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 http://www.ukrocketry.com/ under Rocket Videos it's
10 from bottom called Gyroc
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 http://www.ukrocketman.com/rocketry/gimbal.shtml
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
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
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
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
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!
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!
Bob Kaplow NAR # 18L >>> To reply, there's no internet on Mars (yet)! <<<
Kaplow Klips & Baffle: http://nira-rocketry.org/Document/MayJun00.pdf
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.
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