Drag Coefficient?

I was (attempting) to sim my Aura using this calculator on emrr. (My rocksim trial ran out, as did my spacecad, I can't get open rocket to work, and I havent got the money to buy any software :blush.
The Aura weighs 7 and 7/8 ounces (225 grams), and the body tube is Bt-1.52 (1.635 inch outside diameter). If I leave the drag coefficient as 0.75, it sims to 3044 feet on a G64. However, if i raise or lower the drag coefficient, the altitude changes dramatically. Can anyone suggest a reasonable value for the Aura :confused2: ?

Thanks in advance,

Tom

Try these free programs:
Flight sim: https://www.wrasp.com/wrasp.html
CP/CG: https://www.v-serv.com/vcp/
Drag estimage: https://www.rocketry.org/software/softwareDetails.php?mainID=261

A LOC Aura should have a Cd of around 0.65->0.70 with rounded edges on the fins and nicely painted.

The best way to determine drag coefficient is to launch the rocket with an altimeter and backtrack the same altitude in a simulation by varying the Cd.

-John

As a guess, just based on the shape of the rocket, I would say 0.55-0.6 if it has a near-perfect (auto-quality) finish with rounded fin edges, and 0.65-0.75 with square fin edges and a more typical finish.

Thanks for the helpful links, and the CD values people!

jsdemar said:

Try these free programs:
Flight sim: https://www.wrasp.com/wrasp.html
-John

Click to expand...

Do you happen to know how to change the motor from an Estes A8 using that program (wRASP)?

Thanks in advance,

Tom

rocketman said:

Do you happen to know how to change the motor from an Estes A8 using that program (wRASP)?

Click to expand...

Under the "Data" menu select "First State". In the popup window, select the motor from the list.

wRASP holds all of the engine thrust curves in a single file called RASP.ENG. You can add motors to this file by copy/paste from ENG files found at thrustcurve.org. Make sure there's at least one ";" commend line between motor entries. More about ENG files here:
https://www.thrustcurve.org/raspformat.shtml

There's an older file that contains all of the NAR S&T motors, especially Estes... See: https://www.wrasp.com/v21.html and download the file near the end called nar_0298.eng

-John

WRASP is still my favorite program for altitude simulation!
I have tried to stay on top of all the newer motors out there, but it seems that WRASP is running out of space when it comes to motor files.
I've been having trouble adding more files without having to drastically trim some files.


I've attached the file that I use


JD

View attachment 1ALL.eng