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HacDC_Spaceblimp_2.md

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+## Flight Summary
+
+Flight date: 8/21/10
+
+Time of liftoff: 10:47 (All times are GMT-5)
+
+Time of touchdown: 11:49
+
+Time of recovery: 12:20
+
+Total flight time: 1:02 (62 minutes)
+
+Liftoff to recovery time: 1:33 (93 minutes)
+
+Touchdown to recovery time: 0:31 (31 minutes)
+
+Weight of payload/chute: 1lb 13oz
+
+Total cost of launch: \$320
+
+## Airframe & Rigging
+
+Balloon: 800g Kaymont/Totex latex weather balloon cost: \$69
+
+Parachute Cord: 250-lb test Dacron line
+
+Balloon Cord: 50-lb test Dacron line
+
+Fill: 190 cubic-feet Helium - cost: \$95 (~10# nozzle lift, gas @
+\$0.50/Cu-ft)
+
+Chute: Rocketchutes flat 24" - cost: \$9
+
+Capsule: Insulated lunch pail (free, valued at ~\$7)
+
+## Payload
+
+Canon model PowerShot SD300 running CHDK (Canon Hack Development Kit)
+intervalometer script - cost: \$20
+
+Canon Li battery cost: \$3.25
+
+Canon 2GB SD card: \$6
+
+Falcom (uBlox based) GPS receiver + Serantel Antenna module - cost \$47
+
+Radiometrix VHF Narrow Band 300mW transmitter - cost \$38
+
+Ultralife U9VL-X Lithium-Manganese Dioxide non-rechargable battery cost:
+\$7
+
+Flight computer/Terminal Node Controller (TNC) - cost \$19
+
+[HacDC Spaceblimp Flickr Group
+Pool](http://www.flickr.com/groups/spaceblimp/pool/with/4922202931/)
+
+[aprs.fi Flight
+Map](http://aprs.fi/?call=w3hac-11&dt=1282348800&mt=roadmap&z=11&timerange=3600)
+
+## Some details on the avionics
+
+Our balloon carried a minimalist avionics package consisting of a custom
+built APRS tracker and a Canon PowerShot SD300 digital camera.
+
+The camera is configured to take pictures every 20 seconds using CHDK
+(http://chdk.wikia.com/wiki/CHDK) and one of the stock intervalometer
+scripts. It is powered by its own rechargeable lithium battery and
+operates independently of the tracker.
+
+The tracker is based around an atmega328p AVR microcontroller, running
+code derived from an open source AVR based APRS tracker called the
+WhereAVR (http://garydion.com/projects/whereavr/). By updating the sine
+wave generation code to use filtered 7-bit pulse width modulation in
+place of the 4-bit resistor network, we were able to improve tone
+quality with a reduced part count. A few additional components were
+added, including an I2C eeprom for local backup of flight data, external
+and internal I2C temperature sensors, and a cutdown MOSFET for switching
+power to a short strip of nichrome wire coiled around the balloon line
+(the cutdown system was not used in our final flight because we were
+apprehensive about the complications it added to the balloon rigging).
+
+To keep things light, compact, and simple, we designed a surface mount
+circuit board to integrate all of the trackers components with a Falcom
+FSA03 GPS module and a 300mW Radiometrix HX-1 144.39 MHz transmitter.
+The board was fabricated using the toner transfer method and hand
+soldered.
+
+For an antenna we used the common 300 ohm twinlead j-pole design
+(http://www.qsl.net/wb3gck/jpole.htm), tuned as close as possible for
+use on our frequency (144.39 MHz) and fed with a short length of 50 ohm
+coax cable for routing/strain relief.
+
+The tracker is powered by a single lithium 9v battery, and regulated
+down to 5v and 3.3v by linear regulators on the board. The typically
+undesirable loss of power to heat with these regulators is useful in
+this case for warming the electronics in the extreme cold temperatures
+encountered during the flight.
+
+Each chase vehicle had a radio tuned to 146.415 for simplex
+communication between the vehicles, and another radio tuned to 144.390
+for receiving packets from the balloon. For packet decoding we used
+radios with built in TNCs or laptops with external modems/soundcard
+modems and TNC software (Soundmodem and Xastir for Linux, AGWPE and
+UI-View for Windows).
+
+## Data
+
+The onboard data recorder from SB2 returned: [Media:
+blimp2_eeprom_log.txt](Media:_blimp2_eeprom_log.txt "wikilink")