XPost: sci.space.policy   
   From: joe@strout.net   
      
   In article <3c6b9c1e.0401231956.4e2d9287@posting.google.com>,   
    raf@tiki-lounge.com (Ross A. Finlayson) wrote:   
      
   > I'm wondering about "lava tubes on the moon".  I guess I was under the   
   > impression that besides Earth only Jupiter's moon Io had active   
   > volcanic activity, and I was thinking Luna was a cold chunk of rock.   
      
   Heck no!  The Moon is littered with lava tubes, and big ones too (up to   
   about a kilometer in diameter).  Not that we've actually observed an   
   intact tube yet -- but we observe many rilles, which are most likely   
   collapsed tubes, and gaps in the rilles are most likely intact tubes.   
      
   > Yet, I read here that Luna has a molten, presumably iron, core, thus   
   > that it would have similar magnetic fields to Earth.   
      
   Er, no, the Moon is cold and dead now, with no appreciable magnetic   
   field.  And I don't think it has much iron, either.  The Moon is formed   
   from the Earth's crust; most of the iron in the Earth was already at the   
   core by that time, and didn't go into the Moon.   
      
   (Earth is an unusual planet in that most of the planet's crust is   
   hanging way up over our heads.  This may be why we have dry land, some   
   theorists say, and may be relevant to the development of civilization...   
   but I digress.)   
      
   > Lava tubes, miles long underground caverns similar to lava tubes on   
   > Earth, where higher temperature magma flowed out and left behind open   
   > space, would probably be among the major geologic reasons for their to   
   > be caverns on the moon with the lack of running water.   
      
   Yes, exactly.  Only they're much bigger on the Moon than they are here.   
      
   > I just had never heard of their existence before yesterday, and don't   
   > know of any on the moon itself.   
      
   Dude, you're missing out.  Everybody should know about these.  Do a   
   Google search for "lunar lava tubes" and read a while.  Or even go to   
   the library or Amazon -- there have been a couple of good books about   
   them.   
      
   > I think there should be shortly ten or fifteen satellites about the   
   > moon, these would be necessary for a variety of surface operations.  I   
   > may be wrong, the moon has no appreciable atmosphere, thus no   
   > ionosphere and only line-of-sight radio communications.  A satellite   
   > array would be critical in providing global (?) coverage of   
   > communications availability to surface operations.   
      
   Right.  A communications array is exactly the sort of infrastructure   
   Uncle Sam should be building.   
      
   > I always why there weren't more air-boosted launches, an aerodynamic   
   > launch plane flies a hundred thousand feet high and the launch vehicle   
   > separates and boosts to orbit from high in the sky.  Maybe that's a   
   > misconception from seeing the space shuttle flown around piggyback,   
   > and about how high is low Earth orbit.   
      
   It's not the height that matters; to get to orbit, you need speed.  It's   
   about Mach 27, IIRC.  That's really amazingly fast.  The extra Mach 0.5   
   you might get from the carrier plane is insignificant.   
      
   The only real savings of launch from altitude is that you can tune your   
   rocket engines for vacuum or near-vacuum, instead of having to have some   
   compromise between efficiency at sea level and efficiency at altitude.   
      
   > I was reading about the Shuttle-C for cargo and saving the liquid fuel   
   > tanks in holding orbits, I think that's a good idea.  What prevents   
   > the addition of new modules to the ISS, Freedom, the International   
   > Space Station, every year?   
      
   I think they are adding modules every year now.   
      
   > What's so great about the ISS's orbit that it is there?   
      
   It's a sucky orbit, but it's there because the Russians demanded it --   
   it makes it easier for them to reach.  Which I suppose is a good thing,   
   since they're the only ones able to service it at the moment.   
      
   > Lunar Prospector was about first US moon mission since Apollo 17, then   
   > there's Clementine.   
      
   Yep, and that's about it.  Pathetic isn't it?  But that should be   
   changing now.   
      
   > I guess what I'm trying to figure out is if a   
   > mailbox full of cement was to be launched into lunar orbit, what would   
   > be its costs?   
      
   Good question.  I don't know the answer.  But I suspect that once Falcon   
   I flies, you could get your mailbox of cement plus the translunar   
   injection booster into its payload, in which case, the launch would cost   
   you $6M.  Plus the cost of the booster and cement, of course.  :)   
      
   > It seems pretty expensive to launch a payload into orbit.  That's a   
   > problem with monopolies, although I guess it's a market economy, there   
   > are presumably some crazy regulatory controls on ballistic rocketry.   
      
   Yes, all of that is involved, however this does seem to be changing,   
   with several new and hungry launch companies getting ready for business   
   (such as SpaceX for example).   
      
   > It's a lot easier to fantasize about thousands of launches per year   
   > than to design/build launching something to the moon.   
      
   Too true!   
      
   ,------------------------------------------------------------------.   
   |    Joseph J. Strout         Check out the Mac Web Directory:     |   
   |    joe@strout.net           http://www.macwebdir.com             |   
   `------------------------------------------------------------------'   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)