Scientists float plan to blast water to moon

By Leonard David

Senior space writer

updated 12:35 p.m. ET May 24, 2006

BOULDER, Colo. - A strikingly simple concept would provide efficient water provisions for human outposts and even bases on the moon. The idea is to clobber our already crater-rich neighbor repeatedly with tons of water ice — to establish an "anywhere, anytime" delivery system.

Not only could chucking a payload of water ice to the moon help sustain an expeditionary crew there, the impact would mimic — in experimental form — a comet strike. Therefore, it’s a double-whammy: A science mission wrapped within an exploration capability test mission.

Spearheading the speculative ploy — called SLAM — is Alan Stern, executive director of the Space Science and Engineering Division here at Southwest Research Institute. He’s the lead scientist on another "far-out but on the way" endeavor: the New Horizons spacecraft that is bound for Pluto.

"I hope the SLAM idea stimulates thought and gets people thinking a little bit more out of the box," Stern told Space.com. "When we have people on the moon, they are going to need water. This is an exceptionally efficient, low-cost way to get it there."

Cold traps, lukewarm thoughts
One perplexing issue for scientists and lunar exploration planners is just how much water ice is at the moon’s poles in the first place.

Spacecraft that orbited the moon — the Pentagon’s Clementine (1994) and NASA’s Lunar Prospector (1998-1999) — relayed data that hydrogen, arguably in the form of water ice, might be stashed at the lunar poles within permanently shadowed craters, called "cold traps."

If water ice is there, that resource could be used by visiting astronauts to make rocket fuel and oxygen. But is it there or not? And if so, how much water ice is available, and in what condition for processing?

NASA’s back-to-the-moon thinkers are anxious to sort out the truth about this possible lunar water inventory.

For instance, joining in on the robotic assault on the moon by several nations over the coming years is NASA’s Lunar Reconnaissance Orbiter, or LRO.

Thermal jacket
On LRO’s 2008 mission, a newly announced "secondary payload" is the Lunar Crater Observation and Sensing Satellite, or LCROSS. The LCROSS will monitor the impact of a spent upper stage from the same mission, leftover hardware that would impact a crater in the moon’s south pole area. A plume of material should be tossed high above the moon’s desolate landscape — then sensor-scanned in a look for lunar water ice.

If found, getting at that water ice at the poles won’t be easy. Having people and machinery work in those cold-trap climes would be tough. Light and power reserves aren’t easy to come by. Communications in and out of those locales is an issue, too.

And that’s where SLAM meets these difficulties, head on.

SLAM needs no midcourse correction en route to the moon — nor does it need a spacecraft, for that matter. All that’s necessary is a thermal jacket for the water ice payload that’s flung by rocket booster toward any selected spot on the moon.

"It appears to be entirely feasible, simple and really cheap," Stern said. A proprietary technique would be utilized to keep the water ice ball from being buried too deep on impact.

At lunar impact speeds, virtually all of the ice will come to rest less than 5 feet (1.5 meters) below the surface, if properly pre-fractured. Also, work done on the concept indicates that a majority of the water ice that is slammed into the moon is retained, with only 15 percent vaporized.

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