Or just override the CG in front of calculated CP.
"Celestial Queen" retro-style rocket design and build thread
- Thread starter Azamiryou
- Start date
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Hmm, I might have to do that.
For some reason, adding the "base drag cp correction cone" increases the altitude. Dramatically.
Considering the rocket as it was for my test flight:
OR sim without correction cone: 238'
OR sim with correction cone: 326'
Actual flight as recorded by altimeter: 248'
It looks like the sim without the cone did a much better job of predicting the altitude, unless it was an especially anomalous flight (e.g., early ejection charge).
With half the nose weight removed:
OR sim without correction cone, with CG overriden to be a bit (half caliber) ahead of CP: 360'
OR sim with correction cone: 595'
I'm a bit confused. How does adding the BDCC cone add so much altitude?
Post the file with the base drag hack.
This is the flight test loadout, which actually went ~248'. ("Simulation 5" is the relevant one.)
Hmm, interesting. I'm going to need to study this.
Never mind. It looks like somehow the overridden drag coefficient on the cone was -1.0 instead of 0.0.
Don't know how that happened...
![JumpStart Advanced 2nd Grade [OLD VERSION]](https://m.media-amazon.com/images/I/61GZevnWjfL._SL500_.jpg)
Ah, well you just invented a way to make rockets go higher.
I'm surprised we allow negative values there.
Now I just have to invent some physics to go with it...Ah, well you just invented a way to make rockets go higher.
By the way , if you're making nose spikes out of air dry foam clay, don't put them on a sunny window sill to speed up drying. They'll get Peyronie's disease.
When OR says it's marginal, believe it. A swing test is not always definitive. And the base drag hack's accuracy is open to serious doubt.
Had you overridden the CG to the accurate value in the first place?
Not if you override the Cd of the cone to zero, which is the correct way to do it (if there is a correct way).
Yeah, I was editing that part out while you posted.
just scribble on a chalk border and get some nobel laureates to go "hmmmm" and your finished
I also don't buy into the hack's accuracy, but I do trust the swing test for rockets that aren't too wacky. I could find many examples of stable rockets failing the swing test, but only two unstable rockets that passed the swing test — and both were much odder than this one.
So I believe the rocket is stable. I'm using the hack here not to check stability, but to make the flight simulations run so I can check other stuff, like speed off the rod, apogee, and optimum delay.
The calculated CG is accurate, at least close enough. (I've been weighing things and updating the OR model as I go.)
Paint (Part 1)
The Rusto primer was still pretty gummy and rapidly clogged my sandpaper. Grrr. I still had most of a can of the Harbor Freight Sandable Primer, so I used that for the third and final primer coat. What a difference! I really need to find another primer like this — dries super fast, and sands without clogging to sandpaper at all!After sanding, I airbrushed her in flat black. While it finished drying, I did the motor tubes in chrome. Then I did the whole thing in gold.
Wow, I like that gold! It's tempting to leave it without the amber topcoat. But I suspect the decals won't work well on it, and a clear coat to protect the decals would ruin the look anyway.
Part 2
Amber top coat
lakeroadster
When in doubt... build hell-for-stout!
Very cool, well played.
This would have been a good candidate for rear eject... just think about how cool it would be recovering "under chute" with the rocket intact, floating back to earth.
Now back to your regularly scheduled build thread....
I bet you say that to all the girls.
Even with the long thin fin sweeps sticking out the back, I'm pretty sure they're still more rugged than the nose spike
Also, it would probably need to be upscaled. There's not much space in the rear as it is, and shifting the mass of recovery gear to the back will mean more nose weight -> more total mass -> bigger motor -> less space for recovery gear in the rear.
Coolest would be a side eject, balanced to bring it back horizontal.
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Drawing up the decals, and testing the fit before printing onto decal paper. Getting the curve just right for the front windows was tricky.
Work in Progress
I made up a sheet of decals, but my old graphics software couldn't handle printing it — it kept running out of memory. I had to split it into two half pages to get it to work.I've started applying the decals. Some are rather fiddly, to say the least. It will probably take all evening to finish, but even getting a few on really helps bring it to life.
Second test flight tomorrow.
Those look really good, fit with the theme of the rocket perfectly.
She now bears her name!
Also some pics showing how I use bits of tape to align rows of rivets.
Also some pics showing how I use bits of tape to align rows of rivets.
Really nice build 
Test Flight
When I started to set up at the launch field, I discovered I'd forgotten to bring my launch rods.
I had a friend there to help with filming. Rather than cancel or make him wait while I went home for my rods, I made a bad decision: I decided to fly on the 1/8" rod that was in my range box.
Severe rod whip resulted in a sideways flight. It didn't get high enough for the data logger to detect a launch, so no flight data. Chute ejected fine (at high speed though, so slightly dinged the edge of the tube). The chute worked beautifully. It managed to miss the trees (hooray!) but landed on the sidewalk (aw, man!). The sidewalk broke a fin tip off (easily repaired), put some small dents in the nose cone (NBD), and broke the nose spike (expected and prepared for, it's made to be replaceable and I brought spares).
I'll post video later.
I've already repaired it, and will probably fly again in the next week or so... but maybe not before the contest is over.
Flight
Damage
Repaired
modeltrains
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Patch 'er up between episodes and fly again, that's the sci-fi serial way.
Next episode might be Tuesday — forecast is for light winds, and we might be caught up enough on holiday stuff that I can justify taking a little time for rocketry...
Celestial Queen (final submission)
Key points:
- hand-turned nose and tail cones
- safe foam nose spike cast in 3D printed mold
- hand-sewn silk parachute
- flies on C5 motors
Attached files:
- OpenRocket file
- fin patterns
- decals
- nose spike mold (both scad and stl files)
Takeaways:
- sewing a lightweight silk parachute is a pain...
- ... but totally worth it when you see the rocket coming down under it
- don't use a smaller launch rod than your rocket needs
- small snap swivels can't hold onto heavy nose cones
- I need to get a new graphics program and make some time to learn it
