The Grand SLAM: Rocketing Water to the Moon
By Leonard David
Senior Space Writer
posted: 24 May 2006
06:41 am ET
BOULDER, Colorado A strikingly simple concept would provide
efficient water provisions for human outposts/bases on the Moon.
The idea is to repeatedly clobber our already crater-rich neighbor
with tons of water iceto 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 mimicsin
experimental forma comet strike. Therefore, its a double-whammy:
A science mission wrapped within an exploration capability test
mission.
Spearheading the speculative ploycalled SLAMis Alan Stern,
executive director of the Space Science and Engineering Division
here at Southwest Research Institute (SwRI). Hes the lead
scientist on another far out, but on the way, endeavor the New
Horizons spacecraft that is outbound 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 Moons poles in the first
place.
Spacecraft that orbited the Moonthe Pentagons Clementine (1994)
and NASAs Lunar Prospector (1998-1999)relayed data that hydrogen,
arguably in the form of water ice, might be stashed within
permanently shadowed craterscalled "cold traps"at the lunar
poles.
And, 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?
NASAs 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 NASAs Lunar
Reconnaissance Orbiter (LRO).
Thermal jacket
On LROs 2008 mission a newly announced "secondary payload" is the
Lunar CRater Observation and Sensing Satellite (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 Moons
south pole area. A plume of material should be tossed high above
the Moons desolate landscapethen sensor-scanned in a look for
lunar water ice.
If found, getting at that water ice at the poles wont be easy.
Working people and machinery in those cold trap climes would be
tough. Light and power reserves arent easy to come by.
Communications in and out of those locales is an issue too.
And thats where SLAM meets these difficultieshead on.
SLAM needs no mid-course correction en route to the Moon, nor a
spacecraft for that matter. All thats necessary is a thermal
jacket for the water ice payload thats 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.
Clean water act
SLAM could even serve as an emergency, launch-on-demand service,
Stern continued, for lunar-situated crews in need of a rapid
recharge of oxygen, hydrogen, or liquid water to drink.
SLAM is also, in a way, a "clean water act" for the Moon. No
telling what the quality of water ice, bacteria-wise, might be
available in those darkened polar cratersif indeed its
there.
Another ballistic bonus of SLAM is creation of a calibrated comet
impact crater. The shot-to-the-Moon ball of ice is a little comet,
Stern noted.
Moreover, scientists could study the transport efficiency of water
on the Moon. Molecules of water that are introduced into the lunar
environment from outside sources hop around like being on a griddle
but a certain percentage make their way to the poles. The
survival rate of those water molecules is a great scientific
question, Stern said.
"SLAM is a nexus of three or four things in exploration and
science," Stern said. "I defy you to find a space mission thats
cheaper or simpler" than a mission that involves just two things: A
rocket and a garden hose left behind at the pad, he pointed
out.
Breaking the Gordian Knot
Rockets lifting thousands of gallons of water skyward has been part
of U.S. space history.
In the early 1960s, test missions for the Saturn 1 booster
included hurling water-filled upper stages into space, even dumping
loads of water into Earths upper atmosphere under Project
Highwater.
"SLAM was designed to take advantage of the high performance and
precision injection capability of the existing Atlas 401," said
Bernard Kutter, Manager of Advanced Programs at Lockheed Martin
Space Systems in neighboring Denver.
Kutter explained to SPACE.com that, by utilizing existing Atlas
capabilities, SLAM can provide a low cost, low risk, novel lunar
science mission furthering our understanding of the Moon and water
transport around the Moon.
SwRIs Stern emphasized that SLAM is the output of roughly a dozen
people that tackled a set of issues
to break the Gordian Knot
between the value of polar volatiles and the difficulty of polar
operations.
"To us it made a lot of sense. We couldnt find an obvious flaw in
it
not to say that it doesnt have pros and cons," Stern explained.
One constraint is that an Earth-to-Moon ice ball strike must take
place during lunar night, he said, with mining recovery necessary
before sunrise to prevent ice sublimation after impact.
Thats a practical, real-world problem, Stern observed, just as
deep ocean drilling here on Earth has its problems too. In exchange
for those troubles there are great rewards, he said.
"Were proud of the SLAM idea," Stern concluded. "Itll be up to
others to see if this concept, I guess you could say, holds
water."