How to Prevent a Rocket from Spinning

[Funkworks]

I'm wondering if anyone knows anything about preventing a rocket from spinning, and if so, what are the tricks. It probably helps to have fins with perfectly symmetrical airfoils, but I'm wondering if a square or triangular body shape would help (instead of a standard cylindrical body tube). Maybe there are other ways but nothing comes to mind yet (excluding gyros and electronics for now).

A reason for doing this would be to have a camera pointing sideways toward a point on the horizon.

 

[CalebJ]

Potentially stupid question... Wouldn't preventing it from rotating make it less likely to fly straight?

 

[rockladen]

My 4" Black Brant II has no detectable spin during boost and probably during coasting (can't tell at that altitude since it has no camera). The fins were aligned very carefully and symmetrically airfoiled during construction. I also attribute the non spin to the large surface area of the fins.

 

[neil_w]

A reason for doing this would be to have a camera pointing sideways toward a point on the horizon.

I suspect that a lot of rockets spin because of the asymmetrical drag created by the camera. If the side-facing camera could be contained completely within the airframe, I'll bet that would help. I can think of no reason that a non-cylindrical airframe would offer any benefit.

For what it's worth, my rockets with ring fins fly extremely straight. Normally, if aiming a camera downward, you might not want a ring fin to obstruct the view, but if you're pointing sideways it wouldn't matter.

Potentially stupid question... Wouldn't preventing it from rotating make it less likely to fly straight?

Not really, unless the rocket is intentionally spin-stabilized.

 

[heada]

Making sure fins are 100% straight and no asymmetrical drag is #1. Then you can further mitigate spin by using a reaction wheel, cold gas thrusters, control surfaces, etc. but all of those require advanced electronics.

I've found that tube-fin rockets have the least amount of spin, all things being equal. They have less surface area presented to any cross winds and have a much greater surface area presented to the forward movement.

 

[shockie]

spinning is caused by either offset center fins and/or lift imbalance caused by the fins themselves not being identical to one another in their airfoil Asymmetric details on the model itself can induce spin......

 

[mccr3328]

In my experience tube fin rockets don't spin much ,even with a camera,

 

[numbo]

I concur tube fins spin very little. Also, even with perfect blade fins, a spin can be induced as the rocket moves through a wind shear (many videos show spin changes throughout the flight). A bonus of a mild spin is you can edit the video to give different compass point views of the rocket's flight rather than hoping it stays locked on the orientation you want.

 

[BABAR]

I'm wondering if anyone knows anything about preventing a rocket from spinning, and if so, what are the tricks. It probably helps to have fins with perfectly symmetrical airfoils, but I'm wondering if a square or triangular body shape would help (instead of a standard cylindrical body tube). Maybe there are other ways but nothing comes to mind yet (excluding gyros and electronics for now).

A reason for doing this would be to have a camera pointing sideways toward a point on the horizon.

this box design for some reason works well, maybe because I used cheater strips

https://www.rocketryforum.com/threads/getting-the-fins-on-straight.161696/#post-2042212post 11

for the base attachment fin alignment (slight aerodynamic drag cost, bonus is easy straight attachment and a stronger structural body-fin joint)

also alignment of the fin is really easy, as it sits flat on the work surface while drying.

you could also just build your regular rocket with a small adjustable fin tab, test launch it, and adjust the fin tab to neutralize any rotation.

 

[neil_w]

I'll bet tube fins and/or a ring and you're good to go.

 

[RalPh8]

So I saw a video not too long ago on youtube of a guy that had a two stage rocket and the booster was on bearings so as the fins (and booster section) spun it just spun around the bearings and the rest of the sustainer airframe stayed perfectly stable. It was cool to watch but I can't seem to find the video again for the life of me. I might try this idea in the future. Sure wish I could find the video.

I did find this though:
This video a guys uses small trim tabs on the fins to correct for spin. Seems to work pretty good.

 

[heada]

So I saw a video not too long ago on youtube of a guy that had a two stage rocket and the booster was on bearings so as the fins (and booster section) spun it just spun around the bearings and the rest of the sustainer airframe stayed perfectly stable. It was cool to watch but I can't seem to find the video again for the life of me. I might try this idea in the future. Sure wish I could find the video.

I did find this though:
This video a guys uses small trim tabs on the fins to correct for spin. Seems to work pretty good.

Search for "spin-can" it is part of Jim Jarvis' "I could use a little guidance" thread I think.

 

[JimJarvis50]

So I saw a video not too long ago on youtube of a guy that had a two stage rocket and the booster was on bearings so as the fins (and booster section) spun it just spun around the bearings and the rest of the sustainer airframe stayed perfectly stable. It was cool to watch but I can't seem to find the video again for the life of me. I might try this idea in the future. Sure wish I could find the video.

Yeah, that was me. Just search Youtube for Jiminaus50. There are lots of spin can videos.

To the OP, yes, my system uses gyros to control roll. It's relatively easy to control roll only, but much more difficult to control roll and yaw/pitch. One feature we have added is called "heading hold". It basically generates a correction based on the deviation from the initial roll position. So, it's always trying to work the rocket back to the starting orientation. It's not perfect, but it keeps the rocket oriented basically in the starting position through the flight. Here's an example.

Jim

 

[KenECoyote]

If you have wooden or thick fins, you can correct a recurring spin by filing the leading edge of a fin (or fins) at an angle to correct for it.

 

[jadebox]

As others have said, better fin alignment helps prevent rolls. One of the reasons my rockets tended to get larger over time is that I like putting cameras on my rockets and I found that larger rockets tend to roll slower and it is easier to align the fins better on a larger rocket.

I generally build my fin sections outside of the rocket and design the centering rings with notches that hold the fins in (close to) perfect alignment.

https://www.rocketryforum.com/threads/deja-youbee-a-rebuild-thread.36421/post-339654

 

[RalPh8]

Yeah, that was me. Just search Youtube for Jiminaus50. There are lots of spin can videos.

To the OP, yes, my system uses gyros to control roll. It's relatively easy to control roll only, but much more difficult to control roll and yaw/pitch. One feature we have added is called "heading hold". It basically generates a correction based on the deviation from the initial roll position. So, it's always trying to work the rocket back to the starting orientation. It's not perfect, but it keeps the rocket oriented basically in the starting position through the flight. Here's an example.

Jim

Thanks! I new I’d seen it somewhere.

 

[MetricRocketeer]

Hi everyone,

I am very much out of my depth here. I am just asking a question.

Doesn't spinning help stabilize the flight of the rocket? Perhaps I am totally incorrect on this next point, but I thought that a major development in gun technology was boring its barrel so as to induce the bullet's spinning. Thus, the bullet had more accuracy than the old musket ball, which came out of the barrel with no spin.

Please remember, I am just asking. I am curious how my colleague rocketeers -- those of us who have much more knowledge that I do about such matters -- respond.

Thank you.

Stanley

 

[neil_w]

Doesn't spinning help stabilize the flight of the rocket? Perhaps I am totally incorrect on this next point, but I thought that a major development in gun technology was boring its barrel so as to induce the bullet's spinning. Thus, the bullet had more accuracy than the old musket ball, which came out of the barrel with no spin.

Bullets don't have fins.

The rockets we fly are primarily stabilized through aerodynamic means, i.e. by their fins. A small amount of rotation is usually incidental, and not a significant factor in stability.

Of course, it is possible to make a rocket that spins intentionally, maybe or maybe not to aid in stability. But that's not what we're talking about here.

 

[dhbarr]

Spinning costs energy, so you're going either slower or lower ( or both ) unless you somehow pre-spin.

There are some flights where it makes sense, but most of them are above 30-50k.

 

[MetricRocketeer]

Bullets don't have fins.

Thank you, neil_w and dhbarr.

Good. Now I understand. neil_w's remark especially cleared things up for me. I am glad that I asked the question.

Stanley

 

[Daddyisabar]

Launch in perfectly calm conditions. Black Brants RULE!

 

[KenECoyote]

Doesn't spinning help stabilize the flight of the rocket?

It does if let's say the rocket was built unevenly or has an imbalance in weight or drag and would otherwise veer to one side...then sufficient spin would prevent that imo.

 

[Bruce]

I figured out that my rocket spun one way from watching the onboard video, so I added a correcting tab to one fin. Now it spins one way at first, then stops and spins the other way as the speed increases. What’s going on here?

 

[BABAR]

Hi everyone,

I am very much out of my depth here. I am just asking a question.

Doesn't spinning help stabilize the flight of the rocket? Perhaps I am totally incorrect on this next point, but I thought that a major development in gun technology was boring its barrel so as to induce the bullet's spinning. Thus, the bullet had more accuracy than the old musket ball, which came out of the barrel with no spin.

Please remember, I am just asking. I am curious how my colleague rocketeers -- those of us who have much more knowledge that I do about such matters -- respond.

Thank you.

Stanley

You may be confusing stability with straight trajectory.

rotational spin can and has been used on both model and real life sounding rockets to reduce weathercocking.

it is effective, there is a cost to the aerodynamic efficiency, but weathercocking can reduce peak altitude a lot more than spin.

https://www.apogeerockets.com/education/downloads/Newsletter228.pdf
there ARE spin stabilized rocket, where the spin IS used for stabilization, but they are uncommon and relatively inefficient

https://www.rocketryforum.com/threads/spin-stabilization.5376/
also this

scrolled down to a black and white tubeless rocket named Twisted. Comes up after Moonglow. Also go down to bottom of page and beginning of next page to get the build details

https://www.flickr.com/photos/oflittleinterest/with/9106148437/

 

[BABAR]

I figured out that my rocket spun one way from watching the onboard video, so I added a correcting tab to one fin. Now it spins one way at first, then stops and spins the other way as the speed increases. What’s going on here?

The fin tab effect varies with the velocity of the rocket. Many of my rockets have asymmetric fin designs which cause them to spiral. Extremely inefficient, but also cool, and since I have a small field I don’t care that they don’t necessarily go as high. The rate of rotation varies with speed, indeed some don’t rotate at all during powered boost but roll heavily during delay charge/smoke/coast phase.

 

[Eyesinthesky]

I have found using oversized fins and have a camera hanging off the side of a rocket seems to reduce spin.

 

[BABAR]

I have found using oversized fins and have a camera hanging off the side of a rocket seems to reduce spin.

Beautiful video. Still liked Skelenaut better!

 

[RocketFiles]

I hated waiting for fin glue to set so designed a 3D printed fin holding guide. The site below shows photos of the guide in use. Might be helpful. Good luck.

https://cults3d.com/en/3d-model/gam...-and-holder-for-estes-and-other-stem-projects

 

[Steven]

I put fins on mine.

 

[jqavins]

I've read that 4FNC rockets have less tendency to spin, all else being equal, than 3FNC rockets. I believe I understand why, and it's pretty simple. A cross wind perpendicular to one fin "sees" more area on that side than on the other, so that side is pushed downwind wind more, and, voila, spin. So for the minimum spin, in addition to symmetry and all the other good stuff, if you're using "regular" fins, use four rather than thee.