L. Paul Verhage KD4STH
I'm trying to figure out what altitude Mike and my's flight reached. I've attached a spreadsheet of calculations based on the limited data we have and I attached a screen print of the a packet received during descent from APRS.fi.
The ascent rate for the first 16,000 feet is known from the APRS data. It's either 1,215 fpm if the first ascent record is an outlier or its 1,181 if the first ascent calculation isn't an outlier. I made an assumption the balloon would slow down by 25% at either 40,000 or 50,000 feet.
The time of flight is estimated to 142 minutes, based on the number of pictures taken during the flight. We need to double check that calculation, because we know the balloon was at 16,639 feet on descent (and two miles away from landing).
At a 142 minute flight, the balloon reached between 135,000 and 1421,000 feet. At a 71 minute flight, the balloon reached between 73,000 and 77,000 feet.
The balloon was a Kaymont 3,000 g balloon and the payload weight was around 8 pounds. So the 140,000 foot flight sounds too high and the 71,000 foot flight sounds too low. Since it's a Kaymont balloon, I don't expect it to fail very early. But the descent packet at 16,639 feet makes sense and gives the balloon 50 minutes to descend 59,000 feet. However, the parachute is 5 feet across and porous (it's made from an old hot air balloon and nearly 20 years old with a lot of experience under its canopy). So it could have descended faster than 1,000 fpm.
Do we have wind data from that day and can we run a calculation on the flight assuming 1,200 fpm ascent, 76,000 foot burst, and 1,000 fpm descent and see if the balloon ends up close to its real landing site? As I recall, the higher the balloon ascended at GPSL, the farther west it landed. And this balloon landed farther southwest of any of my balloons that day (one of them reached into the 90,000 foot range).
Dr. L. Paul Verhage
Near Space Evangelist