[amsat-bb] Re: Kick motors on Oscars: How does attitude control work?
samudra.haque at gmail.com
Sun Sep 22 18:04:33 PDT 2013
Which cubesat project ?
On Sun, Sep 22, 2013 at 5:49 PM, Daniel Schultz <n8fgv at usa.net> wrote:
> >I just want to ask a question: If you have a motor of a few hundred
> >Newtons, how to you keep the attitude stable during the burn? For that
> >matter, how do you get the attitude correct for the start of the burn?
> Simple question, simple answer: You use the magnetotorquers to point the
> axis in the right direction, check and check again to make sure you got
> right, then use the magnetotorquers again to spin up the satellite at a
> angular rate (maybe 20 RPM). The angular momentum of the spinning satellite
> keeps it stable while the motor is firing. The motor thrust must of course
> well aligned with the spin axis, but if the thrust vector is not perfect,
> spinning satellite tends to even out the small deviation.
> One of the recent Cubesats carried high power model rocket engines to try
> experimental orbit adjustment. They forgot to spin the satellite and the
> Cubesat tumbled wildly as a result of the motor burn. Some of these groups
> really lacking in basic physics knowledge (and we are not talking about wet
> behind the ears students in that case.)
> Dan Schultz N8FGV
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