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Posted

Context: I am trying to educate/inspire two of my grandchildren but first I have to re-educate myself!

A spacecraft arrives at above orbital speed with a nose first attitude and fires a retro-thruster when tangential to a circular orbit. Taking a simplified case, it used instant de-acceleration to orbital speed and therefore entered into a circular orbit. Would the following be true?

As the spacecraft has no rotational forces acting on it, it would staying pointing basically at the same very far point, and to leave the orbit tangentially at another point, it would need to rotate itself to align its main thruster.

If it used thrusters to give it a small rotational speed it could match its orbit and keep one side facing the planet and its main thruster would stay on the tangential line.

So is my simple applied physics correct or do I need a refresher.

PS I am an Engineer so I am trying to apply knowledge learnt in 1972!

If I have broken any forum rules please be kind!

Posted

Yes, you could make it rotate. In fact, it’s hard to not have it rotate, which is why you might put gyroscopes on satellites. A version of these, reaction wheels, are used to re-orient some craft.

Small satellites also get pushed around and rotate from radiation pressure, called the YORP effect

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