The Bremen Drop Tower
With a height of 146 meters the Bremen Drop Tower is the main laboratory of ZARM and the only laboratory of this kind in Europe. Every day it offers the most economic opportunity for short-term experiments under highest-quality conditions of weightlessness, comparable to one millionth of the Earth’s gravitational force (10-6 g). Since the implementation of the catapult system, a construction developed by ZARM engineers, the experiment duration has been extended to 9.3 seconds - unmatched by any other drop facility worldwide.
Due to its excellent microgravity conditions, the Bremen Drop Tower has received considerable international attention and is well occupied. Scientists from all over the world come to Bremen in order to experiment on different research fields like astrophysics, biology, chemistry, combustion, fluid dynamics, fundamental physics, and materials science as well as conduct technology tests preparing and qualifying hardware for future space missions.
How does the drop tower work?
The functionality of the drop tower is fairly simple: All falling objects are automatically nearly weightless – just like the experiment that has been placed inside the drop capsule, an airtight container of 2.5 meter length and 80 centimeter width.
During a simple drop experiment, the capsule is pulled up to a height of 120 meters to the top of the drop tube and then released. After 4.74 seconds the experiment has landed safely in the deceleration unit filled with polystyrene pellets. Before the experiment, 18 high-performance pumps make sure that the drop tube is almost free of air containing only one ten thousandth of the normal air pressure. Due to the vacuum, the air resistance is so low that the Bremen Drop Tower can provide one of the best quality of microgravity - in some aspects even better than on the International Space Station (ISS). Therefore, ZARM's drop tower facility is an economic and easily accessible alternative to doing research in space.
What is the catapult system?
When breaking ground for the Bremen Drop Tower on May 3, 1988, the installation of a catapult system underneath the building had already been taken into account. 16 years later, the ZARM engineers finished designing the catapult system and it was inaugurated in December 2004. The pneumatically driven system takes 0.25 seconds to accelerate the experiment capsule to a speed of 168 kilometers per hour. The exact force of acceleration is being calculated for each individual experiment in order to throw the drop capsule as close as possible to the top of the drop tube and thus maximize the duration of the flight. After a couple of seconds the deceleration unit has already been moved into place again in order to catch the capsule on its way down.
By doubling the trajectory length we are able to extend the time period spent in microgravity to 9.3 seconds - an experiment duration no other drop facility can provide.