Hi Peter,DB2OS If I well remember in addition with the Magnetorquing ,AO40 was equipped with a 3 axis X-Y-Z stabilization wheel/EPU acting as gyroscopes that never where used except one time I remember to have seen on the P3T TLM the wheels were tested rotating for a short time at a very low numbar of turns ....... or I am wrong ?
Why the 3 axis stabilization wheel/EPU whre never used on AO40 ? Thanks for your answere. 73" de i8CVS Domenico ----- Original Message ----- From: "Peter Guelzow" <peter.guel...@kourou.de> To: <amsat-bb@amsat.org> Sent: Sunday, September 22, 2013 11:21 PM Subject: [amsat-bb] Re: Kick motors on Oscars: How does attitude controlwork? > Hi Burns, > > yes - all Phase 3 satellites use Magnetorquers to control attitude > during perigee. They were pulsed by the IHU on-board computer which was > running a model of the physics and orbital dynamics to trigger the > correct coils at the right moment. This Timing was synchronized with > the Sun sensor... indeed P3 spacecrafts are Spin stabilized... > There was no feedback. Command stations did some calculations based on > Earth and Sun sensor data, but once calibrated the system worked quite > smoothly and predictable... > For the motor burns, the attitude was indeed determined by the Sun and > Earth sensors and several times corrected until the perfect attitude was > achieved.. this took a few days. > Basically a very simple system was simple physics involved... > > 73s Peter > > > On 22.09.2013 22:19, Burns Fisher wrote: > > There has been a lot of discussion about AO-10, 13, and 40 (and maybe > > others) with various kinds of apogee kick motors (and inclination > > changers etc). Rather than fanning any flames, 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? I would not think that electromagnets operating against > > the earth's magnetic field would have enough power with > > such a large motor. > > Obviously it depends on the balance of the satellite relative to the > > position of the kick motor, but still...was the balance really good > > enough to allow magnetic attitude control? > > Was it active (i.e. with feedback)? Does that imply a rate gyro? > > (No MEMS then, I suppose). > > > > Thanks in advance for the technical history lesson... > > > > 73, > > > > Burns W2BFJ _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
