With further respect to surviving solar created radiation, such as from within a lunar mobile pod/transporter or metro bus (LM-1):
From: Henry Spencer
"Something like 10cm of water ("or what water turns into once you run it through a human" --Zubrin) suffices here"
Since we're speaking of what a lunar metro bus must survive, we simply can't exclude those radiation issues as though this is going to be another sunny day "walk in the park" as suggested by those radiation-proof Apollo astronauts, that the likes of wizard Jay along with his army of NASA Borgs worships to death.
Thus it seems reasonable that 100 g/cm2 is being offered as a respectable assessment of the required density in order to meet a survivable criteria for extended space travel. From what I've learned from other sources, I'd tend to believe that Henry is being sufficiently correct, barring any of those horrific solar flares, in which case 1000 g/cm2 might have to become a little more appropriate.
As cosmic background radiation goes, it seems that I've learned from the likes of Henry Spencer and others that we're looking at roughly 1 rem/week (that's only 6 mr/hr), but as such those are far more capable per millirem of creating those hard X-Rays than of what's coming off our sun. Going by the following comments, I'd say cosmic rays are worth nearly a hundred fold as for creating those intensely nasty secondary TBI dosages than of typical solar generated flak, especially if it takes such a horrific density of 10t/m2 (1000 g/cm2) in order to do the trick of protecting your body and soul, as that's at least 100 fold greater than the maximum density being suggested by even the new guard of NASA as for adequately fending off solar induced radiation (including secondary issues) while residing outside the Van Allen zone of death.
With respect to surviving cosmic created plus secondary radiation:
From: Frank Crary
"Cosmic rays are less intense during the solar maximum" and "the rate is ~50 REM/year (1/week) at solar minimum and down to ~20 REM/year at solar maximum."
From: Henry Spencer
"It's *galactic* radiation, specifically cosmic rays, that is a major concern" and "to stop everything, you need maybe ten tons of shield per square meter of surface..."
Even though the lunar nighttime receives mostly cosmic and/or galactic radiation as perhaps attributing a mere influx of 6 mr/hr, however those are seriously hot millirems of perhaps 100+ fold greater overall impact where it counts, thus more or less equal to what 600 mrem/hr of combined influx and of secondary radiation dosage. Therefore the lunar nighttime environment may become a combined 1 rem/hr if there's any residual amount of solar influx that's wrapping itself around the moon, of which lunar nighttime is still offering a reduction of more than 14:1 over the fully illuminated surface and, as Frank Crary as well as Henry Spencer stipulated; whenever there's a great deal of solar maximum underway is when the cosmic radiation is cut by more than half, thus we might be looking at an overall 24:1 reduction if what the solar maximum itself isn't significantly worse off medication than the cure, as would likely have been the case for those two weeks in October/November 2003.
Since we still have no interactive instruments whatsoever on the moon, there's no for-certain measurement of the sorts of solar flare influx that's wrapping itself about the moon, therefore all others or myself can do is to extrapolate and thereby guess at how cold and nasty the lunar nighttime is. Fortunately the earthshine portion of illuminated lunar surface is known to be receiving at least 16 times the equivalent of what moonshine attributes to a clear Earth nighttime, though even of that our atmosphere cuts the worth of moonshine down by at least 20%, thereby the lunar surface should actually be receiving 20 times as much raw illumination and, I'm thinking there should be some measurable reflected solar radiation coming off Earth, though once again fellow snookered folks, because we haven't a darn thing situated on the moon, we've got squat worth of specifics.
The only for-certain safe lunar zone for the likes of October/November is the 3+ meters worth of basalt and of whatever other elements (obtaining as much as 1024 g/cm2) existing between yourself and of what's outside. Though a 1000+g/cm2 level of protection is possible within a limited portion of the LM-1, that amount of shield (if limited specifically to the crew cab) could easily impose another 36 tonnes (6 lunar tonnes worth) into the overall mass of what the LM-1 machinery has to haul about, which isn't out of the question if the total mass becomes as much as 96 tonnes (16 lunar tonnes), just that of the overall track-drive surface contact area may need to become at least 6 m2, unless the lunar surface turns out being more basalt rock than soil.
Being that the lunar soil supposedly clumps so nicely, in an absolute zero H2O environment no less, there shouldn't be all that much concern over track displacement of that mostly basalt soil, thus perhaps the maximum criteria of 6 m2 worth of track should still do the trick with traction and support to spare. When I get the time I'll even create a CAD rendition of what my three brain cells are visualizing with regard to this LM-1 metro bus.
Unfortunately, the outward LM-1 profile might unintentionally become a tad bit gender offensive looking, thereby I'm certain a feminine alternative design of some compromise will have to be accommodated but, there's no way in hell I'm going there, as I'm certain to be getting that one wrong. Perhaps an external facade will help to mask the otherwise questionable profile.
The truly nice aspects about basalt fiber composites, besides the fact that such can be easily derived from as well as processed on the moon, is with somewhat similar chemical binders the composites may include all sorts of heavy elements such as uranium fibers or of whatever other heavy lunar elements are available. Thus extremely dense composites can be applied externally as well as internally throughout the intended protection zone, conforming nicely to their foundation shape, taking the least amount of volume while bonding entirely to the base composite of those mostly pure basalt fibers. Overall, the added density will also further insure the greatest structural integrity per degree of impact worthy resistance, which could be of far more benefit than whatever a little radiation has to offer.
By way of reverse engineering; postulating that the lunar nighttime is offering roughly a 24:1 ratio of being less TBI worthy than of the fully solar illuminated (342 rem/day) lunar surface, perhaps somewhat less of a ratio with regard to the earthshine environment since that zone gets the accumulation of cosmic as well as some greater degree of reflected solar influence via earthshine. Although, with this understanding of the cosmic background being what it is, especially with respect to the lunar proximity to our sun, seems that in order to cut those nasty cosmic rays down to par, as well as for their subsequently creating all those secondary hard X-Rays may take all of ten times the density of the 25 g/cm2 shell of the LM-1 that's surrounding those crew members, thus a crew compartment area or zone within that's provided with 250 g/cm2 is going to become a relatively thick composite volume when sufficient layers of either uranium plating or whatever else is incorporated, and/or as much as 50 cm overall if a composite of uranium/basalt is utilized.
Since a purely basalt density composite fabrication is going to introduce at best 3 t/m3, thus other elements and/or alloys should be introduced if the shell of this LM-1 is going to become sufficiently space efficient, as opposed to being so externally huge/bloated that it can't go into tight places.
Of course, of any specific EVA duration, and/or if the collective hours of EVA exposures is kept to a dull roar, the acceptable annual TBI dosage of perhaps 10 rem/year may not require all that much shielding, as time is the real killer if not a nasty meteorite. I would expect the annual timeline budget per individual associated with those LM-1 EVAs is not going to amount to much over 10%, thus 36.5 days worth (876 hours) of whatever TBI exposure should permit the LM-1 composite of 250 g/cm2 as being within reasonable density and thereby a manageable thickness.
~ The Little LM-1 Engine That Could ~
Obviously sizable PV panels (articulated) mounted above the shell of this pod could offer as much as 48 m2, at 35 w/m2 are worth taking in 1680 watts, which unfortunately isn't worth squat unless the operational load is but 1% of the time, much less if there's only earthshine to work with.
A solution (besides nuclear) may become just that of a modified IC engine, something along the lines of what a diesel engine as right here on Earth (noise pollution and all). The notion that this is impossible is another terrific example of those folks that simply can't think outside their box.
Barring some rather obvious engineering modifications for lubrication, of related seals and of accommodating the required fuel and obvious oxidiser, here's the mental breakdown as this village idiot sees it:
1) In addition to the fuel (C12H26) being injected in essentially the identical manner as with any IC diesel engine, there's an oxidiser (H2O2) that's injected as well.
2) the function of the compression stroke following the H2O2 injection is in principle unchanged, other than for obtaining the appropriate thermal requirements, which obviously isn't going to take all that much.
3) There's obviously NO external atmospheric intake provision.
4) There's obviously an ambient assisted (boosted via vacuum) exhaust port.
This modified IC diesel engine could be as similar as a 4 cycle 3 cylinder format, though with the exhaust being extracted via vacuum, where this relatively small engine could offer rather tremendous energy per ccm, acting almost as a two cycle, in that the exhaust cycle becomes somewhat of another power stroke. Obviously an entirely 2 cycle format is within the cards, since we can inject both fuel and oxidiser and spark ignite, though this 2 cycle format could run itself somewhat dirty as compared to the 4 cycle format.
I'd think the overall energy conversion per kg of fuel and oxidiser is thereby another win-win for powering this LM-1 metro bus. Somewhere I've read that a good ratio of H2O2 oxidiser is 7.5:1, though obviously a richer blend is entirely capable of being accommodated.
True, this is certainly no high-tech fuel-cell solution, though it's certainly doable within existing technology, as well as for being downright clean burning (Green Peace should be damn proud of this one). On top of all this relatively low-tech solution, there is the benefit that this sort of machinery could be affordably serviced while on the moon, having it's fuel and oxidiser shipped and delivered robotically from Earth at perhaps as little as $10/kg if that were to utilize those nifty Chinese delivery rockets, at most $100/kg using the Russian alternatives or even opting for tens of thousands of bucks per kg using American alternatives, after all, there's no radiation shielding requirement nor is speed all that important. Just enough energy to park the delivery at the LSE-CM/ISS in order to off-load and/or transport the entire payload safely down to the surface via tether.
The other aspect of this modified IC diesel engine is it's energy density per ccm of overall machinery volume should become just the ticket, as I'm thinking, if we're moving 16 lunar tonnes worth of LM-1 about, this is going to take all of 225 kw if to be making good speed of advancement while sustaining the crew with sufficient amounts of cold beer and hot pizza and, you obviously are not going to be accomplishing that task with any reasonable array of those PC panels.
Another page I've recently updated that includes matters pertaining to the lunar metro bus (LM-1) is worth a glance, though I'll likely condense both of these pages into a book chapter that's hopefully better composed and offers meaningful calculations to boot.
All this is not to say that I've been sufficiently correct in my math or terminology to the degree of all those NASA infomercials, as I can't even manage to locate my fair share of those WMD. Thus, as imperfect as I am, there's certainly room for your input and, I'll post full credits upon whomever contributes, just like I'll gather up spent flak and return it with love if that's my only alternative.
Speaking of my not being perfect; these a are a few other pages chuck full of my dyslexic way of looking at things. Too bad all the folks telling me how much of a village idiot I am, while how bloody smart they are, of these nice folks being so bent upon their version of self destructing humanity, is that they can't even manage to decipher my apparently encrypted context (maybe they're not actually as smart as we've been informed).