Just another question on the pressure holes. Where do you position them with regard to the pressure sensor?U.S. Water Rockets wrote:Hi Bob,blannoy wrote:Hi,
I just tested it again with higher pressure to start with. This time it worked every time for the three launches.
It seems that it opens quite a bit before apogee. I assume this is unavoidable. The flights were all very stable and there was barely any wind. Could this be due to the static pressure holes? I could put in a delay on the assumption that the starting pressure is always the same.
The reported altitude is way to high (usually 4 digits starting with 10 of 11, so I assume this to be around 1000 feet). Visually I would estimate the height around 60 to 70 meters but it's hard to guess.
Are you positive that the parachute is really deploying before apogee? This is something we have never seen in any testing. We spent a great deal of time working on that part of the code, and if anything it should be biased to being a fraction of a second after apogee, since the altitude is read at regular intervals and so the velocity would have to be zero or negative for a complete interval before the software could detect it. The algorithm is not predictive, because there's very limited memory in these low cost microcontroller boards.
It's possible that the pressure ports may need to be larger due to some unforeseen influence that we never encountered. Just as a guess, perhaps the pressure drops in the part of the rocket where you have the altimeter due to compression of the bottles during launch and the subsequent relaxation of the bottles as the rocket decelerates? This is just a speculation.
Is it possible that from your vantage point on the ground it simply looks to you like the rocket is still going up, but in reality it has stalled at apogee and you are seeing some sort of optical illusion that makes it look at though it is climbing?
The only way to know for sure would be to fly and onboard camera and see if you can hear the servo move before or after the rocket starts coming down.
We've never had one deploy early and we have probably over 100 videos of the altimeter during testing and 100 more videos of the altimeter being used for development of our Radial and Hybrid Deploy techniques. But anything is possible. We just don't know what you could be seeing.