other than fin stabilization?

Jim from MARS in the UK has a wicked acticvly stabalised rocket Uses some very hi tech gyroscope to gimball the motor, not the usual Model helicoptor type as i understand. Very cool and fly's fantastically well using long burn G motors (those AT glider one with about 8 sec burn)

A video can be seen at

I've been thinking about this for several months. Is it possible to use small servos to do thrust vectoring and control the servos with a gyroscope (or a pair (pitch and roll) of piezo electric gyroscopes)? I think there are 6 degrees of freedom gyroscopes out there but I was going for as simple as possible approach.

I remember hearing that the first guided missiles used simple gyroscopes and pushrods to control thrust vanes. Something along those lines shouldn't be THAT hard to do.

I am by no means an EE and have very limited knowledge of ectronics, but I was about to go buy a used circut design college textbook to read up on how I could do something like this. My only worry, what government agency would become interested in me for creating self-guided rockets? Granted, the only guiding it would be would be up.

-Aaron

The hard part is to gage how much correction to apply for a given error vector. Too much, and you over correct. To little and you don't come back on course. You'll need some pretty hefty physics to calculate the amount of force to correct the flight, then calculate the thrust vector.

So now I have to refresh my physics AND learn electronics engineering? I should just go back to school and get it over with.

Honestly, I was thinking of putting in some kind of limiters on the thrust vanes. Along the lines of a max deflection of 5 to 10 degrees. If it over corrects, it will correct it again when it reaches the other side. Under correct and well, it's not nearly as bad as it was before.

I wasn't thinking of converting a horizontal flight into a vertical one or creating a cruise missile, more along the lines of taking a rocket that is starting to lean over and bring it back to vertical. (as what happened on my 1st attempt for my L2 flight a few months ago)

What about introducing a right rate of spin? Would a rocket that is almost stable but spinning at something like 1000 rpm be stable or even less stable?

-Aaron

Aaron, I'm no expert myself, but it seems to me if you induce a high rate of spin, your probably going to lose a specific given amount of thrust, i.e., re-directing energy laterally, which would *probably* take away from the thrust. Or so I imagine...

Would it be a trade off of thrust for stability? If I had to lose 5% of the overall thrust but increased my stability by 50% I might consider it.

For example, if I were to take a scale Saturn V and have scale fins, the rocket wouldn't be stable. If I take that same rocket and put 5 motors in it, each having a 5 degree cant to them so that it induces a high rate of spin, would that increase the stability enough to have a stable flight? Would it make it less stable? One of the methods to stabilize an object in space is to spin it, does the same hold true in an atmosphere? (rifing effect?)

Just ideas popping around in my head.

I guess that canting the motors would induce spin, but I would be inclined to think that the location of the CG would probably have to be pretty carefully figured, sounds like build time, Aaron- maybe some cheap mock-ups before sacrificing a time-intensive scale build or an expensive kit. You know, possibly using smaller "auxilliary" motors, canted and mounted outboard of the primary engines, and mounted oh, say, about parallel with the CG might do the trick...you've given ME something to think about. Keep us posted!

Anybody remember a rocket called the ZNT? Instead of fins it used a bunch of short body tube sections glued around the body tube at the bottom in two or three layers, looked a bit like a "wedding cake". Worked just like fins but weird!

I've heard that some of the Eastern Europe rocket flyers have done just that for Saturn V models, but you'd have to ask some of the Internats flyers to be sure.

Roy nar12605

Correct.

However canting motors outward per Delta increases dynamic stability without spin.

Tech Jerry

Thanx for the correction, Jerry...I did re-think that, just AFTER my post...I better get some sleep! ];>}

Tech post Jerry

Rogue areospace did something similar can't remember what it was called now got one in the loft not flown it for ages.

Damian

I remember now Rogue Areospace Courier - I've just took a pictuer and updated my fleet section. It's the bottom rocket as it was one the first i ever built.

Damian

The video showed Jim's Gyroc 2 a more advanced version of his initial Gyroc1 from the mid 1990's

More information and details on the Gyroc Project can be found on Richard Osbournes website here

Damian

It won't work for 2 reasons. A pyramid or cone is stable if the CG is located far enough forward. A tube is not (the CP would be in the nose cone until it is at a LARGE angle of attack)

Second, if you recess the motor too far, you will rediscover the Krushnik effect. You can only go back about one tube diameter. On a pyramid, the base "diameter" is rather large. On a tube, it is not.

Many years ago, when I first got into competition, and my knowledge was limitied to cardboard cutout stability, I built a C Payload model with minimal fins. According to Cardboard Cutout, that was no fins at all. The rocket was rather unsuccessful, coning at about a 30 degree angle in flight. Without the 1oz payload, it would be totally unstable.

You could replace the tube with a stick!

The Centuri Point was a paper cone that worked on the same priciple. Some folks reported that the exhaust coming out the base could form a vacuum that actully held the rocket down to flat blast deflectors, allowing the rocket to burn on the pad! I used an angled deflector, and never had a problem. The Point flew fine, and the extra-large exhaust looked pretty cool.

The Centuri X-24 lifting was a derivative of the Point, but it had small fins--IIRC they weren't for boost stability, but roll stability when the rocket transitioned into a glide phase.

Putting the engine high up in the rocket is basicly how Goddard's first liquid fueled rocket worked. It had NO body tube just side bars to which the tanks were attached. Also the escape towers on all US space craft from Mercury to Apollo worked the same way, having the engine high above the CG. Should be possible to build a model rocket that way. A few weeks ago on MB there was a flying house with an escape tower rocket mounted above the roof.