Steven Den Beste Strawman

>[mailto:spacesettlers@... On Behalf Of sraj
>
>> In India when building houses you will frequently find a worker
>> throwing bricks to another person at a higher level. When the
>> brick reaches the hands of the worker at the higher level it
>> has almost zero velocity. It should be possible to launch the
>> raw material from the Moon at just the right velocity.
>
>That's pretty much the idea. A payload's journey from the end of the
>mass driver to the L-2 point constitutes a long climb up the gravity
>well of the moon. The payload's velocity declines from a km/sec regime
>to a km/hour one.
>
>And even then, the constant impact of incoming payloads will most
>certainly /not/ require a continuous countering thrust from the RCS, as
>some seem to think. The vector of the impulse will be along one of the
>two stable axes of the L-2 point. The impulses will push the catcher a
>certain distance away from L-2, but will not make it leave. When the
>impulses cease, the catcher will "spring back" to the L-2 point.

The Den Beste article was about the L5 point were the L5 society
wanted to deliver mass driver payloads, NOT about the L-2 point.

The L5 Lagrange point is 60 grade behind Earth orbit around the Sun.
That means about 150 million km orbital distance, from Moon and Earth
away.

To reach this point in a reasonable time frame you would need a lot of
velocity. The brick analogy would fit for a payload which stays in
Moons gravity well, but L5 is way away of the Moon.

If the Moons gravity would reduce the escape velocity to a km an hour,
that would happen near the Moon and the driver payload would need 150
million hours (about 17123 years) to do those 150 million km above but
I dont think L5 could be reached with a simple straight one time mass
driver shot. I guess at least two accelerations and one with direction
change would be needed.

Frank