How to Simulate UFO and Cube-UFO Rockets in RockSim v8

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teflonrocketry1

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Have you seen part 3 of the series of articles I wrote "Simulating Short Wide Rockets in RockSim 8, Part 3"?

https://www.apogeerockets.com/education/downloads/Newsletter162.pdf

I wrote up my techniques on simulating pyramids, cubes and saucer designs using the base drag correction for a flat plate that I developed.

Part four of the series covers simulating spool rockets. I also have two other articles I am working on, one titled "The Tail of the Boosted Dart", and the other titled "The Simulation of Long Skinny Rockets: What Barrowman Left Out Can Be Put Back In"

Bruce S. Levison, NAR #69055
 
hey Bruce, another excellent article!! I enjoyed reading it, haven't tried using it yet. maybe later tonight ... Kudos!
 
Originally posted by teflonrocketry1
Have you seen part 3 of the series of articles I wrote "Simulating Short Wide Rockets in RockSim 8, Part 3"?

https://www.apogeerockets.com/education/downloads/Newsletter162.pdf

I wrote up my techniques on simulating pyramids, cubes and saucer designs using the base drag correction for a flat plate that I developed.

Part four of the series covers simulating spool rockets.

Diggin' up an old thread...

Hey Bruce! Has Part 4 of this series been published yet? I went searching,
but didn't see it...
 
I am still working on the simulation of spool rocket designs article. There seems to be a lot more demand for the long thin rocket simulation article and I had been focusing on completing that article. I would be happy to help you with any spool design simulations in the meantime.

Bruce S. Levison, NAR #69055
 
Originally posted by teflonrocketry1
I would be happy to help you with any spool design simulations in the meantime.
Not really necessary (but appreciated nonetheless). I was just playing around
with your base drag ideas and came up with the attached.

It's probably pretty close, but I doubt the C6 altitude...
 
It's probably pretty close, but I doubt the C6 altitude...
Prompted by this thread - https://rocketryforum.com/showthread.php?t=39424 and a few moments of spare time, I revisited my RS file.

Rather than calc at sim time, I changed the Cd to use 0.80 based on the square nose shape value in Stine, 7th Ed. This yields much more believable altitudes across each motor class. So, now I have a bit more confidence in the base drag technique when applied to spools...

It might be interesting to tape a Perfectflite 15K to the motor shaft and further confirm the sim... Any ideas about how off-center weighting might affect a spool flight path?
 
I bet not much if it's mounted next to the tube. People have flown off center weight in saucers with little ill effect.
 
Rather than calc at sim time, I changed the Cd to use 0.80 based on the square nose shape value in Stine, 7th Ed. This yields much more believable altitudes across each motor class. So, now I have a bit more confidence in the base drag technique when applied to spools...

My own tube fin and ring fin designs have to be simulated as a static cd of 1.2 and 1.08 respectively. I think you are drastically underestimating the drag of the spool...
 
The base drag technique that Bruce documented is oriented to determining the stability of a stubby design rather than setting the Cd. Using an altimeter should help.
 
I think you are drastically underestimating the drag of the spool...
Perhaps. But maybe the 0.80 value plus the base drag effect (needed to produce stability in the sim) are combining to come close to the accepted flat plate Cd value of 1.28 [1]

Like I said, the sim altitudes are at least a bit more believable when using the 0.80 Cd value. This needs to be tweaked with flight testing and hard data. Anyone have a copy of AeroDRAG?

Dibs on this as a NAR R&D project !! ;)


Bruce- how soon until your Part 4 spool article might be ready?



[1] https://wright.nasa.gov/airplane/shaped.html
 
Spools have been studied in a wind tunnel...the report is for sale...link in the other thread (I'm getting confused between the twon in some of my responses :surprised:)
 
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