The Space Elevator

[Thorgalaeg]

However there is some advantages with He-3, something about not neutronic reactions. I have to read on it a bit more.

BTW Thinking on it a bit more, i think that counterweight should a bit beyond geostationary orbit height, so centrifugal force is a higher than gravity, enough to give tension to the CNT cable.

 

[hobbsyoyo]

There are advantages to He3 fusion, namely easier conversion to electricity and less radioactivity, but ease of fusion is not among them.

 

[CavLancer]

I didnt know fusion reactors desintegrated quickly or at all. In any case i think that we wont know until we can keep them working longer than some seconds.

BTW about your question, you are right to some extent. The counterweight will displace the center of rotation of the Earth a bit towards itself.

But there is gravity in space. astronauts at the ISS are not in a real zero-gravity environment, but in an apparent one caused by centrifugal force and gravity cancelling each other. In fact if you stop the ISS which is orbiting at 30,000 km/h, it will fall to the ground like a stone. Since the counterweight is at a geostationary orbit over a point near the equator and rotating synchronized with Earth, which means at a given angular speed of 360º every 24 hours, it will need to be about 36,000 km high where tangential speed will cause a centrifugal force enough to cancel gravity, lower than that it would fall down and higher it would go up into space.

I appreciate the info, Thorgalaeg.

Here's a documentary about fusion disintegrating the walls of the reactor etc and also strip mining the moon of Helium 3.
https://www.youtube.com/watch?v=H9NO84uvrg8

 

[peter grimes]

The fact that they don't take radiation into consideration makes me suspect. It's definitely a challenge for all spacecraft and for something that traverses the Van Allen Belts regularly (as a space elevator would), it would be a pretty significant challenge.

the paper is a brief synopsis of the book. The book goes into much more details so perhaps it's mentioned there.

That's the premise behind the excellent sci-fi movie Moon where they are mining Helium-3 on the moon (where it is deposited by the solar wind) to power commercial fusion reactors on Earth. In fact, Helium-3 is one of the few things that could be commercial mined in space for a profit with current rocket technology as it is that rare on Earth.

on man I don't think I realize that. That adds an interesting dimention to the movie, considering the economic implications

 

[hobbsyoyo]

Yeah but I was wrong on He3 being easier to fuse. It isnt, but it does offer some big advantages compared to other types of fusion. Oh but yeah it would still be a potentially commercially viable mining product in space.

 

[El_Machinae]

It could be that they just didn't think of it. It was only a few people working on the book, and the wisdom of crowds is a real thing. Looking through google scholar, though, nothing leaps out about radiation and CNT vulnerability.

 

[onejayhawk]

Fusion is a thread of its own. Again, we lack the principal ingredient in the recipe. When that changes, progress could be quick.

Power generation in space would be a growth industry if there were a safe way to get it down. Every transmission method is easy to weaponize.

J

 

[El_Machinae]

It will be a growth industry, yeah. You're familiar with the concept of embodied water? Basically, the idea is that buying water-intensive foods is in many ways identical to just wastefully using water to grow your own food.

The same idea could happen with embodied energy. Transmission aside, and products requiring a LOT of energy to produce could effectively ship that energy to Earth by shipping those products home.

And, keep in mind, it needn't be actual materials, either. Hell, an energy-intensive calculation would count.

 

[onejayhawk]

It will be a growth industry, yeah. You're familiar with the concept of embodied water? Basically, the idea is that buying water-intensive foods is in many ways identical to just wastefully using water to grow your own food.

The same idea could happen with embodied energy. Transmission aside, and products requiring a LOT of energy to produce could effectively ship that energy to Earth by shipping those products home.

And, keep in mind, it needn't be actual materials, either. Hell, an energy-intensive calculation would count.

Except that the two biggest consumers of energy are motor vehicles and refrigeration units.

J

 

[El_Machinae]

Yeah, getting space-borne energy to replace planet-consumed energy is tougher.