CSIR develops active aerostat

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The Council for Scientific and Industrial Research (CSIR) has developed a novel active aerostat, which although tethered, has control surfaces to allow it to better withstand the elements and provide better stability than traditional aerostats.

The helium-filled wing shaped balloon is fitted with rigid control surfaces, allowing it to better maintain its position in high wind conditions through the additional lift created by the envelope. This results in better coverage from sensors fitted to the aerostat, as conventional aerostats will be pulled back and buffeted by the wind. The aerostat features an active control system, with an autopilot controlling pitch, roll and yaw.

The CSIR said the active aerostat can be rapidly deployed to its required heights for maximum surveillance. Line tension is maintained within pre-set limits by the active control system.

The system has application in all areas where persistent aerial surveillance is needed and isn’t required to meet the strict civil aviation requirements governing the use of unmanned aircraft systems. Applications could include military and security, farming, wildlife monitoring, crowd control, border surveillance, mining surveillance, shark monitoring, advertising and communications relay.

The active aerostat, designed by the CSIR in collaboration with Dr Ralph Katzwinkel, first flew in April 2016.

The CSIR is no stranger to aerostat research. In 2015 the CSIR was raising funds to acquire an aerostat for its AwareNet project, with some funding coming from the Department of Science and Technology. The plan is to put the aerostat to work monitoring 300 km stretches of South Africa’s coastal and northern borders.

The CSIR’s Francois Anderson believes that with an appropriate mix of mountain-based and aerostat-based radars it should be possible to cost-effectively cover all of South Africa’s land and coastal border zones. South Africa has more than 4 400 km of land borders and a coastal border of a further 2 800 km.

The problem with land-based radar systems, even when radar stations are set up high on mountain tops, is their coverage against surface-based and low-flying targets is limited by the horizon as well as by the terrain casting radar shadows, for instance behind topographical features, such as lower hills or neighbouring mountain ranges, that obscure the line of sight.

When fitted with a special lightweight radar system, relatively affordable aerostats flying at heights up to 1 500 metres above the surface of the Earth are capable of providing low-level coverage up to ranges of 150 km for periods of up to a month at a time.



Over the past two decades aerostats have already been used effectively by the US military in Iraq and Afghanistan, amongst other places. They are also being deployed by an increasing number of countries in border safeguarding roles. In addition, aerostats are perfect platforms on which to mount wideband communications repeaters providing coverage over a wide area.