George Alexander: Assessing the Space Shuttle Program

George Alexander was the Los Angeles Times' science writer from 1972 to 1985.

...Of the 134 shuttle missions launched before this final one, two ended in tragedy: Challenger, which was engulfed in a fireball 73 seconds after launch in 1986; and Columbia, which disintegrated over Texas just 16 minutes before it was due to land at the Cape Canaveral spaceport in 2003.

There were also five missions that came gaspingly close to disaster. In each of them, during the seconds between the start of the shuttle's three liquid-fueled engines and the start of its two huge solid-propellant rocket motors, computers sensed something amiss with the engines and shut everything down, averting almost certain catastrophe.

And at least a dozen other missions could have ended badly, even fatally, because of problems that developed during flight or on takeoff or landing. There were damaged heat-shield tiles, a blown tire, brake failure, leaky chemicals.

But in the shuttle program's 30 years of flights, there were also triumphs. The Hubble Space Telescope was launched in 1990, and five later shuttles between 1993 and 2009 were successfully dispatched to repair and refurbish this wonderful instrument. Shuttles launched two planetary probes, Magellan and Galileo, which went on to Venus and Jupiter, respectively....