Flexible structures offer protection in space

Some remarkable developments of aerospace devices, based on advanced flexible materials, are now hitting the heights. Tom Shelley reports



An Anglo-Italian company is developing a flexible planetary re-entry lifeboat and inflatable space module – as well as products for slightly more down-to-earth applications.
Aero Sekur, which undertakes its manufacturing and R&D in Italy, produces parachutes, flotation air bags and fuel tanks. But the company is also engaged in developing a flexible fabric lifeboat for space vehicles, called the SPacecrew Emergency Module (SPEM), in light of the Columbia Space Shuttle disaster in 2003.
The design that Eureka saw at the recent Farnborough International Airshow was made out of a complex laminate of materials, capable of withstanding the heat of re-entry on its underside. According to Aero Sekur CEO Mark Butler, a flexible, inflatable heat shield is deployed, at an altitude of 100km.
“This allows the capsule to slow down significantly as it crosses the upper layers of the atmosphere,” he says. “The primary requirement is managing the extremely high temperatures generated at the leading surfaces – typically 1400º C – whilst maintaining temperatures of less than 80 deg C close to the crew/payload.”
Ground qualification for the SPEM was carried out in 2005 and final tests are to be performed in the SCIROCCO plasma hypersonic wind tunnel at the Italian Aerospace Research Centre (CIRA) at Capua.
“As the module descends through the lower atmosphere, a parachute and deceleration system is operated to further reduce the landing speed to 10 m/s,” explains Butler. “The inherent buoyancy of the module provides support during sea landings, without additional flotation equipment. This means significant volume and operational cost savings.”

At the same time, Aero Sekur is developing an advanced inflatable module (IMOD) for use in space, in response to a brief by the European Space Agency. It weighs 200kg and can be compacted to one cubic metre for transport.
The solution is made from woven ‘Zylon’, a trademarked name for a poly(p-phenylene-2,6-benzobisoxazole)(PBO), made by the Japanese Toyoba Corporation, said to have originally been invented by the Stanford Research Institute in the 1980s. It has a tensile strength of nearly 6Gpa - twice as strong as aramid fibre - but has to be protected from sunlight, so the module is made of layers of materials in order ensure durability, as well as to maintain the required shape. The module also includes a window structure and is scheduled to become available by the end of 2008.
Slightly more down to earth is a combined parachute and airbag with shock attenuation system for recovering UAVs more safely. While advanced controlled technologies have been developed that allow UAVs to be landed even in difficult conditions, in a military situation, it is not always possible to have a proper runway to land on.
Aero Sekur’s airbag system includes expertise gathered during work on the Mars Lander, although the UAV recovery system is slightly different, in that the Mars Lander bounced on round, inflated air bags, whereas UAVs are protected by shapes that are rather more complex and deflate quicker.

Pointers

A lifeboat module made of flexible fabric is being developed to allow astronauts to re-enter the earth’s atmosphere safely

* A flexible fabric space station module is expected to be ready for use by the end of 2008

* A system has been developed that combines parachutes and air bags to ensure the safe recovery of UAVs when no runway is available


Author
Tom Shelley

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