Slashdot Mirror
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."
If you're like me and are wondering what the heck a gimbal is, wikipedia has an article. Not being an engineer, I still only have but the fuzziest idea of what's going on here; blame a liberal arts background.
Sorry! Slashcode diddled the spaces in the URL.
Here's the working link.
And I'm pretty sure the orginal CSM did not have a gimbled engine. The Saturn did, but with no where near the same range of motion as being discussed here.
Any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so.
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.
Gimbals have been around since...well, if you believe Needham, at least the 10th Century AD in China. A gimbal is just a way of mounting something so it can rotate relative to something else while still being attached to it and moving linearly with it, and the main application has been on boats where equipment like lamps and compasses is suspended in mounts so it can swing. http://www.sailgb.com/p/captains_cabin_lamp/ is a picture of a small gimballed lamp. So long as the centre of gravity of the equipment is below the plane of the mount, the boat can rock underneath and the lamp, compass, cooker or whatever will stay more or less upright.
By using an outer pair of pivots to hold a ring which then has another pair of pivots at 90 degress to which the equipment is attached, you get two axis gimbals which allow for rocking and for pitch, which is important on small boats. It isn't practical to suspend (say) a marine stove from a chain because it would swing all over the place, whereas suspending it from pivots near the top means that the base can swing a bit while the pans stay more or less in the same place.
So all the stuff in Wikipedia about Euler angles is all very well, but a gimbal is just a way of allowing one thing to be attached to another while being able to rotate in one, two or three dimensions relative to it. There are various designs and obviously the Canfield one is a clever one, but there is nothing mysterious about gimbals themselves.
Pining for the fjords
How many thimbles full of Kimball's nimble-gymbal symbol would it take to assemble a cymbal-playing gymbal in Fimbul? Simple.