Charles_McG
Ciderwright
Meet my 1/5 scale Ute Tomahawk. I’ve written about it elsewhere. It has a 38mm mount in the booster and 29mm in the sustainer. It has an Eggtimer Proton in the Tomahawk avbay and an Eggfinder Mini in the nosecone.
It’s had two flights, and I’d like to share my data.
First - she flies easy and straight and I can’t believe that I seem to be the first to talk about this design in 40 years. The Bid Daddy derived booster would fit a 2 grain - but the 1 grain motors make a nice staging altitude.
I’m keeping the flight numbers on the Proton.
Flight 5 was a CTI G78bs to E22ss.
The blue lines are from the Proton, the red lines from OpenRocket (timing adjusted to match the flight) Events picked out for LDA and Channel 2 (separation) and Channel 1 (airstart). First 4 seconds plotted.
Altitude and acceleration.
Altitude and velocity.
Flight 6 was a CTI G115wt to Aerotech F10. Because I -really- wanted to see a long burn sustainer. 8 seconds is awesome- and probably 4 seconds too far into the gravity turn.
Alt and acc
Alt and velocity.
Now, my first thought was that the accelerometer based altitude (Altaccel) was really low. Since it ignores angle, it should read higher than the baro, and it doesn’t. It must be reading a little low, because it reaches apogee several seconds before the baro does. But I’m more concerned with using it as another form of ‘tilt’ detection.
Actually, my first thought was ‘look at those awesome thrust curves and nice velocity data.
Then I merged in the OR data and saw that it actually matched the accelerometer Gs and velocity pretty well. It’s the baro that looks high, at least until a few seconds after burns are done.
Here’s both flights together.
I suspect that I don’t have good isolation from the base of the rocket to the avbay. Though that doesn’t explain the high baro before separation.
That high baro that slowly returns to the main curve throws a twist into the first derivative (velocity) too.
It will help me set the safety limits in the future, though I still don’t understand what’s going on well enough to try the baro-accelerometer deviation limit. That 100-200’ difference at separation and airstart still has me scratching my head.
It’s had two flights, and I’d like to share my data.
First - she flies easy and straight and I can’t believe that I seem to be the first to talk about this design in 40 years. The Bid Daddy derived booster would fit a 2 grain - but the 1 grain motors make a nice staging altitude.
I’m keeping the flight numbers on the Proton.
Flight 5 was a CTI G78bs to E22ss.
The blue lines are from the Proton, the red lines from OpenRocket (timing adjusted to match the flight) Events picked out for LDA and Channel 2 (separation) and Channel 1 (airstart). First 4 seconds plotted.
Altitude and acceleration.
Altitude and velocity.
Flight 6 was a CTI G115wt to Aerotech F10. Because I -really- wanted to see a long burn sustainer. 8 seconds is awesome- and probably 4 seconds too far into the gravity turn.
Alt and acc
Alt and velocity.
Now, my first thought was that the accelerometer based altitude (Altaccel) was really low. Since it ignores angle, it should read higher than the baro, and it doesn’t. It must be reading a little low, because it reaches apogee several seconds before the baro does. But I’m more concerned with using it as another form of ‘tilt’ detection.
Actually, my first thought was ‘look at those awesome thrust curves and nice velocity data.
Then I merged in the OR data and saw that it actually matched the accelerometer Gs and velocity pretty well. It’s the baro that looks high, at least until a few seconds after burns are done.
Here’s both flights together.
I suspect that I don’t have good isolation from the base of the rocket to the avbay. Though that doesn’t explain the high baro before separation.
That high baro that slowly returns to the main curve throws a twist into the first derivative (velocity) too.
It will help me set the safety limits in the future, though I still don’t understand what’s going on well enough to try the baro-accelerometer deviation limit. That 100-200’ difference at separation and airstart still has me scratching my head.
