[X] My Assistant

[abalone]

Entire post of blue-sky engineering culled. See rules. - ADMIN

[abalone]

Entire post of blue-sky engineering culled. See rules. - ADMIN

I cant understand why this post has been culled, fission engines using hydrogen as a working fluid were in the design stage in both the USA and Soviet Union in the 1950s and 60s. the Russians even tested one. If this is blue-sky then someone is lacking a bit of faith that any progress is going to be made
Seems to me there is more blue-sky engineering in harvesting water from the lunar poles than building these engines

"A nuclear engine was considered for some time as a replacement for the J-2 used on the S-II and S-IVB stages on the Saturn V and Saturn I rockets. Originally "drop-in" replacements were considered for higher performance, but a larger replacement for the S-IVB stage was later studied for missions to Mars and other high-load profiles, known as the S-N. Likewise the Soviets studied nuclear engines for their own moon rockets, notably upper stages of the N-1. However, neither design had progressed to the point where they were ready to test before the space race was ostensibly over.

To date, no nuclear thermal rocket has flown, or even reached a stage of development where it could be. The Russian nuclear thermal rocket RD-0410 went through a series of tests on the nuclear test site"
http://en.wikipedia.org/wiki/Nuclear_thermal_rocket

[abalone]

We don't know what form it's in. It may be in a form that's hard to liberate. Furthermore - hydrogen on its own, isn't that useful* It's incredibly light so it's not much of a burden for space flight (consider the Mars Direct ISRU numbers). You tend to need something heavy (oxygen) to do something with it. If it's vast swathes of actual ice down there - then we have rocket fuel, air and water for future crews. If it's just hydrogen, you've still got to take 7/8ths the mass with you.

* apart from filling balloons - but that's not too useful on the moon

Ill try to repeat my original post and see if it get through this time

Hydrogen used as a propellant in a fission rocket has a much higher impulse than when you waste it by burning it with oxygen. Designs for these do exist, you would only have to carry a couple of tens of kgs of uranium and it does not have the same emotive radiation hazard that it would have if launched from Earth. Even at 6.8% water there would be plenty to drink and breathe

And would like to add in support

"Usually, with hydrogen propellant the solid-core design is expected to deliver specific impulses (Isp) on the order of 800 to 900 seconds, about twice that of liquid hydrogen-oxygen designs such as the Space Shuttle main engine."
http://en.wikipedia.org/wiki/Nuclear_thermal_rocket

[stewjack]

I cant understand why

I didn't see your original post, but I suspect you are off-topic. HINT: It has been my experience that the longer or more complex the post, the stronger the requirement for being on topic.

IMO: You just crossed a subjective line - by starting a discussion of nuclear propulsion in a LCROSS impact results thread. Technically the "usefulness of H2O" discussions were probably off-topic, but as in U.S. Football, it is always the player who retaliates for a foul blow that ends up getting the penalty.

Jack
If this post is deleted for being off-topic at least it is my first offense.

[dilo]

In 1978 Russians found water in samples brought back by Luna-24. In 1976 Luna-24 landed in Mare Crisium and drilled a core sample from about 2 m deep in Lunar surface. Their article "Water in the regolith of Mare Crisium (Luna-24)" was published in a Russian publication Geokhiimia but seems to have gone ignored.

Thanks Spin0! This makes me disappointed, did NASA/scientific community deliberately ignored these findings because they are considered unreliable or...

[Phil Stooke]

Not really - they had the same findings from Apollo samples. Everyone thought it was contamination.

Phil

[marsophile]

Not really - they had the same findings from Apollo samples. Everyone thought it was contamination.

If they thought it was contamination, then how did they reach the conclusion that the Moon was "bone dry"? The contamination would mask any negative result. The interpretation should have been that the tests were inconclusive, rather than a definite finding of no water.

[MarsIsImportant]

So instead of doing the hard science to find out whether the results were contaminated, everyone just assumed they were. A startling discovery 30 to 35 years ago that would have changed the paradigm for space exploration back then was simply shrugged off as an errant reading, not once but twice from two separate sources and experiments. They simply did not believe the data.

Unfortunately this type of thing is not all that uncommon, just normally a little less dramatic. Pride comes before the fall.

[Phil Stooke]

I agree that people may have rejected their findings too quickly, but it wouldn't have 'changed the paradigm'. The amounts we are talking about, a molecule or two thick, will make no difference at all to anything. Only the possible concentrations at the poles have the chance to change the paradigm.

As for the bone dry thing, the lunar surface even with these molucules adhering to it is dryer than any bone. That old conclusion referred to chemically or geologically active water, and it's still true today. The problem here is overhyping of the recent results. Water, yes, but not as we know it, or in any useful amount. LCROSS results may still be different.

Phil

[dilo]

The amounts we are talking about, a molecule or two thick, will make no difference at all to anything.

Phil, I think that 0.1 wt% water isn't so negligible, even though not very usable for human activities, perhaps... however, let's consider also the amount of water seemed to increase with depth!

[MarsIsImportant]

I noticed the depth thing too. That is potentially significant. We won't know for sure one way or another until more exploration is done. A lot of that exploration may depend upon the results from this LCROSS mission. I hope we get it sooner rather than later.

[Guest_Sunspot_*]

Interesting article from New Scientist.

"Was moon-smashing mission doomed from the start?"

http://www.newscientist.com/article/dn1799...-the-start.html

[Phil Stooke]

Part of the problem with the water story is that we are getting inconsistent statements. As I understand it the water is only a few molecules thick on the very surface of the regolith, and much of it leaves the surface when heated during the day, then reforms as the sun sets. That is very little water. Then we have statements about getting a glass of water out of a tonne of regolith - or whatever the specific amount is. I think these are not compatible, and the only way I can reconcile them is to say that the tonne of regolith is not dug up in one place but scraped in a layer 1 mm thick over a large area. In other words the bulk regolith is 'bone dry' and a very thin surface layer has all the water. I might be wrong here, but I think not. As far as I know the water detected by M3 is not chemically active - not producing clay minerals in significant quantities, for instance. Obviously we need a lot of follow-up studies of this, but it does seem to me that the water story has been exaggerated in the media.

Phil

[djellison]

d the only way I can reconcile them is to say that the tonne of regolith is not dug up in one place but scraped in a layer 1 mm thick over a large area. In other words the bulk regolith is 'bone dry' and a very thin surface layer has all the water.

That's the idea I got as well - and is the figures I used when estimating just how useful it might be.

[Greg Hullender]

But now I think we do know that the various probes only claimed to have measured the top mm or so -- I don't see anyone claiming to have proven the H2O was limited to the top mm.

Given a porus medium being subjected to a daily barrage of hydrogen, and knowing how motile hydrogen is, I find it difficult to believe that it wouldn't permeate the regolith to considerable depth. The regolith should be in equilibrium with respect to hydrogen content -- losing as much as it gains in any given day -- but given a slight preference to move down (caused by gravity) plus a tendency of anything very far below the surface to stay put (caused by lower temperatures) I can't see how that equilibrium would be reached with hydrogen limited to just the top mm.

As everyone says, with any luck we'll see some exciting real data in a few months. And perhaps this will excite some interest in lunar rovers with some digging capability.

--Greg