experiments do not miss the Earth and need to be  decelerated. Otherwise they would hit the ground with about 50 m/sec. This has to be avoided under all circumstances. Therefore a cylinder (8 meters tall) completely filled with tiny styrofoam pellets is directly located below the drop tube.


The 8 m tall container filled with styrofoam pellets where all dropped experiments are decelerated after the free fall.


Obviously it is not possible to simply drop an experiment in this tower. The experiment needs to fit into special capsules. You have to install counterweights for a perfect balance. Otherwise the capsule would tumble during the fall.


One of the standard capsules for drop experiments  at ZARM (left image). In the right image you can see the top cover for this capsule including the release mechanism.


Such a drop capsule is been closed with a special cover at the top. A special winch is ued to lift the capsule to the top of the drop tube. A well calibrated release mechanism guarantees that the capsule is released without any disturbations to the microgravity. In this way a microgravity of  10–6 of the gravity of Earth or better can be obtained. By the way, this is better microgravity than on board of the ISS. At the ISS the movements of the astronauts (and sometimes the ones of mauosnauts, too ;-)) and other moving parts are limiting the quality of the microgravity.


18 high-performance punps are used to evacuate the entire drop tube. The vacuum in the tube enables almost perfect microgravity during free fall.

One important condition to reach almost perfect microgravity during free fall is to evacuate the entire drop tube. An impressive system of 18 pumps is removing the air from the tube during a process taking more than one hour.



The catapult system underneath the drop tower. The pneumatic system is accelerating the experiment capsule towards the top of the tower. This enables to double the duration of the microgravity to 9.3 seconds. And this is a world record for a facility on planet Earth!


Are you already impressed by all this great facts? I really am. And the ZARM team can top that by doubling the duration of the free fall phase to 9.3 seconds! How does this work? There is a mode where you start the free fall when the capsule is going up. An unique catapult system is installed underneath the drop tube. It can accelerate the experiment capsule in a way that the capsule almost touches the top of the tube before falling down again. How clever is this? The drop tower at ZARM is the only drop tower on Earth that is using this fabulous technique. Woohoo!

Now you may think there is an issue with this catapult method. How is the experiment capsule been captured and decelerated after the fall? Shouldn’t the capsule crash now into the catapult after the fall? No fear, the deceleration cylinder is located between the catapult and the drop tube. For the catapult launch it is been removed from the path of the capsule. When the capsule is flying towards the top the deceleration cylinder is being moved quickly to the capture position below the drop tube ready to capture the capsule after free fall. What a cool system! And it always works!


This is a fairing section for experiments to fly with the high altitude rocket called REXUS. The REXUS program with support of the German Aerospace Agency DLR allows students to fly experiments almost to space. Many of the experiments for the REXUS launches are tested here first to see if they perform well under microgravity conditions.


Scientists from all over the world are using the drop tower in Bremen for microgravity experiments in several research areas. Often experiments are tested if they work in microgravity before they fly on satellites or the ISS.

Schoolchildren and students can also perform experiments at the drop tower facilities in Bremen. Several programs exist:

  • DroPS: School kids can conduct microgravity experiments in this program organized by the German Aerospace Agency.
  • Drop Your Thesis: ESA Education is offering the opportunity for students to perform experiments as part of their work for a thesis.
  • REXUS-Programm: DLR offers the opportunity to students to fly microgravity experiments on board of the high altitude rockets called REXUS. Often these experiments are first tested here at the drop tower.

In the case that you have a cool idea for an experiment in the drop tower (or you want to look for more information) please go to the links provided for the three programs listed above.



View over Bremen and more from the top of the tower in about 140 meters altitude.  Scientists have meetings here. During weekends you can rent this room for instance for your wedding ceremony! Yeah!

The tour of the tower was ending at the top at an altitude of 140 meters with a breathtaking view all over the city of Bremen and more. There are some rooms where the scientists can meet. And, oh wonder, during the weekend you can organize to have your wedding ceremony here. And now I only have to find a charming mouse for marrying.  😉

Many thanks go to Dr. Koenemann for the great guided tour. That was fantastic. And I am considering to take the given opportunity for falling down the tower with an experiment during my next visit. Hopefully I will not forget to bring my spacesuit with me for this adventure. 🙂


The exhibition & conference center in Bremen.  In 2018 the 69th International Astronautical Congress will take place here October 1-5.  I plan to attend and to help to organize fantastic activities for school kids of all ages.


There is one important note to add to my report. We (my mission director and yours truly) had an interesting talk with the charming Mrs. Czurgel. We talked about how we can help to organize an interesting program for kids of all ages during the 69th International Astronautical Congress in Oktober 2018. We are honoured to be tasked for this interesting endeavour and are really looking forward to it. Many thanks, Mrs.Czurgel!

And now this long report is really coming to an end! 😉

Yours truly,



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