ABOUT midway through “When We Left Earth,” a sweeping new video history of the American space program, the former NASA flight director Eugene F. Kranz looks into the camera with an intensity that is almost frightening.
“The power of space was to raise our aspirations to those things that are possible,” he says, “if we will commit.”
He punches each of those last four words, so it comes out “If. We. Will. Commit!”
Those four words lay out the underlying argument of the six hours of a NASA documentary that goes far beyond recounting history, and which begins on Sunday at 9 p.m., Eastern and Pacific times, on the Discovery Channel.
Mr. Kranz is not just making a statement. He’s asking a question — will we commit? — and issuing a challenge: Well?
Mr. Kranz, who was the famous flight director on the nearly tragic Apollo 13 mission — Ed Harris played him in the 1995 movie “Apollo 13” — has still got the flattop. He’s still wearing a flashy vest, just like the ones he wore for missions stretching from the initial Mercury program to today’s space shuttle. But he’s decades older than that kid in the pictures from the early days.
So is the space program.
The future is 50 years old.