[AR] Re: Calculating CDs (was Re: In praise of Open Rocket)
- From: "John Stoffel" <john@xxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sun, 3 Jan 2021 22:01:17 -0500
<mark.spiegl@xxxxxxxxx> writes:
OpenRocket Bug:
When the launch site altitude is 0, OR and RAS agree. However, when the
launch site altitude is
non-zero, OR deviates significantly.
Example numbers for one of my test cases:
OR launch site 0 -> altitude 90K
RAS launch site 0 -> altitude 90K
OR launch site 5000 -> altitude 100K
RAS launch site 5000 -> altitude 120K
What happens if your launch site is -1000 feet? Just wondering... no
clue about any of this math at all, just like looking for edge cases.
But here's the conundrum with the 5000 ft launch site:
At burnout: OR and RAS Altitude and velocity are identical
During coast: CDs identical, Drag force(lbf) identical,
Weirdness: Coast velocity very different, Max altitude very different
It seems if OR had a bug in the base simulator or atmosphere models,
the 0 altitude sims wouldn't work either.
Taking suggestions. :-)
How long does it take to run simulations starting at 0 to 1000 looking
for where the divergance rises? Or is it a discontinuity or just a
simple step function?
John
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