Re: Burt Rutans plans for a manned mission to Mars


royls@xxxxxxxxx wrote:
On Fri, 12 May 2006 03:34:02 GMT, Fred J. McCall
<fmccall@xxxxxxxxxxxxx> wrote:

"steve" <stephen.colbourne@xxxxxxxxxxxxxxx> wrote:

:There is one potentially cheap way of getting into orbit that is just
:about possible to achieve with current materials and that is the
:rotating space elevator. This requires a long cable approx 1000km
:length attached to either a large mass at one end in low Earth orbit or
:twice the length without the mass (double ended).
:This cable rotates at such a speed that even though at the Cg is at
:orbital speed the lower end is travelling at a much slower speed
:allowing sub-orbital craft and even potentially aircraft to transfer
:mass which will then be transported upto orbital speed by the cable.
:Powering the whole cable, could be achieved by electro means or plasma
:drives.
:
:This will be built within the next decade I believe.

Yeah? How do you think they'll get it up?

It would most likely be constructed in space, from lunar or asteroidal
materials -- so a decade does seem rather optimistic.

However, sending it up by a bootstrap process is not as far-fetched as
you might imagine. The rotating elevator has one great, overwhelming
advantage over rockets: positive feedback. You can start with a very
small modular system that can't lift very much and requires the
payload to be boosted to near orbital speed before it hooks it; but if
the payload is more elevator modules, the system quickly becomes more
powerful, able to lift more payload and/or from a lower boost speed.

Because even the very small initial system's lifting capacity is
enormously larger than any contemplated rocket-based system -- it can
lift a payload several times a _day_ -- if it is initially devoted
entirely to strengthening itself, in a very short time it would be
able to lift a 10-ton payload from the back of a subsonic aircraft. A
short time after that, it would be able to lift a standard 40-foot
shipping container full of stuff right off the ground. More arms can
then be added to make a "pinwheel," tripling or quadrupling its
lifting capacity, to thousands of tons per day.

You're confusing an elevator with a rotovator.

An interesting point about rotovators is that they're not good for
reaching their orbit. They're very good at reaching higher orbits. In
fact, with a rotovator operating, Low Earth Orbit would be pretty much
abandoned.

.

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