In order to fly to the REXUS sounding rocket, the entire experiment setup must be able to fit into the limited space of the rocket module. The mechanical design of the experiment module is built with different tiers. At the top, the measurement and control electronics are housed, which automatically controls the whole experiment. Below the electronics there are three drawers, so-called late-access modules.
Three measuring chambers are attached in two late-acces modules. In these measuring chambers the actual experiment takes place. In the third and lowest late-access module various containers are situated providing the necessary fluids for the experiment. In each measuring chamber there is a frog egg (oocyte) on which the ion flow is measured through the cell membrane during the flight. Because living frog eggs are used, they should be loaded into the rocket as late as possible loaded. Therefore, they are inserted in the experiment module right before the start with the help of these late-access modules. These modules have to be reliably connected to the board electronics and the distribution system for the fluids.
During the flight, the oocytes are exposed to various liquid solutions, which are enriched partly with pharmacological agents. The exchange of these liquids is operated with compressed air. Therefore,two compressed air tank and a compressed air regulator are housed at the lower end of the experiment setup.
During the flight, the structure of the experiment module has to withstand very high mechanical loads. At the start, the missile is accelerated by 20 times gravity. In addition, the construction has to resist very strong vibrations caused by the rocket engine.
Because the rocket will take-off during spring in the far north of Sweden (Kiruna), the temperature on the launch pad may be down to -30°Celsius. During the flight the outer shell of the missile will be heated up to 130°Celsius by the air friction. For the frog eggs, the temperature inside the measurement chambers must be between 10°C and 20°C. Therefore, the experiment has to be perfectly insulated. Furthermore, the late-acess modules are equipped with heating foils, so that they can be heated, if necessary.
Despite all these requirements, the design of the experiment setup must not be too complicated, but still should be light and strong enough. To guarantee the functionality of the whole construction, only suitable components must be procured and installed. For cost and time reasons mainly conventional components are used. However, these components are usually not designed for such harsh conditions and have no space flight approval. This has the consequence that all components and their interaction must be tested under actual conditions, more precisely function under strong vibration and vacuum conditions. It is a challenge to recreate these tests on Earth as realistic as possible, respectively to simulate them. To ensure a correct function of the experiment, the whole module must be analyzed and tested in stages. This includes many calculations and computer simulations, and many conventional tests, such as shaking table, vacuum and heat chamber.
The pictures show the first 6 eigenmodes of the structure with the corresponding frequencies and the temperature distribution in the setup with the heating foils. The excitation should not be in the frequency ranges shown. Otherwise this may lead to very strong momentum of structural.