I was thinking of additional braking methods for landing on the moon.

[snikt]
> Could we take a lava tube, surround the interior with an electromagnetic
> coil, and use that for the braking action? I was also thing we could fill
> the tube with a gas and use the gas for atmospheric breaking requiring
only
> a very small atmosphere. (We have to store our mined O2 somewhere, using
it
> for a braking mechanism for craft seems reasonable.)
>

Why use a lava tube for electromagnetic braking? You can just use a mass
driver (perhaps with special adaptations) operating in "reverse mode": it
would convert the kinetic energy of the ship into electricity instead of
doing the inverse (and regular) operation. It could be located in the
surface as any conventional mass driver, and used to shot things to space
when there is no ship landing. Of course, the operation of sliding a ship
into a mass driver track at kilometers per second is risky at best - but
that would also be the case with the lava tube. One imagines that such an "inverse mass-driver" would have a "bugle flare"at the entrance. If the decelerating coils were using a "pull-only" method, then there would be a strong centering force. Damping out oscillations might be tricky, though.

Another consideration for using the lava tubes is that if the craft is
oscillating, then the force of the oscillation could in part be absorbed by
the lava tube wall, whereas it seems to me a free standing mass driver would
require a great deal more structure to withstand the oscillations.

I don't understand this. Lava tubes turn corners, and so would not seem
useful.
Jay S. Huebner at jhuebn@...

Really? Never mind the tubes then, and chalk it up to my ignorance of lunar
(or any) geology.

I didn't think any lunar lava tubes had actually been positively
identified as yet. Am I mistaken? If so, where have they been seen?

We actually know next to nothing about lunar lava tubes, they have not
been directly observed, although there are some candidate targets.