[amsat-bb] Re: AMSAT history

Bob McGwier n4hy at idaccr.org
Mon Oct 30 08:32:08 PST 2006

I have not uploaded my AO-40 directory yet.  It is insufficiently 
complete.  I have pictures I think almost no one else has seen and I 
want to flesh these out a bit before I upload them.

In the Phase 3A, AO-10, AO-13 directories you will see curved tubes in 
the arms of the spacecraft near the tips.  These tubes have their ends 
welded closed.   They have glycerin in them.

As the spacecraft undergoes maneuvers from the motor firings to 
magnetorque attitude control adjustments,  the spinning spacecraft tends 
to wobble.  When the launcher pops us off the vehicle,  it can easily 
impart a wobble.  This wobble is called nutation.  By placing the curved 
tubes in an arc parallel with the principal spin axis for the 
spacecraft,  when there is this wobble,  it causes the glycerin to move 
up and down in the tube.  This movement of this viscuous fluid in the 
tube converts the angular momentum of the wobble into heat and "dampens" 
the wobble out.  This wobble is called nutation,  and these tubes are 
called nutation dampers.   The shape, placement, etc. are optimized to 
maximize coupling with the spinning frame and to get enough damping so 
that the wobbles are gone in a few minutes.


Jim Jerzycke wrote:
> Yes, nostalgis seems to be part of getting older.
> I have one question concerning the AO-40 pictures. I
> see a curved pipe with "crimped" ends in many of the
> pictures. What is/was it for?
> 73, Jim  KQ6EA
> --- Bob McGwier <n4hy at idaccr.org> wrote:

Robert W. McGwier, Ph.D.
Center for Communications Research
805 Bunn Drive
Princeton, NJ 08540
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