I have a short news article in the April issue of Physics World about Obayashi Corportions's announcement of plans to build a space elevator by 2050:
"Japanese construction firm unveils ambitious space-elevator vision," Physics World, April 2012, p. 8.
Their design is no surprise to anyone who knows the subject -- it's the basic "Brad Edwards" plan outlined in his book with Eric Westling (discussed in my earlier feature on space elevators in Physics World) -- and Obayashi's plans are largely aspirational. But they are a big, established company with huge financial resources.
In other space elevator news, Michael Laine was recently on The Space Show talking about his resurrection of Liftport and their feasibility studies of a lunar space elevator. That podcast is here.
I like the inverted pyramid model of a space elevator. A single carbon nanotube does not seem to be the most elegant solution. By tethering counter rotating rings the centrifugal forces allows for mass to be distributed in orbit. The rotation speed of the rings helping to provide active tension control of the system. The rings form an inverted pyramid that makes the distance to Earth for a single nano-tube strand effectively shorter. The majority of the weight is in the upper atmosphere. Active solar sails providing both energy for counter rotation of the masses, and the side forces needed to counter the gravitational pull of the Moon.
Basically, a large mass in the upper atmosphere is floating in relation to a larger stationed orbiting mass. Mass being rotated are on very long cables. When rotated the are closer to Earth, and when slowed, farther from Earth. The rotation in a vacuum is very low friction, so if there is a motor or energy failure it just keeps doing what was doing before; stable.
This floating mass in the upper atmosphere is only 50 miles or less from Earth, and so one or more space elevator individual cables can potentially connect to that much shorter distance.
As loads are heavier, the counter rotating rings slow down to compensate for the load. And speed up for light loads. To keep the strain on the cable within tolerances.
This requires much more nanotube cable, but I believe it makes the system more feasible.
Just a thought,
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