On Start the Week, as the first Briton heads into space for two decades, Andrew Marr explores the future of space travel. Kevin Fong is an expert in space medicine and in this year's Royal Institution Christmas Lectures looks at how to survive in outer space. The Astronomer Royal Martin Rees questions whether human space travel is worth the money or the risk, while the astrophysicist Carole Haswell searches distant galaxies for habitable exoplanets. Stephen Baxter is a writer of hard science fiction who, as a member of the British Interplanetary Society, investigates star ship design and extra-terrestrial liberty.