On February 20, 1962, the spacecraft Friendship 7 rose on a pillar of fire, piloted by lone astronaut John Glenn.
Leaving the coast of Florida far behind, the space capsule orbited the earth three times, traveling 81,000 miles in less than four hours.
As the craft began its descent from space, mission controllers in Houston received a warning signal: a sensor indicated that the capsule's heat shield was in danger of detaching. If the heat shield came loose during re-entry, the capsule would burn like a meteor--and John Glenn would die.
There was no way to fix the problem in space. The capsule was already approaching the outer fringe of the atmosphere. As the tiny spacecraft fell toward Earth, the heat shield glowed red-hot--then white hot. Soon, a hot cloud of ionized gas particles called plasma surrounded the capsule.
Because radio waves cannot penetrate plasma, the spacecraft experienced a total communications blackout--what astronauts and mission controllers call a "black hole".
The minutes crawled by and the suspense mounted in the Houston control room. NASA engineers felt totally helpless.
Finally, after five minutes of silence, mission controllers...