uberpixel wrote:uberpixel wrote:
Will this work?
I wanted to provide an update that I had several successful deployments this weekend with my updated payload design.
It was very sunny however, and I did encounter the sunlight related false trigger several times. After putting a sunshade over the pressure sensor, everything worked perfectly!
This is just further confirmation that if you follow (all of) the instructions provided by USWR for this Altimeter (including the pressure port size recommendations and the sun-shade for the pressure sensor) it should work very consistently.
One other thing, my max altitude was reportedly 252 feet. This was somewhat disappointing since the simulator here (
http://polyplex.org/rockets/simulation/) predicted a flight of 445 feet for my 9.6L rocket @ 80psi. Not sure how my rocket may differ from the idealized design used for the simulator but there would appear to be either a significant discrepancy between my rocket and the ideal, or the altimeter is wrong. I just watched the latest video on USWR site showing the AlTImeter's performance vs. a commercial option to be very similar. That has me thinking that my rocket must deviate from the design assumptions used by the simulator or my pressure sensor is faulty. Maybe I'll try dropping a "Standard Altitude Marker" streamer to see if I can confirm the altitude.
-uberpixel
Thanks for the praise of our documentation and pointing people at the recommended setup. That's good to hear from a 3rd party launcher.
Regarding the altitude readings. There is a very good chance that the altitude is accurate. Wayyyyyyyy back when we first started launching, we were making FTC rockets that we simulated and thought we were going 700-800 feet high. We bought our first altimeter and launched it and were stunned to find out that the rocket was actually going 400 feet. It sure looked to use from the ground like 800 feet. The simulators were saying it went that high. The rocket was not cooperating.
We got a second altimeter from a different source, and while the two never agreed exactly, they were within 25 or 30 feet of one another and were in the 400 foot range. There will always be a little bit of error between two barometric altimeters unless you have really super tight controls on all variables (sunlight, wind, power supply, CPU oscillator calibration, etc. but the readings were showing the simulator and our calibrated eyeballs were way off.
What we did from that point on was to play with the drag coefficient and other simulator parameters until the simulator agreed with our launch, then we tried launching and simulating with different pressures and found that the simulator was a lot more accurate once we dialed in the exact drag coefficient of the rocket.
We also discovered that the simulator did not do a good job with restrictions to air flow like tornado tubes, even if they were above the water line. Those were hard to calibrate and tune out, so we stopped using rockets with multiple segments, because it hurts the max altitude.
Hopefully, you will be able to dial in your rocket simulator and get better matching results and then be able to work on improving the rocket apogee height maximum.
We enjoyed that part of the project as much as building the rockets. But we're weird like that!
Have fun!