One of the defining moments of the 20th century was when Neil Armstrong set foot on the Moon. Since then, sending humans into space has been blighted by disasters and fraught with problems and expense. With technology now available to send unmanned craft into deep space, should we be sending human beings to explore our solar system or leave it to remote-controlled craft? Quentin Coopergoes to the British National Space Centre to head the debate on the future of space travel. Producer Pamela Rutherford