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As a friend of mine likes to say: If its worth engineering it is worth over engineering. He has been working on his automated can crusher for at least 3 years.
I am interested in what makes the flights behave the way they do. That is why I wrote the prediction software. Back when Ron Meadows had a latex balloon make it to Morocco there was interest in making latex floaters. Soon after that the mylar pico balloons got popular and the latex floater interest died out.
As Bill pointed out most of the latex floaters have been big balloons. I think that is because the trackers were a lot heavier. Now with the pico trackers being used I would think smaller latex should work as Gur found out. One thing that I would like to understand is the amount of degradation UV actually does. Ron's balloon stayed up a week or more and I have had balloon shards that spent the summer in the AZ desert that seemed in pretty good shape. Maybe I should try some timed exposures in the desert and see if I can measure the change over time.
On Tuesday, June 25, 2019, 8:49:05 AM MST, Michael Hojnowski <kd2eat@...> wrote:
I wonder if all the "sciencing" is
overkill. Couldn't you just fly it like a standard pico. Give
yourself 5-10 grams free lift, let go, and walk away? It'll
either burst or it won't. Any less free lift than that is
untenable, so if it bursts, then floaters with latex would be an
unreliable thing for sure. If it works, then you can start
worrying about how long they last due to UV, etc.
Mike / KD2EAT
On 6/25/2019 11:08 AM, Joe WB9SBD wrote:
I have Jerry's data here
somewhere also. I'll also try to find it.
One thing I do remember tho, the differential was very very
small. Which makes total sense, if you do the math by taking
the tensile strength of the latex, and calculate what the
surface tension on that latex would be at it's failure point
the pressure differential is very small.
I remember when I did the calculations using the math way, it
came in like within 1% of what Jerry actually measured.
Near Space Sciences
30 years and 70 flights,,,
Rolling Ball Clock
On 6/25/2019 9:40 AM, Jerry via
I did some measurements on balloons that were discussed
on the list but never presented anything at gpsl. I flew
a flight with a differential pressure sensor on the
balloon and measured the pressure curve.
I'm still on the road after GPSL but will dig up what I
did when I get home next week.
On Tuesday, June 25, 2019, 5:13:04 AM MST, BASE_DePauw
I don't have a copy of the paper, but recall
James Flaten of U Minnesota talking about internal
and external pressure of a latex balloon back in
2011. Shortly before burst the internal pressure
exceeds the external. James thought that it could be
possible to use this difference to cut away from the
balloon just before burst to avoid post burst chaos.
My students and I talked about floating large
payloads at 20 km at GPSL2017 in Hutch.
On Tue, Jun 25, 2019, 12:27 AM Bill
Brown via Groups.Io <email@example.com
Empirically, I have planned quite a few
latex floater flights using lightweight
payloads and low free lift. My best success
has been with payloads under 2.5 pounds and
just a few ounces of positive lift. Less than
250 ft/min ascent rate can often achieve float
with lightweight payloads. However, the best
balloons to use for this are 1200 gram or
larger. NG0X managed to float a payload on a
1000 gram balloon. However, this balloon
(KD0VJI-11) was just a small 600 gram balloon.
But the total flight train weight was just
over 2 ounces with about 3 ounces of free lift
and it worked great, which is quite an
accomplishment for such a small balloon and an
amazing peak altitude for a 600 gram balloon
as well (101,430 feet).
But apparently the amount of lifting gas
was below the breaking force of the latex
until the UV radiation eventually degraded the
latex after a day or two.
There was a paper presented at GPSL a few
years ago describing this effect to predict
the success conditions for floating a latex
balloon measuring the internal pressure of the
balloon during flight. Does anyone remember
who gave that talk or have a copy of it?
- Bill WB8ELK
From: BASE_DePauw <hlbrooks@...
To: GPSL <GPSL@groups.io
Sent: Mon, Jun 24, 2019 9:19 am
Subject: Re: [GPSL] KD0VJI11 latex floater
over North Dakota Athens AL N4SEV11 floater
and PB0AHX1 floater with APRS and RTTY
in the balloon stretches like a
spring obeying Hooke's law. The
more that the balloon is stretched
the more force that is needed to
stretch it further. Additionally,
the spring constant for latex is
not constant, but actually
increases dramatically in the last
few centimeters of stretch before
the latex breaks (and the balloon
small amounts of lifting gas,
either hydrogen or helium, are in
a large balloon, there are not
enough gas molecules to exert the
required force to stretch the
balloon to the breaking point.
On Mon, Jun 24, 2019 at
12:04 AM Gur Lavie <gurlavie@...
Whats the physics behind a
Latex becoming a floater ?
Does it mean it was
completely “under” filled ?
Can this be intentionally
planned and launched ?
On Sun, 23 Jun
2019 at 22:10 Bill Brown via
flight. I believe this
is the smallest
balloon (600 gram) to
They are flying a
without the solar
panels but with a 4
AAA lithium battery
pack. It worked
through the entire
night at -50 deg C or
below and is still
doing great after 27
hours aloft. After the
foamcore, tape and
bubble wrap the
payload came in at 65
grams (about 2.3
ounces). They put 140
grams (about 5 ounces)
neck lift into the 600
gram latex balloon.
The ascent rate was
below 250 ft/min most
of the flight and it
floated around 101,000
feet. It is still
flying over North
Dakota and has made it
through mid-day so
also launched a
Skytracker from the
Athens AL Field Day
site this morning and
it is floating nicely
heading over central
TN at the moment
PB0AHX-1 is flying
over Germany at the
moment with a
Skytracker that I
modified to output 50
baud RTTY after the
transmission. You can
hear it on 145.300 MHz
via one of the many websdr.org
receivers in Europe.
I could hear it well
from a couple of
websdr radios in
western Germany this
From: Jim Reed <jim.reed@...
To: GPSL <GPSL@groups.io
Sent: Sun, Jun 23, 2019
Subject: [GPSL] Floater
- was not the plan
HAM radio club asked
us to put a balloon
they could track for
their field day. I
guess we messed up in
into a floater. It is
a 600 gram latex
balloon flying one of
Been floating for
about a day now at
100k. Kinda neat to
see the track.
thought I would share
for those that are
into that stuff.
Howard L. Brooks
Professor of Physics and Astronomy
241 Julian Science and Mathematics
602 S. College Street
Greencastle, IN 46135
Office: (765) 658-4653
FAX: (765) 658-4732