Hey! So I recently launched an experimental thrust vector controlled rocket to 91 meters! The flight went great but upon descent, the barometer started giving strange values. I suspect this could be due to the barometer receiving the airflow when it entered descent since there was no parachute. When the rocket came down, it was at a horizontal position, perfect for messing up barometer data. My question is wether that would actually cause barometer data to get messed up. Below is a picture of the barometer data which it stopped logging 1 second after it started descending.
This is also the maximum altitude reading which is why it peaks out at certain places. The barometer is an MS5607.
Hello JRD_Propulsion
Take a view into the data sheet of the sensor selected wrt environmental data like shock, vibration etc.
It might be worth explaining the axes of your plot. Presumably the X axis is time in seconds and the Y axis is a value coming back from the pressure sensor?
I might hazard a guess that the flat line and step change just after '3' could be caused by a value that has overflowed - maybe a 16 bit value stored in an 8-bit variable.....
I'm not a model rocket guy, but might expect to see a curve of some description up to apogee and then another curve as gravity brings the rocket back down.
The x axis is the time since liftoff was detected and y axis is the filtered altitude (using a very simple kalman filter). So the top line is not a problem since this was the maximum altitude. I have a function to store the current altitude as the max altitude as long as the current altitude is greater than the max altitude if that makes sense
What controller did You use?
Posting the autoformatted code in code tags as well as the numbers giving the plot would likely help us.
As already told, numerical overflow etc is suspected.
TVC_FLIGHT_8:12:23.TXT (127.7 KB)
So here is the full flight data. Also, no the weird lines in the data is not a mistake. I should have just posted the raw altitude data instead of the max altitude. `/*
Detect that the vehicle has entered descent stage
*/
void descent_detect(double dt)
{
if (alt_max > baro_alt_filtered) {
descent_time += dt;
if (descent_time >= 1) {
NeoPixel_yellow();
state++;
}
}
}` This was the code used to figure out the max altitude data I posted
here is a picture of the rocket and a picture during free fall. You can see the huge cutout. So the original question is why did the barometer altitude data go up while the rocket was in freefall? So do you guys think my original theory makes sense? The barometer altitude data is extremely important to me as I plan on using it for propulsive landing.
Increasing altitude means decreasing pressure. Might it happen that the barometer air inlet was on top of the falling rocket?
Can you also show the raw pressure data in your diagram?
So I never actually recorded pressure data. in the file I sent you can only find max alt or filtered alt. The inlet was on the side where the green light is on the picture I sent as well as from the bottom of the rocket.
this is the code:
/*
Detect apogee
*/
void max_altitude() {
// Update the previous altitude with current altitude
float prev_alt = alt;
if (millis() - previousTime >= delayTime) {
previousTime = millis(); // Update the previous time
alt = baro_alt_filtered;
// Check if altitude change is below the threshold
if (alt > prev_alt)
{
alt_max = alt;
}
}
}
Not a good idea 
The bug typically sits where you don't expect it.
Where is that light during descent?
Depending on the up/down position of the inlet you can get increased or decreased pressure values.
I meant the green light of the rocket when it is on that white table when it was not flying. When it was flying, since it was so bright outside it was impossible to record the light then.
Really, all I would like to know is if the weird data at the end was caused by the airflow coming into the airframe during descent. I know that I will never know that for sure but I wanted to see if other people agree with me.
Ok so I think I figured it out. You can see in the picture that both the accelerometer and barometer readings get affected at around the same time(the spike at around 67-68). So whatever happened affected the whole rocket and it was probably the violent descent the rocket entered. It was going really fast and really high. For the landing stuff, the rocket will be going way slower and not as high (20-25meters) and the rocket wont be flipping out of control after burnout so I dont think it will be an issue.
When you look back at the max alt code I sent, it will make sense to you.
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