Date   
Re: Barometric pressure sensor for HABs?

Hank Riley
 


I've been using GPS for altitude on my balloons, but I'm working with a
student who's interested in trying a barometric pressure sensor attached
to an arduino with my next HAB flight.   I've got a pile of BMP180s
laying around, but  they only seem to be rated for 9,000m.  It looks
like the BMP280 has the same issue.  I'm expecting 36,000 meters or so.

The limit of 9000 meters is a matter of staying within the very high accuracy performance specs of the Bosch devices.

They may well work acceptably at much higher altitudes.  There's quite a high range of pressures to handle over that span of 0 to 100,000 feet, from around 1000 mb down to 11mb.

So, two questions.

1) Is there a better series of devices to use?

Certainly nothing I know of that's digital, low priced, and very accurate at lower altitudes.  It would be very worthwhile to test how well the BMP devices work outside of their intended range on a flight with GPS for comparison.

2) The last time I screwed with the BMP180, the altitude formulas I
found didn't seem to work.  It was thousands of feet off, just at ground
level.  

If the actual local barometer is not taken into account, errors of about a thousand feet can happen assuming the average sea level pressure of 1013 mb is presumed by the formula and the barometer is either low or high in comparison.  There must have been something wrong for it to be off by thousands of feet at ground level.  Notice that the Adafruit formula gives 0 feet elevation for ground level because the pressure equals the local pressure (1 raised to any power = 1).

This formula, used by Adafruit for the Arduino, is correct up to the first step (start of tropopause) in the standard atmosphere at about 36,000 feet:

Note: Altitude is in meters

altitude = 44330 * {1-[(pressure/local_pressure) ** (1/5.255]}

I can create for you a more complex fitted curve that will cover 0 to 100,000 feet, or you can just use a table for the standard atmosphere or a spreadsheet.

By the way, no matter what sensor you use, you'll be happy to get within a few thousand feet of the correct altitude for those higher ranges of altitude owing to the small pressures being measured and the fact that the standard atmosphere is just an approximation of your slice of the atmosphere at launch.

Hank

Re: Barometric pressure sensor for HABs?

Hank Riley
 

You could get a sounding for the day for a little refinement.  I just tried that and there was a difference of 360 meters from the Standard Atmosphere.  That height is subject to the radiosonde system inaccuracies as well.

I would definitely encourage you to fly at least a BMP180/280 to see how it does higher up.


On Wednesday, September 12, 2018, 2:53:57 AM EDT, Hank Riley via Groups.Io <n1ltv@...> wrote:

By the way, no matter what sensor you use, you'll be happy to get within a few thousand feet of the correct altitude for those higher ranges of altitude owing to the small pressures being measured and the fact that the standard atmosphere is just an approximation of your slice of the atmosphere at launch.

Re: Barometric pressure sensor for HABs?

Steve Aerospace
 

The  MS5611 is a better chip to use for HAB - its rated down to 10mbar (approximately 28km).   Both the BMP180 and BMP280 have an erratic output value issue outside of their rated range.

    Steve G8KHW

On 12/09/2018 01:39, Michael Hojnowski wrote:
Heya,

I've been using GPS for altitude on my balloons, but I'm working with a student who's interested in trying a barometric pressure sensor attached to an arduino with my next HAB flight.   I've got a pile of BMP180s laying around, but  they only seem to be rated for 9,000m.  It looks like the BMP280 has the same issue.  I'm expecting 36,000 meters or so.  So, two questions.

1) Is there a better series of devices to use?
2) The last time I screwed with the BMP180, the altitude formulas I found didn't seem to work.  It was thousands of feet off, just at ground level.  If there is a "defacto" subroutine to use for calculating altitude from a pressure sensor that everyone's using for HABs, I'd love a pointer.

Thanks for any tips!
Mike / KD2EAT


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Re: Barometric pressure sensor for HABs?

Mark Patton
 

Hi Mike,

We've flown the MS5611-01BA03 with good success. It is specified down to 10mb.  Even without setting the local barometric pressure, it is generally within 100 Ft  of actual altitude at launch.  At birst altitude, it can be off by a thousand feet or more.  

Be sure you factor in temperature and the factory calibration data.  The data sheet does a good job of explaining the steps to get to temperature compensated barometric pressure with modifications for low temperature.  Watch out for the the size of the resultant math.  They specify 32 and 64 bit integer math which can introduce errors if not done right.

There is one equation for calculating altitude at launch, and another for high altitudes.  I don't recall what the second equation is or what altitude it kicks in at off the top of my head.  I think it is around 36K feet..

I hope this helps.
Mark - KC0D

Re: Barometric pressure sensor for HABs?

Hank Riley
 

Yes, the first step is at 36K as mentioned in my first post.  The next two are at 65.6 Kfeet and 105 Kfeet.

So up to 105 Kfeet there are three regimes of the Standard Atmosphere:  0 - 36, 36 - 65.6, and 65.6 - 105.

I believe adequate accuracy can be achieved by a single formula fitted to that entire range 0 - 105.


On Wednesday, September 12, 2018, 7:36:29 AM EDT, Mark Patton <kc0d@...> wrote:

There is one equation for calculating altitude at launch, and another for high altitudes.  I don't recall what the second equation is or what altitude it kicks in at off the top of my head.  I think it is around 36K feet..

NASA Breaks a Balloon Altitude Record

L. Paul Verhage KD4STH
 

Re: NASA Breaks a Balloon Altitude Record

Bruce Coates
 

How many balloons could we fly with 60 million cubic feet of He?  ;-)

------ Original message------
From: L. Paul Verhage KD4STH
Date: Thu, Sep 13, 2018 7:06 AM
Cc:
Subject:[GPSL] NASA Breaks a Balloon Altitude Record

Re: NASA Breaks a Balloon Altitude Record

Mark Conner N9XTN
 

Well, if you figure ~250 cu ft for a typical 1200g balloon, around 240,000.  That's a lot of ARHAB flights!

If they were paying commercial rates for their helium (which I think is approaching $1/cu ft again), that'd be $60M for their lifting gas for that mission.  Somehow I doubt they're paying that much.

73 de Mark N9XTN

On Thu, Sep 13, 2018 at 12:58 PM Bruce Coates <bruce.coates@...> wrote:
How many balloons could we fly with 60 million cubic feet of He?  ;-)

------ Original message------
From: L. Paul Verhage KD4STH
Date: Thu, Sep 13, 2018 7:06 AM
Cc:
Subject:[GPSL] NASA Breaks a Balloon Altitude Record

Re: NASA Breaks a Balloon Altitude Record

Joe WB9SBD
 

If the goal was max altitude I'm surprised they did not use H2?

Joe WB9SBD

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

On 9/13/2018 12:58 PM, Bruce Coates wrote:
How many balloons could we fly with 60 million cubic feet of He?  ;-)

------ Original message------
From: L. Paul Verhage KD4STH
Date: Thu, Sep 13, 2018 7:06 AM
Cc:
Subject:[GPSL] NASA Breaks a Balloon Altitude Record


Re: NASA Breaks a Balloon Altitude Record

L. Paul Verhage KD4STH
 

Can you imagine paying that kind of money for a balloon launch? A flight into space on a Falcon 9 is about the same price.


On Thu, Sep 13, 2018, 12:37 PM Mark Conner N9XTN <mconner1@...> wrote:
Well, if you figure ~250 cu ft for a typical 1200g balloon, around 240,000.  That's a lot of ARHAB flights!

If they were paying commercial rates for their helium (which I think is approaching $1/cu ft again), that'd be $60M for their lifting gas for that mission.  Somehow I doubt they're paying that much.

73 de Mark N9XTN

On Thu, Sep 13, 2018 at 12:58 PM Bruce Coates <bruce.coates@...> wrote:
How many balloons could we fly with 60 million cubic feet of He?  ;-)

------ Original message------
From: L. Paul Verhage KD4STH
Date: Thu, Sep 13, 2018 7:06 AM
Cc:
Subject:[GPSL] NASA Breaks a Balloon Altitude Record

Re: NASA Breaks a Balloon Altitude Record

Hank Riley
 

The usage of helium for the typical amateur balloon refers to ground level conditions, similar to Standard Temperature and Pressure which is 20 Celsius and 1013 millibars pressure.

The 60 million cubic feet of the NASA "Big 60" balloon refers to the fully inflated envelope at its peak (equilibrium) altitude of 159,000 feet.  The pressure there is under a millibar, so the gas is expanded over a thousand times in volume over what it was on the surface.  The standard atmosphere specifies a mild temperature very near STP, but during the day there must be significant heating to the envelope.  I'll just deal with the pressure difference which dominates.

So whittle those 240,000 amateur balloons down to more like 240 as a result of dividing by 1000.  And now the low volume, retail customer cost estimate is $600,000 instead of $60 million.

Sanity/error check on the 240,000 balloon answer:  

             Mark was using as typical a 1200 gram balloon and 250 cubic feet.  For helium
             that's good for about 8 pounds of payload according to Liftwin.

             The NASA instrument payload was 200 kilograms = 441 pounds.

             8 x 240,000 = 1,920,000 pounds of payload lift = 960 tons lift!  Impossible.

The specific solution is as follows neglecting extra balloon gas heating beyond ambient and giving STP gas volume:

At 159,000 feet, it's .992 millibar and 271 Kelvin.  STP is 1013 millibars and 273 Kelvin.

60 * 10**6 * .992 / 1013 * 273 / 271 = .059 * 10**6 = 59,000 cubic feet  (for the on-the-ground volume of helium for the Big 60)

Hank
_______________________________________________________


Well, if you figure ~250 cu ft for a typical 1200g balloon, around 240,000.  That's a lot of ARHAB flights!

If they were paying commercial rates for their helium (which I think is approaching $1/cu ft again), that'd be $60M for their lifting gas for that mission.  Somehow I doubt they're paying that much.

Re: NASA Breaks a Balloon Altitude Record

Mark Conner N9XTN
 

Hank, nice job on going the next step with the math which I didn't do.  

73 de Mark N9XTN

On Thu, Sep 13, 2018 at 10:51 PM Hank Riley via Groups.Io <n1ltv=yahoo.com@groups.io> wrote:
The usage of helium for the typical amateur balloon refers to ground level conditions, similar to Standard Temperature and Pressure which is 20 Celsius and 1013 millibars pressure.

The 60 million cubic feet of the NASA "Big 60" balloon refers to the fully inflated envelope at its peak (equilibrium) altitude of 159,000 feet.  The pressure there is under a millibar, so the gas is expanded over a thousand times in volume over what it was on the surface.  The standard atmosphere specifies a mild temperature very near STP, but during the day there must be significant heating to the envelope.  I'll just deal with the pressure difference which dominates.

So whittle those 240,000 amateur balloons down to more like 240 as a result of dividing by 1000.  And now the low volume, retail customer cost estimate is $600,000 instead of $60 million.

Sanity/error check on the 240,000 balloon answer:  

             Mark was using as typical a 1200 gram balloon and 250 cubic feet.  For helium
             that's good for about 8 pounds of payload according to Liftwin.

             The NASA instrument payload was 200 kilograms = 441 pounds.

             8 x 240,000 = 1,920,000 pounds of payload lift = 960 tons lift!  Impossible.

The specific solution is as follows neglecting extra balloon gas heating beyond ambient and giving STP gas volume:

At 159,000 feet, it's .992 millibar and 271 Kelvin.  STP is 1013 millibars and 273 Kelvin.

60 * 10**6 * .992 / 1013 * 273 / 271 = .059 * 10**6 = 59,000 cubic feet  (for the on-the-ground volume of helium for the Big 60)

Hank
_______________________________________________________


Well, if you figure ~250 cu ft for a typical 1200g balloon, around 240,000.  That's a lot of ARHAB flights!

If they were paying commercial rates for their helium (which I think is approaching $1/cu ft again), that'd be $60M for their lifting gas for that mission.  Somehow I doubt they're paying that much.

Re: NASA Breaks a Balloon Altitude Record

Joe WB9SBD
 

Don't forget the weight of that Giant Balloon!
My "LITTLE" 300,000 Cubic Footer

weighs 31 pounds

Joe WB9SBD

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

On 9/13/2018 10:51 PM, Hank Riley via Groups.Io wrote:
The usage of helium for the typical amateur balloon refers to ground level conditions, similar to Standard Temperature and Pressure which is 20 Celsius and 1013 millibars pressure.

The 60 million cubic feet of the NASA "Big 60" balloon refers to the fully inflated envelope at its peak (equilibrium) altitude of 159,000 feet.  The pressure there is under a millibar, so the gas is expanded over a thousand times in volume over what it was on the surface.  The standard atmosphere specifies a mild temperature very near STP, but during the day there must be significant heating to the envelope.  I'll just deal with the pressure difference which dominates.

So whittle those 240,000 amateur balloons down to more like 240 as a result of dividing by 1000.  And now the low volume, retail customer cost estimate is $600,000 instead of $60 million.

Sanity/error check on the 240,000 balloon answer:  

             Mark was using as typical a 1200 gram balloon and 250 cubic feet.  For helium
             that's good for about 8 pounds of payload according to Liftwin.

             The NASA instrument payload was 200 kilograms = 441 pounds.

             8 x 240,000 = 1,920,000 pounds of payload lift = 960 tons lift!  Impossible.

The specific solution is as follows neglecting extra balloon gas heating beyond ambient and giving STP gas volume:

At 159,000 feet, it's .992 millibar and 271 Kelvin.  STP is 1013 millibars and 273 Kelvin.

60 * 10**6 * .992 / 1013 * 273 / 271 = .059 * 10**6 = 59,000 cubic feet  (for the on-the-ground volume of helium for the Big 60)

Hank
_______________________________________________________


Well, if you figure ~250 cu ft for a typical 1200g balloon, around 240,000.  That's a lot of ARHAB flights!

If they were paying commercial rates for their helium (which I think is approaching $1/cu ft again), that'd be $60M for their lifting gas for that mission.  Somehow I doubt they're paying that much.


Floater Balloon - VA5BNC-15

Bruce Coates
 

Hi

Sorry for the short notice but things have been a bit hectic.

On Sunday morning, September 30 I launched my first floater, VA5BNC-15 from Saskatoon, (52.1N, 106.6W).  It survived the first night and has made it all the way from Saskatoon to somewhere off the east coast of Newfoundland.  If I'm very lucky, will make it across the pond in the next 48 hours.  It should switch to 144.800 in the mid-atlantic, but if there are any European stations that can listen on 144.390, that would be appreciated.  During the day, it beacons once per minute at 13 seconds after the minute and at night, it's on a roughly 15 minute cycle.

https://aprs.fi/#!call=a%2FVA5BNC-15&timerange=86400&tail=86400

Please pass this on to anyone who many be interested.

73, Bruce - VE5BNC

2019 GPSL Save the Date!

Mike, n0mpm
 

GPSL will be in Pella, IA,, June 13, 14 and 15.  Genelle is planning to recreate our Wednesday evening picnic at our house for those that come in on Wednesday afternoon.   We are busy planning an interesting day of tours on the 13th.  
It’s not too soon to consider giving a presentation.
Watch for additional information after the New Year..
Mike. n0mpm
Pella Explores Near Space (PENS)

Re: 2019 GPSL Save the Date!

Mark Conner N9XTN
 

Mike,

Looking forward to it!  We really enjoyed our time in Pella at your last GPSL.  

73 de Mark N9XTN

On Sat, Oct 6, 2018 at 10:48 AM Mike, n0mpm <morgamp52@...> wrote:
GPSL will be in Pella, IA,, June 13, 14 and 15.  Genelle is planning to recreate our Wednesday evening picnic at our house for those that come in on Wednesday afternoon.   We are busy planning an interesting day of tours on the 13th.  
It’s not too soon to consider giving a presentation.
Watch for additional information after the New Year..
Mike. n0mpm
Pella Explores Near Space (PENS)

Re: 2019 GPSL Save the Date!

L. Paul Verhage KD4STH
 

Here here! It was a great event in 2013.


On Sat, Oct 6, 2018, 10:14 AM Mark Conner N9XTN <mconner1@...> wrote:
Mike,

Looking forward to it!  We really enjoyed our time in Pella at your last GPSL.  

73 de Mark N9XTN

On Sat, Oct 6, 2018 at 10:48 AM Mike, n0mpm <morgamp52@...> wrote:
GPSL will be in Pella, IA,, June 13, 14 and 15.  Genelle is planning to recreate our Wednesday evening picnic at our house for those that come in on Wednesday afternoon.   We are busy planning an interesting day of tours on the 13th.  
It’s not too soon to consider giving a presentation.
Watch for additional information after the New Year..
Mike. n0mpm
Pella Explores Near Space (PENS)

Stargazing Almanac

L. Paul Verhage KD4STH
 

I'm experimenting with a free monthly astronomy newsletter. If you're interested, you can subscribe at, https://stargazingalmanac.substack.com/

aprs.fi and Google Maps

Mark Conner N9XTN
 

Crossposting this from the APRSSIG, since there are so many aprs.fi users here.

73 de Mark N9XTN

Date: Tue, 16 Oct 2018 09:32:36 +0300 (EEST)
From: Heikki Hannikainen <hessu@...>
To: aprssig@...
Subject: [aprssig] aprs.fi and Google Maps API pricing changes, status
        update
Message-ID: <alpine.DEB.2.20.1810160919570.6015@...>
Content-Type: text/plain; charset="utf-8"; Format="flowed"


Hi,

Here's the current status of aprs.fi, Google Maps API pricing, and 
Leaflet/OSM mapping.

As most of you already know, Google bumped up the pricing of the Maps API 
significantly this summer, so that aprs.fi would have paid about 
4000-5000? (4500-5700 USD) per month to use the fine maps, and assorted 
services (superb address search, and a few other goodies). Understandably, 
that'd be more than I could pay, and a difficult amount to come up as 
donations or subscription fees, every month.

As a contingency plan I made a port of aprs.fi using Leaflet for mapping. 
Leaflet can load map tiles from tile servers (or services) which generate 
PNG map images from, for example, OSM data. A few individuals and 
companies reached out to me and offered to provide access to their tile 
servers for PNG OSM maps, either for free, or for a discount. This version 
is still running on https://beta.aprs.fi/.  It uses Geonames for address 
search, which is not that great. Google can actually do proper searching 
of street addresses in Finland (or Japan, in Japanese), for example, while 
Geonames will only find cities and towns. OSM maps are better than Google 
maps in some places in the world, and less good in others.

At the same time I exchanged several emails and some phone calls with 
Google's representatives in the sales support, and eventually in the Maps 
API team, and explained the situation. The advertisement income for a site 
like this is simply nowhere near the Maps API fees; it's on a different 
decade, and there are other costs to cover, too.

Google has some programs for nonprofits, crisis response organisations, 
news media and startups, but I'm not eligible for any of those options, as 
I'm not a registered nonprofit organisation or a growth-mode startup with 
venture capital; I'm a one-man-and-a-cat sized private limited company, 
which doesn't make practical profit from the web site though. It's just 
easier to do the finances and taxes this way, and it helps me do some odd 
consulting jobs sometimes. It's a hobby.

Crisis responder organisations (Red Cross, local ARES teams, etc) use 
aprs.fi from time to time in some form, but they're only eligible for free 
Maps API for up to two months at a time. 
(https://developers.google.com/maps/billing/understanding-public-programs)

In the end, the good folks at Google Maps figured they still would like to 
support aprs.fi. They configured additional monthly credits for my billing 
account, so that I won't be charged for the time being, and indicated that 
a more permanent process/solution would be figured out later.

As the combination of Google Maps, their reliable tile servers, address 
search and street view is pretty good, I plan to keep using it as the 
primary solution for the time being.

The Leaflet variant does work, and I plan to keep it available, perhaps at 
a more permanent address than the current 'beta'. It's also useful for 
running separate service instances for different purposes than APRS.

   - Hessu, OH7LZB, AF5QT  

Rasberry Pi and High Altitude Balloons

Jason Unwin
 

Our Civil Air Patrol Squadron got some Raspberry Pi kits for STEM activities. We might have a couple left over when we are done. I am wondering if there are any kits or additional "sensors" we can add to the basic Raspberry Pi for a HAB flight. Specifically something to help track the payloads and possibly a way to log air temperature, density, humidity, or maybe even cosmic radiation. Any thoughts and links to ideas is greatly appreciated.


Jason Unwin
KF5UEF