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Hank talks about space elevators, and why we shouldn't expect to see one any time soon.

References for this episode can be found in the Google document here: http://dft.ba/-33cf
[Intro Music]

You know I'm all about space exploration. I talked a lot about the challenges that we as a species face in doing it whether we're sending people to mars or just getting clean laundry to the International Space Station.

So a lot of you have asked, "Why not get together as humanity and build a space elevator?" That's an anchored cable system that reaches thousands of miles into space. Popular idea because on paper the benefits are obvious.

Launching a space craft currently costs about \$22,000 per kilogram. A space elevator could potentially lower that number to less than \$1,000 per kilogram.

And just about every space elevator proposal follows the same basic blueprint: you have a base station that serves as your anchor point, a cable, a climbing mechanism, and a counterweight at the end of the cable.

The inertia of the counterweight caused by the rotation of the earth, not centrifugal force, would keep the cable taut. And once the climbing mechanism got above geostationary orbit, it would be pulled toward the counterweight.

And look, I love the idea, but I'm just going to say it. We're going to be sending humans to mars long before we have a space elevator.

First, in order to remain stationary relative to the rotating earth, the end of the elevator needs to reach at least 35,000 kilometers (21,750 miles) out into space. Ideally, it'd be more like 100,000 kilometers (62,000 miles), which is like a quarter of the distance to the moon. Second, the counterweight needs to be really heavy in order to remain stable.

Some have suggested harnessing an asteroid to act as the counterweight. Nah, I honestly can't think of a better idea given that the rocket power necessary to bring a man-made that far out into space does not exist.

Third, and most importantly, we're going to need a cable that's insanely strong, light, and flexible, which pretty much needs we're going to need carbon nanotubes.

Everyone loves nanotubes which have the potential to be one hundred times stronger than steel and as flexible as plastic. They're made of molecular strands of carbon molecules arranged into hexagons and they consist of more empty space than mass.

Scientists have already constructed nanotube strands with a length and diameter ratio of 132,000,000x1 which means they are very long relative to their girth, but really long is also relative. The longest fiber yet manufactured is about 30 centimeters (11.8 inches). So yeah, we've got a ways to go before we can build a 35,000 km long space elevator cable.

Despite all these hefty road blocks, people are trying to build a space elevator or at least they're thinking about trying. Google is rumored to be investigating space elevators at its ultra-secretive Google x-lab.

And in early 2012, the Japanese construction firm Obayashi Corporation announced that it plans to build an elevator capable of transporting space cationers to 36,000 km (22,400 mi) above the earth with a counterweight at 100,000 km. The company says that it'll be operational by 2050 which makes this a plan in the same way that my plan to be on Mars by 2030 is a plan.

Thanks for watching and getting smarter with us here on Sci-Show. If you wanna subscribe you can go to youtube.com/scishow. If you have questions or comments or ideas for us please leave those down along in the comments or you can get in touch with us on Facebook or Twitter. Goodbye.

[Outro Music]