Editors' note: This is part of a series examining 50 years of space exploration. In the 50 years since Sputnik's launch, there have been numerous advances and setbacks, as humans endeavor to learn ...

it is with deep, heartfelt sorrow. I address you here this afternoon at 11:40 a.m. This morning Space program experienced a national tragedy with the explosion of the space shuttle Challenger.

While on leave in January 1986, NASA administrator James Beggs turned on the television and spotted icicles on Challenger's launch tower. A day later, seven astronauts lost their lives. When you ...

Sunday marks the 38th anniversary of the Challenger space shuttle explosion, a disaster that killed seven people 73 seconds after launch.An O-ring failure blamed on cold weather doomed the shuttle ...