Mechanical Technology January 2015

⎪ Innovative engineering ⎪

Phoenix hybrid sounding rocket launched

During August last year, the Aerospace Systems Research Group of the University of KwaZulu-Natal (UKZN) launched its Phoenix-1A hybrid sounding rocket at the Denel Overberg Test Range. MechTech talks to Michael Brooks, aerospace research group leader (right of picture) and research associate Jean Pitot.

“A sounding rocket is a high‑at- mosphere, instrument-carrying rocket designed to take measurements and perform scientific experiments during a relatively short sub-orbital flight,” Brooks explains, adding that hybrid motor technology is ideal for these types of applications and for student development. Describing the three basic types of rocket motor, he says that liquid propel- lant technology is used for the larger rockets. Typically these have a tank of liquid oxygen and a separate tank of a fuel such as kerosene. The fuel and the oxidiser are mixed and ignited to create the expanding combustion gases that produce the rocket’s thrust. “The hardware required to pump the oxidiser and fuel is very complicated, expensive and heavy. And it is dangerous to use these fuels at institutions such as uni- versities,” he says. “Liquid technology does not scale well, either, so it is not really feasible for small-scale sounding rockets.” At the opposite end of motor tech- nology are the solid-fuel rockets that are, in essence, similar to those used for fireworks. “With solid-fuel rockets, the combustion fuel and oxidiser are mixed in advance, then packed into

E stablished in 2009 in UKZN’s Mechanical Engineering de- partment, Brooks says aero- space research is not new to the university and that Natal University had been active in the field since the 1950s. “We chose the name Phoenix to reflect the resuscitation of a programme started by our predecessors,” he says. The Phoenix research programme involves the development of a series of hybrid sounding rockets, for human capital development purposes and, eventually, for use by the African sci- entific community for physics research. Following successful lab-scale tests on wax/nitrous oxide rocket motors – along with the development of HYROPS, a hy- brid rocket performance simulator that models rocket performance and flight paths – the group set about designing and making its Phoenix-1A, a hybrid rocket with a theoretical apogee of 10 km, capable of delivering a payload of 1.0 kg.

The Phoenix-1A hybrid sounding rocket immediately prior to launch at the Overberg Test Range. the rocket’s combustion chamber. From the moment you ignite it, the motor will burn, and it can’t be stopped until all the fuel is spent. As with liquid technol- ogy it is very difficult to do solid motor research at a university because the fuel is explosive and, therefore, dangerous,” Brooks points out. Hence the use of hybrid rocket mo- tors. “A hybrid rocket uses a solid plas- tic, rubber or wax fuel and a separate liquid or gaseous oxidiser. The fuels are not premixed,” says Brooks. The solid fuel UKZN is using is a cylinder of paraffin wax – Sasol 0907, a mix of saturated, long-chain alkanes – with a

Under development, UKZN’s aerospace Group’s Phoenix-1A, a hybrid rocket with a theoretical apo- gee of 10 km, capable of delivering a payload of 1.0 kg.

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Mechanical Technology — January 2015