misho wrote:Ok - thanks. That's interesting... I'll try to research this a bit more. There's a space simulator/game out there with literally millions of users, (Kerbal Space Program), and their G-scale instrument shows 1G on the surface. I can't believe no one ever noticed this...
I try to question and I accidentally delete you post, but here is the respond anyway
...and I DID get results I expected, but I tested it on a limited number of scenarios (on the launch pad, in orbit, re-entry and under parachute). I'm guessing, under certain conditions I would get erroneous results, but I left it as is for now and implemented a few other things that depended on a G-factor, even if not entirely properly implemented...
It should work 100% of the time and give correct result.
and this is the last answer I am going to give regarding this issue.
first of all the question you ask was no what I said.
...I was told that technically, G-force readout should actually indicate zero-G on the earth's surface, as well as in a stable orbit. This is due to the fact that G-force is measured using accelerometers (which measure a change in velocity) and since we down here on Earth surface, when standing still, don't change our velocity (neglecting earth's rotation effects), our G-factor should be 0.
I said the acceleration you measure should be zero on the landing pad and 1 g what in orbit, I did not say should be zero I said 1 G.
but never mind what I said this si what IO go by.
Acceleration is measured as the rate of change of velocity over time is no the value of G
form the newton secund Law of motion, on an inertial frame, the acceleration of a body is give by this
m * dv / dt = f1 + f1 + f2 + ....
one of the f is the gravity, so what an accelerometer measure is the value
dv / dt = (f1 + f2 + 3 + .....) / mass
when mass is the mass of the piezo electric device, if you do not believe me then I do no know what else to say, but a look at how they device work will tell you exactly what I said.
https://www.omega.com/prodinfo/accelerometers.htmlnow when you posted the question, there a bunch foe people provide lot and answer what are all incorrect or partially right for the wrong reason.
The person who said this:
"Accelerometers do not measure change in velocity. An accelerometer in a non-rotating, non-thrusting spacecraft above the Earth's atmosphere will register 0 g, even though the spacecraft's velocity vector is changing all the time"
immediately follow by this.
....Accelerometers do not measure change in velocity".
does not seems to realized he is contradicted himself, he mentioned a lot stuff, bungee jumper, Iphone, self driving car and even pluto, to drive home he used to work a NASA,
But work for NASA does not make him an expert, and judging by his answer I do not think he is knows what this devices work the way the do.
He is confusing accelerometers with scales.
Scale like the accelerometers of phones measure displacement,
accelerometers measure velocity changes.
The reason an accelerometer on the space craft measure zero G is because the device is in the same frame as the Rocked, so there is no relative change of velocity between the rocket and the accelerometer.
The part he got right is when he said this
That accelerometers do not measure acceleration due to gravity presents a challenge for spacecraft that self-navigate their position/velocity state. Such spacecraft need to have an onboard model of gravitation so that the acceleration due to gravity can be added to the accelerometer reading. This calculated value will be somewhat erroneous
basically this is that in order for the instrument give you the values as if the frame of the aircraft was an inertia frame reference *(want tat is no rotation or accelerating which the rocket is),
the instrument has to be calibrated which is what the function that I gave you does.
He know the instruments calibrates and he mention a bunch of unrelated stuff to justifies his answer be to mu knowledge he does no really know what he is talking abut. He is talking like a person who drive a car how has experiment with car but the does no know how car really work.
The point is the NewtonGetAcceleration function returns the Inertia acceleration (meaning relative to the origin of the world) of the body, according to newton equation of motion form there you can make any calculation you want.
ask for the second dude who said this:
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This is incorrect. G is not zero on Earth's surface. You're conflating two things: G-force, which is a force as a result of gravity, and acceleration, which produces a force as a result of movement.
I do not even know what to said here, this self appointed expert super moron just straw man what I sad, I never said G is zero on the surface for the earth, I said when the body is a rest the sum of the weight plus the ground reaction forces is zero. so the acceleration will be zero.
But at this point I believe you have what you need, you are free to use it or do something else.
It does not make any difference to me.