Tragedy struck when the Space Shuttle Challenger disintegrated just 73 seconds into flight. Hours earlier, engineers argued to cancel the launch, amid fears of such a tragedy – so why did it go ahead?
Massive engineering mistakes occur all over the world, some with devastating consequences. These are assessed by design teams, eyewitnesses, and experts who analyze what went wrong and how the engineers fixed the mistakes.
Survivors and witnesses recall March 11 2011 - when Japan was hit by a devastating tsunami of 40-foot waves, killing 20,000 and triggering a nuclear meltdown.
