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The LNCMI helps the Ariane rockets to better fly...

From magnets to rockets; magnetic levitation studies of liquid hydrogen

Gravity interferes strongly and universally with many phenomena and processes. Examples range from the boiling of liquids, via crystal growth and the effects of container walls on processes, to cell division in living tissues. To understand and control this influence, one has to study the same phenomena and processes in the absence of gravity, or under microgravity conditions. Such a microgravity environment can be realized

• in a spaceship in orbit (like International Space Station)

• in sounding rockets (e.g. European Space Agency (ESA) Maxus, 13 minutes microgravity)

• in ballistic phases of aircraft flight (e.g. NOVESPACE ‘ZeroG’, 22 seconds microgravity)

• in drop towers (e.g. ZARM Bremen, 5 seconds microgravity)

Apart from the drop towers, hampered by very short microgravity durations, access to these environments is extremely limited and very costly, the most extreme case being the ISS. Another way to achieve microgravity conditions is the compensation of gravity with the use of a strong static magnetic field gradient. Such a gradient exerts a force on any medium, which can compensate gravity. This method has many advantages: 

• microgravity can be maintained over long periods

• ample access and availability

• low cost

• control of the effective gravity

One of the areas where microgravity and its effects are evidently of the utmost importance is space transportation. Just to get into space, one has to have a detailed understanding of the behavior of rocket fuels, like liquid hydrogen and oxygen, under reduced gravity conditions.

In the frame of the Research and Technology program of the Direction des Lanceurs of the Centre National des Etudes Spatiales (CNES), engineers of the Laboratoire National des Champs Magnétiques Intenses (LNCMI, CNRS) and the Service des Très Basses Temperatures (SBT, CEA) in Grenoble have designed and constructed a dedicated large volume magnetic levitation station and the corresponding cryogenic sample environment to study the boiling behavior of liquid hydrogen in reduced gravity conditions, down to zero gravity.

This world-wide unique installation was put into operation in June this year, and the results obtained in it are used to better understand and model the behavior of this essential rocket fuel, improving the efficiency and safety of the space transportation.