Revision as of 05:10, 18 March 2010

This page describes technologies that can be used for a near-space balloon launch.

Camera/Imaging

Canon Powershot

Using the CHDK project, you can run arbitrary software on the camera's CPU. Project Icarus used CHDK to disable the LCD display and loop, taking a picture every 5 seconds.

The cheapest new Powershot is $150, but these models haven't been ported yet. The cheapest supported Powershot (new) is $270 from Best Buy (which is too much). A more practical option is to find a cheap used Powershot.

Benefits: no microcontroller required, high quality images
Drawbacks: cost

Cheap camcorder

dealextreme.com has cheap digital camcorders (no lcd display or other frills) for $50-$70.

http://www.dealextreme.com/details.dx/sku.31878
Cost: $55
Mass: 296 grams

Benefits: no microcontroller required, video
Drawbacks: image quality of stills

"Real" camcorder

http://accessories.dell.com/sna/products/Camcorders/productdetail.aspx?c=ca&l=en&s=dhs&cs=cadhs1&sku=A2612051
US $120 Kodak ZX1 HD camcorder
Benefits: decent picture, video (get what you pay for)

Cheap camera, disassembled

We take a cheap camera, like Gus's $25 camera, take it apart, and hook up some simple electronics to take a picture each 5 seconds.

Benefits: low mass (strip stuff we don't need), can separate lens/ccd from electronics for heat management
Drawbacks: extra electronics work, crappy resolution (300K pixels? -- you get what you pay for)

Cell phone

If we are going to include a cell phone anyway, maybe we can use its camera. I think this only works if we can load our own software into the cell phone. Eg, like an Android based cell phone.

Drawbacks: cost

Camera placement

Some people have used two cameras: one pointed at horizon, for those "curvature of the earth" shots, one pointed down

Batteries

Lithium Photo (Lithium / Manganese Dioxide)

Non-rechargeable, 3V.
Rated for continuous or photoflash output
Operating Temperature: -40C to 60C
Energizer "123" $10 1500mAh 16.5g Specs: http://data.energizer.com/PDFs/123.pdf

Cylindrical Lithium (Lithium / Iron Disulphide)

1.5V, matches standard battery sizes
Rated for continuous output
Higher energy density (more energy per unit mass)
Energizer "L91 Ultimate Lithum" AA size; 14.5g 3200-4300mAh, http://data.energizer.com/PDFs/l91.pdf

Lithium / Thionyl Chloride (Li / SOCl2)

3.6 V, Highest energy density, highest operating temperature range (to -55 C)
at -55C, energy reduced to 50%

Lithium Polymer

Weather Balloons

http://www.novalynx.com/400-balloons.html
http://www.yunhuanelectronics.com/Meteorological_balloons_manufactured.htm
http://www.scientificsales.com/category-s/25.htm?gclid=CLTRov69vqACFQUMDQod2Gv1TQ
http://www.kaymont.com/pages/sounding-balloons.cfm

Project Icarus used a 300g Kaymont balloon. For this balloon, Kaymont recommends:

• 0.97 cu m of helium
• 250 g payload weight

producing the following behaviour:

• 117 cm diameter at release
• 810 g nozzle lift (before accounting for payload)
• 320 m/min rate of ascent
• 77 min to max altitude
• 24.7 km bursting altitude

Adding more payload decreases net lift, slowing the ascent. Adding more helium increases ascent speed (or allows bigger payload), and decreases bursting altitude.

Balloon math, explains some terminology:
http://balloon.pbworks.com/BalloonMath

Hydrogen and Helium

Hydrogen is cheaper and more buoyant, but it is also quite dangerous. If we use hydrogen, we need somebody with the training and skills to handle it safely, to be our safety officer. Dangers of hydrogen are discussed here: http://www.eoss.org/pubs/faqloon.htm

Helium costs:

• need tank, regulator, gas (also hose, balloon nozzle adapter for filling)
• TSC stores: empty tank purchase: $200, refill: $52
• TriCounty Welding:
  • size 16: 2.4 cu m, $62 + $50 refundable deposit. We get to keep the tank for a week. Tank is 49 lb.
  • size 50 smart top: 8.9 cu m, $140 + $50 deposit, includes 1 week tank rental. Tank is 134 lb.
  • longer rentals are available -- need to become a registered customer
  • regulator is ~$75 (need to research flow rate)

A typical mission requires 1 cu m of helium. Max legal limit (CAR regulations) is ~3 cu m, for a high altitude mission.

How To Guides to Near Space Missions

http://www.eoss.org/pubs/faqloon.htm
http://balloon.pbworks.com/
http://moo.pl/~tygrys/balloon/