From 4 key players, a sense of regret and a call to action

— -- Rocket expert frustrated

In 1945, the United States brought Konrad Dannenberg, now 95, to this country from Nazi Germany to help launch rockets. Then the government held him back — until the Soviets launched Sputnik.

Dannenberg fell in love with rockets as a high school student in Hanover, Germany. So strong was his desire to work on space exploration that during World War II he agreed to join a Nazi rocket team, headed by legendary rocket engineer Wernher von Braun, as a propulsion expert.

"The Army was the only rich uncle (with) enough money to pay for the things we wanted to do," he says unapologetically about his decision. During the war, von Braun's group developed the first rocket to go into space, the V-2, which was made by slave labor hundreds of miles from the rocket-design shop.

Recognizing the Germans' expertise, the Americans spirited von Braun, Dannenberg and 116 other rocket experts to the United States. Working for the U.S. Army, the Germans designed a ballistic missile called the Redstone.

Von Braun wanted to use the Redstone to loft a satellite into orbit in 1955, Dannenberg says, but the Eisenhower administration blocked the plan. Two years later, the Soviets launched Sputnik I.

"We were definitely disappointed," Dannenberg says. "We could've done it earlier." Now he is philosophical. Sputnik "woke up a lot of people in this country," he says. Four months after Sputnik, a modified Redstone carried the first U.S. satellite into orbit.

Dannenberg went on to help direct the development of the Saturn V. The massive rocket launched U.S. astronauts to the moon.

Today, Dannenberg has a bigger frustration: His adopted country has not sent humans to visit other planets and doesn't seem eager to do so. He says such exploration is crucial, in part because of the possibility of a catastrophe on Earth.

"I think it's a foolish thing," he says, of America's de-emphasis on space exploration. "As von Braun said, 'If you do it when you need it, it's too late. You missed the boat.' "

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