Stopping Rocket Spin: A Space Physics Mystery

[sophiecentaur]

When I was at Uni, in the 60s, we had a brief course on 'Space Physics'. It had a hotch potch of topics in it and one of them was about actually launching satellites.
'In those days', apparently, vehicles were rotated during the launch and this rotation had to be eliminated once they were in orbit. I have a vague memory of being told about about a technique that was described for slowing or stopping the rotation which consisted of a mass on a tether that was wrapped around the rocket / satellite. As it unwound, it was supposed to re-distribute the angular momentum to leave part of the load not spinning.
Does anyone know about this? It has been bugging me for years because I just can't remember the details or work out from scratch what they did.

 

[HallsofIvy]

I've never heard of such a thing! It sounds very complex and "Rube Goldberg"ish to me. My understanding is that rotation is controlled by small rockets on the body that fire tangent to the rocket body. The U.S. space shuttle, which has wings, has small "attitude rockets" on the wings that first perpendicular to the wings.

 

[sophiecentaur]

You are talking in the present tense. I refer to techniques that were used, presumably in the '50s.
I don't think that the course at Reading Uni was particularly 'fanciful' and the textbook was ok in other respects, so I'm sure it wasn't just moonshine. (Shame is that I only ditched the book a few years ago - pre my membership of PF). If you remember, in those days, even a simple directional servo wasn't all that simple to achieve. If you could just load a vehicle with a coil of twine and a small mass and then guarantee to eliminate spin, it would be easier than a load of valves and batteries.
[Edit: PS. Rube Goldberg had his English equivalents in Heath Robinson and Emmet. Great fun and the source of many money making inventions for sure]

 

[sophiecentaur]

I just found a reference to what I was talking about: HERE.

At last - I can relax, it was really used! Some great references at the end of the wiki article.

 

[pmacias]

Yes, I am familiar with this technique. It is called a "spin-stabilized system" and it is commonly used in space missions to control the rotation of a satellite or rocket. The basic principle behind this technique is conservation of angular momentum. By adding a rotating mass on a tether, the angular momentum is redistributed and the rotation of the system is slowed down or stopped.

There are different variations of this technique, but the most common one involves using a spinning flywheel or a reaction wheel attached to the satellite or rocket. The flywheel is initially spinning in the opposite direction of the rotation of the system. As the flywheel spins, it creates a torque that counteracts the rotation of the system and eventually brings it to a stop.

Another variation of this technique is using a tethered mass that is released at a specific point during the launch. As the mass unwinds from the tether, it creates a counter-torque that slows down the rotation of the system.

This technique is important in space missions because it allows for precise control of the orientation of the satellite or rocket, which is crucial for tasks such as pointing antennas or solar panels towards the sun. I hope this helps to answer your question and alleviate your curiosity.