CEV Revolutionary Gimballed Thrusters

simonbp writes "A Tennessee Tech Professor has proposed an innovative gimbal mount for 'inclusion to the design of [NASA's] CEV (Crew Exploration Vehicle), revolutionizing the vehicle's RCS (Reaction Control System) and solar panel orientation capabilities.' This will allow for nimble maneuvering and for the solar cells to maximize power production."

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Link to actual animation

[Animats]

If you don't want to plow through all the blogodreck and registration, here's the animation of the Canfield joint (quicktime).

As a rocket engine gimbal, this doesn't look promising. It's a rather bulky mechanism; the linkage is much larger than the engine bell. It requires fifteen bearings, not including the three motors. The standard solution, a gimbal ring arrangement, only requires four. The bearings also have to handle off-center loads, never a good thing. Bearings in space are headaches; lubrication is tough and temperature changes can jam them.

The motors are in a weak position from a leverage standpoint; the engine thrust is applied directly to the motor shafts, so they (and their gear trains) must be strong enough to overpower the thruster. In a gimbal ring arrangement, the bearings are usually placed so that the center of thrust is at the center of the gimbal, so that the bearings, not the actuators, take almost all the thrust. Very large engines, like the Space Shuttle and Saturn V main engines, have been successfully gimballed that way.

The three motors don't seem to add redundancy; it looks like they all have to be working.

For comparison, here's a simple gimbal from Amadillo Aerospace, Carmack's rocket program.

In reality, having many fixed reaction thrusters is probably more reliable than have a few steerable ones. Fewer moving parts.