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The General Protection Fault 2 High Altitude Balloon

by Bryan A. Thompson

Last Updated  03/27/2008




The primary goal of this mission is to obtain high resolution images from high altitude. 

  • The mission will carry a higher resolution imaging system with upgraded battery and RAM to record the entire flight. 
  • We will test our ability to launch a balloon without it sinking or crashing into a tree or littering the launch site with pieces of itself. 
  • We will use the launch to again test our ability to track it as it ascends to over 100,000ft and then back to ground level. 
  • The mission will test our ability to learn from the past and recover the payload without having to borrow an axe from the landowner and chop his tree down to get the capsule/wreckage back. 


When and Where?

Launch date is for the General Protection Fault 2 has been rescheduled for 04/06/2008.  We'll be plotting the projected track three days before the flight, and we'll choose a launch location that places the landing near to flat clear ground.

Click Here for a complete schedule of testing and flight dates (Google login required).



Mark and Nathan Bookout, Ryan Lantzer, Eric Sigler and Jennifer Song, Nathan Neulinger, and Bryan Thompson have all been involved in the design of the balloon.  Malcolm Hays has joined the bunch to help document the experiments.



Did you ever wonder where the balloons went when you let go of them?  Whatever happened to them?  I did.  So I got the idea to install a tracking device in the balloon to find out where it went, and a camera to capture what it sees along the way.

You know, lots of people ask why we're doing it.  And I gotta say - I really dont know.  It's been a huge amount of work, but it sure has been fun.   Personally, Im doing it for the adventure of it all.  If I get a picture from 100,000ft as a souvenir, so much the better. 




Balloon and Chase Vehicle Tracking Systems

Click Here to see the balloon capsule electronics package


Energy and Weight Budgets

Click Here to see the Energy and Weight Budget spreadsheet (your Google Acct Required)


Camera Shutter Release

Click here for information on adding a remote shutter release to the Tracker2.



Coming Up

  • 3/29/2008 - Tracking practice
  • 4/3/2008 - Site Selection
  • 4/5/2008 - Final Check and Van Prep
  • 4/6/2008 - Launch Date



A View Inside the Capsule - Click Here for more pics



Progress as of 03/10/2008

  • Worked on a ground tracking system.  Sounds like we're heading toward a solution with multiple laptops running multiple OSes and using different sources of data instead of having all the data available at one time and location.
  • Built a circuit that mixes the multiple audio sources of the crossband radio and sends them to the Cessna intercom.  Added DC blocking caps, level control pots and an isolation transformer.  Seemed to work on the bench.


Progress as of 03/09/2008

  • Dismantled a perfectly good battery for the camera and removed the battery.  Created a power adapter to allow us to connect the larger external camera battery to the camera. 
  • Mounted a strobe light in the capsule using Silicone.
  • Mounted radio and camera in balloon using Velcro.
  • Capsule is now complete.  Click Here to see it.
  • Tested multiple methods of controlling Radio Push To Talk via a serial port.  Transistor didn't work, reed relay worked.


Progress as of 03/08/2008

  • Borrowed a scanner at Radio Shack to monitor the non-APRS traffic.
  • Doug Kelly joined us and loaned us some comms equipment.  Turns out he had a KAN3+ TNC in his car, so we may be able to make the ground crew an APRS waypoint after all.
  • We successfully tracked the balloon capsule for 5 full hours today, and only used about 1/3 of the energy in the batteries.
  • The camera was still offline due to a missing power adapter.
  • MarkB experienced transmit issues with one of the ground based radios.
  • There were minor issues with squelch on the plane crossband radio.  The experiment with patching the plane intercom into the output of the cross-band radio was a total failure. 
  • Click here to see the flight track from today
  • Click here to see the raw data from today


Progress as of 03/07/2008

  • Came to the realization that we're not getting a Tracker2.  I love those things, but a recent posting by Scott Miller indicates that the next batch is completely sold and that there may be supply problems.  I totally hate this.  He has a great product, but every time I've tried to buy one, I've had to wait. 
  • Decided to construct my own hardware decoder.  It really wouldn't be that hard to decode the data stream from the audio signal, but it would be a project to turn that serial stream into serial data.
  • Group decides to go in the face of experimental data and use software based decoding on the ground and in the air.  This totally fails to take into account the superior input range of the NJM2211 FSK decoder IC (which is 2mV - 3Vrms).  They also want to do this despite the fact that Nathan N has blown up the sound cards in two laptops already.  It fails to take into account the fact that the RS232 PTT cable that we built just totally didn't work.  OK, I'm out-voted.  Less work for me.  Throw me in the briar patch, already.
  • Since we're not using a Tracker2 on the ground, I returned everything I purchased to connect the ground radio to the ground Tracker2.  Well - everything I could, anyway. 
  • Spent 4 hrs waiting to DL Linux into a VM so that we could test its ability to decode AX25 and non-AX25 packets, even though we are only going to be decoding AX25 packets.  Result?  Couldn't figure out how to do it and gave up. 
  • Charged the batteries in preparation for the capsule flight tomorrow.  We won't be able to decode them, so I'll have to get the info off the internet when I get home.


Progress as of 03/06/2008

  • Manufactured and tested the attenuator cables to connect the plane-based cross-band repeater to the Cessna intercom system.  Worked great!
  • Manufactured and tested a Serial RTS-based PTT cable for the plane radio.  This didn't really work at all.
  • Manufactured and tested an attenuator cable to allow a Yaesu VX7R to be safely connected to a laptop sound card.  While we didn't blow another laptop sound card, it failed miserably.  I think pretty much every audio-based APRS packet decoder software we've tried has failed this way.  If it ever worked, it was much less sensitive than the hardware-based Tracker2 modems, and if we tried the same setup on something with a slightly different sound card, it failed again. 
  • Did the preliminary weight calculations and it looks like about 800 ft/sec lift at this point.
  • Did the preliminary Helium budget and decided that ~250 cu ft would be required.


Progress as of 03/02/2008

  • Tested the balloon capsule electronics.  Worked both on the ground and in the air.  Got lots of data from aprs.fi and everything appears to be working correctly.
  • Configured profile switching for 3000ft and when the capsule went above that altitude, it did switch profiles.  When it came below the decending altitude configured in the OT2 (2500ft), it switched profiles again.
  • Tested the ground tracker HT (Icom) and radio cable - all worked as expected.
  • Weighed the capsule.  So far it is at 1121g without the camera or camera power cable or chute or radar reflector.  Still need to work on getting rid of some weight.
  • Still need to connect the plane crossband repeater to the plane intercom.  Need a line to level converter for this.  Mark will buy one and Bryan will hack it to work.
  • Still need to build Nathan an RS232 Serial PTT ckt for use with his laptop.  Also need to build audio cables to connect his HT to his laptop sound card. 
  • Most importantly, we found out not to put Malcolm in the plane on the day of the launch!


Progress as of 02/29/2008

  • Got cables from Argent.  Built ground radio cable for Icom and did preliminary ground tracker system testing.
  • Assembled components into capsule with exception of antenna and camera. 
  • Added info about the capsule electronics to this site.


Progress as of 02/25/2008

  • Fabricated strobe assembly and tested.
  • Balloon electronics completed.
  • Ordered specialty cables for ground tracking device from ArgentData.com.


Progress as of 02/24/2008

  • Added Polyswitch self-resetting fuses to the voltage regulator board.  This will protect everything from a Lithium Ion explosion in the case of a short or polarity reversal.
  • Added 3.7V input / 1.5V output regulator and second polyswitch to the voltage regulator board.  This is to power the camera (3.7V) and Strobe (1.5V).
  • Purchased a USB-Serial adapter for a second serial port on the laptop.  This will allow us to use a USB GPS on the ground tracker.  Using a custom script, we will output the NEMA string to the virtual COM port created by the USB-serial adapter.  From there, the serial connector on the USB-serial connector is connected to the GPS COM port on the Tracker2.  The laptop serial port will be connected to the computer COM port on the Tracker2.  Seems a bit excessive to get a GPS connected to the Tracker2, but the screen is blanking out on the Garmin eTrex Vista Serial, so that's what we decided to do.


Progress as of 2/23/2008

  • Remade all cables in the balloon capsule. Cut out about 4 ft of serial and power cables and cable ties to lighten everything.


Progress as of 02/21/2008

  • Added camera shutter release relay and tested.  It worked fine. 
  • Added a 12V reed relay to the high current output of the T2 for the purposes of enabling a strobe and buzzer to assist us in locating the capsule when it returns to Earth.  Experimented with a few options for configuring the powered output.


Progress as of 02/20/2008

  • Created Lithium Ion batteries required for the balloon. 
  • The group decided to purchase additional Tracker2's from ArgentData.com to use on the ground tracking van and in Nathan's plane, however they're out of stock until the end of the month.


Progress as of 02/19/2008

  • Implemented proposed camera shutter release hack for Tracker2.  Click here for more info.


Progress as of 02/17/2008

  • We recovered the capsule intact, so it will be reused for the imaging flight.  Vacuum testing on various foam samples on the night of 2/16/08 revealed that the Styrofoam container is most suitable for high altitude purposes.  We will reuse the capsule recovered from last time, and we will cut the height to reduce weight.
  • The double-bazooka antenna was broken during the last flight, so it will have to be rebuilt.  We'll try to make it lighter and find a better way to attach it to the capsule.  We may try a standard whip or stubby antenna.  Testing in a rocky valley area will be performed as a worst-case scenario. 
  • A Nikon Coolpix P4  8.2 Megapixel camera has been acquired and hacked to add a remote shutter release.  It was a super-easy camera to hack, and I highly recommend it for this purpose. 
  • Need to find a suitable lightweight 5V DPST relay to serve as the shutter release for the new camera and install.
  • We need to reconfigure the system battery for lighter weight and less run time.
  • We need to create a second battery to power the camera. 
  • Tested the Y cable for the ground receiver.  It does allow the OT2 TNC to connect to both GPS and Computer serial port simultaneously. 
  • We may add a strobe and/or buzzer to make it easier to locate the craft.  This would be powered by the remaining energy in the cam battery and switched on via the Tracker2 relay after the craft landed (or triggered by a profile switch based on altitude within a few thousand feet of landing). 
  • The OT+ TNC that we used on the last flight is F'd.  The analog inputs for voltage and temp measurement are blown and it can't send those as a part of the data stream.  Because the OT+ is missing so many features of the T2 (serial shell, and packet decoding, remote "relay", etc), I'm thinking that it's not worth it to buy another one, just buy an OT2 instead.  But the OT2 is missing a feature that was present on the OT+ that we were using for controlling the shutter release on the camera (the output on X1 pin 9 that goes high when the TNC is ready to transmit).  It was super-useful for firing photos at the same time the data was transmitted, which tied the photo to a place and time and meant we didn't need an additional timer ckt for the camera.  But then I look at the value of having a hardware TNC on the ground and think that maybe we'll just rely on our ability to view data on sites like findu.com.  The profile switching of the Open Tracker + or Open Tracker 2 OT2m when tied to altitude has proved not work reliably in the past, however there is new firmware available. 






Eric Sigler and Jennifer Song provided the flight and balloon and parachute, the Helium, a super-incredible harness to securely hold the payload, and the onboard camera, as well as dinner and ice cream on construction and testing nights.


Nathan Neulinger has provided the use of his aircraft during testing and final tracking, and he wrote some software to allow him to navigate the aircraft to the last received position of the balloon.


Bryan A. Thompson and RollaPhoto.com have provided GPS, Open Tracker modems on the ground and in the air.  Bryan designed and built the tracking system, including the custom batteries, voltage regulator board, and about 100 custom cables required to connect all of this stuff!


Ryan Lantzer has written some awesome Perl tracking scripts were using on the ground tracker. They communicate with GPS and radio modem and dynamically generate a KML file that is plotted in Google Earth.  He also assisted with the assembly and testing of the GPS and interconnect cables. 



Mark and Nathan Bookout have provided the communications systems and services that were using, including the ground and air radios and antennas used by them.  They've also been responsible for rallying support of the local amateur radio operators, which has helped us tremendously.  They designed the double-bazooka antenna that was used for the GPF1 flight.


<Insert Pic of Doug Here - Doug, send this to me if you happen to read this>

Doug Kelly supplied us with comms equipment and expertise on the day of the chases.




Our friends at Plan B Power Systems (PlanBPower.com) have provided the ground and air batteries, chargers, voltage regulators and power inverters used for the mission.


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