Ever since Neil Armstrong first set foot on the Moon back on 20 July 1969, people have become accustomed to the notion of space travel. Millions watched that first lunar landing on black and white television sets, their hearts in their mouths, aware of how arduous and hazardous an undertakin it was, and of the many things that could go wrong. With Armstrong's now famous words "That's one small step for man, one giant leap for mankind", what had once been considered impossible had now been achieved. Guided by a computer that was much less powerful than the ones used by today's average school students, all three astronauts of the Apollo 11 mission made it safely back to Earth. <br> Following the Moon landings, space travel rapidly became unexceptional to the public, as innovations succeeded each other. By the early 1980s, the great rockets previously used in the American space programme had been replaced by the space shuttle. When the Challenger space shuttle took off on 28 January 1986, the world seemed to have lost its wonder at the amazing achievements of the astronauts involved. But this was going to be no ordinary excursion, and <br>millions of people tuned in to witness the take-off on TV. It was special because Christa McAuliffe aged 37, an ordinary teacher and mother, was about to become the first civilian in space. She planned to give two 15-minute lessons from orbit: the first to demonstrate the controls of the spacecraft and explain how gravity worked, and the second to describe the objectives of the challenger programme. Christa hoped to communicate a sense of excitement and rekindle interest in the space programme. With the eyes of students across the nation upon her, she might have inspired an entirely new generation of astronauts and space scientists. <br> Tragically, she never returned to her classroom as the shuttle exploded just over a minute after taking off in Florida, and all seven astronauts on board were killed. The world went into shock, most people having assumed that this space flight would be no more dangerous than travelling in an aeroplane. How wrong they had been! Instantaneously, excitement and optimism turned into terror and failure. It was the most disastrous space accident ever, and it cast a shadow on people's hearts. <br>"I can remember that day so clearly, watching the take-off on TV at school, said one student. "There was an ordinary teacher on the Challenger, and we were all very excited. We didn't have much patience waiting for the launch. We had seen the smiling faces of the astronauts waving to the world as they stepped into the shuttle. Then, little more than a minute after take-off, we saw a strange red and orange light in the sky, followed by a cloud of white smoke. The Challenger had exploded in mid-air and we all started screaming. <br> Following the shock of the Challenger disaster, space shuttle flights were suspended for nearly three years while the cause of the disaster was investigated, and some of the shuttle's components were redesigned. But there was never any doubt that manned flights would continue, and on 29 September 1988, the space shuttle programme resumed with the successful launch of Discovery. <br> It has now been over 30 years since the loss of Challenger and although the lives of its crew were cut tragically short, they take their place alongside the other heroes of space exploration, such as Gagarin, Tereshkova, Armstrong and Yang Liwei. The memory of those seven will live forever, written in the stars, inspiring us to join them in humanity's greatest journey of exploration and discovery. The sacrifice of the Challenger calls to us, reminding us that we must continue to reach for the stars, no matter how distant they might seem. <br>