Anybody Ever Install a Gyroscope in an LPR / MPR Rocket?

[Ladykate]

Is that you Debbie?

Yes... yes... that is I.

 

[alexzogh]

I tried this a few years ago, starting with the concept of a reaction wheel.

https://www.rocketryforum.com/threads/roll-control-with-a-reaction-wheel.158467/
I was about as successful as BPS Space was. I could 'kind of' control roll, but that was it, the negatives were just too high.

 

[Paul Howard]

I still think the original idea of a "pull the string, step back and launch" is intriguing and worth trying (considering some of the other bad inherently unstable or minimal stability things I've see here and elsewhere, I don't perceive this whole concept to be an worse than plenty of other things/ideas that were launched.

That said, I think a good unpowered test would be to try this: Make a mock-up of the design that pragmatically works best such as the gyroscope at the top, use a paper towel tube, add cardboard fins with tape, load everything like parachute, motor, etc. 1st - WITHOUT THE GYRO SPINNING - Do the "swing on a string" test for stability. If not stable, add fin size or nose weight, etc. 2nd - WITH THE GYRO SPINNING let the rocket hang from the same "balancing string" STATIONARY (No "swinging on the string") and see if you have any wobble/precession motion develop.

If your mock-up test-build works out OK, then proceed to the real thing - That's 2 cents.

 

[lakeroadster]

I still think the original idea of a "pull the string, step back and launch" is intriguing and worth trying (considering some of the other bad inherently unstable or minimal stability things I've see here and elsewhere, I don't perceive this whole concept to be an worse than plenty of other things/ideas that were launched.

That said, I think a good unpowered test would be to try this: Make a mock-up of the design that pragmatically works best such as the gyroscope at the top, use a paper towel tube, add cardboard fins with tape, load everything like parachute, motor, etc. 1st - WITHOUT THE GYRO SPINNING - Do the "swing on a string" test for stability. If not stable, add fin size or nose weight, etc. 2nd - WITH THE GYRO SPINNING let the rocket hang from the same "balancing string" STATIONARY (No "swinging on the string") and see if you have any wobble/precession motion develop.

If your mock-up test-build works out OK, then proceed to the real thing - That's 2 cents.

Probably the most productive build is to take my existing "THUNK!" GDS rocket and​

• cut off the spin tabs,
• make a new nose cone,
• install the Gyro in the nose cone and,
• launch it.

​

I've been contemplating removing the fins from THUNK! and silo launching it anyway... just to prove that the spin tabs were indeed what made it stable during the coast phase.​

 

[H_Rocket]

Good point. I've never flown at an organized event. I always fly here locally.

I also always run simulations, and swing test the rockets before launch.

I'm dubious as to whether there is a simulation program out there that would dial in the effects of gyro stabilization. And since you are trying to maintain vertical (I think) a swing test would likely fail.

That is, of course, unless you are trying to determine if it is stable with the gyro quiescent and using just the fins for stability.

 

[lakeroadster]

I'm dubious as to whether there is a simulation program out there that would dial in the effects of gyro stabilization. And since you are trying to maintain vertical (I think) a swing test would likely fail.

That is, of course, unless you are trying to determine if it is stable with the gyro quiescent and using just the fins for stability.

I agree. The only use of the simulation here is to show the rocket is unstable. Which is good, because if the silo launched rocket flies stable, then one would think the gyro made the rocket stable.

 

[jqavins]

Something like this maybe?
View attachment 534191

Hmm, I'd imagined maybe something like this, with or without a clear payload tube (which would need a hole for the string.)

Hmm? So, why would the rocket spinning about its longitudinal axis be an issue? That would make it more stable, right?

My GDS Thunk! rocket has spin tabs... and the roll rate is what makes it stable while coasting.

I'll buy one and do some testing.

IF you were relying on the gyro to offer stability, and IF you were planning to use an internal motor to get the gyro spinning and maintain it, the counterrotation of the body would have some tendency to reduce its effectiveness, because the angular momentum form the gyro going in one direction and that from the body going in the other tent to cancel. But I don't think that matters if the rocket is aerodynamically stable and the gyro is for show. And since you've mentioned the gyro using a pull string, the whole counterrotation point is moot anyway.

I wasn't talking about the old mechanical gyros (although I did work on them in another life)- at least not on purpose. I was talking about electronic gyros and kid's toys. If the intent is to install a gyro on a rocket, there are off-the-shelf solutions that aren't terribly expensive. A kid's toy would be hard to make practical but you could launch it anyway. So I was wondering what the intent was.

I suspect (could be all wet) that you're both imagining something and missing something. Imagining that this meant to have a practical effect, and missing that it would just be really cool.

I'm now thinking of abandoning fins. Another GDS powered rocket that is silo launched, Gyro-Thunk! GDS stability during thrust, then gyro stability during the coast.​

Ah, well, never mind my suspicion. If I were doing it, the cool factor would be my only reason.

Why would the rocket try to spin in the opposite direction?

I surmise the counterrotation worry came form the assumption that the gyro would be spun up by an internal motor, an assumption that I'm pretty sure was incorrect. Any motor that pushes the gyro this way also pushes the rocket body that.

I'm not the Dude.... you're the Dude....​

Which one of you abides?

I'm dubious as to whether there is a simulation program out there that would dial in the effects of gyro stabilization. And since you are trying to maintain vertical (I think) a swing test would likely fail.

That is, of course, unless you are trying to determine if it is stable with the gyro quiescent and using just the fins for stability.

For software, I'm beyond "dubious" and into pretty darn sure there's nothing in the hobby or consumer market that will. There's probably some five digit per seat per year corporate market software for it.

I'm also pretty sure that a swing test with the gyro spinning would be worse than useless. Since a swing test must of necessity involve a substantial pitch/yaw rate, the gyro will sent the rocket into paroxysms of precession, even if it would have been stable is straight flight.

The major drawback of gyro stabilization is that can't ever supply a restoring torque as great or greater than perturbing torque. That means that too a first order, it can't work alone; it can reduce your needed fin area, but never do away with fins. On the other hand, bullets don't have fins and spin alone makes them stable, so the first order analysis is clearly not sufficient.

 

[Ladykate]

I suspect (could be all wet) that you're both imagining something and missing something. Imagining that this meant to have a practical effect, and missing that it would just be really cool.

Ah, well, never mind my suspicion. If I were doing it, the cool factor would be my only reason.

I think there is mutual confusion and intent. Kinda cool if not meant to work. Kinda crazy if the intent was to stabilize something. It seems both are being considered. I will abide (appropriate reference credit here) with the non-working/kinda cool position.