High Altitude Balloon Eclipse 2017

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A high altitude balloon launch is a fun way to observe near space. I want to observe and record the August 21 2017 eclipse using one.

Task list

  • Build the payload
    • Needs to be done soon so that we can weigh it, figure out how much helium we need, how big of a balloon and parachute to buy
    • Test it by placing in freezer
    • FAA has limits on size and weight
    • Test by dropping from a drone
  • Find a launch location

Things that anyone can research and help out

  • Figure out how to reduce spinning some ideas
  • Figure out how to attach the line to the payload
  • How does the launch process work
  • Make a complete launch checklist (Started at Launch checklist)
  • Figure out what the failure methods for the parachute are and how to minimize problems

Sub pages

General information

Rules and regulations

  • Payloads must be under 6 pounds.
  • Payloads less than 6 pounds and greater than 4 pounds cannot exceed a package weight/size ratio of three ounces per square inch. You can determine this by dividing the total package weight by the area in square inches of the smallest surface.
  • Rope or cable connecting your payload or balloon may not have a tensile strength greater than 50 pounds.
  • The entire weight of all payloads cannot exceed 12 pounds in total weight. This does not include the weight of the balloon.
  • Cell phones are not permitted to transmit in flight on high-altitude weather balloons. See ideas section for phone idea.
  • HAB laws and regulations
  • airport/airspace + eclipse map

Tutorials and situation reports

APRS

Ideas and brainstorming

  • Payload
    • TrackSoar
    • GoPro
    • Canon camera running CHDK
    • Raspberry Pi with camera module
    • LoRa radio package (time-lapse camera, external temp, GPS) running modified Pi-in-the-sky software by Dave Akerman capable of logging to habhub.org
  • I'm worried about losing the payload. I've read a lot of success stories, and a lot of failure stories, so I'd like to have redundant position reporting.
    • The primary right now is TrackSoar using APRS, but if we lose direct contact, and there are no APRS IGates nearby (which is likely considering how sparse Wyoming is), that would be bad.
    • We could include an Android phone with a custom app that first records video, then switches on the GPS and waits for touchdown. Once on ground, disable airplane mode and either send SMS or send data to aprs.fi to report position. Unfortunately, Android 4.2+ disallows toggling airplane mode from apps, so we either need an old phone or a rooted phone.
    • Turn on a Raspberry Pi access point after some time. Use the directional WiFi antenna from the space to track it.
    • Could also use a secondary warbler in the 900 MHz ISM band and a directional antenna to locate it.

Payload

Now in Python executable format!

items = [
# name/description, weight in grams, optional amount (assumed to be 1 if omitted)
# power
('Energizer Ultimate Lithium AA battery', 15, 5),  # 2 for TrackSoar, 3 for secondary radio
('2 AA battery case', 15.6),
('3 AA battery case', 26.8),
('USB power pack', 111),
('4 port slim USB hub', 35.9),
('USB A to Micro cable', 11.9, 2),
# video
('Raspberry Pi Zero', 9.2, 2),  # Excludes Pi from LoRa package
('Micro SD card', 0.3, 2),
('Raspberry Pi camera module revision 2 + cable', 3.3, 2),
('360 camera', 152),
('aluminum 360 camera mount, estimated (not cut yet)', 56.5),
# radio
('TrackSoar', 18.1),
('Complete LoRa Radio package (electronics, GPS antenna, camera, temp sensor, 3 Lithium AA battery pack, cabling', 181),
('secondary recovery radio (electronics, 3 Lithium AA battery pack)', 87.5),
# container
('polystyrene container', 44.3),
('polystyrene lid', 24.6),
# miscellaneous
('dog tag', 2.5),
('hand warmer', 22.1, 2),
('LED throwie light', 15.1),
# rigging
('Everbilt 5/32" polypropylene rope, estimated (full weight is 73.5g for 45 ft.)', 50),
('3 ft. Rocketman high altitude parachute', 70),
('foam cutouts (full weight with no cutouts is 41g)', 30)
]

grams = sum(item[1] * (item[2] if len(item) == 3 else 1) for item in items)
print(grams)  # 1091.7 as of 2017-08-04
pounds = grams * 0.00220462
print(pounds)  # 2.4067 as of 2017-08-04

Notes on recovery

  • The balloon is likely to fly 50 miles or more, so it will probably be smart to have a recovery team separate (and downwind) from the launch team.

Notes on Tracksoar and APRS

  • In order to receive APRS packets by audio DSP on a laptop, squelch has to be turned on.
    • This means launch and recovery teams need to set squelch for the local noise environment. Optimum squelch levels can change throughout the day!

Notes on power consumption

  • LoRa
    • Current consumption at 5V in (will be higher when running on the nominal 4.5 V 3-AA cell battery pack): 200-250mA taking photos and transmitting at 10mW output
  • 360 camera
    • When charging and using the internal battery to record high definition video, power consumption is 0.48A (steady) at 5V. The camera will continue recording after external power is disconnected.
    • When running with the Pis and a USB hub, they draw average 1.03 A at 4.85 V. The power jumps a bit; I did some spot readings by glancing at the power meter and got these numbers: [1.15, 1.13, 1.27, 1.06, 1.07, 1.08, 1.09, 1.05, 0.92, 1.11, 1.06, 1.02, 1.21, 0.95, 0.94, 1.2, 0.94, 0.96, 1.04, 1.11, 1.1, 0.95, 1.11, 1.07, 1.14, 1.11, 1.02, 0.96, 1.22, 1.05, 0.95, 1.1, 1.11, 1.01, 1.01, 1.13, 0.96, 1.07, 0.93, 0.91, 1.03, 1.14, 0.96, 1.01, 1.06, 0.99, 0.99, 1.07, 1.06, 1.03, 1.12, 0.94, 0.96, 0.97, 1.06, 1.02, 0.94, 1.05, 1.12, 1, 1.24, 1.03, 0.96, 1.05, 0.93, 0.88, 1.01, 1.03, 1.02, 0.97, 1.07, 1.05, 0.95, 1.03, 0.93, 0.96, 1.12, 0.91, 0.97, 0.96, 1.03, 1.04, 1, 1.09, 0.95, 1.08, 1.01, 1, 1.04, 1.1, 0.99, 1, 1.05, 1.07, 0.99, 1.02, 1.04, 1.08, 1, 1, 1.03, 1.07, 1.12, 0.91, 1.07, 0.99]
    • The maximum reading was 1.27A, the minimum 0.88.
    • I disabled BlueTooth, WiFi, and HDMI on the Pis and that dropped usage maybe 20 mA.
    • Running off that 5V 1A 5000mAh USB power supply, it was kicking out 1.25+=0.05A at 4.80V, but the regulator started getting warm. Surface temperature of that battery was 110F. We might want to switch to a 2A battery pack. It's 59g more, but also 10Ah, so that's nice. Maybe the LoRa can run on it?
  • Pi Zero W + camera
    • 0.33 A at 5.00 V, but bounced around a lot, raw readings: [0.28, 0.26, 0.25, 0.3, 0.24, 0.31, 0.32, 0.31, 0.3, 0.31, 0.33, 0.31, 0.29, 0.33, 0.24, 0.25, 0.27, 0.35, 0.35, 0.24, 0.32, 0.26, 0.4, 0.37, 0.33, 0.34, 0.38, 0.34, 0.41, 0.34, 0.39, 0.3, 0.3, 0.32, 0.35, 0.26, 0.34, 0.24, 0.33, 0.28, 0.26, 0.39, 0.33, 0.19, 0.32, 0.25, 0.17, 0.32, 0.27, 0.33, 0.35, 0.33, 0.32, 0.28, 0.38, 0.25, 0.33, 0.4, 0.35, 0.26, 0.33, 0.31, 0.31, 0.34, 0.35, 0.24, 0.36, 0.29, 0.37, 0.2, 0.28, 0.34, 0.25, 0.35, 0.35, 0.28, 0.24, 0.33, 0.38, 0.24, 0.31, 0.39, 0.37, 0.26, 0.27, 0.25, 0.27, 0.33, 0.35, 0.22, 0.26, 0.4, 0.39, 0.2, 0.35, 0.32, 0.32, 0.26, 0.23, 0.39]

Notes on Secondary Recovery Radio

  • Should transmit really annoying AM tone on 40.68 MHz
  • Estimated output power ~25 mW
  • Estimated 10-12 hour battery life (most things are powered off at high altitude)
  • Circuit design is done, working on board layout (2017-07-30)
  • Components are soldered, sends transmission confirmed (2017-08-08)
  • Now it just needs altitude adjustment...
    • Could climb a high peak, and adjust so it's just barely off
    • Could use a vacuum chamber (if we can get our hands on one)

Notes on Gas

Project log

  • 2017-07-16 Idea initially conceived. Brandon's call sign programmed into TrackSoar. Started scoping out launch sites and figuring out regulations and payload.
  • 2017-07-18 Ran launch simulations to determine good launch locations, based on eclipse path and public access of land near launch and expected landing sites. Started work on LoRa and radio squealer secondary tracking and recovery methods.
  • 2017-07-21 Built initial prototype of payload insulation and housing.
  • 2017-07-24 Initial test of insulation in freezer. External temperature was close to -1 C, Raspberry Pi internal CPU temperature started at 62 C then dropped steadily to 47 C over the course of 4 hours. The internal battery lasted nearly 11 hours. The Pi's shutdown when low on disk space script did not execute because pitch black video compresses very well.
  • 2017-07-25 LoRa software working, tested distance to over 10 miles with small antenna.
  • 2017-07-26 Bought 1 pound of dry ice for low temperature testing. This was probably too little and will need more later. Placed insulated payload in box with dry ice at bottom with flashing LED to try to maximize video size. After 3 hours, internal temperature under 1 Pi reached -1 C, while battery temperature reached 15 C. Note though that the Pi side was resting on the dry ice and was much colder. Repeated experiment with dry ice touching both sides; battery approached 2 C on side facing Pi and -9 C on side facing out but was able to power both Pis for 2.25 hours.
  • 2017-07-26 Finished 3 receivers (2 w/ Raspberry Pi for logging telemetry and location and slow-scan digital video and capable of internet upload + 1 portable unit based on Teensy-LC with bitmap LCD display for location/recovery). With exception of final antennas and perhaps image size/quality tuning, LoRa package is ready-to-go.
  • 2017-07-27 Did RF Link budget calculations for LoRa radio and researched yagi antennas. Should be able to have sufficient signal for 100+ miles while balloon is in the air.