Bartold-4 released @ 10:09am, 10/12/23

Sienkowski-11 released @ 10:05am, 7/8/23

Current location:

• altitude 19156 ft

• Port Huron, Michigan / Sarnia (We're in Canada!)

• aprs.fi – live APRS map 

Bartold-3 Stats!

Bartold-3:

• flew 59 miles ESE from its launch point for 181 minutes to its touchdown in Lake Erie.

• guested to a max speed of 41 knots.

• soared to a max altitude of 23,782 feet (per GPS, with an estimated max of 24,400 feet).

• emitted 83 data packets, 70 of which were received by an APRS gateway station.

• broke its longest stretch of radio silence of 50 minutes after crossing Lake Saint Clair.

• broadcasted to 7 stations of a distance more than 20 miles, with the furthest hearing Bartold-3 over 116 miles away!

Flight status: Success!

Flight analysis

Bartold-3 flew 59 miles from our launch site across Lake Saint Clair, through Canada, and into its watery resting place of Lake Erie, reporting a peak altitude of 23,782 feet!

It reached a max speed of 41 knots (47 mph).

During the flight, Bartold-3 encountered 50 minutes of radio silence over Lake Saint Clair and Canada, after which, it began its SUD (Slow Unscheduled Descent).

2023-06-10 10:46:37 EDT: N8EPK-11>VA3APW-3:/144632h4230.40N/08255.60WO116/016/A=007774 018TxC  10.10C  759.99hPa  5.02V 06S

2023-06-10 11:40:13 EDT: N8EPK-11>METMOR:/154008h4217.79N/08234.63WO129/038/A=023782 019TxC -17.00C  400.76hPa  5.05V 05S

It reported its maximum altitude of 23,782 feet (as determined by GPS) after approximately 50 minutes of silence. Thereafter, it reported its slow descent over the course of 102 minutes with a final transmission of:

2023-06-10 13:22:51 EDT: N8EPK-11>W8QT-1:/172246h4202.45N/08203.33WO057/011/A=000917 083TxC  23.30C  976.71hPa  5.13V 10S

Max Altitude

Looking at the ~20 minutes of flight before radio silence, we can see an approximate linear gain in altitude at a rate of 325 ft / minute.

A period of 54 minutes of radio silence could result in a gain of 17,550 feet on top of its elevation of 7775 feet, resulting in an expected altitude of 25,325 feet! 

This closely aligns with the reported maximum altitude of 23,782 feet while allowing for one of the balloons to pop or deflate enough to jostle the radio back into transmission!

If we approximate the descent with a linear rate of 225 ft/minute, and solving for the intersection of the ascent and descent lines we arrive at a maximum height of 24,400 ft after 64 minutes into the launch!

Estimating coefficient of air resistance during descent:

Bartold-3 descended 23,000 feet in 104 minutes.

We don't know if one balloon popped, or two, so let's do the calculation for both, and estimate which seems more acccurate.

Our balloon had about 40 grams of free lift prior to launch, and with a lopsided fill, let's assume a split of +15g and +25g.

If the balloon with more lift popped, it would have a net weight of 23g:

18g (electronics) + 20g (popped balloon) - 15g free lift = 23g

If both balloons popped, the net weight would be 58g:

18g (electronics) + 2*20g (popped balloons) = 58g

Plugging all of this into an online air resistance calculator, this gives coefficients of about 0.44 (if both popped), and 0.18 (if one popped).

A sanity check, that our falling object (consisting of small electronics and a foil mylar balloon or two) is neither perfectly spherical or hemispherical, and more similar to an airplane wing or the rough shape of car, suggests 0.18 is our coefficient of air resistance. This further suggests evidence for only one of the two balloons popping! 

(2nd sanity check: +40g of free lift takes 64 minutes to go up, so -58g of dead weight would likely take less time to go down moving through similar air)

10:25am, June-10th, 2023: Balloon Launched!

Scheduled to launch at 10:00am and delayed by 25minutes to ensure communications were functioning, Bartold-3 was released!

Current altitude is about 10,000ft and location is over Lake Erie.  

Some data points  here.

June-8th, 2023: T-41 hours