OpenRocket: negative accelleration at T=0?

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Well-Known Member
Jul 22, 2020
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I will repeat the disclaimer that we can agree this doesn't really affect anything, more of a philosophical discussion at this point.
In this case, I believe rather strongly that most users would expect that in the plots, a = dv/dt, where v is w/respect to the ground, and therefore a stationary rocket has acceleration=0 until it starts moving. It's as simple as that. If the internal calculations naturally lead to anything different, then it is the developer's job to modify the presentation of the data to make more sense.
And in this case we all definitely have the right to demand our money back until it's fixed. :)
I'm going to file an issue with OpenRocket to fix this, sometime in the future (who knows when).
IMO, a perfectly acceptable fix would be to simply not plot anything before a>0, v>0, alt>0 — which I've been referring to as "liftoff", but OR seems to wait about 0.1s after the rocket starts to move before labeling the "liftoff" event — it probably has some altitude minimum > 0 before it declares liftoff.