(Henry J. Cobb) wrote in message . com...
Would a Space Elevator
http://flightprojects.msfc.nasa.gov/fd02_elev.html be a greater risk
to human life per mission than the current space shuttle?

While the risk of failure on any one trip would be less, when the rope
breaks it'll wrap around the Earth and strike several cities rather
than burning up a half dozen astronauts.

-HJC

Uh, no. Liftport has a page of 'Frequent Misconceptions' @

http://www.liftport.com/pages/index....ge&pageID=1234

Statement: If it breaks, it will create a massive catastrophe all
around the Earth.

Q: How easy would it be to break?

A: Very difficult. The planned position of the elevator avoids
hurricanes, lightning and other extreme weather. The ribbon is
engineered to be twice as strong as it needs to be to support itself
and any planned cargo attached to it.


Statement: It will wrap itself all the way around the Earth,
destroying everything near the Equator.

A: The majority, the long end out in space, gains enough speed that it
burns up in the atmosphere, with the lower portion falling into the
sea. Only a thousand kilometers or so will reach the surface,
fluttering down with the force of a falling sheet of paper.


Q: For the portion that doesn't burn up in a fall- what effect will it
have on the environment?

A: New York City tickertape parades have made bigger messes.
Comparatively it will put much less dust, dirt, debris and chemicals
into the environment than wildfires of the American west, any one of
the large expendable rockets, or a month of natural meteors hitting
Earth. The ribbon is light (7.5 kilograms per kilometer) so, any
pieces that fall to earth will slow down, in the air, to about the
same terminal velocity as that of an open newspaper page falling. It
will not have enough momentum to cause mechanical damage when it comes
down. We have considered other health risks such as inhalation of very
small fragments and believe this will not be a problem but we are
conducting studies to make sure this isn't a problem. Since we are
aware of the possible problems now we can design the elevator to avoid
these problems.


Q: How large a wave/disturbance would it generate?

A: The wave/disturbance would be nonexistent. As above, there just
isn't enough mass, even in later, larger, ribbons, to generate such
energy dispersion. There might be a small amount of light as a line in
the sky as the ribbon burns up but after that it will be a few pieces
of black film fluttering to Earth. Because of the size, distribution
and winds, it is conceivable that only a few people would even see the
event in any way and just as few would find actual pieces of the
ribbon.


Q: What would happen to the surviving portion?

A: The ribbon that fell to Earth could be recovered for study but
because of the amount and distribution it would be difficult to find
many pieces. The pieces that do land would eventually degrade but not
for a very long time. Keep in mind that this is mostly a stable form
of carbon; it doesn't do anything. The debris would resemble long hair
and would probably be broken up in interactions with animals, plants,
wind, fish and waves. In fiber form it would be much too large to
inhale and would probably work its way through a digestive system
unaffected. The only debris we have any concern about is if it were
reduced to nanotube size. This we don't understand yet so we will
study this to see if there is a problem and then probably also design
the ribbon to remain in larger pieces if it re-enters.

The ribbon above the break, including the counterweight, would move
slowly to a higher orbit, from which it may well be possible to
recover it, splice a new section to the bottom, and fly it back down
to the anchor.


Q: What would happen to anything climbing the ribbon at the time it
broke?

A: The short answer is that some payloads will fall (below the break
and below 24,000 km altitude), some will enter low orbit (below the
break and between 24,000 km and GEO) and some will be tossed to high
Earth orbit (above GEO) depending on where the payloads are and where
the break is. However, what happens also depends on the reaction of
the payload. In other words, what happens depends on lots of factors.
Escape pods or re-entry vehicles may be required depending on designs.

~er