Getting astronauts to Mars will take all the spacefaring expertise the United States can muster, including advanced propulsion technologies such as solar-electric engines and perhaps even nuclear rockets, according to NASA Administrator Charlie Bolden.

In statements made during a visit to the Aerojet Rocketdyne plant here last Thursday (May 28), Bolden stressed that he'd like to slash the travel time required to send astronauts to Mars.

"Right now it's about an eight-month mission; we'd like to cut that in half," Bolden told reporters after speaking to Aerojet Rocketdyne workers for 30 minutes or so. [Superfast Propulsion Concepts (Images)]

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