A lot has changed on Earth since Col. Al Worden floated far beyond its orbit - more than 200,000 miles away, alone in space.
Technology and cultural barriers have been broken. Private entrepreneurs have blasted through the Earth's orbit. And China has celebrated the completion of its second manned space mission.
Worden, the Command Module pilot on NASA's Apollo 15 mission, recently talked with TechWeb about what he believes have been the most significant changes in technology and the space race. As NASA sets its sights on another manned trip to the moon, the former Systems Studies Division chief and senior aerospace scientist at NASA's Ames Research Center also provides insights about the past, present and future of space exploration.
Worden embarked on the fourth manned lunar landing mission with companions David R. Scott and James B. Irwin in 1971. His photograph, Earthrise, is well known, more than three decades after it graced the cover of National Geographic.
His crew was the first to use a moon-rover. On a two-person buggy, Worden's partners traveled the moon's surface. Worden orbited the moon alone for three day. He was 1,000 times farther away from home than today's astronauts living aboard the International Space Station.
"That was the best part of the flight," he said. "I loved it."
Worden said he spent his whole career working toward that goal. The West Point graduate and Air Force pilot said he was unafraid the entire time. He described takeoff as "nothing."
"You don't even know you're off the ground," he said. "It's so slow."
Worden and his crew were in space for 12 days and experienced neutral gravity. He said they were well prepared. At 73, still he vividly recalls the physical sensations.
"It was like swimming under water," he said. "It's not like falling suddenly. It was like we were falling forever. We spent almost two weeks doing nothing but falling."
They actually did a bit more than that.
Scott and Irwin were on the moon. They explored Hadley Rille and the Apennene Mountains on the southeast edge of the Mare Imbrium (Sea of Rains). The crew mapped the lunar surface.
According to NASA, their mission recorded the largest payload to travel in earth and lunar orbits. NASA estimated that the launch pad bore more than 6.5million pounds of weight when Apollo 15 lifted off. According to the mission log, liquid oxygen and hydrogen, used as cryogenic propellants, accounted for about 750,000 pounds. That's almost twice the weight of the International Space Station.
"I think the biggest thing that's happened since then to benefit space travel is miniaturization," he said. "Today we can get a gigabyte in an IPod."
Smaller technology means each mission can carry more gear with less weight and less fuel.
A new vehicle excursion program, which NASA states uses safer equipment than shuttles, may be the greatest leap in space program developments, Worden said.
Another advance that has caught public attention is private venture success with reaching space.
Though that's a milestone, Worden said people shouldn't get their hopes up about widespread commercial space travel in the near future.
"It's just kind of a line in the sand," he said. "When you go beyond the line, you're in space."
He said that's a far stretch from sending commercial spacecraft to circle the earth or spend significant time more than 62 miles above land and sea.
"It's too damned expensive," he said. "It makes no sense for private enterprises to put people into space. I think the government is probably the only organization that has the resources to do that. It's going to be many, many years down the road."
Though a manned flight to Mars will also be expensive, that is likely to be the next step after a planned 2018 return to the moon, Worden said.
"When we go to Mars, it's going to be the most exciting thing since we went to the moon," he said. "It's going to get the world's attention."
He also said it will be so expensive that no country is likely to go it alone.
"We're in a new era of exploration and we'd all be a lot better off if we did it in cooperation with those countries that have the technology to go into space," he said.
Though he said the Chinese will be the "big guns" in space, his views are dramatically different from James Oberg, a retired U.S. space engineer.
Oberg told Voice of America that China's recent foray into space added heft to the country's claims of military strength. "It enhances every statement or promise and – I'm afraid to say – every threat that Chinese diplomats make overseas," Oberg said.
However, Worden thinks China could help the United States get people to Mars.