美国国家公共电台 NPR NASA's Other Asteroid Mission: Grab A Chunk And Put It In Orbit Around The Moon（在线收听）

NASA's Other Asteroid Mission: Grab A Chunk And Put It In Orbit Around The Moon

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A NASA spacecraft is on its way to an asteroid. The robotic probe launched yesterday and will collect a bit of dirt from the asteroid and bring it back to Earth. This isn't the only asteroid mission the space agency has in the works. NASA also wants to send astronauts up to study an asteroid. And NPR's Nell Greenfieldboyce reports that the human mission has a lot of critics.

NELL GREENFIELDBOYCE, BYLINE: The idea of visiting an asteroid goes back to 2010. President Obama went to Kennedy Space Center and announced he wanted astronauts to go out beyond the moon and ultimately to Mars.

PRESIDENT BARACK OBAMA: We'll start by sending astronauts to an asteroid for the first time in history.

GREENFIELDBOYCE: Trouble is, flying people to an asteroid turned out to be really hard. The trip would take months. So NASA settled on a slightly different plan - send a robot out to retrieve an asteroid and bring it over to the moon. That way the astronauts could study it in lunar orbit.

MARCIA SMITH: It wasn't sending people to an asteroid; it was bringing an asteroid to people. But you were still demonstrating some of the technologies that NASA wanted to demonstrate as part of its long-term goal of sending humans to Mars.

GREENFIELDBOYCE: Marcia Smith is a space policy analyst and consultant. She says the original so-called asteroid redirect mission also proved to be daunting. It was difficult to find a small asteroid to target.

SMITH: They ultimately made the decision to not move an entire asteroid, but just pluck a boulder from the asteroid surface and bring the boulder to the astronauts. So that is the current plan.

GREENFIELDBOYCE: Having a robot go out tens of millions of miles, grab a multi-ton, car-sized boulder and then drag it to the moon, plus sending people up to study this rock will cost something like $2 billion. Smith says a lot of people are asking this question.

SMITH: If your long-term goal is to go to Mars, do you need to spend $2 billion doing this mission, or can you spend it better doing other things?

GREENFIELDBOYCE: NASA says this is worth the money. Michele Gates is NASA's program director for the mission. She says, when a crew flies up to the captured boulder in the mid-2020s, it will be a significant advance.

MICHELE GATES: It'll be the first time we've brought humans back to the lunar vicinity. They'll actually be 50,000 miles past the surface of the moon - farther than people have ever been before.

GREENFIELDBOYCE: And, Gates says, the mission will use a new kind of solar-electric propulsion.

GATES: This technology that we'll be demonstrating is truly a leap from where we currently are and a significant step and contribution to what we'll need for deeper-space human missions.

GREENFIELDBOYCE: But others say, if you just sat down and tried to chart a path forward to Mars, it's hard to imagine that you'd include capturing part of an asteroid. Leroy Chiao is a former astronaut who works with NASA's Advisory Council. He says, if he was still part of the astronaut corps, he would be psyched to fly around the moon.

LEROY CHIAO: And if there happened to be an asteroid there that we can fly in formation with or, you know, a boulder, that's fine. But I'd be just as happy not flying in formation with a boulder (laughter).

GREENFIELDBOYCE: Given that NASA's stated goal is to get to Mars in the 2030s, he just doesn't see the point of this.

CHIAO: On a technical level, I don't think it's worth doing. But in order to satisfy the president and the White House administration's desire to do something with an asteroid, this, I think - I believe this is what NASA figured out they might be able to afford.

GREENFIELDBOYCE: He says this asteroid mission is a product of budget constraints and politics. He personally thinks we'd learn a lot more about how to explore Mars if we did something like set up a moon base to test out habitats and rovers and space suits.

CHIAO: But frankly, you know, the moon was perceived as President Bush's program, so I don't think that was really a starter, politically.

GREENFIELDBOYCE: It's the next president, along with Congress, who will have to decide where astronauts should go next - whether NASA should still boldly go to a piece of an asteroid or do something else. Nell Greenfieldboyce, NPR News.

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