Category Archives: Space Tethers

GEO Orbital Debris Mitigation Paper Excerpts

Back in 2006, I helped a high-school student (Daniel Rodrigues) who was interested in momentum-exchange tethers to write a paper for a high-school class about a concept for a tether that would remove spent geosynchronous satellites from their orbits quickly, … Continue reading

Posted in Orbital Debris Remediation/Mitigation, Orbital Dynamics, Space Tethers | Leave a comment

Random Thoughts: µ-xGRF

I’ve previously blogged a few times about Kirk Sorensen’s xGRF (variable Gravity Research Facility) concept as a way to answer the critical questions of how humans respond to hypogravity. Kirk’s concept involved a lab spacecraft and counterweight connected by a … Continue reading

Posted in Random Thoughts, Space Tethers, Variable Gravity | 7 Comments

Random Thought: Dragon V2 as an xGRF Platform?

Review: How Much Gravity Do We Need, and Why Do We Care? One of my hobby horses that I’ve blogged about a few times is the question of how much gravity do humans need to be healthy? As I’ve pointed … Continue reading

Posted in Commercial Crew, Commercial Space, NASA, Space Development, Space Settlement, Space Tethers, SpaceX, Variable Gravity | 35 Comments

Someone is Wrong on the Internet!

And ironically, it’s XKCD What-if that is wrong. Well, not wrong by commission, but wrong by omission. First off, I’m a huge fan of both XKCD (well the 98% of their comic strips that are SFJ) and XKCD-What If. If … Continue reading

Posted in Humor, Propellant Depots, Space Tethers, Space Transportation | 5 Comments

Steve Canfield and his marvellous mechanical joint

In previous posts I’ve mentioned that when I first got to NASA I worked in the Propulsion Research Center, which was a fun place to work because you got to think about and try just about anything you wanted to … Continue reading

Posted in Space Tethers | 17 Comments

The Meaning of “Characteristic Velocity” for Tethers

On my earlier post where I first showed the Moravec mass ratio, I introduced the concept of the “characteristic velocity” of a material, without making any attempt to explain what, if anything, this might mean. When I first read about … Continue reading

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Recursive Algorithm for Moravec’s Mass Ratio

Computing the mass ratio for a tapered tether (tether mass/tip mass) was first done (to the best of my knowledge) by Hans Moravec in an appendix to his unpublished 1978 paper, “Non-Synchronous Orbital Skyhooks for the Moon and Mars with … Continue reading

Posted in Space Tethers, Space Transportation, Technology | 9 Comments

Momentum Exchange Tethers — Early History

The history of momentum-exchange tethers goes back many, many years but is bound by a common thread that, until recently, limited the realization of this technology. That common thread is the need for high specific tensile strength. The first idea … Continue reading

Posted in Space Tethers, Space Transportation, Technology | 5 Comments

A Tether Technology Anniversary

Rotating momentum-exchange tethers are a very exciting technology, but one of my first thoughts after being exposed to the technology was the tricky rendezvous. The space industry has spent all kinds of money and time on satellite rendezvous, and these … Continue reading

Posted in Space Tethers, Space Transportation, Technology | 8 Comments

MXER Tether Intro #1: Simple Untapered Tethers

So I’ve started out telling you that momentum-exchange tethers are great. Why? you might ask. Well, because a spinning momentum-exchange tether is capable of transferring a fair fraction of the orbital energy and angular momentum in its orbit to a … Continue reading

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