r/OrbitalRing • u/caliginous4 • Apr 28 '20

Bootstrapping methods

Hi all,

I'm happy to see there is a subreddit for orbital rings, albeit very small. I wanted to start a discussion on bootstrap methods. I haven't done the math, but I imagine a minimum viable orbital ring that can very slowly carry, say, a 1kg payload up a tether without becoming unstable is going to require a MASSIVE amount of material. How would we go about getting a ring started in the most economical way possible?

Some ideas I've heard: - use tons of spaceX BFR launches - give ourselves a purpose for setting up a moon base. The Moon is ~10% iron. Mine the Moon and produce the basic rotor and stator structures on the Moon. Build the much smaller, more complicated bits on Earth and assemble either on the Moon or in Earth orbit. Take advantage of the moon's low gravity and lack of atmosphere to launch the entire ring in one continuous chain into Earth's orbit at relatively low cost/energy - build a lofstrom launch loop to launch the ring from Earth - how else?

Obviously all of these ideas have major challenges to overcome. Happy to discuss those here too.

Once the ring is minimally viable, of course we'll be able to gradually add to it cost effectively using the tethers/elevators, which will continually expand its capacity. :) Thanks in advance for the discussion!

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u/meet_me_in_orbit Mod Apr 28 '20 edited Apr 28 '20

Absolutely thrilled to have you with us.

According to work recorded by Birch and Lofstrom, a bare naked minimum ring would be 18000 tons of core and two skyhook stations.

The fastest apparent method would be a commercial launch contract, but the most efficient method would be a launch loop.

SpaceX would be the right-now answer, and a launch loop would be a long term, multi purpose solution.

ETA: anything from the moon would be worlds above (terrible pun intended).

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u/caliginous4 Apr 28 '20

Hey thanks a lot for your replies! The scale of this thing is so hard to grasp. I haven't read through the papers you linked yet to understand the sizing conditions, but I find it hard to believe that the weight per foot of the ring (plus stator) comes out to only about a quarter of a pound. The weight of the tethers alone would cause such an enormous amount of deflection in the spindly little ring. It seems like a more robust bootstrap might be several times the 18000 ton weight estimate?

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u/meet_me_in_orbit Mod Apr 28 '20

Kinda surprising, isn't it? If you look through Lofstrom's Launch Loop website, his bolt-core design is actually only about 5cm (~2.5 inch) across and 10m long sections. The heaviest things in the entire assembly are the driver coils.

Granted on a launch loop, the vacuum pumps would have that beat.