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NASA Briefs Preliminary Plume Findings from Moon Mission
Holder of the Tw...
post Nov 15 2009, 05:56 AM
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As I recall from the blog site (someone correct me on this if I'm wrong), every bit of the hydrazine was successfully vented, or used.

QUOTE (tanjent @ Nov 14 2009, 10:41 PM) *
Any attempt to set up shop and utilize trace amounts of lunar water will have to invest heavily just in thermal insulation alone... But to significantly lower the costs of exploration we need at least a recognizable "dirty snowfield," not the Atacama desert.


I'm afraid I must disagree. In a vacuum, you don't have to invest heavily in thermal shielding. Proper reflection and disposal of waste heat (here, it would be upward toward the sky) and careful use of insulating materials in the proper location (thermally isolate the wheels on a rover, keep them cold) would enable the enviroment to be maintained as long as the rover didn't stay in one spot very long. Witness the Spitzer telescope, which maintains its innards during the current warm mission at 30 degree K, even in constant direct sunlight.

Earlier, use of the 100 ppm implanted regolith hydrogen was considered as a cost effective resource (by Harrison Schmidt, among others), even though it would require much higher roasting temperatures to obtain. Water ice will require less energy to get out.

As far as infrastructure, a landed vehicle could be refueled over time using its own propellant tanks for storage. You just need the rover dropping off its load multiple times.
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Geert
post Nov 16 2009, 06:26 AM
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Last night we had quite a bit of rain here in the "jungle" of northeast Thailand, and rain in this time of the year is a bit exceptional.

However, our local radiostation just announced the reason in its hourly news bulletin: the rain was caused by the American moon rocket, crashing on the moon. It had taken the water a bit of time to reach Earth, but last night it arrived!

No kidding, this is the official news bulletin..
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nprev
post Nov 16 2009, 06:36 AM
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Um...we're sorry? rolleyes.gif tongue.gif


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Stu
post Nov 16 2009, 06:41 AM
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Better get under cover Geert; there should be a nasty shower of red rocks coming your way soon, knocked off Mars by the impact of Beagle 2. On behalf of the British people, I apologise in advance... wink.gif


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JohnVV
post Nov 16 2009, 07:20 AM
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QUOTE
No kidding, this is the official news bulletin..

post a link
That is , sad to say, something i might expect to hear on the news these days .
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marsophile
post Nov 16 2009, 06:12 PM
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One interesting question is: to what degree does the estimated concentration of hydrogen compounds in the plume match the concentration of hydrogen calculated from the neutron spectrometer measurements of Cabeus from LRO and Prospector? The neutron spectrometer measurements are averaged over a larger region, so if the concentration in the plume is smaller, it seems to imply larger patchy concentrations elsewhere in the crater. (I think Colaprete made this point in press conferences before the impact.) If the concentrations are about the same, then we can possibly extrapolate what the neutron spectrometer measurements mean in terms of specific compounds.
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Holder of the Tw...
post Nov 16 2009, 06:49 PM
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I don't have the LRO results. This paper, which interpreted everything in terms of implanted solar hydrogen, gave 1500 plus/minus 800 ppm by weight hydrogen from Prospector data.

If entirely in the form of water - just for the sake of argument - that would give you between 6.3 and 20.7 parts per thousand (or 6,300 to 20,700 ppm) by weight H2O. In reality we already know the hydrogen exists in various forms and compounds.
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PFK
post Nov 16 2009, 10:50 PM
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Just to be clear, when I mentioned the organic content of the Centaur I certainly didn't mean to imply this would have implications for water measurements. I was thinking more of the "C-H" compounds they alluded to.
I'd agree entirely that it would be possible to make an inventory of this that would indicate how much "stuff" could be generated. And if this total is way below what is seen on the organic front then there's no issue - and I presume it is. Predicting what would be generated by such a powerful impact is, however, much harder. In reality, I suspect, all manner of small fragments will fly.
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nprev
post Nov 17 2009, 12:35 AM
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Most of the organics on the booster would presumably be wire insulation: PTFE, Kapton, etc. Would it be reasonable to assume that most of this stuff was subjected to high heat & subsequently decomposed into simple organics almost instantaneously during the impact?

IIRC, there's a fair amount of carbon in lunar soil already, and definitely a lot of oxygen. There might be a detectable excess of hydrogen and nitrogen from breakdown of the booster's wire insulation, but according to Phil this has been "tared out" of the observations.


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Phil Stooke
post Nov 17 2009, 01:29 AM
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There is also a lot of doubt about how a manufactured object behaves in an impact. A rock hitting the Moon at several km per second behaves in ways we understand fairly well, but how does an impacting rocket stage behave? Some of its kinetic energy is used up bending metal. The top end of the impactor may not hit the surface at the same speed the bottom end did due to the complex behaviour of the structure. It's not as simple as a shock wave moving through a rock. I am not so sure that a bundle of insulated wires is going to be vaporized. We don't know a lot about this situation. I think these kinds of uncertainty generally act to reduce contamination of the type discussed here, but I expect we'll see more experiments on the ground to try to get a better handle on it.

Phil


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Greg Hullender
post Nov 17 2009, 05:25 AM
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Note that the impact was at only 2.5 kps.

http://lcross.arc.nasa.gov/rationale.htm

And it was not expected to vaporize more than 10% of the ice. Instead, they were counting on the Sun to do that.

--Greg

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marsbug
post Nov 20 2009, 03:52 PM
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New scientist has confused me. I know I shouldn't put too much faith in what they report these days but they've said:
QUOTE
The solar wind is expected to form water in minute amounts, amounting to concentrations of no more than 1 per cent in the lunar soil.

LCROSS team members are still analysing the data, but calculations suggest the concentration of water is higher than that. "The data are consistent with a total hydrogen content in the range of several per cent," says Colaprete.


This is from their report on the Lunar Exploration Analysis Group meeting, so I was hoping for some interesting tidbits, but I'm just confused! Is the water content several percent, or the hydrogen content? Does anyone know of any other reports from the Lunar Exploration Analysis Group?


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mcaplinger
post Nov 20 2009, 04:01 PM
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QUOTE (marsbug @ Nov 20 2009, 07:52 AM) *
New scientist has confused me.

I'll spare you my opinion of the subject publication...

I think it's premature to discuss the LCROSS results before a peer-reviewed paper is published. IMHO, the LCROSS team didn't do anyone any favors announcing their preliminary results at a press conference.


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marsbug
post Nov 20 2009, 04:11 PM
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I think you're right!


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marsophile
post Nov 20 2009, 06:20 PM
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QUOTE (mcaplinger @ Nov 20 2009, 09:01 AM) *
I think it's premature to discuss the LCROSS results before a peer-reviewed paper is published. IMHO, the LCROSS team didn't do anyone any favors announcing their preliminary results at a press conference.


I disagree. The press conference did no harm and gave the public, who paid for the mission, exactly what they needed. This mission was funded, by the way, by the Exploration Systems Mission Directorate, not the Science Mission Directorate. The papers and conference reports, when they appear, will give the science community what they need.

The New Scientist article seems to plainly say that the hydrogen concentration, not the water concentration, was several percent, but obviously any report in a popular magazine should be viewed with due skepticism.
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