Drop towers
The Bremen Drop Tower is a large facility, unique in Europe. The groundbased short-term microgravity laboratory is open for scientists from all over the world. In comparison to orbital systems the drop tower represents an economic alternative with permanent access.
Since its inauguration in September 1990, the 146-m concrete tower with its inner 110-m metallic shaft is a landmark on the Bremen University campus. It serves as an important supplement to either existing or planned orbital or suborbital platforms for microgravity research.
As of October 2008, 5000 drop experiments have successfully been carried out. The installation delivers 4.74 s of near-weightlessness up to three times a day. In order to double the microgravity time to 9.3 s,, a catapult system has been implemented into the drop tower operation routine. With the drop tower catapult, the capsule performs a quasi-vertical parabola instead of being dropped.
The microgravity laboratory system itself is a cylindrical capsule with a diameter of 800 mm and a length of 1.6 m or 2.4 m, depending on the space required for experimental studies. Inserted platforms, held in aluminium profiles, form a modular drop capsule structure.
The whole capsule is closed pressure-tight with an aluminium cover after the integration of the experiment. Using a winch, the drop capsule is pulled up to a height of 120 m. After that, the drop-tube, designed as a vacuum unit, is closed pressure-tight. The actual steel drop tube stands detached at a height of 13 m without any connection to the tower itself on the 2 m thick roof of the deceleration chamber.
The detachment of the inner shaft from the tower provides quiescent conditions inside the drop-tube even during stormy weather when the concrete tower may be shaking.
The 1700 m3 tube and the deceleration chamber is then evacuated to eliminate aerodynamic forces on the falling capsule.
A system of 18 pumps with a capacity of 32 000 m2/h requires around one and a half hours for the evacuation.
The capsule is then released at a residual pressure of 10 Pa. An ultimate microgravity quality with residual accelerations less than
10-5g0 will be detected during the freefall of 110 m as well as during the vertical parabolic flight induced by the drop tower catapult system. MO<A deceleration unit, filled with polystyrene pellets, decelerates the vehicle. For retrieval, the vacuum chamber is reflooded with preconditioned air within 20 minutes. Then, the experiment as well as the results are immediately at the scientists' disposal.
For more information
About the drop tower and how to apply, please visit the ZARM website: http://www.zarm.uni-bremen.de/
Or contact:
Dipl.- Ing. Christian Eigenbrod
ZARM | FAB - Drop Tower Operation and Service Company mbH
c/o University of Bremen
Am Fallturm
28359 Bremen
Germany
Phone: +49(0)421 218 4078
Fax: +49(0) 421 218 3889
Email: eigen @ zarm.uni-bremen.de
Students
In the framework of ESA's educational activities, ESA is also organising regularly drop tower opportunities for students at master or Ph.D. level through the "Drop Your Thesis" programme.
Interested students should contact:
- Dr Natacha Callens at dropyourthesis@esa.int
Or have a look at:
Last update: 17 November 2011
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