Parameters for for Warp 9 for METEOR or other motor simulators?

dr_innovation

Member
Joined
Jul 12, 2022
Messages
9
Reaction score
2
Location
Colorado Springs, CO
Been looking/googling for the parameters needed to simulate Warp 9 propellant in any free simulator. I use https://meteor.open-sky.fr/ but could switch if needed. A bunch of the parameters can be found from https://www.rocketmotorparts.com/Warp-9__Propellant_Grains/cat1577810_2151788.aspx and "AeroTech Warp-9™ Propellant White Paper" which I found at (https://d11fdyfhxcs9cr.cloudfront.net/templates/170652/myimages/warp-9_white_paper.pdf) but neither one lists specific heat ratio and I'm not sure I've got the others right (e.g. Molar Mass) Attached is the screenshot of what I have in Meteor. When I try to simulate I get a computation failure which says it may be the pressure is too low for in combustion chamber. Any insights/help appreciated.


1657648435659.png
 

G_T

Well-Known Member
Joined
Dec 29, 2011
Messages
2,772
Reaction score
731
That density value would be in pounds per cubic inch.

Without any known info, APCP not containing carbonates or nitrates, nor any exotic burn rate catalysts, has an exponent of 0.4. Unless you know otherwise, use that.

Lots of test stand data, obtained with small motors (say, two grain 75mm or smaller) is more than somewhat suspect. Slagging seriously affects the results with small nozzle throats. I tended to use a 6000 for testing, some years back, for that reason. But you burn a lot of AP that way. Small test motors may yield an exponent like what you showed, but larger motors may show a different exponent. The problem is having too small a motor to burn the propellant sufficiently, within the combustion chamber, and having slagging cause the effective Kn to be wildly off.

If your characteristic velocity is theoretical rather than measured or computed from real test data, derate the velocity. Energy is lost in doing things like heating the nozzle. The smaller the motor, the farther from theoretical characteristic velocity you'll get.

And if the propellant is metalized (Al, Mg, Zn, etc) and is small, some portion of the metals is simply being melted and blown out the nozzle. The smaller, the worse it gets. That SERIOUSLY degrades C* (characteristic velocity) and will affect the other numbers.

Gerald
 

dr_innovation

Member
Joined
Jul 12, 2022
Messages
9
Reaction score
2
Location
Colorado Springs, CO

"Gamma" is the specific heat ratio.

Everything else you need is on the data sheet.
Thanks.. I had tried that. Turns out the problem was that I was mixing units in Meteor. There are two coefficients on the sheet did not have units and the majority of the data was in SI so I presumed SI burn rate and coefficient. After using imperial measurements for everything I get a model that simulates. However the number still seem quite off (e.g. I get way more thrust when trying to simulate data for a G339N-P (Model 81313) While I don't know the full detals (e.g. for shape I just used a cylinder which should not proce max thrust). I'll keep approximating but though I'd post this in case anyone has insights (and to address the paramter setting). For the G3339N-P the rough specs are:
  • Burn Time: 0.4 sec
  • Total Impulse: 110.0 Newton-seconds
  • Motor Length: 97 mm
  • Max Thrust: 375.0 Newtons
  • Total Mass: 181.0 g
  • Propellant Mass: 48.0 g
and in Meteor I get

1657898249266.png

1657902389800.png



While I can match mass and total impulse but max thrusts are much larger. Is the difference in geometry enough to cause that?
 
Last edited:
Top