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 hypogravity1. Kirk’s concept involved a lab spacecraft and counterweight connected by a reelable tether. You’d start in a near-microgravity state with the system oriented radially in a gravity gradient stabilized configuration. Then by reeling the tether in, you would change the rotational inertia of the system, causing it to rotate to conserve angular momentum. Et voila! Instant artificial gravity at a rate that’s driven by how far you reel the tether in.
xGRF Spin-up Recap
The challenge has been that even though this is a relatively cheap way of getting to a variable gravity research facility, it’s still an expensive prospect overall. And the reelable tether concept has some non-trivial technical risk, both in the reeling mechanism, the tether itself, and the dynamics of reeling it in and out and how that needs to be done to do this maneuver without exciting unwanted vibrations, precession etc.
So what if we solved both problems by starting with a µxGRF–a cubesat-scale xGRF tether dynamics demonstration? Cubesats are relatively cheap2, so they might enable a ...