Date   
Re: GPSL 2020 dates

Mark Conner N9XTN
 

Not having worked Field Day in years, I had to go look to see what time it starts - 1800Z on Saturday. 

So far, most everyone either prefers the June date or has no preference.  June corn is shorter.  :)

- Mark

On Wed, Aug 7, 2019 at 1:32 PM Bill Brown via Groups.Io <wb8elk=aol.com@groups.io> wrote:
Either date works for me. If Field Day weekend is chosen maybe we can get a special FD credit arranged for FD balloon contacts through crossband or simplex repeaters or copying a special CW or digital message sent from a balloon. 

-Bill WB8ELK


On Aug 6, 2019, at 10:27 AM, Mark Conner N9XTN <mconner1@...> wrote:

Prospective GPSL 2020 attendees,

I'm starting to contact local venue providers on a GPSL 2020 location.  I have received a favorable response from University of Nebraska-Omaha and we may be able to use one of their auditoriums for the Friday sessions.  This would be the same location as the 2005 GPSL sessions for those of you who attended that year.

As mentioned previously, the usual Fathers' Day weekend date is not feasible for the Omaha area due to the College World Series.  The two alternatives that would work best are:
  • June 25-27, 2020
  • July 9-11, 2020
If your group has a strong preference for one of those dates, let me know either on or off-list by Friday, August 16th.  I would like to set a date with UNO before the end of the month so that we get the auditorium reserved.

73 de Mark N9XTN

Re: GPSL 2020 dates

Bill Brown
 

Either date works for me. If Field Day weekend is chosen maybe we can get a special FD credit arranged for FD balloon contacts through crossband or simplex repeaters or copying a special CW or digital message sent from a balloon. 

-Bill WB8ELK


On Aug 6, 2019, at 10:27 AM, Mark Conner N9XTN <mconner1@...> wrote:

Prospective GPSL 2020 attendees,

I'm starting to contact local venue providers on a GPSL 2020 location.  I have received a favorable response from University of Nebraska-Omaha and we may be able to use one of their auditoriums for the Friday sessions.  This would be the same location as the 2005 GPSL sessions for those of you who attended that year.

As mentioned previously, the usual Fathers' Day weekend date is not feasible for the Omaha area due to the College World Series.  The two alternatives that would work best are:
  • June 25-27, 2020
  • July 9-11, 2020
If your group has a strong preference for one of those dates, let me know either on or off-list by Friday, August 16th.  I would like to set a date with UNO before the end of the month so that we get the auditorium reserved.

73 de Mark N9XTN

Re: GPSL 2020 dates

Nick
 

Hi Mark,

 

The June 25-27 date is good with EOSS.

 

73,

Nick

NØLP

 

 

From: GPSL@groups.io <GPSL@groups.io> On Behalf Of Mark Conner N9XTN
Sent: Tuesday, August 6, 2019 9:27 AM
To: GPSL@groups.io
Subject: [GPSL] GPSL 2020 dates

 

Prospective GPSL 2020 attendees,

 

I'm starting to contact local venue providers on a GPSL 2020 location.  I have received a favorable response from University of Nebraska-Omaha and we may be able to use one of their auditoriums for the Friday sessions.  This would be the same location as the 2005 GPSL sessions for those of you who attended that year.

 

As mentioned previously, the usual Fathers' Day weekend date is not feasible for the Omaha area due to the College World Series.  The two alternatives that would work best are:

  • June 25-27, 2020
  • July 9-11, 2020

If your group has a strong preference for one of those dates, let me know either on or off-list by Friday, August 16th.  I would like to set a date with UNO before the end of the month so that we get the auditorium reserved.

 

73 de Mark N9XTN

 

Re: GPSL 2020 dates

L. Paul Verhage KD4STH
 

Either day will work for me. Thanks


On Tue, Aug 6, 2019, 9:27 AM Mark Conner N9XTN <mconner1@... wrote:
Prospective GPSL 2020 attendees,

I'm starting to contact local venue providers on a GPSL 2020 location.  I have received a favorable response from University of Nebraska-Omaha and we may be able to use one of their auditoriums for the Friday sessions.  This would be the same location as the 2005 GPSL sessions for those of you who attended that year.

As mentioned previously, the usual Fathers' Day weekend date is not feasible for the Omaha area due to the College World Series.  The two alternatives that would work best are:
  • June 25-27, 2020
  • July 9-11, 2020
If your group has a strong preference for one of those dates, let me know either on or off-list by Friday, August 16th.  I would like to set a date with UNO before the end of the month so that we get the auditorium reserved.

73 de Mark N9XTN

Re: GPSL 2020 dates

Mark Conner N9XTN
 

Zack W0ZC reminded me that the June 25-27 date is also Field Day weekend, so please consider that in your planning.  

73 de Mark N9XTN

On Tue, Aug 6, 2019 at 10:27 AM Mark Conner <mconner1@...> wrote:
Prospective GPSL 2020 attendees,

I'm starting to contact local venue providers on a GPSL 2020 location.  I have received a favorable response from University of Nebraska-Omaha and we may be able to use one of their auditoriums for the Friday sessions.  This would be the same location as the 2005 GPSL sessions for those of you who attended that year.

As mentioned previously, the usual Fathers' Day weekend date is not feasible for the Omaha area due to the College World Series.  The two alternatives that would work best are:
  • June 25-27, 2020
  • July 9-11, 2020
If your group has a strong preference for one of those dates, let me know either on or off-list by Friday, August 16th.  I would like to set a date with UNO before the end of the month so that we get the auditorium reserved.

73 de Mark N9XTN

Re: GPSL 2020 dates

Jeff Ducklow
 

Hi Mark -

Thank you for your efforts in organizing this.  I have not been able to attend since 2015 due to family commitments on father’s day weekend, so I’m looking forward to attending my second GPSL.  

My preference would be the June 25-27th date.

Thank you,

Jeff Ducklow
N0NQN

On Aug 6, 2019, at 10:27 AM, Mark Conner N9XTN <mconner1@...> wrote:

Prospective GPSL 2020 attendees,

I'm starting to contact local venue providers on a GPSL 2020 location.  I have received a favorable response from University of Nebraska-Omaha and we may be able to use one of their auditoriums for the Friday sessions.  This would be the same location as the 2005 GPSL sessions for those of you who attended that year.

As mentioned previously, the usual Fathers' Day weekend date is not feasible for the Omaha area due to the College World Series.  The two alternatives that would work best are:
  • June 25-27, 2020
  • July 9-11, 2020
If your group has a strong preference for one of those dates, let me know either on or off-list by Friday, August 16th.  I would like to set a date with UNO before the end of the month so that we get the auditorium reserved.

73 de Mark N9XTN


GPSL 2020 dates

Mark Conner N9XTN
 

Prospective GPSL 2020 attendees,

I'm starting to contact local venue providers on a GPSL 2020 location.  I have received a favorable response from University of Nebraska-Omaha and we may be able to use one of their auditoriums for the Friday sessions.  This would be the same location as the 2005 GPSL sessions for those of you who attended that year.

As mentioned previously, the usual Fathers' Day weekend date is not feasible for the Omaha area due to the College World Series.  The two alternatives that would work best are:
  • June 25-27, 2020
  • July 9-11, 2020
If your group has a strong preference for one of those dates, let me know either on or off-list by Friday, August 16th.  I would like to set a date with UNO before the end of the month so that we get the auditorium reserved.

73 de Mark N9XTN

Re: Lynqme?

Clif Brown
 

I ordered three of these off of Idegogo just over a year ago thinking they might be of use in HAB recovery.

I think originally they were promised in January, now they're quoting August.

This is usually a bad sign, but when (if?) I get them, I'll post a report here.

-Cliff
KW4CL

Re: Lynqme?

Joe WB9SBD
 

Or like milliwatts of TX power.

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 7/19/2019 12:55 PM, Garrett, Mark wrote:
Joe:

I did a search on the device and couldn't find what frequencies it uses.  Will have to go into the FCC site and search for it there.  Three miles is probably tops line of sight to the other device.

On Fri, Jul 19, 2019 at 11:30 AM Joe WB9SBD <nss@...> wrote:
In the video it talks about only a 3 mile range of coverage.

Joe WB9SBD

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 7/19/2019 11:13 AM, Garrett, Mark wrote:
Interesting device.  Might be worth the experiment if it does not shut down if it gets above say 60 K like some other GPS devices.  It would also be interesting to know its frequencies of operation and how it behaves if you get behind some terrain or down in a corn field.  

On Fri, Jul 19, 2019 at 10:15 AM Larry <larry.phegley@...> wrote:
Does anyone know anything about this or have any experience with it?


 Larry   KJ6PBS



--
Mark Garrett, KA9SZX
Tri States Public Radio




--
Mark Garrett
Tri States Public Radio
WIUM Macomb, IL
WIUW Warsaw, IL
WVKC Galesburg, IL
K292GR Burlington, IA
Office (309) 298-1104
Cell    (309) 255-6987
Fax    (309) 298-2133

Re: Lynqme?

Mark Conner N9XTN
 

If it's physically hackable, you could conceivably attach a gain
antenna onto the ground half of the system and improve the range.

On Fri, Jul 19, 2019 at 12:10 PM Michael <mw@...> wrote:

Interesting. Works up to 3 miles, so I’d bet it is a GPS married to a LORA RF chipset with a small processor to send and listen for a unique ID packet with coordinates.

--Michael Willett

On Jul 19, 2019, at 11:13 AM, Garrett, Mark <ma-garrett@...> wrote:

Interesting device. Might be worth the experiment if it does not shut down if it gets above say 60 K like some other GPS devices. It would also be interesting to know its frequencies of operation and how it behaves if you get behind some terrain or down in a corn field.

On Fri, Jul 19, 2019 at 10:15 AM Larry <larry.phegley@...> wrote:

Does anyone know anything about this or have any experience with it?

https://lynqme.com/

Larry KJ6PBS

--
Mark Garrett, KA9SZX
Tri States Public Radio

Re: Lynqme?

Garrett, Mark
 

Joe:

I did a search on the device and couldn't find what frequencies it uses.  Will have to go into the FCC site and search for it there.  Three miles is probably tops line of sight to the other device.

On Fri, Jul 19, 2019 at 11:30 AM Joe WB9SBD <nss@...> wrote:
In the video it talks about only a 3 mile range of coverage.

Joe WB9SBD

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 7/19/2019 11:13 AM, Garrett, Mark wrote:
Interesting device.  Might be worth the experiment if it does not shut down if it gets above say 60 K like some other GPS devices.  It would also be interesting to know its frequencies of operation and how it behaves if you get behind some terrain or down in a corn field.  

On Fri, Jul 19, 2019 at 10:15 AM Larry <larry.phegley@...> wrote:
Does anyone know anything about this or have any experience with it?


 Larry   KJ6PBS



--
Mark Garrett, KA9SZX
Tri States Public Radio




--
Mark Garrett
Tri States Public Radio
WIUM Macomb, IL
WIUW Warsaw, IL
WVKC Galesburg, IL
K292GR Burlington, IA
Office (309) 298-1104
Cell    (309) 255-6987
Fax    (309) 298-2133

Re: Lynqme?

Michael
 

Interesting. Works up to 3 miles, so I’d bet it is a GPS married to a LORA RF chipset with a small processor to send and listen for a unique ID packet with coordinates. 

--Michael Willett

On Jul 19, 2019, at 11:13 AM, Garrett, Mark <ma-garrett@...> wrote:

Interesting device.  Might be worth the experiment if it does not shut down if it gets above say 60 K like some other GPS devices.  It would also be interesting to know its frequencies of operation and how it behaves if you get behind some terrain or down in a corn field.  

On Fri, Jul 19, 2019 at 10:15 AM Larry <larry.phegley@...> wrote:
Does anyone know anything about this or have any experience with it?


 Larry   KJ6PBS



--
Mark Garrett, KA9SZX
Tri States Public Radio

Re: Lynqme?

Joe WB9SBD
 

In the video it talks about only a 3 mile range of coverage.

Joe WB9SBD

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 7/19/2019 11:13 AM, Garrett, Mark wrote:
Interesting device.  Might be worth the experiment if it does not shut down if it gets above say 60 K like some other GPS devices.  It would also be interesting to know its frequencies of operation and how it behaves if you get behind some terrain or down in a corn field.  

On Fri, Jul 19, 2019 at 10:15 AM Larry <larry.phegley@...> wrote:
Does anyone know anything about this or have any experience with it?


 Larry   KJ6PBS



--
Mark Garrett, KA9SZX
Tri States Public Radio


Re: Lynqme?

Garrett, Mark
 

Interesting device.  Might be worth the experiment if it does not shut down if it gets above say 60 K like some other GPS devices.  It would also be interesting to know its frequencies of operation and how it behaves if you get behind some terrain or down in a corn field.  

On Fri, Jul 19, 2019 at 10:15 AM Larry <larry.phegley@...> wrote:
Does anyone know anything about this or have any experience with it?


 Larry   KJ6PBS



--
Mark Garrett, KA9SZX
Tri States Public Radio

Lynqme?

Larry
 

Does anyone know anything about this or have any experience with it?


 Larry   KJ6PBS

Space Men on PBS American Experience -- 100% manned high altitude scientific ballooning

Hank Riley
 

Wonderful show with loads of beautiful black and white and color footage going back to the first manned high altitude capsules of the 1930's which led to a space race of sorts between the US and the Soviet Union where the score was kept in thousands of feet of altitude.

Later on in this documentary first aired in 2016 the focus is on Project Manhigh.

I can't say enough good things about this documentary.  Not artificially jazzed up (over the top sound and visual effects) as so many of the NOVA shows have been for years.

Space Men | American Experience | PBS



AIRED JULY 9, 2019

Space Men

THEY WERE THE FIRST TO BRAVE THE UNKNOWN.

Film Description

In the late 1940s, the notion of space travel lived squarely in the realm of science fiction. But a young Army doctor named John Paul Stapp saw no limit to how far mankind could go—he had his eyes set on the heavens. By the 1950s and early '60s, a small band of high-altitude pioneers exposed themselves to the extreme forces of space, long before NASA's acclaimed Mercury 7 would make headlines. With a fraction of NASA’s budget and none of its renown, Stapp's Project Excelsior would send Captain Joseph Kittinger to a record-breaking 102,800 feet above Earth, lifted not by rocket, but by balloon. Though largely forgotten, this group of daring explorers would be the first to venture into the frozen vacuum on the edge of our world, testing the very limits of human physiology and ingenuity in this deadly realm.


Re: KD0VJI11 latex floater over North Dakota Athens AL N4SEV11 floater and PB0AHX1 floater with APRS and RTTY

Steve Aerospace
 

My guess would be that the pressure drops as the balloon is released because the envelope is under less tension - held to the ground the full lift of the balloon is transferred into envelope tension - when in free flight the tension is reduced to that of just the payload weight. The difference is the result of the drag force as the balloon moves through the air - balloon shape differences too due to the movement.

    Steve G8KHW/AJ4XE

On 02/07/2019 22:22, Jerry via Groups.Io wrote:
Now that I am back from my 4995 mile trip to GPSL, I thought I would finish out this thread by posting my graphs from my internal pressure measurements.  Below is the original email and the attached graphs.  Since this was written I think the best explanation is that I had the outside measure port just below the balloon.  It should have been outside the influence of the balloon.  The graph does show a pretty significant rise in differential pressure just before burst.  If the amount of helium (or hydrogen) cannot overcome this pressure increase to maintain the lift, the balloon will float.

=====================
Original post:

I finally have the data on the differential pressure during a flight.  This was a 1000 gram balloon.  The ascent was about 1100 Ft/Sec with a burst altitude of 87,000 feet.

The pressure and temperature was measured at the end of a tube that went about 20 inches into the balloon.  The tube fed the pressure to a differential pressure transducer outside the neck of the balloon.

As expected there was a peak pressure as the balloon started to inflate.  This quickly started to drop off as the balloon inflated as expected.

At launch the pressure suddenly dropped 0.003 PSI.  I suspect that was due to the acceleration possibly on the actual transducer.  If anyone has another explanation I would love to here it.

Again as expected the pressure dropped as the diameter increased. 

As the balloon approached burst the pressure did increase as expected.  The increase from the minimum was about 0.008 PSI.  I don't think we can judge how this compares to the initial peak because of the offset during Ascent.

The temperature was probably as expected.  During fill the internal temp was a little lower than the outside temp which can be explained by the cooling from the helium pressure change.  Once in flight the internal temperature lags a little but not by a significant amount.

I think some other groups measured internal pressures and would love to know how these compared.

Graphs should be linked to this email.

Jerry




On Tuesday, June 25, 2019, 6:44:51 PM MST, Jerry via Groups.Io <jerrygable@...> wrote:


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.  

Jerry Gable
Balloon Flight Prediction tools
http://www.s3research.com


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.

Joe WB9SBD
Near Space Sciences
30 years and 70 flights,,, 

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 6/25/2019 9:40 AM, Jerry via Groups.Io wrote:
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.

Jerry Gable
Balloon Flight Prediction tools
http://www.s3research.com


On Tuesday, June 25, 2019, 5:13:04 AM MST, BASE_DePauw <hlbrooks@...> wrote:


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.

Howard

On Tue, Jun 25, 2019, 12:27 AM Bill Brown via Groups.Io <wb8elk=aol.com@groups.io> wrote:
Hi Gur,

  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




-----Original Message-----
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

Gur,

My students investigated this phenomena a few years ago, inspired by Ron K6RPT (https://www.popsci.com/technology/article/2011-12/amateur-radio-balloon-makes-record-transcontinental-transatlantic-flight/) and his transoceanic flights plus a near floater of our own that carried a load of 3 kg (BASE 67 in 2011).

The latex 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 bursts).

When 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.

Howard, KC9QBN
BASE, DePauw

On Mon, Jun 24, 2019 at 12:04 AM Gur Lavie <gurlavie@...> wrote:
Hei Bill,

Whats the physics behind a Latex becoming a floater ? 

Does it mean it was completely “under” filled ?
Can this be intentionally planned and launched ?

Thanks

Gur

On Sun, 23 Jun 2019 at 22:10 Bill Brown via Groups.Io <wb8elk=aol.com@groups.io> wrote:
Fascinating flight. I believe this is the smallest balloon (600 gram) to achieve a stratospheric float. They are flying a Skytracker board 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 far.

Callsign: KD0VJI-11

We 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 (Callsign: N4SEV-11).

Also, PB0AHX-1 is flying over Germany at the moment with a Skytracker that I modified to output 50 baud RTTY after the second APRS 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 morning.

The RTTY telemetry is displayed on tracker.habhub.org under the callsign PB0AHX.

- Bill WB8ELK





-----Original Message-----
From: Jim Reed <jim.reed@...>
To: GPSL <GPSL@groups.io>
Sent: Sun, Jun 23, 2019 9:15 am
Subject: [GPSL] Floater - was not the plan

KD0VJI-11

Our local HAM radio club asked us to put a balloon they could track for their field day. I guess we messed up in the helium calculation. 😊

It turned into a floater. It is a 600 gram latex balloon flying one of Bill’s skytrackers. Been floating for about a day now at 100k. Kinda neat to see the track.

Just thought I would share for those that are into that stuff.



--
Howard L. Brooks
Professor of Physics and Astronomy
241 Julian Science and Mathematics Center
DePauw University
602 S. College Street
Greencastle, IN 46135
hlbrooks@...
Office: (765) 658-4653
FAX: (765) 658-4732


-- 
Steve Randall
Random Engineering Ltd
steve@...
+44 7802 242135

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Re: KD0VJI11 latex floater over North Dakota Athens AL N4SEV11 floater and PB0AHX1 floater with APRS and RTTY

Jerry
 

Now that I am back from my 4995 mile trip to GPSL, I thought I would finish out this thread by posting my graphs from my internal pressure measurements.  Below is the original email and the attached graphs.  Since this was written I think the best explanation is that I had the outside measure port just below the balloon.  It should have been outside the influence of the balloon.  The graph does show a pretty significant rise in differential pressure just before burst.  If the amount of helium (or hydrogen) cannot overcome this pressure increase to maintain the lift, the balloon will float.

=====================
Original post:

I finally have the data on the differential pressure during a flight.  This was a 1000 gram balloon.  The ascent was about 1100 Ft/Sec with a burst altitude of 87,000 feet.

The pressure and temperature was measured at the end of a tube that went about 20 inches into the balloon.  The tube fed the pressure to a differential pressure transducer outside the neck of the balloon.

As expected there was a peak pressure as the balloon started to inflate.  This quickly started to drop off as the balloon inflated as expected.

At launch the pressure suddenly dropped 0.003 PSI.  I suspect that was due to the acceleration possibly on the actual transducer.  If anyone has another explanation I would love to here it.

Again as expected the pressure dropped as the diameter increased. 

As the balloon approached burst the pressure did increase as expected.  The increase from the minimum was about 0.008 PSI.  I don't think we can judge how this compares to the initial peak because of the offset during Ascent.

The temperature was probably as expected.  During fill the internal temp was a little lower than the outside temp which can be explained by the cooling from the helium pressure change.  Once in flight the internal temperature lags a little but not by a significant amount.

I think some other groups measured internal pressures and would love to know how these compared.

Graphs should be linked to this email.

Jerry




On Tuesday, June 25, 2019, 6:44:51 PM MST, Jerry via Groups.Io <jerrygable@...> wrote:


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.  

Jerry Gable
Balloon Flight Prediction tools
http://www.s3research.com


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.

Joe WB9SBD
Near Space Sciences
30 years and 70 flights,,, 

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 6/25/2019 9:40 AM, Jerry via Groups.Io wrote:
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.

Jerry Gable
Balloon Flight Prediction tools
http://www.s3research.com


On Tuesday, June 25, 2019, 5:13:04 AM MST, BASE_DePauw <hlbrooks@...> wrote:


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.

Howard

On Tue, Jun 25, 2019, 12:27 AM Bill Brown via Groups.Io <wb8elk=aol.com@groups.io> wrote:
Hi Gur,

  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




-----Original Message-----
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

Gur,

My students investigated this phenomena a few years ago, inspired by Ron K6RPT (https://www.popsci.com/technology/article/2011-12/amateur-radio-balloon-makes-record-transcontinental-transatlantic-flight/) and his transoceanic flights plus a near floater of our own that carried a load of 3 kg (BASE 67 in 2011).

The latex 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 bursts).

When 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.

Howard, KC9QBN
BASE, DePauw

On Mon, Jun 24, 2019 at 12:04 AM Gur Lavie <gurlavie@...> wrote:
Hei Bill,

Whats the physics behind a Latex becoming a floater ? 

Does it mean it was completely “under” filled ?
Can this be intentionally planned and launched ?

Thanks

Gur

On Sun, 23 Jun 2019 at 22:10 Bill Brown via Groups.Io <wb8elk=aol.com@groups.io> wrote:
Fascinating flight. I believe this is the smallest balloon (600 gram) to achieve a stratospheric float. They are flying a Skytracker board 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 far.

Callsign: KD0VJI-11

We 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 (Callsign: N4SEV-11).

Also, PB0AHX-1 is flying over Germany at the moment with a Skytracker that I modified to output 50 baud RTTY after the second APRS 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 morning.

The RTTY telemetry is displayed on tracker.habhub.org under the callsign PB0AHX.

- Bill WB8ELK





-----Original Message-----
From: Jim Reed <jim.reed@...>
To: GPSL <GPSL@groups.io>
Sent: Sun, Jun 23, 2019 9:15 am
Subject: [GPSL] Floater - was not the plan

KD0VJI-11

Our local HAM radio club asked us to put a balloon they could track for their field day. I guess we messed up in the helium calculation. 😊

It turned into a floater. It is a 600 gram latex balloon flying one of Bill’s skytrackers. Been floating for about a day now at 100k. Kinda neat to see the track.

Just thought I would share for those that are into that stuff.



--
Howard L. Brooks
Professor of Physics and Astronomy
241 Julian Science and Mathematics Center
DePauw University
602 S. College Street
Greencastle, IN 46135
hlbrooks@...
Office: (765) 658-4653
FAX: (765) 658-4732


Re: Trackers

Joe WB9SBD
 

10 DB too much power.

Joe WB9SBD

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com

On 6/29/2019 3:20 PM, Christopher Rose wrote:
https://www.byonics.com/mtt4b

-----------------------------------------

From: "Mustafa Tan"
To: GPSL@groups.io
Cc:
Sent: Saturday June 29 2019 3:05:17PM
Subject: Re: [GPSL] Trackers

Hi Joe,

Check this out:


TA2MUN

On Sat, Jun 29, 2019 at 5:04 PM Joe WB9SBD <nss@...> wrote:
I really Miss these Units.

What is out there that is closest to it?

Joe WB9SBD
--

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com



--

Re: Trackers

Christopher Rose
 

https://www.tracksoar.com/tracksoar-comparison-2/

-----------------------------------------

From: "Mustafa Tan"
To: GPSL@groups.io
Cc:
Sent: Saturday June 29 2019 3:05:17PM
Subject: Re: [GPSL] Trackers

Hi Joe,

Check this out:


TA2MUN

On Sat, Jun 29, 2019 at 5:04 PM Joe WB9SBD <nss@...> wrote:
I really Miss these Units.

What is out there that is closest to it?

Joe WB9SBD
--

The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com