Dozens of astronauts are preparing to splash down in Cape Town at the end of the month to plot everything from a Mars landing to the "crisis of space junk".

Commemorating 50 years since man first left the planet, the International Astronautical Congress will seek ways to replace the retired space shuttle and to spark an "African Astronaissance".

The week-long event will also mark a homecoming for the country's greatest space exports, including Jakob van Zyl, an ex-Stellenbosch student now head of strategy for Nasa's Jet Propulsion Laboratory, and former Pretoria pupil Elon Musk.

Described by President Barack Obama as the man leading the privatisation of space, Musk has developed a rocket which may carry America's future astronauts.

Held at the Cape Town International Convention Centre from September 30, the event will also showcase South Africa's new space agency, Sansa, and the wares of a local R140-million-a-year space industry, which already has three small satellites in orbit.

Astronaut Dr Leland Melvin, who flew his last space mission in 2009, said key space benefits for Africa included improving "water-purification systems, making food last longer (and) better harvests and disaster prediction ".

Melvin is looking forward to leading a Nasa team in workshops for 400 pupils from the Western Cape, who will compete in quizzes to win the chance to participate in the event.