In 1970 three astronauts on Apollo 13 just got home alive after technical problems hit their mission - a story told in the hit movie starring Tom Hanks.
In 1986 the space shuttle Challenger exploded on take off, killing all seven astronauts. The problem was a leaky seal on a fuel booster.
In 1999 Nasa lost two (unmanned) craft going to Mars, in one instance because its engineers hadn't decided whether to work in inches or centimetres.
In February 2003 the space shuttle Columbia fell apart as it entered Earth's atmosphere, killing all seven astronauts on board. Foam insulation had broken off the shuttle, breaking a heat shield on the craft.