i'm going to try and finally launch my own high altitude balloon HAB-SAT gadget!
demonstrate ability to continuously store and transmit basic telemetry, including
Temperature inside package
Temperature outside package
from 10 minutes before launch to 1 hour after landing;
reach Tropopause (~15km altitude) and observe subsequent increase in temperature;
Primary system: Adafruit 433 MHz RFM96 / M0 Feather, PA1010D GPS receiver, 2x BME680 pressure/temp sensor
Backup system: SPOT Trace satellite GPS tracker
POWER BUDGET -- conservative
2x Energizer Ultimate Lithium AA battery -- 4000mAh combined, at -40F
RFM96 transmit current / duty cycle: 125mA / 6%
GPS tracking current / duty cycle: 30mA / ?%
Monopole TX antenna gain: +3dBi
Free space path loss at 50km: 120dB
Yagi RX antenna gain: +7dBi
RFM96 RX sensitivity: -148dBm
Margin: +2dB ... real close ...
-> basically if the total mass of the flying thing is less than 4 pounds (1814 grams) then these rules don't apply to us, although it is still good practice to call the nearest air traffic control and tell them the predicted flight path
MASS BUDGET -- conservative
-> Takeaway summarized in graph below (using Hwoyee brand balloon specs) (plot code)
I think we can get away with a 300g balloon and about 50 cu.ft. of helium.
Lowkey I might just buy a couple of these little 55 cu.ft. tanks from a welding supply shop.