Digest Number 310

> > Most of the mass drivers that I have read about
use a
> circular track for acceleration. So, instead of a
hole

Which would those be ?<

I can't find it. Where ever I got the idea from it
stuck in my head. Sorry for the misinformation. All
the mass drivers I looked up now were straight tube
linear acceleration types.

>Why is this better than a straight driver ? <

It would require less construction and less room. You
would accelerate around the same circle until you
achieved the desired velocity.

Actually I don't think either is practical to achieve
escape velocity due to atmospheric drag.
Below is a quote from
http://www.permanent.com/massdriv.htm

>Unfortunately, the Mass Driver is feasible to operate
only on the Moon, because it needs vacuum. A Mass
Driver operating on Earth would cause meteoric
friction heat to such hypervelocity, Mach 40 (!)
payloads, at the dense bottom of Earth's atmosphere
(ocean of air) as they left the catapult tunnel.
Secondly, the air would aerodynamically deflect such
objects in unpredictable ways thereby making them miss
the collector up in geostationary orbit. Thirdly, an
operable Mass Driver on Earth would require a long
vacuum tunnel (much longer than on the Moon, since the
escape velocity is higher). Fourth, the air would
create hypersonic sonic boom shockwaves that would be
loud for a long distance. Individual payloads would
have to be massive enough to punch thru the atmosphere
in an acceptable way; such massive payloads demand a
lot of the catapulter as well as the orbital based
catcher/collector.

I still believe that a magnetic accelerator type
catapult could save a lot by launching either a rocket
or a scramjet-rocket.