My understanding of Gravity Gradient is that a small spacecraft with a long boom and tip mass will align in an UP/Down attitude. But it is bi-stable so either end can be up and be stable.
What about a small satellite with TWO booms (dipole wires) in opposite directions with small tip masses, it will be just as stable as before but I may even get by with half the mass on each end. More or less. When I mean “stable” I mean roughly up down, anything within +/- 40 degrees is still a vertical HF antenna…. Besides faraday rotation will rotate the received pattern every whichaway anyway.
I disagree with an opinion I have received that says “gravity gradient” wont work with dual opposite end tip masses. Says one has to be bigger and it cannot be in the middle. I disagree.
Any professionals have an opinion?
Bob, Wb4aPR
From: http://www.jhuapl.edu/techdigest/views/pdfs/V03_N5_1964/V3_N5_1964_Fischell....
A quote:"The mass on the end of the dumbbell closest to the center of the earth is attracted to it by a force that we denote F. The force on the other mass we will denote f. Even if these masses are equal it is easy to see that force F will be larger than f. "
The article goes on to say that the torque produced will keep the closer end pointed towards Earth. This paper actually starts with the assumption that the two end masses are the same, then goes on to say that it will still work even if the masses are different.
So, I'm siding with Bob.
Full disclosure: I'm not a professional, but I do teach physics.
Steve AI9IN
On 2016-08-24 18:11, Robert Bruninga wrote:
My understanding of Gravity Gradient is that a small spacecraft with a long boom and tip mass will align in an UP/Down attitude. But it is bi-stable so either end can be up and be stable.
What about a small satellite with TWO booms (dipole wires) in opposite directions with small tip masses, it will be just as stable as before but I may even get by with half the mass on each end. More or less. When I mean "stable" I mean roughly up down, anything within +/- 40 degrees is still a vertical HF antenna.... Besides faraday rotation will rotate the received pattern every whichaway anyway.
I disagree with an opinion I have received that says "gravity gradient" wont work with dual opposite end tip masses. Says one has to be bigger and it cannot be in the middle. I disagree.
Any professionals have an opinion?
Bob, Wb4aPR _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
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