He said: “Yeah, they didn’t have enough computer capacity to put all the programs in that we needed to go to the Moon and come back.
“So they left one out and it was called the ‘Return to Earth’ program, uhh, which might have been a little problem if we’d lost our communications.
“But we were very success-oriented, so it didn’t slow us down any.
“But what the computer did for us is it calculated the angles and location for us.”
Mr Worden appeared on the Google campus in 2011 for a Talks at Google lecture.
The astronaut spoke about the behind-the-scenes of the Apollo 15 mission, shedding light onto the technical difficulties of the time.