[AR] Re: Nozzle shapes
- From: "contact@xxxxxxx" <contact@xxxxxxx>
- To: arocket@xxxxxxxxxxxxx, Ben Brockert <wikkit@xxxxxxxxx>
- Date: Mon, 18 Nov 2013 09:26:48 +0100 (CET)
Concerning the "Rao nozzle":
There are two types of nozzles which may be designated as a "Rao nozzle":
1. Truncated nozzles designed using method of characteristics (including TOC -
thrust optimized contour, and TIC - truncated ideal contour). Rao published the
method to design TOC in 1958. The method is very close to that described in
paper I have posted last time.
2. Nozzles designed using parabolic approximation method. Rao published the
method in 1960.
Therefore this can be confusing when people say "Rao nozzle" without
qualification what they actually mean: Rao TOC or Rao parabolic nozzle.
Concerning the nozzle design methods in RPA:
In the current version, RPA can design both parabolic approximate contour and
TIC with restriction to fit to specified nozzle exit area ratio. Further
restrictions for TIC (e.g. nozzle length or nozzle weight), as well as TOC will
be implemented in one of the further versions.
Alexander Ponomarenko
http://www.propulsion-analysis.com
> Ben Brockert <wikkit@xxxxxxxxx> hat am 18. November 2013 um 03:51 geschrieben:
>
>
> Alexander, is the Rao output of RPA a fit mathematical function or is
> the file it generates from the MoC without that approximation step?
>
> Ben
>
> On Sun, Nov 17, 2013 at 7:38 PM, Norman Yarvin <yarvin@xxxxxxxxxxxx> wrote:
> > The way the Rao paper gets its curves is by (1) doing the precise
> > calculation, via the method of characteristics, and (2) fitting a
> > second-order polynomial curve to the result. The idea was to make it
> > easy for people to build nozzles without having access to a computer
> > and code to do the full calculations. Judging by your remarks, he was
> > less than perfectly successful at this. If he were writing the paper
> > these days, he'd probably just put the method-of-characteristics code
> > on github and not bother about polynomial approximations. Output
> > could consist of closely-spaced (r,z) coordinate pairs.
>
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