Lunar Elevator System

I can't dispute your logic. I got the number of 300,000 km by
calling the local observatory and after a minute or so they gave me
that number. Perhaps the astronomer didn't understand my question,
thus giving me the wrong answer.

That said, a 90,000 km tower is a monumental engineering project
compared to a 30 km rotating system, with a 190 km tether. I guess
the trade-off would be the frequency of uplifts.

> Why 300,000 km ? Isn't the correct number 90,447 km ?
>
> Luna's mass is M=7.349E22 kg
> The gravitational constant is G=6.672E-11 N m^2 / kg^2
> The magnitude of the velocity vector in a circular orbit is v_circ
= sqrt
> ( mu / r ),
> where mu=G*M and r is the radius from the center of mass.
>
> So, for instance, the magnitude of the velocity vector of a
circular orbit
> at the Moon's surface is sqrt(mu/1.74E6) = 1679 m/s, where 1.74E6
is the
> radius of the moon in meters.
>
> The distance traveled in one orbit is 2*pi()*r, and the orbital
period is
> 2*pi()*r / v_circ.
>
> It takes the moon 28 and a quarter days to turn about its axis.
The
> value of r that equates the orbital period to 28.25 days is 90447
km, or
> 54268 miles.
>
> Is a tether 90447 km in length feasible?
>
> Ron
> ******
>
> "victoriatangoman"
> 04/03/02 02:46 AM
>
> > Ian Woollard wrote,
> >
> > "A fiber with a tensile of 73 Gpa exists; the required strength
> > is 72.5 Gpa. However, a) we need a safety factor b) we need to
> > be able to splice the fibers together, and in practice that
> > loses 15-30% of the strength."
> >
> > What is the required strength for a space elevator from the
Lunar
> surface
> > to lunar orbit?
> > Do currently-existing materials suffice to build such a lunar
> elevator?
> > Would a lunar elevator be a simpler technological solution to
the
> problem
> > of moving large amounts of material off the moon than the
O'Neill-
> heritage
> > mass driver/mass catcher system?
>
> ...
> A true lunar elevator would have to extend to greater than
> 300,000 km from the lunar surface to have the center of mass in a
> lunar synchronus orbit. Such a long fixed length is not
technically
> feasable because the distortions that would be caused by the
earth's