Textile antennas for use in space
In Steven Spielberg’s film of the 1980s, all that was needed for E.T. to build an aerial to telephone home were a few everyday objects, including an umbrella and a coat hanger. These days, our little Extra Terrestrial would doubtless have to create something a bit more elaborate to communicate with his home planet.
As you read these lines, some 2700 satellites are racing round the Earth, more or less above your head. They are monitoring the weather, recording changes in the climate and providing telecommunication and navigation services. There is a lot going on up there, you might say, but that is nothing compared to what is yet to come: the space travel company Blue Origin (founded by Amazon boss Jeff Bezos), Facebook and Elon Musk’s SpaceX aerospace company, are looking to launch thousands of additional satellites into orbit over the coming decades, in order, for instance, to be able to connect people in remote regions to high-speed internet. (Please fly over my house!)
If things turn out as HPtex project partners expect, then textile antennas like these for use in space, will, in future, also be built in Europe / Source: ESA/LSS
Ever more data in orbit
With growing numbers of satellites, the amount of wave activity in space is also increasing; specifically the quantity of electromagnetic waves. For it is the latter that carry data on the weather, the climate and so on, from Earth to the satellites, where they are picked up by antennas and then processed, so that scientists can read off the information. Up to now, satellite antennas like this have generally been between two and three metres in diameter. But this is hardly likely to be sufficient in future to capture the huge waves of data.
Establishing satellite expertise in Europe
“The increasing complexity of civil and military applications based in space will, in future, demand different solutions,” says Peter Rauhut, CEO of HPS, who specialise in systems for industrial space travel. In order to be able to deal with the growing amounts of data, Rauhut and his team are working closely with the Fraunhofer Application Center for Textile Fiber Ceramics TFK and other partners to create a new generation of satellite antennas. “We are developing reflectors with diameters of up to 20 metres,” says Rauhut. Similar reflectors are already being manufactured, but almost exclusively in the USA. “We want to establish expertise here in Europe too,” insists Rauhut. In their work, the research scientists and engineers are banking on materials and processes from the textile industry. To be able to better develop these for their purposes, they have created their own company, HPtex – a subsidiary of HPS – and Iprotex, who manufacture fine stitch-bonded and knitted fabrics for use in industry.
Carefully thought out: the folding metal fabric is affixed to a structure made from CFRP / Source: HPtex
Textiles unfold in space
So, for instance, the folding arms which link satellites to their reflectors are made from carbon fibre reinforced plastic (CFRP / CRP). The reflector itself, the core of the antenna, uses an ultrafine knit of gold-coated wolfram (or molybdenum), thinner than a human hair. The fabric conducts electricity and has a reflective surface, which means that it is ideal for ‘receiving’ the incoming electromagnetic waves – i.e. the data – coming from Earth. The designers are, however, not too keen on the terminology of ‘antennas in space’. They prefer to talk – and we are entering new linguistic territory here – of ‘large deployable reflector subsystems’.
The fact that they can be folded plays a crucial role because it means that the packed size can be reduced. And, although the new type of antenna is larger than those used today, it is expected to be lighter in weight, thanks to the CFRP. “When satellites are launched into Earth orbit, every kilogram of payload costs around € 2000 at today’s prices – that is significantly cheaper than at the time of the first moon landing, when it was ten times as much, but there is still room for further reduction,” says space-antenna specialist Rauhut. The first reflector-antenna, with a diameter of five metres, should be ready by the end of 2020. “Then we’ll do tests in the conditions that they will meet in space,” adds Rauhut, who is confident that the development of folding space antennas using textile materials has only just begun in Europe.
