# BBC Documentary on Carbon Nanotubes and the Space Elevator

The BBC Documentary series, “Visions of the Future” recently aired an episode talking about Carbon Nanotubes and the Space Elevator.

Courtesy of the magic of YouTube, this video is now online.  You can tell that this video is slightly dated as it discusses the Space Elevator Game prizes of “half a million dollars” (it’s double that now), but it was made just before the last competition; the teams from DeltaX and LaserMotive make a cameo appearance.

## 5 thoughts on “BBC Documentary on Carbon Nanotubes and the Space Elevator”

1. Noel Hughes

All discussions of a space elevator ignore the basic laws of physics. Conservation of energy implies that mass moved from the Earth surface to any height must acquire potential energy equal to mgh, where m = mass, g = the acceleration due to gravity and h = altitude. If at the same time the mass is accelerated (a geosynchronous body, while it looks to be motionless, is actually traveling at roughtly 3.1 km/sec) it must also acquire kinetic energy equal to .5*mv^2, where v is the velocity imparted. Assuming a two week trip up, a 10000 kg body would require an average of about 40 megawatts of power which is, very roughly, the average generating capacity of a typical power plant in the United States.
A claim of several elevator proponents is that once a body has reached the top of the elevator, getting to other planets requires only releasing from the elevator system. However, to leave the vicinity of the Earth, escape velocity must be achieved, which is approximately 11 km/sec which means that only about 8% of the kinetic energy required for Earth escape has bee imparted to a body in geosynchronous orbit.
There are many other issues that I have yet to see addressed.

2. Libor Micek

Just today I have come across your (not new at all) objection answered. Already in the discussion of Artusjan’s original concept in the former Soviet Union in the sixties the question was asked. Put simply, Earth’s rotation is imparting all the energy (you have calculated at 40MW). By each sling shot off of space elevator the Earth’s rotation is slowed down a tiny bit. The 6378 km radius of Earth is serves as the sling’s arm.