I540 to Mach 2 - 38mm Flying Case

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The concern I originally had that brought up the shock questions was more if there might be a shock created by the step in front of the fins. If there is, would the shock be enough to disrupt airflow over the fins, and thus stability? How would it affect the center of pressure?

-Hans
 
If you're flying reasonably above Mach 1, you're nearly guaranteed to develop some variety of shocks around any stepped surface. Shocks do not necessarily detach the flow from the surface (fins in this case), so aerodynamics still work. You'll just see a step up in drag. I do believe, though, that the CP tends to move forward approaching Mach 1, and then drifts backwards again above Mach 1. This phenomenon would be due to the Prandtl-Glauert effect (subsonic) and its supersonic analog, the Ackeret rule.
 
It flew today at URRG..... Everything was recovered intact and it flew stable :) And WOW it was fast!!

Going through data now, and preliminary analysis shows that the CTI I540 was more like an I700 it maxed out the XTRA's 105g accelerometer so the velocity data may not be as accurate as I hoped. Right now seems like Mach ~1.85.

It hooked a right out of the tower, and continued arrow straight until the motor burned out. About 1/2 sec in there was a loud pop, though deeper, and a puff of smoke in the smoke trial. The thrustcurve generated from the accelerometers confirms this strange event - 650 N off the pad, rising to 800 N at 1/4 sec, then falling to 700 at 1/2 sec in, then abruptly dropping to ~60 N at 0.6 sec and maintaing that for about 1/2 sec for a total of ~1.05 sec burn. Nothing like the nice even 1 sec ~550 N burn that is published for the I540. Also, I calculated the total mpulse from the thrustcurve I created and it was only around 475 N-s.

Any ideas what caused this? Should I have glued the grains in?


Additionally, despite having set it to ignore the pressure sensor on ascent, the accel data shows the XTRA fires the apogee charge after only 9 seconds of coast at ~380mph. Because of this it only reached around ~9,500 feet. Looking at the sims it should have coasted for around 20 seconds, and at 9 secs of coast it shows the rocket around 10,000 ft, so if it had continued up I think it would have easily reached 11-12,000'.

Overall though, I am very happy. It flew great, and was successfully recoverd intact - and that's all that really matters in the end! Also, I got to see some awesome flights by others with motors much larger than I've ever seen before in person, so that made the 5 hour drive well worth it as well! Pictures, video and data to come in the next few days, I've got a lot!
 
RocketHunter said:
It flew today at URRG..... Everything was recovered intact and it flew stable :) And WOW it was fast!!

Going through data now, and preliminary analysis shows that the CTI I540 was more like an I700 it maxed out the XTRA's 105g accelerometer so the velocity data may not be as accurate as I hoped. Right now seems like Mach ~1.85.

It hooked a right out of the tower, and continued arrow straight until the motor burned out. About 1/2 sec in there was a loud pop, though deeper, and a puff of smoke in the smoke trial. The thrustcurve generated from the accelerometers confirms this strange event - 650 N off the pad, rising to 800 N at 1/4 sec, then falling to 700 at 1/2 sec in, then abruptly dropping to ~60 N at 0.6 sec and maintaing that for about 1/2 sec for a total of ~1.05 sec burn. Nothing like the nice even 1 sec ~550 N burn that is published for the I540. Also, I calculated the total mpulse from the thrustcurve I created and it was only around 475 N-s.

Any ideas what caused this? Should I have glued the grains in?


Additionally, despite having set it to ignore the pressure sensor on ascent, the accel data shows the XTRA fires the apogee charge after only 9 seconds of coast at ~380mph. Because of this it only reached around ~9,500 feet. Looking at the sims it should have coasted for around 20 seconds, and at 9 secs of coast it shows the rocket around 10,000 ft, so if it had continued up I think it would have easily reached 11-12,000'.

Overall though, I am very happy. It flew great, and was successfully recoverd intact - and that's all that really matters in the end! Also, I got to see some awesome flights by others with motors much larger than I've ever seen before in person, so that made the 5 hour drive well worth it as well! Pictures, video and data to come in the next few days, I've got a lot!
Click to expand...

You should not have disabled the barometric sensor on ascent. That is the cause of the inaccurate deployment. It has a Kalman filter so it ignores the transient from the Mach transition.

It would not, however, ignore the unchanging altitude of a sealed avionics bay, which is what that feature is for. I may have mentioned this before...
 
Link to one pic I managed to upload from my phone:
https://flic.kr/p/psph25

So does anyoneknow why the motor burned much faster than it should have? A peak of 800N or possibly more (maxed out at sensor @105g) for a commercial motor with a peak of barely 600N doesn't just seem like a normal variation due to manufacturing tolerances. Also, it only produced about 70% of its listed impulse, around ~460N-s versus the listed 635N-s. There was huge drop in thrust from over 600N to ~60N at 0.6 sec into the burn; in the videos there is a very audible pop that corresponds to this. Could it have spit a grain or something due to the crazy acceleration it experienced? Could something like this really make it lose ~175N-s of impulse?

The extremly early apogee deployment (9 sec versus simulated 20+) is weird because the accelerometer data says it was still going 380mph when it sensed apogee. If the baro sensor was disabled it should have been using the accel data for detecting apogee, and why would it sense apogee if it knew it was still traveling at 380mph?
 
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1) It sounds like you spit the nozzle at 0.6s into your burn. If the nozzle was spit out, the motor is no longer pressurized, so the thrust and delivered Isp go way down. Did you bond the grains into the liner?

2) Why did you disable the baro sensor on the way up? The AIM has a Kalman filter that allows it to ignore bogus barometric pressure data such as supersonic shock pressure. Apogee detection via accelerometer is very very difficult to do correctly.
 
Coleman,,
With everything you're saying...
And the EXTREME - SEVERE coolness of that flight,,
there is only one option......

Do over.......................

Teddy
 
Did you sim the flight and did you read the altimeter manual and understand how the altimeter handles out or range data before this flight? I don't think so.......

The GPS will loose lock under high acceleration and the barometric altimeter will give incorrect pressure altitudes during supersonic flight so the only data available to determine the motor performance is the accelerometer data. but your flight exceeded the range of the sensor, so all bets are off when you perform the thrust curve analysis with invalid/incomplete data.......

Garbage in provides garbage out........which is what you got and you didn't recognize it.

Bob
 
Coleman, that was a fantastic flight! Glad I got to see it! did you have any luck finding the pink panther?
 
Coleman,

I to have an Aim Extra. Care to share what you are using to create a thrust curve from the accelerometer data? A spreadsheet perhaps?

Ben
 
CarVac said:
You should not have disabled the barometric sensor on ascent. That is the cause of the inaccurate deployment.
Click to expand...

Could you elaborate on why that is the cause of the inaccurate deployment? Thank you.


bobkrech said:
Did you sim the flight and did you read the altimeter manual and understand how the altimeter handles out or range data before this flight? I don't think so.......

Bob
Click to expand...

I have read through the Aim XTRA's manuals (plural because there is more than one version) but I do not remember seeing anything about what happens if you exceed the specification ratings for a given sensor. Perhaps you know where it states that and in which version (if not all)? Thank you.
 
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ben said:
Coleman,

I to have an Aim Extra. Care to share what you are using to create a thrust curve from the accelerometer data? A spreadsheet perhaps?

Ben
Click to expand...

I used an excel spread sheet. Force= Mass * acceleration, so weight of rocket * acceleration in G's * 9.8 = thrust in newtons. Total impulse is area under the curve, I used a Riemann sum - basically finding the sum of the areas of lots of rectangles, each with a base of the time step of the data, and height the data value. I tired using the trapezoidal method for more accuracy but it yielded nearly identical results so I just used the simpler right Riemann sum (RRAM).
Since 30% of the rockets mass is propellant, I did add in a function that subtracted the weight of the burned propellant over time - with a burn of 0.6 sec and 65 data values, I subtracted 1/65 of the propellant mass for every new data value. A rough approximation, but the thrustcurve was pretty linear over the 0.6 sec so it should work OK.

bobkrech said:
Did you sim the flight and did you read the altimeter manual and understand how the altimeter handles out or range data before this flight? I don't think so.......

The GPS will loose lock under high acceleration and the barometric altimeter will give incorrect pressure altitudes during supersonic flight so the only data available to determine the motor performance is the accelerometer data. but your flight exceeded the range of the sensor, so all bets are off when you perform the thrust curve analysis with invalid/incomplete data.......

Garbage in provides garbage out........which is what you got and you didn't recognize it.

Bob
Click to expand...

First off, I have read through the manual and saw no mention of how it handles out of range data. i disabled the Bari sensor because my av bay was mostly sealed, mostly because to vent it properly I would have needed vent holes in the NC and personally I didn't want Mach 2+ air flowing directly into my av bay.
Second, of course I ran many many simulations. With the I540 he simulated acceleration was ~80G's - well within the 105 G limit. There was no reason to suspect the rocket would accelerate more than 30% faster than simmed - it is a commercial motor, and shouldn't have that large of a variance in performance.

Sorry I may have been a bit misleading in that it only exceded 105 G for less than 0.1 of a sec, so it hardly affects the data at all. Even if it exceeded 105 g by 20 G's (which it very likely didn't based upon the data before and after the 0.1 sec) over 0.1 sec that's (0.1s)*(20G)*(9.8)*(0.89kg)=17.44 N-s, which still leaves the motor performance missing 150 N-sec. Definetly not garbage data.

My main question was why it acted so differently than the published thrustcurve. When I get home I tonight I will attach both my thrustcurve and the CTI Published one to show the large discrepancy.





Lastly, about the early deployment. I understand that doing it via accelerometer is not always very accurate, but it shouldn't be an order of magnitude off. It doesn't explain why the altimeter would sense apogee by only using the accelerometer when the same acclerometer sensor is saying the rocket is moving at 380 mph..... Shouldn't the logic be "apogee is reached when velocity=0" or when "vertical acceleration=0"? And wouldn't the error caused by the accelerometer assuming the rocket is perfectly vertical cause a late deployment, not an early one?
 
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RKeller said:
Coleman, that was a fantastic flight! Glad I got to see it! did you have any luck finding the pink panther?
Click to expand...

Thanks! Unfortunately I never found the Pink Panther, never got even a peep out of the BRB transmitter except for during the flight. My guess is either it landed in water and shorted the tracker (unlikely) or the CTI ejection charge failed and it came in ballistic, destroying the rocket and tracker (also unlikely, I haven't had nor seen a non-VMAX ejection charge fail to ignite). Weird! I'll just have to make a new and better one! :)

onebadhawk said:
Coleman,,
With everything you're saying...
And the EXTREME - SEVERE coolness of that flight,,
there is only one option......

Do over.......................

Teddy
Click to expand...

Good idea! ;)
 
A5tr0 An0n said:
Could you elaborate on why that is the cause of the inaccurate deployment? Thank you.




I have read through the Aim XTRA's manuals (plural because there is more than one version) but I do not remember seeing anything about what happens if you exceed the specification ratings for a given sensor. Perhaps you know where it states that and in which version (if not all)? Thank you.
Click to expand...

Because the baro sensor was completely disabled on ascent, and the GPS is pretty hopeless under extreme acceleration such as this flight, its only estimate of the state of the rocket (e.g. velocity and altitude) during ascent comes from the accelerometer.

The accelerometer clipped, so we KNOW that the deployment couldn't possibly have been at the right time.
 
CarVac said:
Because the baro sensor was completely disabled on ascent, and the GPS is pretty hopeless under extreme acceleration such as this flight, its only estimate of the state of the rocket (e.g. velocity and altitude) during ascent comes from the accelerometer.

The accelerometer clipped, so we KNOW that the deployment couldn't possibly have been at the right time.
Click to expand...

Yes baro is out of the question but the board still has two other options for detecting apogee, accelerometer and GPS. Yes the GPS is not an option during the high acceleration but by time the vehicle was at the deployment altitude I would be surprised if it had not regained lock, especially seeing as the vehicle was costing for ~9 secs and only traveling at ~380mph. I doubt at this point in the flight the acceleration was too high for the XTRA's GPS. The AIM XTRA is relatively good and quick at regaining GPS lock and that is based off personal experience and others.

In regards to the accelerometer I am curious if that contributed to any fault. As stated it was exceeded for a very short time (~0.1s) so assuming the board still functions properly after a limit has been exceeded then he would of had 2 methods for apogee detection. Maybe you know from your experiences working with Gary and/or Entacore what happens with the board after a limit is reached but I have yet to find where it states anything related to it?


P.S. Please be aware that I made the assumption that GPS lock was regained and that the board functions properly after a limit is reached.
 
Here is the velocity and acceleration graph; it ends just before 10 seconds - when the apogee charge was fired - notice it is still moving very quickly, and clearly not at apogee. Why would it think it was based off of this data?

Untitled3.jpg

Simulation Plot. Notice the time to apogee - over 22 seconds.

Motion Vs. Time.png

Motor thrust curve, compare this to the published thrust curve for the CTI I540 below it - very different! Total calculated impulse was 469 N-s, well below the published 635 N-s, even if it is a slight underestimate due to maxing the accelerometer for 0.1 secs.

Untitled4.png

simfile1398_1000x600n.png

GPS Plot:
I540-gpspic.jpg
 
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Coleman I'm really proud of you....
I'm not kiddin....
This flight was a very serious technical undertaking,,,,
Not only did you finally do it,,,
as far as I'm concerned it was a total success....
So many more things could have gone wrong,,
and wrong enough for you to not have the rocket back....

You have the rocket back,,, intact,,,, after a M2+ flight !!!!!!!!!!!!!!!!!
On an I motor !!!!!!!!!!!!

Good for you Coleman,,,,
I really am proud of you.....
VERY well done...........

And with everything that's happened,,,,
It's not a joke,,,,

I call do over........................

Teddy
 
RocketHunter said:
Here is the velocity and acceleration graph; it ends just before 10 seconds - when the apogee charge was fired - notice it is still moving very quickly, and clearly not at apogee. Why would it think it was based off of this data?

View attachment 185700

Simulation Plot. Notice the time to apogee - over 22 seconds.

View attachment 185703

Motor thrust curve, compare this to the published thrust curve for the CTI I540 below it - very different! Total calculated impulse was 469 N-s, well below the published 635 N-s, even if it is a slight underestimate due to maxing the accelerometer for 0.1 secs.

View attachment 185701

View attachment 185708

GPS Plot:
View attachment 185699
Click to expand...

The user interface might be computing the velocity based on all the data including the barometric sensor, while the deployment ignored the pressure as you instructed.

I remember that you can turn the filtering on and off in the ui, so that might be the case.
 
Consider that the flight was far from vertical. The same thing occurred with my Mongoose 54, although the altimeter that popped the charge was a barometric.

550 mph deployments do wonders on 1/4" Kevlar.

Mongoose_54_Apogee_Screen_shot_apogee.jpg
 
RocketHunter said:
First off, I have read through the manual and saw no mention of how it handles out of range data. i disabled the Bari sensor because my av bay was mostly sealed, mostly because to vent it properly I would have needed vent holes in the NC and personally I didn't want Mach 2+ air flowing directly into my av bay.
Second, of course I ran many many simulations. With the I540 he simulated acceleration was ~80G's - well within the 105 G limit. There was no reason to suspect the rocket would accelerate more than 30% faster than simmed - it is a commercial motor, and shouldn't have that large of a variance in performance.

Sorry I may have been a bit misleading in that it only exceded 105 G for less than 0.1 of a sec, so it hardly affects the data at all. Even if it exceeded 105 g by 20 G's (which it very likely didn't based upon the data before and after the 0.1 sec) over 0.1 sec that's (0.1s)*(20G)*(9.8)*(0.89kg)=17.44 N-s, which still leaves the motor performance missing 150 N-sec. Definetly not garbage data.

My main question was why it acted so differently than the published thrustcurve. When I get home I tonight I will attach both my thrustcurve and the CTI Published one to show the large discrepancy.

Lastly, about the early deployment. I understand that doing it via accelerometer is not always very accurate, but it shouldn't be an order of magnitude off. It doesn't explain why the altimeter would sense apogee by only using the accelerometer when the same acclerometer sensor is saying the rocket is moving at 380 mph..... Shouldn't the logic be "apogee is reached when velocity=0" or when "vertical acceleration=0"? And wouldn't the error caused by the accelerometer assuming the rocket is perfectly vertical cause a late deployment, not an early one?
Click to expand...

A saturated digital sensor tends to give the max output value. It's pretty much like the clipping phenomenon you might see on an oscilloscope.

I agree with onebadhawk--you did an awesome job with this!
 
RocketHunter said:
Motor thrust curve, compare this to the published thrust curve for the CTI I540 below it - very different! Total calculated impulse was 469 N-s, well below the published 635 N-s, even if it is a slight underestimate due to maxing the accelerometer for 0.1 secs.
Click to expand...

I haven't analyzed your data in detail, but in calculating the N-s from your acceleration data, don't you need to account for drag? Perhaps this is why you're coming up low.

I don't know why the motor burned so fast. If all of the N-s were delivered in 0.6 seconds instead of 1.1 seconds, then your acceleration would have been above the capability of the altimeter. If the acceleration reported during the first 0.6 seconds is low, then your apogee prediction would have been early.

Sorry if I'm barking up the wrong tree here, but you should clearly try this flight again. I'd do it with an altimeter having a hardware-based mach lockout, such as a MAWD or HA45 or RRC2 mini. Just put the vents through the nosecone shoulder.

Jim
 
RocketHunter said:
I used an excel spread sheet. Force= Mass * acceleration, so weight of rocket * acceleration in G's * 9.8 = thrust in newtons. Total impulse is area under the curve, I used a Riemann sum - basically finding the sum of the areas of lots of rectangles, each with a base of the time step of the data, and height the data value. I tired using the trapezoidal method for more accuracy but it yielded nearly identical results so I just used the simpler right Riemann sum (RRAM).
Since 30% of the rockets mass is propellant, I did add in a function that subtracted the weight of the burned propellant over time - with a burn of 0.6 sec and 65 data values, I subtracted 1/65 of the propellant mass for every new data value. A rough approximation, but the thrustcurve was pretty linear over the 0.6 sec so it should work OK.



First off, I have read through the manual and saw no mention of how it handles out of range data. i disabled the Bari sensor because my av bay was mostly sealed, mostly because to vent it properly I would have needed vent holes in the NC and personally I didn't want Mach 2+ air flowing directly into my av bay.
Second, of course I ran many many simulations. With the I540 he simulated acceleration was ~80G's - well within the 105 G limit. There was no reason to suspect the rocket would accelerate more than 30% faster than simmed - it is a commercial motor, and shouldn't have that large of a variance in performance.

Sorry I may have been a bit misleading in that it only exceded 105 G for less than 0.1 of a sec, so it hardly affects the data at all. Even if it exceeded 105 g by 20 G's (which it very likely didn't based upon the data before and after the 0.1 sec) over 0.1 sec that's (0.1s)*(20G)*(9.8)*(0.89kg)=17.44 N-s, which still leaves the motor performance missing 150 N-sec. Definetly not garbage data.

My main question was why it acted so differently than the published thrustcurve. When I get home I tonight I will attach both my thrustcurve and the CTI Published one to show the large discrepancy.





Lastly, about the early deployment. I understand that doing it via accelerometer is not always very accurate, but it shouldn't be an order of magnitude off. It doesn't explain why the altimeter would sense apogee by only using the accelerometer when the same acclerometer sensor is saying the rocket is moving at 380 mph..... Shouldn't the logic be "apogee is reached when velocity=0" or when "vertical acceleration=0"? And wouldn't the error caused by the accelerometer assuming the rocket is perfectly vertical cause a late deployment, not an early one?
Click to expand...
You have a lot of conflicting data. Your simulations certainly predicts a much longer coast to apogee, and I would agree that the I540 should have quite a different performance than you believe you obtained, so we have to look at what physical observables you have to describe the discrepancies.

1.) A suggestion was made that you spit or split the nozzle. Was there a nozzle in the motor when you recovered it and what did it look like?

2.) How hot was the air temperature, and the propellant? The propellant burn rate is temperature dependent, and if the rocket was sitting out in the sun for a long period of time, the propellant could have gotten quite hot, substantially hotter than the air temperature. Hot propellant burns much faster than cold propellant, providing more thrust and higher chamber pressure. If your motor did spit out a nozzle at 0.66 seconds, then the behavior of your derived thrust curve could be correct.

3.) A comment was made about the flight being highly non-vertical. Yes, No maybe so? Did anyone make a video of the flight? Depending on exactly how the velocity/altitude data is processed and the attitude/trajectory of the rocket was during the flight, you could have reached vertical apogee and still had a 380 mph horizontal speed.

4.) Did the rocket go unstable during the flight? Did it tumble around? Where is the rest of the data for the flight? Unless the rocket/data system was destroyed, there should have been data beyond the first 10 seconds of the flight. You should have linear and 3D accelerometer, 3D gyro and 3 G magnetometer and the GPS data. What did that look like?

If there is indeed more flight data available, we can probably figure out what happened.

Bob
 
Here is a picture of the flight Bob, does appear to have strayed away from 90.

15394976022_190b73f584_c.jpg
 
JimJarvis50 said:
your acceleration would have been above the capability of the altimeter. If the acceleration reported during the first 0.6 seconds is low, then your apogee prediction would have been early.
Jim
Click to expand...

What i've been trying to get at is that while apogee detection may be early in real life, per what the sensor sees shouldn't it be 100% accurate?

The GPS did not have lock until after apogee, so the only sensor affecting deployment was the accelerometers.

Look at the acceleration curve from the I540 flight. The crazy noise to the right is the high-speed deployment. It senses apogee when vertical acceleration= -1 G.

I540-accel.png

Now look at two previous flights i have had with the XTRA - again the crazy spikes to the right are deployment. here, apogee is when vertical acceleration= ~0, which makes sense - the rocket is horizontal at apogee, so no vertical acceleration.

H170-accel.png

h100-accel.png

So why on the I540 flight did it predict apogee when the acceleration= -1 G, versus acceleration= 0 G for every other flight I've flown with the XTRA?

Also, these two other flights did use the baro sensor for apogee. Looking at the velocity plots generated from the accel data for these flights, the velocity was around 10-20 m/s at deployment, meaning if instead the accelerometer sensor had been used to determine apogee (when velocity=0), the accelerometer deployment would have actually been late - the opposite of what happened with the I540.
 
RocketHunter said:
What i've been trying to get at is that while apogee detection may be early in real life, per what the sensor sees shouldn't it be 100% accurate?

The GPS did not have lock until after apogee, so the only sensor affecting deployment was the accelerometers.

Look at the acceleration curve from the I540 flight. The crazy noise to the right is the high-speed deployment. It senses apogee when vertical acceleration= -1 G.

Now look at two previous flights i have had with the XTRA - again the crazy spikes to the right are deployment. here, apogee is when vertical acceleration= ~0, which makes sense - the rocket is horizontal at apogee, so no vertical acceleration.

So why on the I540 flight did it predict apogee when the acceleration= -1 G, versus acceleration= 0 G for every other flight I've flown with the XTRA?

Also, these two other flights did use the baro sensor for apogee. Looking at the velocity plots generated from the accel data for these flights, the velocity was around 10-20 m/s at deployment, meaning if instead the accelerometer sensor had been used to determine apogee (when velocity=0), the accelerometer deployment would have actually been late - the opposite of what happened with the I540.
Click to expand...

One thing you can do is check the math for your altimeter. You simply calculate the time-weighted acceleration where acceleration is positive and the time-weighted acceleration where acceleration is negative. Zero velocity occurs when these quantities are equal (at least, that's what the altimeter thinks is zero velocity). If these values are equal for your flight, then the math is being done correctly. And then, if the positive part of the time-weighted acceleration is low because the sensor was maxed out, the altimeter would calculate zero velocity too early and you would get an early deployment.

On the other hand, if the graph you posted previously (with the red and blue curves) was from the altimeter, and the altimeter "thought" the velocity was still 380 mph, then I don't know why it would have fired a charge.

Edit - ... and the reading was still -1G's because the rocket was still traveling fast, with drag generating a -1G acceleration.

Jim
 
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bobkrech said:
You have a lot of conflicting data. Your simulations certainly predicts a much longer coast to apogee, and I would agree that the I540 should have quite a different performance than you believe you obtained, so we have to look at what physical observables you have to describe the discrepancies.

1.) A suggestion was made that you spit or split the nozzle. Was there a nozzle in the motor when you recovered it and what did it look like?

2.) How hot was the air temperature, and the propellant? The propellant burn rate is temperature dependent, and if the rocket was sitting out in the sun for a long period of time, the propellant could have gotten quite hot, substantially hotter than the air temperature. Hot propellant burns much faster than cold propellant, providing more thrust and higher chamber pressure. If your motor did spit out a nozzle at 0.66 seconds, then the behavior of your derived thrust curve could be correct.

3.) A comment was made about the flight being highly non-vertical. Yes, No maybe so? Did anyone make a video of the flight? Depending on exactly how the velocity/altitude data is processed and the attitude/trajectory of the rocket was during the flight, you could have reached vertical apogee and still had a 380 mph horizontal speed.

4.) Did the rocket go unstable during the flight? Did it tumble around? Where is the rest of the data for the flight? Unless the rocket/data system was destroyed, there should have been data beyond the first 10 seconds of the flight. You should have linear and 3D accelerometer, 3D gyro and 3 G magnetometer and the GPS data. What did that look like?

If there is indeed more flight data available, we can probably figure out what happened.

Bob
Click to expand...

1. The nozzle was still there but very pitted and with small pieces missing from the edges. Just took out the liner, and was surprised at what I found:

Photo Sep 30, 3 46 38 PM.jpg

Photo Sep 30, 3 43 26 PM.jpg

2. According to the XTRA housed in the (black) NC the rocket was around 95 degrees fahrenheit at launch. It did not sit out at the pads in the sun for very long.

3. Yes it was definitely not vertical. But I still cannot grasp how with only the accelerometers it would know it reached apogee while going 380 mph - the vertical velocity has to equal 0 at some point - for a vertical flight this is apogee, for a non-vertical this is after apogee.


[video=youtube_share;L12TkX1RGXw]https://youtu.be/L12TkX1RGXw[/video]

4. No it was completely stable all through the burn, other than hooking a right out of the tower . It was recovered fine, I just didn't link all the data because there is soooo much, and including the entire flight makes seeing details about the burn/coast much harder. Here's a link to all the raw data, FYI launch was at ~709.95 seconds:

https://www.dropbox.com/s/g3jgdakguoybkhm/I540_raw-data.xls?dl=0


P.S. How cool is this...

Photo Sep 29, 4 04 06 PM (1).jpg
 
This is normal for the liners depending on the reload. I have been told most of the liner holes or shape change happens after motor burn out because of the heat still in the case. I have seen this a lot with my CTI reload flights.
 
JimJarvis50 said:
On the other hand, if the graph you posted previously (with the red and blue curves) was from the altimeter, and the altimeter "thought" the velocity was still 380 mph, then I don't know why it would have fired a charge.

Edit - ... and the reading was still -1G's because the rocket was still traveling fast, with drag generating a -1G acceleration.

Jim
Click to expand...

Exactly - the altimeter "thought" it was still moving at a high rate of speed, and yet it fired the apogee charge anyway. I will email David at entacore to inquire about how the accelerometer is used to sense apogee, he has been very helpful in the past.

JimJarvis50 said:
I haven't analyzed your data in detail, but in calculating the N-s from your acceleration data, don't you need to account for drag? Perhaps this is why you're coming up low.
Click to expand...

This may be the case, as the accelerometer measures net force, and the thrust would equal the Net Force + Drag Force.

Looking at Openrocket, the drag force increases sort of linearly from 0 N to 130 N at max speed. Using this, the loss of impulse due to drag would be roughly 65 N-sec (and this is a bit generous). Adding this to the total impulse I calculated before, 469 N-sec, and adding in the maximum feasible losses due to the maxed sensor for 0.1 sec (17 N-s) I get 548 N-s which still leaves me short of 635 N-sec.

Overall though I care less about this and more why it burned so extremely fast. Accounting for drag forces means the thrust curve I posted earlier has overall lower thrust than the actual motor put out, meaning it could have possibly produced almost 900 Newtons of peak thrust - 50% more than the published thrust curve.

onebadhawk said:
Coleman I'm really proud of you....
I'm not kiddin....
This flight was a very serious technical undertaking,,,,
Not only did you finally do it,,,
as far as I'm concerned it was a total success....
So many more things could have gone wrong,,
and wrong enough for you to not have the rocket back....

You have the rocket back,,, intact,,,, after a M2+ flight !!!!!!!!!!!!!!!!!
On an I motor !!!!!!!!!!!!

Good for you Coleman,,,,
I really am proud of you.....
VERY well done...........

And with everything that's happened,,,,
It's not a joke,,,,

I call do over........................

Teddy
Click to expand...

Thank you teddy, thats exactly how I feel, I'm just glad it flew stable, held together, and that I recovered it intact! You know, I do have a second I540 thats waiting to fly.... ;)
 

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