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Data vs. simulation.

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Zeus-cat

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Your apogee numbers are pretty close. The velocities don't match up well; are the units the same?

Looked at it a little more. Did you have an early deployment? Looks like you might have still been going up when it deployed. That may account for the lower altitude than the sim; although you are only off by about 50 feet or so. Hard to read the simulation graph.
 

markkoelsch

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If you are within 5-10% you should not worry about it at all.

A certified motor easily have more variation than you see between the sim and measured data.

Velocity measurement from barometric data is a bit hit or miss.
 

Larry Curcio

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Your rocket had considerable speed at apogee. The simulation had zero speed there - indicating a vertical simulation. The rocket turned more than the simulation predicted (vertical simulations don't gravity-turn at all, actually) indicating any combination of the following:

1) Launcher whip

2) Weathercocking

3) A launch angle not perfectly vertical

4) Something else like that there

Actual ascents are rarely near-perfectly vertical. That said, the correspondence isn't bad.
Think of it this way, if you launch it again, you'll get different numbers. A simulation cannot be more predictive than real-world variability.
 

Bat-mite

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Your rocket had considerable speed at apogee. The simulation had zero speed there - indicating a vertical simulation. The rocket turned more than the simulation predicted (vertical simulations don't gravity-turn at all, actually) indicating any combination of the following:

1) Launcher whip

2) Weathercocking

3) A launch angle not perfectly vertical

4) Something else like that there

Actual ascents are rarely near-perfectly vertical. That said, the correspondence isn't bad.
Think of it this way, if you launch it again, you'll get different numbers. A simulation cannot be more predictive than real-world variability.
You lost me there. I am seeing a velocity of just over zero at drogue deployment.
 

Bat-mite

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Your apogee numbers are pretty close. The velocities don't match up well; are the units the same?

Looked at it a little more. Did you have an early deployment? Looks like you might have still been going up when it deployed. That may account for the lower altitude than the sim; although you are only off by about 50 feet or so. Hard to read the simulation graph.
No. The sim is in FPS; the flight data is in MPH. Peak velocity of about 175 fps in the sim would equal 263 mph. RRC3 showed 242, so not so far off.
 

Bat-mite

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All things considered, I thought the sim was very accurate. I'll match up my units next time. :)
 

UhClem

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?? I'm seeing ~425 fps at apogee - just shy of 8 seconds ??
I see it too. But the velocity is derived from barometric data on the RRC3 so I wouldn't put too much faith in it. The pressure altitude data does show something happening at about 7 seconds which is well before apogee. Motor ejection perhaps.
 

Larry Curcio

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I see it too. But the velocity is derived from barometric data on the RRC3 so I wouldn't put too much faith in it. The pressure altitude data does show something happening at about 7 seconds which is well before apogee. Motor ejection perhaps.
Sorry. Thought I was looking at mixed data. If it's baro data, it's just vertical velocity at best - and (you're right) numerical differentiation of baro data doesn't give you the best.

Thanks, David
 
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