Wednesday, 23 July 2014
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Levitating 'space furnace' bound for Space Station

Astronauts on the International Space Station (ISS) will this summer get to play with a “space furnace” that can levitate samples of metal.

German researchers hope to use the electromagnetic levitator (EML) to learn more about alloy materials by studying them a microgravity environment, where they won’t separate into their constituent metals when melted, as would happen on Earth.

The EML uses an electromagnetic field to heat the metal samples but also to suspend them in mid-air so they can be studied without any interference from a container.

Dr Christoph Pütz, director of microgravity payloads at Airbus Defence and Space, which developed the EML, said the system would help scientists study ‘the essential material properties you cannot determine very precisely on the ground’.

‘Thermoconductivity, viscosity, diffusion coeffient and things like that,’ he said. ‘Those parameters are important for predicting behaviour in casting processes, for example.’

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Source: Airbus Defence and Space

Metal samples will be held in cages of rhenium wire before being levitated by electromagnetic fields.

Scientists have actually been conducting similar experiments for decades as access to microgravity environments grew, from the 20 seconds of weightlessness provided by parabolic flights through the atmosphere to several weeks aboard the space shuttle.

The Airbus team developed the EML as a way for researchers at the German Aerospace Centre’s User Control Centre in Cologne to control and monitor experiments aboard the ISS over a much greater period of time while themselves remaining on the Earth.

The 360kg-system comprises a vacuum chamber with a magazine of up to 18 spherical metal samples. When a sample is being studied it is fed into a wire cage in the vacuum chamber until the electromagnetic field is switched on, which then levitates the sample so that it is freely suspended but held precisely in position to avoid interference by any external disturbances.

Another field then heats the sample (by inducing electric currents in it) to close to 2,000°C and a high-speed data camera captures up to 30,000 images a second as it melts and then re-solidifies once the heating field is deactivated.

/h/s/u/Airbus_space_furnace_2.jpg

Source: Airbus Defence and Space

The primary challenge for Airbus was making the EML safe for the crew of the ISS.

As well as shrinking the technology to make it suitable for the ISS, the Airbus team had to build a diagnostic system to allow the EML to be controlled and monitored in real time by the scientists on the Earth.

‘The most challenging thing we had to master was the safety aspects,’ said Pütz. ‘The samples are at very high temperatures and have to be contained, and you have an evaporation effect from the sample … that is toxic and a hazard to the crew. So we have to implement a dedicated container that shut downs electronically if something happens.’

Another challenge was developing sample-holding cage, which had to be made of very thin wires so that it wouldn’t obstruct the camera’s view of the samples but also had to withstand very high temperatures and so was made from rhenium, which itself creates challenges for welding.

The EML and the first batch of samples is due to be sent to the ISS on the European resupply spacecraft ATV-5 and is expected to operate until at least 2020.


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