servos for rocket fins... Doable ????

[yevgeny]

Hello guys....
hope you are all fine...
well i had a discussion opened with some friends about how would servos perform if installed for rocket fins?????
am asking you because your more knowladgable than me, so is it possible that i can install servos to controll my rocket fins ????? and would they perfom rightfully???? and if so what are the drawbacks if any and what type of servos shall i use for example?????
thanx you guys and i appreciate your help ))
have a nice day to all of you

 

[mkmilion]

....but I have to tell you that it's against the NAR Safty Code. If you add guidance that would make it a missile thus making it against code.

 

[yevgeny]

dear mkmilion

that is perfectly right, however in my part of country there are no rules for model rocketry that concerns this part of the hobby,
i appreciate your comment, but do you have any other comment regarding the technicalities ??
thanx alot dear mkmilion

 

[MarkABrown]

If you've already got fins, you've probably already got static stability once the rocket gets up to speed. Why would you want to add guidance?

 

[yevgeny]

well Mr. MarkABrown
this was a matter of discussion not for reall implementation i guess , sor far ). we just opened the subject for reall techniocalities. i don not know ehy should i do this but WHAT IF just we assumed the disscussion ))

 

[hokkyokusei]

Originally posted by MarkABrown
If you've already got fins, you've probably already got static stability once the rocket gets up to speed. Why would you want to add guidance?

You might want them to cancel any roll, to make a stable camera platform. I've seen this tried, but it didn't work

 

[yevgeny]

well, thats one nice reason to install a a fin with a servo...
but can hokkyokusei tell us more on the experiment which failed
i mean like do you know what went wrong or what factors where underestimated ?????
thanx hokkyokusei

 

[Stymye]

having a servo set up that will react fast enough would be the tough part

 

[hokkyokusei]

Originally posted by yevgeny
well, thats one nice reason to install a a fin with a servo...
but can hokkyokusei tell us more on the experiment which failed
i mean like do you know what went wrong or what factors where underestimated ?????
thanx hokkyokusei

I'm afraid I can't really remember. IIRC it had servos that moved tabs on the fins rather than move the whole fin.

There was a light sensor, which was meant to orientate the rocket with respect to the sun.

During the flight the rocket spun _very_ fast, so presumably the tabs went to the end of their travel and stayed there. It could have been due to many factors.

 

[yevgeny]

well lets assume that we do not need speed right here we need just to do the right action with the right power (equivelant to the G load and speed).............
would that be possibel??? (assuming time is not a problem !!!)

 

[Justy]

If you forget about a few convienient facts, will it work? Sure. Similarly, the Tacoma Narrows Bridge would have worked if not for wind, and if we could ignore a few laws of physics while keeping others it would be possible to put satellites into orbit with Estes BP motors.

I was reading about this just last night: Brittain Fraley (Delta V Rocketry) built a rocket with a piezoelectric gyro controlling a set of fins to stop roll. It doesn't point the rocket in any direction, it just keeps the rocket from spinning. Without the stabilizer the rocket spins 6-and-a-bit times in its flight, with the stabilizer it spins less than a quarter turn. Link here.

If you had a fast enough servo, you could move fins for real rocket guidance; that's how a missile works, right? But they use specially made, military grade servos. Could you do it with everyday off-the-shelf RC servos? That's beyond me.

 

[mkmilion]

I know that the A4 rocket (later known as the V2) used moveable fins to direct the rocket and they didn't move all so fast.

 

[edwardw]

Rollerons have been used to help guide a rocket before. They are little tabs hinged on the fins that have a wheel that rotates in the slipstream. Once they get spun up they react to any roll or turn by moving the rocket in the other direction. The Sidewinder Missile uses them. If you google rollerons there is a lot of information.

Edward

 

[Austin]

Guys,

This discussion is getting way off the rules and regulations we fly under. In summary, yes, the military uses guidance, but they dump millions into research and development and even some of those don't work. For us, it would be impossible to design and build such a thing, nor would we ever consider it.

For all practicality here, we discuss model to HPR rocketry and guidance is strictly prohibited by the rules we all follow, so I see no further point in continuing with this thread.

Carl

 

[yevgeny]

well guys
i thank all people in there comments and ideas , and i would take in mind our friend's CTulanko advice.
anyway thanx guys, though i thought we could have some sort of technical study here.
any way
have a nice day

 

[MarkABrown]

I have no problem with technical discussions. However, here is how I see this thread. Yevgeny, it appears to me that English is not your primary language nor are you a citizen of the United States, since you stated that rules about guided missiles don't apply where you are. You've only posted 8 times since your joining on March 6th, 2004 and none of those posts explained who you are, where you are from or what your interests in rocketry are. In another thread you claimed that you didn't know much about rocketry but you were designing your own motors and wanted to know how to guage their power.

I don't mean this as an attack on you but, since you've provided no information about yourself, I can only assume that you want this information for some nefarious purpose or you belong to some government agency just trying to see how easy it is to get information from this forum. Am I paranoid? Maybe, but I'd rather be safe than sorry. There are just too many radical extremists in the world today who think that killing innocent people is the way to get what they want. I, for one, don't want to provide any information that may help them.

 

[powderburner]

Mark,

I think you were correct in being a bit suspicious about this thread.

Aside from all the technical problems with using model airplane RC servos to try to move rocket fins, even if I knew how and had experience, this is not how I would hand over the info.

Only real qstn remaining: who's gonna call the Feds?

 

[nOrM]

Where exactly does the NAR or anyone else prohibit using active means to direct a rocket's flight?

The R&D competition at NARAM 30 was won by a sun seeking rocket so I'd have to say it's probably ok w/ NAR. Also, some means of insuring a straight up flight might be considered a improvement in safety.

Then again, I'd also want to know yevgeny's motives if they would care to post them.

nOrM

 

[HeadHunter]

All very good points...even though I am suspect of yevgeny's motives...next time your out in the bottom of an empty, dry lake bed... put the old helmet on, put old besty in reverse, stand on the gas pedal and try and control it. Should pretty much simulate trying to steer a rocket with RC gear.

By the way, have you rented any white vans in Utah recently...

 

[yevgeny]

well guys........
am a bit shocked guys... but i wont blame you for this suspesion, coz in some way it is justified, nowdays you know nothing about who is nice or bad.
just to give you a hint, you can find from most of my postings that am still a beginner who want to explore more in this hobby, i might be a handmade thing guy, want to do most of the stuff with my hand, and thats why i thought why not do the motor with my self. am not yet experienced in the field and thought that with posting of my ideas i will find "guidence" (again ) from other experts here. i did find help however.
i just keep on asking questions that get in my mind and this thread was one opened because some friends had a discussion on this idea. i know this could be classified as illegal or out of the rules, but by all means my motive was to know and explore more in the field... i mean what would i do with an estes-like rocket less that a kilo ?????? am still a beginner for God's sake
anyway.
am sorry if i did bother people and rase suspesion, but my intention was pure for the sake of knowledge .... i know knowledge is power... and power corrupts .... and...... ))) i was just joking.
anyway obviously the topic is closed by now .
thanx guys and have a nice day.

 

[MarkABrown]

yevgeny,
You still haven't told anyone who you are, where you are, how long you've been in rocketry, why you are interested, what you hope to accomplish in rocketry, etc...

You'll get much more help if you'd just introduce yourself and update your profile to include your location and age. People wouldn't have been so suspicious if you'd have just done these few simple things. It's not too late to reduce everyone's apprehension about this thread.

I'm interested in what you and your friends have been discussing and would like to hear what you'd like to accomplish in rocketry.

 

[AndyC]

I can uderstand the concern expressed here - but what a sad reflection on the times we are living in...
...on another note, surely r/c rocket gliders ARE 'legal', so isn't the line here a bit vague....

andy.

 

[Dwight]

several points.

RC Servo’s to make the rocket guidable is a questionable idea even if it were perfectly within the code.

The rocket has a boost usually less than 3 seconds. You are not about to guide anything in those 3 seconds, the entire idea is to have the rocket stable at speeds greater than 30mph. Taking it straight up.

After those 3 seconds you are talking about a small rocket that is traveling directly away from you at likely over 100mph ( and more likely over 400mph ). and at an altitude of several hundred feet.

You would have to know the orientation of the rocket ( not likely ) as it turns. basically you aren’t going to guide anything on the way up, except to make an otherwise stable rocket head off in an unexpected direction ( not a good idea )

On the way down you have a recovery system. if it is a parachute or streamer than your fins wont do squat.

The one application that would work well is servo controls on a glider recovery.

Recently I have been building boost gliders. The Quest Intrepid is a good and cheap example of that kind of glider. ( however I extended the elevators and made them adjustable ) Gives great flights.

My next boost glider is going to be a scratch built design but much larger, glider based on a 29mm body tube.

After that I may build a glider with RC servos for controlled flight.

There is a place in rocketry for RC controlled surfaces, but it just is not the fins. That is going to just destroy your rocket, and possibly get someone hurt.

Just a tip

And by the way, it is not the age we live in that makes it a problem, that has been in the code for over 30 years. And for good reasons, they are trying to make sure no one builds a rocket guidance system for hitting a target, basically a guided missile. That kind of effort would bring the authorities down on the entire hobby in a hurry, which is why the rest of us are telling you “don’t do that”.

But look on the bright side, there is a place for servo controlled surfaces, try a project with that in mind. But go slow, trying to bite off more than you can chew will hand you a drastic failure and discourage you. Start slow, build something simple, then build something a little better.

As series of successes using a small amount of money each time is a whole lot better than shooting for the moon with no experience.

 

[Hospital_Rocket]

As a historical note, didn't the V2 use vanes in the jet to steer rather than adjustable fins. In any case the guidance was for stability not targeting as it was an unguided ballistic missle - essentially, if I point it in this direction, add this much thrust, and do a parabolic computation, and it should come down right where I want it..more or less.

As I used to design servo projects, I would normally find this thread fascinating however I am also a bit paranoid for two reasons. Not so much because I don't know Yvegny (that is reason 2). It is more because high speed servo systems are the realm of people who know the engineering of motor design and feedbck systems. There is absolutely no way you can properly design a control system that a fast moving rocket requires without that knowledge. While I respect anyone's knowledge by defaullt, someone would have to prove to me with extensive mathematical modeling and low speed testing that they have a stable servo system before I would let them within a mile of a launch pad.

And setting the R/C rocket gliders aside, a open loop servo system would never have the dynamics needed.

Question though - Do kits like the Astroblaster violate the MR code with respect to guidance in our hobby?

 

[vjp]

Originally posted by Hospital_Rocket
As a historical note, didn't the V2 use vanes in the jet to steer rather than adjustable fins. In any case the guidance was for stability not targeting as it was an unguided ballistic missle - essentially, if I point it in this direction, add this much thrust, and do a parabolic computation, and it should come down right where I want it..more or less.

The V-2 used aerodynamic fin tabs, in addition to thrust deflection vanes. These were used for stability as well as guidance; the V-2 was in fact a guided missile, just not a particularly accurate one.

 

[Hospital_Rocket]

Hokay

I just thought that the gyro system was used to keep the missle flying in the direction pointed, Then at a preset time the motor shut off, it arced over an became a 2000lb artillery shell. To the best of my knowledge in the original V2 there was no intelligence to the guidance, and the landing point was comitted at launch.

I do stand corrected that there were both vanes and fins.

My reference:

https://www.v2rocket.com/start/makeup/design.html

 

[prowlerguy]

I hate to be a pain, but this has bothered me for a while. How can I reconcile claims that active stabilization is strictly off-limits with the facts that such a project won a NARAMS R&D award and BGs are allowed to exercise flight control during boost? If it was against NAR rules, why did they give a prize for it? I always interpreted that rule to be a prohibition against guiding TO A TARGET, but even that seems to be allowed by R/C BG.

If someone could perfect active stabilization, then a whole variety of scale models could be constructed, and wind could become less of a factor (imagine no weathercocking on large cross section models). Why is there so much hostility when it is mentioned?

 

[vjp]

Originally posted by Hospital_Rocket
Hokay

I just thought that the gyro system was used to keep the missle flying in the direction pointed, Then at a preset time the motor shut off, it arced over an became a 2000lb artillery shell. To the best of my knowledge in the original V2 there was no intelligence to the guidance, and the landing point was comitted at launch.

I do stand corrected that there were both vanes and fins.

My reference:

https://www.v2rocket.com/start/makeup/design.html

I guess what defines "guidance" is a just matter of semantics. It's apparently not a closed-loop system, applying corrections to the flight path to offset deviations and reduce the CPE of the impact point. Rather it simply appeared to follow a preset program to put it on a predetermined trajectory, designed to put the missile somewhere in the ballpark.

 

[vjp]

With all the talk about "guidance" being against the safety code, I'd just like to point out that the NAR safety code does not in fact contain any sort of prohibition against this, anywhere. Item #8 states: "Flight Safety. I will not launch my rocket at targets, into clouds, or near airplanes, and will not put any flammable or explosive payload in my rocket" - which ought to be obvious to anyone, and is plain old common sense.

Active stabilization systems have been flown many times at NAR events, John Pursley's Mercury Redstone and George Gassaway's sunseeker rockets come to mind.

Also, I feel there there should be a clear demarcation between "stabilization" and "guidance" when referring to this sort of activity. "Guidance" implies techniques used to "guide" a rocket from point A to point B. "Stabilization" merely connotes keeping the rocket oriented properly during flight, and can't possible convey any kind of sinister potential.

So from my point of view, we ought to drop the word "guidance" from any model-rocketry related activity along these lines and use "stabilization", which seems to me to be more appropriate.

Just my 2 cents, FWIW.

 

[Dwight]

I could not agree more, but I don’t think stabilization is what the original poster was referring too.

He was talking aobut guiding a rocket with servos atached to movable fins.