- May 5, 2020
- Reaction score
Opening up a space where we can talk about using the tools on Thrustcurve and allow John to have a single place to get feedback.
If you use spacers, that would complicate this, obviously. That was my motive for requesting the capability of asking for only favorite motors (already added), but that's not quite the same thing -- I use that for the reloads I have, not the cases I have.Will start it off with a topic from another thread - requesting to have motor case size added to results to better choose motors for the hardware you have.
Do you mean the list at the bottom of the guide page?what happened to the existing rockets archive?
Good idea; I've added a recovery weight column (second to last).
At the risk of asking for too much, one more add and my workflow in TC would be complete - multiple rail lengths.
The simulator in ThrustCurve.org is very basic; it's just to get an idea of which motors will work for a rocket. I would trust a real simulator such as RockSim or OpenRocket if accuracy really matters.Is there something in TC I need to change to get an accurate sim for the larger motor?
Considering the two smaller motors were almost dead on in TC, is there an issue using larger motors? That is a large discrepancy.
The higher, faster, longer the rocket flight, the more the assumptions in TC break down. Things like constant CD, constant air density, etc. As John said, it is quick simulation. Consider that TC runs hundreds of simulations in a fraction of a second. Rocksim is solving more complicated equations and takes longer.
In this particular example, what is likely throwing off your TC calculation is the constant CD of 0.6. That drag is way too high, for way too long, and reducing the altitude by a lot.
I looked a little closer at the TC results and an interesting thing became apparent. The Loki motors at similar impulse levels were much closer to Rocksim than the AT motors. For example, the Loki L-1400 and L-1040 motors were within a 1000 feet of Rocksim results, but the AT motor discrepancies widened as the impulse increased. Not sure how to interpret those results, but it doesn't seem like Cd is the main discrepancy if one motor manufacturer's results are close but another manufacturer is off by as much as 30%.
Another good point. TC uses the latest data it has in the DB and RockSim and OpenRocket use whatever you most recently downloaded (or what they came packaged with).Yes, I forgot to mention that motor files are usually the biggest culprit. Are TC and RS using the exact same thrust vs. time points?
Yes it does. Most of the times when you have a table of results, it will have a final column that is a check mark. You can select all with the check in the header or individual motors with the checks in the row. Below the table will be a "Compare" link.If it does already, can someone point me in the direction of how to do it?
Yes, I think there is a problem. The certification documents give the overall length, which isn't actually very useful. There are three possible lengths:What say you? Since it is designed to fit in 18mmx70mm, should it be in the same group as 18mmx70mm or should it be listed as it's true 18mmx81mm? This came about when searching for a motor to match a Big Bertha that was 4.9oz dry and I knew a C18W should work but I didn't see it until I made the max motor length 90mm.
Ah, you're right that path (My Stuff | Rockets) doesn't have the options. There an extra form for the motor guide here, which is how it got out of sync. (There were some other options missing too, because I forgot about this path.) I've replaced this with just a link so it'll always direct you to the regular form now.I noticed that the options for Temperature, Base Altitude, and Stable Velocity only appear sporadically. If I select a rocket via My Rockets on the right hand column, they usually appear. If I select a rocket via My Stuff > Rockets in the top menu bar, then those options usually do not appear.
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