Well, I was just trying to get the guys to even think in the direction
of the inertial frame. (which is quite difficult) If I threw that at
them right off the bat they would probably run lol. Naaa really your
quite correct and thanks for pointing that out.
I'm just in a guidance mindset at the moment. I can't stay here too long
right now I have other things I have to do. But I will be getting back
to it at some point. Thanks for the great discussion.
My wife and I divorced about 6 months ago and I've got a lot more time
to get work done again.
So I better get to work.
Monroe
-------- Original Message --------
Subject: [AR] Re: Star Trackers, was Re: Re: Spin stabilized rocket
From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
Date: Thu, December 27, 2018 3:55 pm
To: arocket@xxxxxxxxxxxxx
On Wed, Dec 26, 2018 at 11:07:55PM -0700, Monroe L. King Jr. wrote:
That all makes sense. The problem I have is we have code with an earth
frame and we need to go to an inertial frame and I don't know how to do
that. I don't even know where to start to rewrite the code.
Part of what might be puzzling is that there's a very good chance that
the code already implicitly assumes an inertial frame (as in not
having any corrections for Coriolis force and such) and the existing
users are just accepting the resulting inaccuracy. In that case it's
mainly the initial values that need changing: instead of starting at
zero m/s, you'll be starting out moving with the rotation of the
earth. Code alterations might then be needed so that the atmosphere,
too, can be modeled as moving at the same velocity.
By the way, with Ardupilot, the software assumes that it will
constantly be making corrections as a result of feedback. Coriolis
force errors are infinitesimal at first, so when flying a plane the
software doesn't have any difficulty correcting them out just as it
would correct any other random perturbation. But when going for
orbit, the assumption that minor corrections can constantly be made
doesn't apply: you may be doing one burn, waiting, then doing another.
During the wait period it's impossible (or at least much harder) to
correct the flight path.