[amsat-bb] Re: Kick motors on Oscars: How does attitude control work?

[Samudra Haque]

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
> spin
> axis in the right direction, check and check again to make sure you got
> that
> right, then use the magnetotorquers again to spin up the satellite at a
> high
> 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
> be
> well aligned with the spin axis, but if the thrust vector is not perfect,
> the
> spinning satellite tends to even out the small deviation.
>
> One of the recent Cubesats carried high power model rocket engines to try
> an
> 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
> are
> 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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