45 years ago tonight, everyone looked to the skies to see a magnificent sight, man's first walk on the moon. A feat inspired by the cold war. And now, so many questions about America's place in space... See More
45 years ago tonight, everyone looked to the skies to see a magnificent sight, man's first walk on the moon. A feat inspired by the cold war. And now, so many questions about America's place in space and our relationship with Russia are giving new ideas for exploring the final frontier. Here's Clayton Sandell. The eagle has landed. Reporter: 45 years ago today, the future arrived. That's one small step for man. One giant leap for mankind. Reporter: Millions watched Neil Armstrong and buzz aldrin go where no one had gone before. It was the height of the cold war. The U.S. Had now won the space race against the soviets. Secures its place as the leader in cosmic exploration. Touchdown confirmed. Reporter: From the Mars rovers, the Hubble telescope, and the international space station. But then -- The space shuttle pulls into port for the last time. Reporter: Three years ago, the shuttles were retired. Sent to museums. U.s. Astronauts lost their own ride to space. Forced to buy seats on Russian rockets. And before Malaysia 17 was shot down, new tensions were rising between the U.S. And Russia over Ukraine. The deputy prime minister threatened this spring. If America wants astronauts in space, it should get a trampoline. That does not sit well with former nasa administrator Michael griffin. We're in a hostage situation. Russia can decide that no more U.S. Astronauts will launch to the international space station. That's not a position I want our nation to be in. Reporter: But now, there's a new space race. Three private companies competing for billions in nasa dollars to build a brand-new ride for American astronauts. So this is the cst-100- Reporter: Chris Ferguson commanded the last shuttle flight. He's helping Boeing sell this design that can seat seven. We're waiting for the government go-ahead. To start building. Reporter: Space-x has the dragon. The first commercial ship to deliver supplies to the international space station. And then there's dream chaser. Sierra Nevada's smaller, sportier version of the space shuttle. Former astronaut Steve Lindsey took us aboard. Tight squeeze. It is. Reporter: Nasa wants the wing launch to happen in 2017. Many want us to go beyond. Buzz aldrin wants us to go back to the moon. Then on to Mars. We don't have to repeat what we did 45 years ago. But we don't ignore the moon. It's very important for technology, commerce, science. Reporter: That next giant leap perhaps to an asteroid or Mars, will be costly. But explorers like Katherine Coleman inspired by Apollo 11 say, it's well worth it. Humanity's first footsteps on the moon taught us what we can accomplish for all mankind when we focus on a common goal. It's time for our next giant leap. We're meant to explore our universe. Reporter: For "This week" Clayton Sandell, ABC news, Denver. And we end with good news. For the third week in a row, the Pentagon reported no deaths of service members in Afghanistan. That is all for today. Thanks for sharing part of your Sunday with us. Check out "World news" with David Muir tonight. I'll see you tomorrow on "Gma."
This transcript has been automatically generated and may not be 100% accurate.