This page tracks Launch 4, planning in progress, a foil balloon launch.
Just the one: TTGO TBEAM
Three Energiser Lithium AAA's
Duration not tested!
36” Qualatex silver “foil” balloon
Approximate weight of 37g, approximate internal volume of 0.1cu m before envelope stretching.
This means they can lift payloads of approx. 60g (or slightly more if you allow for stretching). However experimenters typically aim for payloads of the order of 20 - 40g per balloon in order to attempt to make them float.
Total Payload Weight = ~60g
I looked through the data here: http://ukhas.org.uk/projects:microballoons:data?s=foil
and modified the predictor from here: http://ukhas.org.uk/_media/guides:burst3.xls
with a balloon weight of 37g and a burst diameter of about 0.70m for a 'if it bursts' flight.
Therefore, based on my 60g payload, to get an ascent rate of 1m/s = 4g free lift with a 71 min time to burst at 14,260ft. I assume a Descent rate of 5m/s.
Or I could use 2 balloons, to get an ascent rate of 1m/s = 5g free lift with a 267 min time to burst at 55,971ft. I assume a Descent rate of 5m/s.
Predictor based on Marston launch site here: http://predict.habhub.org/hourly/marston/ or anywhere http://habhub.org/predict/ or http://weather.uwyo.edu/upperair/balloon_traj.html (and KML viewer here: https://www.doogal.co.uk/KmlViewer.php)
Flight Document created http://habitat.habhub.org/genpayload/
Doc ID: XX Document: XX
Launching XX around XX a single tracker foil launch, from a site near Wellingborough (Northants).
Primary tracker: RFM22B based, $$HABTRK, 434.150Mhz (434138400 on my rx), USB, RTTY, 470Hz Shift, ASCII-7, 50 Baud, Parity none, 1 Stop bit
$$HABTRK, id, time, lat, lon, alt, sats, vinmv, rfm_temp.
Documentation is here: http://ukhas.org.uk/projects:jimbob:launch3