Friday, October 30, 2015

Hope to resume space blogs soon.

I'm not dead. I've been up to my ears in alligators lately -- with paying projects (thank God!).

Hope to resume blogging soon. Some things I want to do:

Tethers and elevators

I'm eager to adapt Chris Wolfe's spreadsheet and examine a variety of tethers and elevators.

A few scenarios I want to look at:

There's a large population of dead sats in a graveyard orbit just above geosynch. These could act as a momentum bank for a vertical tether above geosynch.
I also want to look at a low earth orbit rotovator. It will be tricky adding tidal stress to the rotovator's stress from centrifugal force, but I think I can tweak Wolfe's spreadsheet to do the job.

Lunar elevator going from Mösting Crater through a balance point at EML1
Lunar vertical tether from an anchor mass at 30,000 km altitude

Phobos anchored vertical tether.
Deimos anchored vertical tether.

Clarke style elevators from Ceres. Using Chris' spreadsheet I will be able to look at elevators of various lengths. Down the road a Ceres beanstalk might even throw stuff to trans-earth orbits.

I want to examine Clarke style elevators from Vesta.

Boundaries of our bodies/extended phenotype

Awhile ago I reviewed a James Patrick Kelly story where a large fraction of the populace dwells in cyber-space. A trend in science fiction was been to explore artificial digital worlds rather than outer space. I opined that as telepresence improves, robotic avatars will become common place. The line between digital existence and meat space will blur.

Well, recently Kelly wrote an essay on prosthetics. It was a rich source of information, full of great web links (the norm for Kelly's Asimov articles). I want to talk about Kelly's essay. Also prosthetics and boundaries of our body. Many already regard dentures or lens implants as part of ourselves. I believe the same will become true of robotic arms and other body parts. And if we come to regard a prosthetic arm as an extension of our body, what is the difference between an arm attached to our shoulder or a robotic tele-arm thousands of kilometers away?

Robert Reed has written science fiction stories of god like beings whose minds and bodies extend throughout multiple star systems. That's not going to happen any time soon, but I do hope to see our "bodies" extend to the moon and near earth asteroids. In my lifetime.

I believe it will be advances in robotics that enable us to move beyond Cradle Earth.


LocalFluff said...

It seems to me that the line between meat and digits is blurred already by nature. What is microbiology if not a computing machine? Copying, storing, adding, dividing, selecting, transforming, checking, executing, networking, terminating with extreme precision. We don't understand what we ourselves are.

I'm listening this Halloween to an audio book version of Paradise Lost by John Milton from the mid-17th century. The language is like Shakespeare on crack, cubed. If I say I understand half of it, I cannot be more than half a liar. It is kind of the Saga of Christianity. There are angels and God and creation of worlds and Hell and of a creature, man, which possesses the mysterious power of free will. "They pass the Planets seven, and pass the fixt, And that Crystalline Sphear". In spite of tremendous progress, I'm not sure we're much the wiser at the core of the issue today. I also recommend Hieronymous Bosch's paintings of heavens, worlds, men and flying angels if you still want some Halloween mood.

Peter McArthur said...

I use an iterative approach similar to Chris Wolfe's to calculate the changing forces while extending a tether. The tether is shaped somewhat like a very stretched diamond. Reels in the middle will extend the tether outward. The tether can be extended more rapidly by having more reels. The rotational speed slows as extension occurs due to conservation or angular momentum. If extended enough, the rotation can be nullified relative to the body the tether is orbiting. This allows for simplified docking to the ends of the tether and maintenance. The speed at which a spacecraft is released from the tether can also be adjusted by changing the rotational speed.

Cererean said...

Re. a lunar tether, the best material to use, if possible, would be basalt fibre, because it's something Luna has a lot of (as does Vesta). There might be the potential to launch a low mass tether from Terra and then use it to bootstrap a full elevator, which would of course make transporting Lunar fuel to L1 much cheaper, as well as significantly reducing the costs of resupplying the base.

Given that it would be equatorial though, and the first colonies would probably be polar, it would probably be advisable to build a trans-Lunar railroad to go with it... which itself would influence settlement patterns. Could a ground-based straddle beam monorail work, using sintered regolith to construct the beam? Hmmm. On the one hand there wouldn't be air resistance, but on the other, conventional rubber wheels would not be suitable, and other aspects come into play that would limit it's top speed. It's a distance of roughly 2700 km, so at 150 km/hr it would take 18 hours to go from Shackleton City to Stalktown...

Cererean said...

Actually, come to think of it, autonomous trucks would probably be a good way to get started. At 15 km/hr, probably powered by fuel cells, they'd make the trip in 8 days. That's not unreasonable, since there wouldn't be anyone onboard.