[AR] Re: dynamic stability
- From: "Monroe L. King Jr." <monroe@xxxxxxxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Thu, 21 Aug 2014 11:43:22 -0700
If you have already designed and built the rocket vertical is the
obvious choice. If you have not designed and built it add hard points to
your design for horizontal.
A laser beam makes a good bore-site for alignment of your equipment.
Millwrights have an awesome laser tool designed to align long shafts and
massive equipment you can prob rent one or borrow one. (or you can make
something that will work)
You can use an oscilloscope and transducers for rough balance (such as
speaker voice coils) and accelerometers for finer balance (which you may
not need this precise).
If your rocket is too flexible you could be in for a rough ride.
Pressurizing tanks may help? You can also make a tube to hold your
entire rocket and balance the tube first. Then balance your rocket in
it.
You can also balance it in sections
Monroe
> -------- Original Message --------
> Subject: [AR] Re: dynamic stability
> From: Carl Tedesco <ctedesco@xxxxxxxxxxxxxx>
> Date: Thu, August 21, 2014 10:29 am
> To: arocket@xxxxxxxxxxxxx
>
>
> Thanks Bill. Now to figure out how to spin a 21 foot long, 12" diameter
> rocket.
> --- Carl
>
> On 8/21/2014 9:43 AM, Bill Claybaugh wrote:
> > Carl:
> >
> > I believe FAA is looking for the 6DOF moments which are required inputs to
> > any dispersion analysis.
> >
> > If your vehicle is fully axisymmetric the pitch and yaw moments should be
> > the same. However, that is rarely the case in the payload and any
> > asymmetry will induce coning unless balanced. This is why dynamic
> > balancing is required on all professional payloads.
> >
> > If you are flying a liquid I would strongly recommend dynamic balancing the
> > entire vehicle (a very good practice even if you are flying a fully
> > symmetric solid--density variations in the propellant can influence
> > stability). Static stability testing is not sufficient.
> >
> > Bill
> >
> > Sent from my iPhone
> >
> > On Aug 20, 2014, at 15:45, Carl Tedesco <ctedesco@xxxxxxxxxxxxxx> wrote:
> >
> >> I am starting the process for getting a class 3 waiver for a rocket
> >> launch. Most of the FAA required documentation looks straight forward. One
> >> piece of information they require is "The dynamic stability
> >> characteristics for the entire flight profile." A static stability
> >> analysis is straight-forward, but I have never done a dynamic stability
> >> analysis.
> >>
> >> How have folks on this list addressed this requirement? Is this software
> >> driven analysis or just hand-calculations? Does anyone have an analysis
> >> they could share? If software analysis is the norm, can anyone point me to
> >> affordable software?
> >>
> >> --- Carl
> >>
> >> --
> >> Carl Tedesco
> >> Flometrics, Inc.
> >> 5900 Sea Lion Place, Suite 150
> >> Carlsbad, CA 92010
> >> tel: 760-476-2770 ext. 515
> >> fax: 760-476-2763
> >> ctedesco@xxxxxxxxxxxxxx
> >> www.flometrics.com
> >>
> >>
> >
>
> --
> Carl Tedesco
> Flometrics, Inc.
> 5900 Sea Lion Place, Suite 150
> Carlsbad, CA 92010
> tel: 760-476-2770 ext. 515
> fax: 760-476-2763
> ctedesco@xxxxxxxxxxxxxx
> www.flometrics.com
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